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MINISTRY OF SCIENCE AND EDUCATION OF THE REPUBLIC OF KAZAKHSTANSTATE UNIVERSITY NAMED AFTER SHAKARIM, SEMEY

Document of 3 level by MQS EMCD

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EMCD Educational - methodical materials

for discipline «Physical and Colloidal Chemistry»

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EDUCATIONAL-METHODICAL COMPLEX OF DISCIPLINE

«Physical and Colloidal Chemistry»

For the specialty 5B011200– «Chemistry»

Educational - methodical materials

Semey2013

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Content

1. Glossary of discipline 32. Brief synopsis of the lectures 73. Laboratory work 464. Self-study of students 555. Test and Measurement tools 58

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1 GLOSSARY OF THE COURSE «PHYSICAL AND COLLOIDAL CHEMISTRY»

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2. BRIEF SYNOPSIS OF THE LECTURES

Lecture № 1-3. Chemical structure and properties of polymer moleculesPurpose: familiarize with the definition of polymer molecules by the general formula, composition, classification of polymersKey questions:

1. Basic concepts of polymer chemistry.2. Nomenclature of polymers.3. Classification of carbo-and hetero-polymers.4. Characteristic properties of polymer molecules.

Summary:1. Basic concepts of polymer chemistry.A polymer in its simplest form can be regarded as comprising molecules of closely related

composition of molecular weight at least 2000, although in many cases typical properties do not become obvious until the mean molecular weight is about 5000. There is virtually no upper end to the molecular weight range of polymers since giant three-dimensional networks may produce crosslinked polymers of a molecular weight of many millions. Polymers (macromolecules) are built up from basic units, sometimes referred to as ‘mers’. These units can be extremely simple, as in addition polymerisation, where a simple molecule adds on to itself or other simple molecules, by methods that will be indicated subsequently. Thus ethylene CH2=CH2 can be converted into polyethylene, of which the repeating unit is —CH2-CH2—, often written as (-CH2 - CH2-)n, where n is the number of repeating units, the nature of the end groups being discussed later. The major alternative type of polymer is formed by condensation polymerization in which a simple molecule is eliminated when two other molecules condense. In most cases the simple molecule is water, but alternatives include ammonia, an alcohol and a variety of simple substances. The formation of a condensation polymer can best be illustrated by the condensation of hexamethylenediamine with adipic acid to form the polyamide best known as nylon:

This formula has been written in order to show the elimination of water. The product of condensation can continue to react through its end groups of hexamethylenediamine and adipic acid and thus a high molecular weight polymer is prepared. Monomers such as adipic acid and hexamethylenediamine are described as bifunctional because they have two reactive groups. As such they can only form linear polymers. Similarly, the simple vinyl monomers such as ethylene CH2=CH2

and vinyl acetate CH2:CHOOCCH3 are considered to be bifunctional. If the functionality of a monomer is greater than two, a branched structure may be formed. Thus the condensation of glycerol HOCH2CH(OH)CH2OH with adipic acid HOOC(CH2)4COOH will give a branched structure. The condensation is actually three dimensional, and ultimately a threedimensional structure is formed as the various branches link up. Although this formula has been idealised, there is a statistical probability of the various hydroxyl and carboxyl groups combining. This results in a network being built up, and whilst it has to be illustrated on the plane of the paper, it will not necessarily be planar. As functionality increases, the probability of such networks becoming interlinked increases, as does the probability with increase in molecular weight. Thus a gigantic macromolecule will be formed which is

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insoluble and infusible before decomposition. It is only comparatively recently that structural details of these crosslinked or ‘reticulated’ polymers have been elucidated with some certainty. Addition polymers are normally formed from unsaturated carbon-to-carbon linkages. This is not necessarily the case since other unsaturated linkages including only one carbon bond may be polymerised.

Addition polymerisation of a different type takes place through the opening of a ring, especially the epoxide ring in ethylene oxide CH2-CH2. This opens as —CH2CH2O—; ethylene oxide

Оthus acts as a bifunctional monomer forming a polymer as H(CH2CH2O)n-CH2CH2OH, in this case a terminal water molecule being added. A feature of this type of addition is that it is much easier to control the degree of addition, especially at relatively low levels, than in the vinyl polymerisation described above. Addition polymerisations from which polymer emulsions may be available occur with the silicones and diisocyanates. These controlled addition polymerizations are sometimes referred to as giving ‘stepwise’ addition polymers.

2. Nomenclature of polymers.Source-Based Nomenclature For Homopolymers:RULE 1The source-based name of a homopolymer is made by combining the prefix “poly” with the name of the monomer. When the latter consists of more than one word, or any ambiguity is anticipated, the name of the monomer is parenthesized.Example 1 Source-based name: polystyreneStructure-based name: poly(1-phenylethylene)Example 2Source-based name: poly(vinyl chloride)Structure-based name: poly(1-chloroethylene)Generic NomenclatureRULE 2A generic source-based name of a polymer has two components in the following sequence: (1) a polymer class (generic) name (polyG) followed by a colon and (2) the actual or hypothetical monomername(s) (A, B, etc.), always parenthesized in the case of a copolymer. In the case of a homopolymer,parentheses are introduced when it is necessary to improve clarity. PolyG:A polyG:(B) polyG:(A-co-B) polyG:(A-alt-B)Note 1 The polymer class name (generic name) describes the most appropriate type of functional group or heterocyclic ring system.Note 2 All the rules given in the two prior documents on source-based nomenclature can be applied to the present nomenclature system, with the addition of the generic part of the name.Note 3 A polymer may have more than one name; this usually occurs when it can be prepared inmore than one way.

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Note 4 If a monomer or a pair of complementary monomers can give rise to more than one polymer,or if the polymer is obtained through a series of intermediate structures, the use of generic nomenclature is essential.Example 3

Generic source-based names - polyurethane:[butane-1,4-diol-alt-(hexane-1,6-diyl diisocyanate)]-block-polyester: [(ethylene glycol)-alt-(terephthalic acid)]Structure-based name: poly(oxybutane-1,4-diyloxycarbonyliminohexane-1,6-diyliminocarbonyl)-block-poly(oxyethyleneoxyterephthaloyl)Example 4

Generic source-based name: polyamide:[hexane-1,6-diamine-alt-(adipic acid)]-graft-polyether:(ethylene oxide)RULE 5In the case of carbon-chain polymers such as vinyl polymers or diene polymers, the generic name is tobe used only when different polymer structures may arise from a given monomeric system.Example 5Generic source-based name: polyalkylene:(buta-1,3-diene)Source-based name: poly(buta-1,3-diene)Structure-based name: poly(1-vinylethylene)Example 6Generic source-based name: polyalkenylene:buta-1,3-dieneSource-based name: poly(buta-1,3-diene)Structure-based name: poly(but-1-ene-1,4-diyl)Example 7 Generic source-based name: polyalkylene:acrylamideStructure-based name: poly[1-(aminocarbonyl)ethylene]Example 8Generic source-based name: polyamide:acrylamideStructure-based name: poly[imino(1-oxopropane-1,3-diyl)]

3. Classification of carbo-and hetero-polymers.Homopolymers: one type of repeating units (but different architectures)

Copolymers: different types of repeating units (and microstructures)6

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Polymers can be classified in several different ways-according to their structures, the types of reactions by which they are prepared, their physical properties, or their technological uses. From the standpoint of general physical properties, we usually recognize three types of solid polymers: elastomers, thermoplastic polymers, and thermosetting polymers. Elastomers are rubbers or rubberlike elastic materials. Thermoplastic polymers are hard at room temperature, but on heating become soft and more or less fluid and can be molded. Thermosetting polymers can be molded at room temperature or above, but when heated more strongly become hard and infusible. These categories overlap considerably but are nonetheless helpful in defining general areas of utility and types of structures. The structural characteristics that are most important to determining the properties of polymers are: the degree of rigidity of the polymer molecules, the electrostatic and van der Waals attractive forces between the chains, the degree to which the chains tend to form crystalline domains, and the degree of cross-linking between the chains. Of these, cross-linking is perhaps the simplest and will be discussed next. Consider a polymer made of a tangle of molecules with long linear chains of atoms. If the intermolecular forces between the chains are small and the material is subjected to pressure, the molecules will tend to move past one another in what is called plastic flow. Such a polymer usually is soluble in solvents that will dissolve short-chain molecules with chemical structures similar to those of the polymer. If the intermolecular forces between the chains are sufficiently strong to prevent motion of the molecules past one another the polymer will be solid at room temperature, but will usually lose strength and undergo plastic flow when heated. Such a polymer is thermoplastic. A crosslink is a chemical bond between polymer chains other than at the ends. Crosslinks are extremely important in determining physical properties because they increase the molecular weight and limit the translational motions of the chains with respect to one another. Only two cross-links per polymer chain are required to connect all the polymer molecules in a given sample to produce one gigantic molecule. Only a few cross-links reduce greatly the solubility of a polymer and tend to produce what is called a gel polymer, which, although insoluble, usually will absorb (be swelled by) solvents in which the uncross-linked polymer is soluble. The tendency to absorb solvents decreases as the degree of cross-linking is increased because the chains cannot move enough to allow the solvent molecules to penetrate between the chains. Thermosetting polymers normally are made from relatively lowmolecular- weight, usually semifluid substances, which when heated in a mold become highly cross-linked, thereby forming hard, infusible, and insoluble products having a three-dimensional network of bonds interconnecting the polymer chains. Polymers usually are prepared by two different types of polymerization reactions-addition and condensation. In addition polymerization all of the atoms of the monomer molecules become part of the polymer; in condensation polymerization some of the atoms of the monomer are split off in the reaction as water, alcohol, ammonia, or carbon dioxide, and so on. Some polymers can be formed either by addition or condensation reactions. An example is polyethylene glycol, which, in principle, can form either by dehydration of 1,2- ethanediol (ethylene glycol), which is condensation, or by addition polymerization of oxacyclopropane (ethylene oxide):

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4. Characteristic properties of polymer molecules.Polymers are polydisperse. Polymer materials are

composed of a collection of chains with a distribution of lengths/masses (and are typically characterized Mn by the average mass and the breadth of the distribution).

Polymers often exhibit a continuous range of phase behavior. (Are “viscoelastic”.) Polymers deform and flow throughout this range but with different timescales.

Polymer properties are dictated almost entirely by Monomer structure; Average molecular weight; and Degree of crosslinking (to a lesser extent).

Polymers are produced on an industrial scale primarily, although not exclusively, for use as structural materials. Their physical properties are particularly important in determining their usefulness, be it as rubber tires, sidings for buildings, or solid rocket fuels. Polymers that are

not highly cross-linked have properties that depend greatly on the forces that act between the chains. By way of example, considera polymer such as polyethene which, in a normal

commercial sample, will be made up of molecules having 1000 to 2000 CH, groups in

continuous chains. Because the material is a mixture of different molecules, it is not expected to crystallize in a conventional way. Nonetheless, x-ray diffraction shows polyethene to have very considerable crystalline character, there being regions as large as several hundred angstrom units in length, which have ordered chains of CH, groups oriented with respect to one another like the chains in crystalline lowmolecular-weight hydrocarbons. These crystalline regions are called crystallites. Between the crystallites of polyethene are amorphous, noncrystalline regions in which the polymer chains are essentially randomly ordered with respect to one another. These regions constitute crystal defects. Quite good platelike crystals, about 100 A thick, have been formed from dilute solutions of polyethene. In these crystals, CH, chains in the anti conformation run between the large surfaces of the plates. However, the evidence is strong that when the CH, chains reach the surface of the crystal they do not neatly fold over and run back down to the other surface. Instead, the parts of a given chain that are in the crystalline segments appear to be

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connected at the ends of the crystallites by random loops of disordered CH, sequences, something like an old-fashioned telephone switchboard. The forces between the chains in the crystallites of polyethene are the so-called van der Waals or dispersion forces, which are the same forces acting between hydrocarbon molecules in the liquid and solid states, and, to a lesser extent, in the vapor state. These forces are relatively weak and arise through synchronization of the motions of the electrons in the separate atoms as they approach one another. The attractive force that results is rapidly overcome by repulsive forces when the atoms get very close to one another. The attractive intermolecular forces between pairs of hydrogens in the crystallites of polyethene are only about 0.1-0.2 kcal per mole per pair, but for a crystalline segment of 1000 CH, units, the sum of these interactions could well be greater than the C-C bond strengths. Thus when a sample of the crystalline polymer is stressed to the point at which it fractures, carbon-carbon bonds are broken and radicals that can be detected by esr spectroscopy are generated. In other kinds of polymers, even stronger intermolecular forces can be produced by hydrogen bonding. This is especially important in the polyamides, such as the nylons, of which nylon 66 is most widely used.

The effect of temperature on the physical properties of polymers is very important to their practical uses. At low temperatures, polymers become hard and glasslike because the motions of the segments of the polymer chains with relation to each other are slow. The approximate temperature below which glasslike behavior is apparent is called the glass temperature and is symbolized by Tg

When a polymer containing crystallites is heated, the crystallites ultimately melt, and this temperature is usually called the melting temperature and is symbolized as Tm. Usually, the molding temperature will be above Tm and the mechanical strength of the polymer will diminish rapidly as the temperature approaches Tm. Another temperature of great importance in the practical use of polymers is the temperature at which thermal breakdown of the polymer chains occurs. Decomposition temperatures obviously will be sensitive to impurities, such as oxygen, and will be influenced strongly by the presence of inhibitors, antioxidants, and so on. Nonetheless, there will be a temperature (usually rather high, 2000 to 4000) at which uncntalyzed scission of the bonds in a chain will take place at an appreciable rate and, in general, one cannot expect to prevent this type of reaction from causing degradation of the polymer. Clearly, if this degradation temperature is comparable to Tm as it is for polypropenenitrile (polyacrylonitrile), difficulties are to be expected in simple thermal molding of the plastic. This difficulty is overcome in making polypropenenitrile (Orlon) fibers by dissolving the polymer in N,N-dimethylmethanamide and forcing the solution through fine holes into a heated air space where the solvent evaporates. Physical properties such as tensile strength, x-ray diffraction pattern, resistance to plastic flow, softening point, and elasticity of most polymers can be understood in a general way in terms of crystallites, amorphous regions, the degree of flexibility of the chains, cross-links, and the strength of the forces acting between the chains (dispersion forces, hydrogen bonding, etc.). A good way to appreciate the interaction between the physical properties and structure is to start with a rough classification of properties of solid polymers according to the way the chains are disposed in relation to each other.1. An amorphous polymer is one with no crystallites. If the attractive forces between the chains are weak and if the motions of the chain are not in some way severely restricted as by cross-linking or large rotational barriers, such a polymer would be expected to have low tensile strength and whenstressed to undergo plastic flow in which the chains slip by one another.

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2. An unoriented crystalline polymer is one which is considerably crystallized but has the crystallites essentially randomly oriented with respect to one another. When such polymers are heated they often show rather sharp Tm points, which correspond to the melting of the crystallites. Above Tm these polymers are amorphous and undergo plastic flow, which permits them to be molded. Other things being the same, we expect Tm to be higher for polymers with stiff chains (high barriers to internal rotation).3. An oriented crystallline polymer is one in which the crystallites are oriented with respect to one another, usually as the result of a cold-drawing process. Consider a polymer such as nylon, which has strong intermolecular forces and, when first prepared, is in an unoriented state. When the material is subjected to strong stress in one direction, usually above Tm, so that some plastic flow can occur, the material elongates and the crystallites are drawn together and oriented along the direction of the applied stress. An oriented crystalline polymer usually has a much higher tensile strength than the unoriented polymer. Cold drawing is an important step in the production of synthetic fibers.4. Elastomers usually are amorphous polymers. The key to elastic behavior is to have highly flexible chains with either sufficiently weak forces between the chains or a sufficiently irregular structure to be unstable in the crystalline state. The tendency for the chains to crystallize often can be considerably reduced by random introduction of methyl groups, which by steric hindrance inhibit ordering of the chains. A useful elastomer needs to have some kind of cross-linked regions to prevent plastic flow and flexible enough chains to have a low Tm. The important difference between this elastomer and the crystalline polymer is the size of the amorphous regions. When tension is applied and the material elongates, the chains in the amorphous regions straighten out and become more nearly parallel. At the elastic limit, a ~e~nicrystallinseta te is reached, which is different from the one produced by cold drawing of a crystalline polymer in that it is stable only while under tension. The forces between the chains are too weak to maintain the crystalline state in the absence of tension. Thus when tension is released, contraction occurs and the original, amorphous polymer is produced. The entropy of the chains is more favorable in the relaxed state than in the stretched state. A good elastomer should not undergo plastic flow in either the stretched or relaxed state, and when stretched should have a "memory" of its relaxed state. These conditions are best achieved with natural rubber (cis-poly-2- methyl- 1,3-butadiene, cis-polyisoprene) by curing (vulcanizing) with sulfur. Natural rubber is tacky and undergoes plastic flow rather readily, but when it is heated with 1-8% by weight of elemental sulfur in the presence of an accelerator, sulfur cross-links are introduced between the chains. Thesecross-links reduce plastic flow and provide a reference framework for the stretched polymer to return to when it is allowed to relax. Too much sulfur completely destroys the elastic properties and produces hard rubber of the kind used in cases for storage batteries. The chemistry of the vulcanization of rubber is complex. The reaction of rubber with sulfur is markedly expedited by substances called accelerators, of which those commonly known as mercaptobenzothiazole and tetramethylthiuram disulfide are examples: Clearly, the double bonds in natural rubber are essential to vulcanization because hydrogenated rubber ("hydrorubber") is not vulcanized by sulfur. The degree of unsaturation decreases during vulcanization, although the decrease is much less than one double bond per atom of sulfur introduced. There is evidence that attack occurs both at the double bond and at the adjacent hydrogen(in a manner similar to some halogenations) giving crosslinks possibly of the following types:

The accelerators probably function by acting as sulfur carriers from the elemental sulfur to the sites of the polymer where the cross-links are formed.

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Thus the simple linear polymers, polyethene -CH2CH2-, polymethanal -CH2-O-, and polytetrafluoroethene - CF2-CF2 - , with regular chains and low barriers to rotation about the bonds in the chain tend to be largely crystalline with rather high melting points and low glass temperatures. The situation with polychloroethene (polyvinyl chloride), polyfluoroethene (polyvinyl fluoride), and polyethenylbenzene (polystyrene) as usually prepared is quite different. These polymers are much less crystalline and yet have rather high glass temperatures, which suggests that there is considerable attractive force between the chains. The low degree of crystallinity of these polymers is the result of their having a low degree of regularity of the stereochemical configuration of the chiral carbons in the chain. The discovery by Natta in 1954 that the stereochemical configurations of chiral centers in polymer chains could be crucial in determining their physical properties has had a profound impact on both the practical and theoretical aspects of polymer chemistry. Natta's work was done primarily with polypropene and this substance provides an excellent example of the importance of stereochemical configurations. What properties would we expect for polypropene? If we extrapolate from the properties of polyethene, -CH2-CH2-, Tm = 1300 and Tg = -120°, and poly-2 methylpropene - CH2-C(CH3)2-, which is amorphous with Tg = -70°, we would expect that polypropene would have a low melting point and possibly be an amorphous polymer. In fact, three distinct varieties of polypropene have been prepared by polymerization of propene with Ziegler catalysts. Two are highly crystalline and one is amorphous and elastic. These polymers are called, respectively, isotactic, syndiotactic, and atactic polypropene. The differences between their configurations are shown in Figure:

If we could orient the carbons in the polymer chains in the extended zig-zag conformation of Figure, we would find that the atactic form has the methyl groups randomly distributed on one side or the other of the main chain. In contrast, isotactic polypropene has a regular structure with the methyl groups all on the same side of the chain. Many other kinds of regular structures are possible and the one of these that has been prepared, although not in quantity, is the syndiotactic form, which has the methyl groups oriented alternately on one side or the other of the polymer chain. There are striking differences in physical properties between the atactic and isotactic forms. The atactic material is soft, elastic, somewhat sticky, and rather soluble in solvents such as 1,1,2,2-tetrachloroethane. Isotactic polypropene is a hard, clear, strong crystalline polymer that melts at 1750. It is practically insoluble in all organic solvents at room temperature, but will dissolve to the extent of a few percent in hot 1,1,2,2-tetrachloroethane. Although both linear polyethene and isotactic polypropene are crystalline polymers, ethene-propene copolymers prepared with the aid of Ziegler catalysts are excellent elastomers. Apparently, a more or less random introduction of methyl groups along a polyethene chain reduces the crystallinity sufficiently drastically to lead to an amorphous polymer. The ethene-propene copolymer is an inexpensive elastomer, but having no double bonds, is not capable of vulcanization.

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Polymerization of ethene and propene in the presence of a small amount of dicyclopentadiene or 1,4-hexadiene gives an unsaturated heteropolymer, which can be vulcanized with sulfur in the usual way. dicyclopentadiene The rationale in using these particular dienes is that only the strained double bond of dicyclopentadiene and the terminal double bond of 1,4-hexadiene undergo polymerization with Ziegler catalysts. Consequently the polymer chains contain one double bond for each molecule of dicyclopentadiene or 1,4-hexadiene that is incorporated. These double bonds later can be converted to cross-links by vulcanization with sulfur. Polychloroethene (polyvinyl chloride), as usually prepared, is atactic and not very crystalline. It is relatively brittle and glassy. The properties of polyvinyl chloride can be improved by copolymerization, as with ethenyl ethanoate (vinyl acetate), which produces a softer polymer ("Vinylite") with better molding properties. Polyvinyl chloride also can be plasticized by blending it with substances of low volatility such as tris-(2-methylphenyl) phosphate (tricresyl phosphate) and dibutyl benzene- l,2-dicarboxylate (dibutyl phthalate) which, when dissolved in the polymer, tend to break down its glasslilce structure. Plasticized polyvinyl chloride is reasonably flexible and is widely used as electrical insulation, plastic sheeting, and so on.

QUESTIONS FOR SELF-CONTROL:1. Could we name molecule of oleic acid as a macromolecule of polymer: CH3-(CH2)7-CH=CH-(CH2)7-COOH ?2. Specify the structural unit of the macromolecule:...-CH2-CH=CH-CH2-CH2-CH=CH-CH2-CH2-CH=CH-CH2-...3. The degree of polymerization of the macromolecule is ...

4. What is the molecular weight of polypropylene macromolecule, if the degree of polymerization n = 1000?5. What is the average molecular weight of polyethylene, if 20% of macromolecules have a molecular weight of 280000, 30% macromolecules – 18000, 50% macromolecules - 2000?

REFERENCES:1. “Nomenclature of regular single-strand organic polymers, 1975”, Pure Appl. Chem. 48, 373–385 (1976). Reprinted as chapter 5 in Ref. 7.2. “Nomenclature of regular double-strand (ladder and spiro) organic polymers 1993”, Pure Appl. Chem. 65, 1561–1580 (1993).3. “Structure-based nomenclature for irregular single-strand organic polymers 1994”, Pure Appl. Chem. 66, 873–889 (1994).4. L. Mandelkern, An lntroduction to Macromolecules, Springer-Verlag, New York, 1992.5. R. G. Treloar, lntroduction to Polymer Science, Springer-Verlag, New York, 1990. An excellent and simple introduction to the relationship of polymer physical properties to structure.6. Шур А.М. Высокомолеклурные соединения, М., 1981г.

Lecture № 3-4. General characteristics of the processes of polymers.Objective: To become familiar with the processes for producing polymers.Key questions:1. Basic ways of polymer synthesis.2. General characteristics of the processes of polymers obtaining.

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3. Features of polymerization and polycondensation processes.

Summary:1. Basic ways of polymer synthesis.

Types of reactions

Condensation

Addition

Ring opening

2. General characteristics of the processes of polymers obtaining.There is a very wide variety of condensation reactions that, in principle, can be used to form high

polymers. However, as explained above, high polymers can be obtained only in high-yield reactions, and this limitation severely restricts the number of condensation reactions having any practical importance. A specific example of an impractical reaction is the formation of poly- 1,4-butanediol by reaction of 1,4-dibromobutane with the disodium salt of the diol:

It is unlikely that this reaction would give useful yields of any very high polymer because E2 elimination, involving the dibromide, would give a doublebond end group and prevent the chain from growing. A variety of polyester-condensation polymers are made commercially. Ester interchange appears to be the most useful reaction for preparation of linear polymers:

Thermosetting space-network polymers can be prepared through the reaction of polybasic acid anhydrides with polyhydric alcohols. A linear polymer is obtained with a bifunctional anhydride and a bifunctional alcohol, but if either reactant has three or more reactive sites, then formation of a three-dimensional polymer is possible. For example, 2 moles of 1,2,3-propanetrio1 (glycerol) can react with 3 moles of 1,2-benzenedicarboxylic anhydride (phthalic anhydride) to give a highly cross-linked resin, which usually is called a glyptal:

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The first stage of the reaction involves preferential esterification of the primary hydroxyl groups with the anhydride. In the next stage, in the formation of the resin, direct esterification occurs slowly, particularly at the secondary hydroxyls. Normally, when the resin is used for surface coatings, esterification is carried only to the point where the polymer is not so cross-linked as to be insoluble. It then is applied to the surface in a solvent and baked until esterification is complete. The product ishard, infusible, and insoluble, being cross-linked to the point of being essentially one large molecule.A wide variety of thermosetting polyester (alkyd) resins can be made by similar procedures. The following polybasic acids and anhydrides and polyhydric alcohols are among the other popular ingredients in alkyd formulations:

Articles in which glass fibers are imbedded to improve impact strength often are made by mixing the fibers with an ethenylbenzene (styrene) solution of a linear glycol (usually 1,2-propanedio1)-butenedioic anhydride polyester and then producing a cross-linked polymer between the styrene and the double bonds in the polyester chains by a peroxide-induced radical polymerization. A variety of polyamides can be made by heating diamines with dicarboxylic acids. The most generally useful of these is nylon 66, the designation 66 arising from the fact that it is made from the six-carbon diamine, 1,6-hexanediamine, and a six-carbon diacid, hexanedioic acid:

The polymer can be converted into fibers by extruding it above its melting point through spinnerettes, then cooling and drawing the resulting filaments. It also is used to make molded articles. Nylon 66 is exceptionally strong and abrasion resistant. The starting materials for nylon 66 can be made in many ways. Apparently, the best route to hexanedioic acid is by air oxidation of cyclohexane by way of cyclohexanone: 1,6-Hexanediamine can be prepared in many ways. One is from 1,3-butadiene by the following steps: nylon 6 can be prepared by polymerization of 1-aza-2-cycloheptanone (E-caprolactam), obtained through the Beckmann rearrangement of cyclohexanone oxime. One of the oldest known thermosetting synthetic polymers is made by condensation of phenols with aldehydes using basic catalysts. The resins that are formed are known as Bakelites.

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A very useful group of adhesives and plastics is based on condensation polymers of bisphenol A and chloromethyloxacyclopropane (epichlorohydrin, CH2-CH – CH - Cl). The first step in the formation of \ O /epoxy resins is to form a prepolymer by condensation polymerization of the sodium salt of bisphenol A with the epoxide.

The formation of a prepolymer involves two different kinds of reactions. Oneis an S2-type displacement, and the other is oxide-ring opening of the product by attack of more bisphenol A. Usually, for practical purposes the degree of polymerization n of the prepolymer is small (5 to 12 units). The epoxy prepolymer can be cured, that is, converted to a three-dimensional network, in several different ways. A trifunctional amine, such as NH2CH2-CH2NHCH2CH2NH2, can be mixed in and will extend the chain of the polymer and form cross-links by reacting with the oxide rings. Alternatively, a polybasic acid anhydride can be used to link the chains through combination with the secondary alcohol functions and then the oxide rings. The most important type of addition polymerization is that of alkenes (usually called vinyl monomers) such as ethene, propene, ethenylbenzene, and so on. In general, we recognize four basic kinds of mechanisms for polymerization of vinyl monomers - radical, cationic, anionic, and coordination. The elements of the first three of these have been outlined. The possibility, in fact the reality, of a fourth mechanism is essentially forced on us by the discovery of the Ziegler and other (mostly heterogeneous) catalysts, which apparently do not involve "free" radicals, cations, or anions, and which can and usually do lead to highly stereoregular polymers. With titanium-aluminum Ziegler catalysts, the growing chain has a C-Ti bond; further monomer units then are added to the growing chain by coordination with titanium, followed by an intramolecular rearrangement to give a new growing-chain end and a new vacant site on titanium where a new molecule of monomer can coordinate:

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In the coordination of the monomer with the titanium, the metal is probably behaving as an electrophilic agent and the growing-chain end can be thought of as being transferred to the monomer as an anion. Because this mechanism gives no explicit role to the aluminum, it is surely oversimplified. Ziegler catalysts polymerize most monomers of the type RCH=CH2, provided the R group is one that does not react with the organometallic compounds present in the catalyst. In contrast to coordination polymerization, formation of vinyl polymers by radical chain mechanisms is reasonably well understood- at least for the kinds of procedures used on the laboratory scale. The first step in the reaction is the production of radicals; this can be achieved in a number of different ways, the most common being the thermal decomposition of an initiator, usually a peroxide or an azo compound. Many polymerizations are carried out on aqueous emulsions of monomers. For these, water-soluble inorganic peroxides, such as ammonium peroxysulfate, often are employed. Other ways of obtaining initiator radicals include high-temperature decomposition of the monomer and photochemical processes, often involving a ketone as a photosensitizer. Addition of the initiator radicals to monomerproduces a growing-chain radical that combines with successive molecules of monomer until, in some way, the chain is terminated.

3. Features of polymerization and polycondensation processes.Addition

Condensation

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QUESTIONS FOR SELF-CONTROL:1. Ozonizations of natural rubber and gutta-percha, which are both poly-2-methyl-l,3-butadienes, give high yields of CH3COCH2CH2CH3 and no CH3COCH2CH2COCH3. What are the structures of these polymers?2. The radical polymerization of ethenylbenzene gives atactic polymer. Explain what this means in terms of the mode of addition of monomer units to the growing-chain radical.

REFERENCES:1. L. Mandelkern, An lntroduction to Macromolecules, Springer-Verlag, New York, 1992.2. R. G. Treloar, lntroduction to Polymer Science, Springer-Verlag, New York, 1990. An excellent and simple introduction to the relationship of polymer physical properties to structure.3. Шур А.М. Высокомолеклурные соединения, М., 1981г.

Lecture #5. Radical polymerizationPurpose: familiarize with main steps of the radical polymerization, its mechanism and means of implementing.Key questions:1. Main stages of radical polymerization2. Initiation and its effectiveness3. Propagation and termination reactions of macroradicals4. Means of Polymerization implementing

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Summary:1. Main stages of radical polymerizationIn what is known as chain polymerization, the polymerization reaction requires the presence of an initiator: a reactive species that serves to start the reaction. When we polymerize ethylene, we write the reaction nCH2=CH2 --> (-CH2-CH2-)n

but this begs the questions about what is at the end of the chains and how successive monomers are added, i.e. the reaction mechanism. A major method to produce polyethylene is free radical polymerization. The polymerization mechanism can be described in four stages:

1. Initiation2. Propagation3. Transfer 4. TerminationThe term free radical describes what is formed when we break a single bond in any organic

molecule in such a way that we obtain two fragments, each of which had an unpaired electron, e.g.CH3-CH2-CH2-CH2-CH2-CH3 --> CH3-CH2-CH2. + .CH2-CH2-CH3

where the periods represent unpaired electrons on the terminal carbons. Compounds with unpaired electrons are free radicals: they are very reactive, just as atomic oxygen or fluorine would be. A stable electronic structure is achieved for C, O and F when they have eight electrons in their outer shell, as is achieved by sharing in covalent bond formation. If this structure is not present, then there is a tremendous driving force to acquire a share of the necessary electrons, which is translated into high reactivity. Thus free radicals are likely to react rapidly with any candidate that can supply the additional necessary electrons, and the pi electrons of the double bond of ethylene are such a potential source. Polymer initiation occurs when ethylene reacts with a free radical R. The latter acquires a share one of the electrons involved in the double bond:R. + CH2=CH2 ---> R-CH2-CH2.2. Initiation and its effectivenessA typical initiator for polymerization of ethylene is benzoyl peroxide, which breaks into two benzoyl free radicals:C6H5CO-O-O-CO-C6H5 ---> 2C6H5-COO.We talked about peroxides in an earlier lecture, pointing out that they are unstable and tend to give up oxygen. For example hydrogen peroxide H2O2 is used as a bleaching agent because it will give up an oxygen to form the more stable H2O. This oxygen is acquired by colored unsaturated molecules, which after reaction lose their color. Organic peroxides have the structure R-O-O-R' where the hydrogens of H-O-O-H have been replaced by organic groups (which do not need to be identical). Organic peroxides in general are unstable, and can detonate when subjected to shock. Benzoyl chloride is one of the more stable, but even so it needs to be handled with care.3. Propagation and termination reactions of macroradicalsThe R. + CH2=CH2 ---> R-CH2-CH2. reaction simply transfers the "problem" of the unpaired electron to the end of the attached ethylene unit, so the result is simply a larger free radical, which can then react with another ethylene:R-CH2-CH2. + -CH2=CH2 ---> R-CH2-CH2-CH2-CH2.and so on:R-CH2-CH2-CH2-CH2. + CH2=CH2 ---> R-CH2-CH2-CH2-CH2-CH2-CH2.and eventually ---> R-(CH2-CH2)n-CH2-CH2.This growth of the polymer chain is called propagation. It is a chain reaction, which can continue until we run out of monomer, assuming of course that no other reactions are possible. The number of free radicals does not change: they are not consumed in the reaction, except where termination occurs, when two free radicals come together to form a covalent bond:R-(CH2-CH2)n-CH2-CH2. + .CH2-CH2-(CH2-CH2)n'-R---> R-(CH2-CH2)n+n'+2-RFree radical polymerization as described here is used commercially to produce low density poly(ethylene) (LDPE), and also poly(methylmethacrylate) (PMMA), poly(acrylonitrile) (PAN; -(CH2-

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CH(CN)-)n) and poly(vinyl chloride) (PVC). In all four cases the polymerization involves opening a double bond. Another peroxide initiator is t-butyl peroxide used for example to polymerize vinyl chloride to produce PVC:(CH3)3C-O-O-C(CH3)3 ---> 2(CH3)3C-O.(CH3)3C-O. + CH2=CHCl ---> (CH3)3C-O-CH2-CHCl. ---> ---> (CH3)3C-O-(CH2-CHCl)n-CH2-CHCl.To summarize so far, in the initiation stage we produce highly reactive free radicals:Initiator ---> 2R.and R. reacts with a monomer moleculeR. + M ---> R-M.effectively creating a larger free radical. Propagation then proceeds by adding further monomer molecules, which continually regenerates the terminal active site.R-M. + M ---> R-M-M. ---> R-(M)2-M. ---> ---> R-(M)n-M.The number of free radicals stays constant, and reaction continues until we run out of monomer, unless termination occurs when two free radicals react with each other:R-(M)n-M. + .M-(M)n'-R' ---> R-(M)n+n'+2-R'Reaction will cease when all free radicals are disposed of in this manner, and this might occur before all the monomer is polymerized. So one has to control the amount of initiator and the reaction conditions to make sure complete polymerization occurs, but to avoid too much initiator, which can lead to too many molecules and thus low molecular weight. One can see that there will be statistical chance of reaction at the ends of growing molecules, and so we get a distribution of molecular weights.But the reaction is more complex than described so far. Free radicals are very reactive, so the growing polymer molecules R-(M)n-M. can also react with other polymer molecules, not only with the monomer. These reactions are called transfer reactions:R-(M)n-M. + A-B ---> R-Mn+1-A + B.Here A-B is an existing polymer molecule prepared earlier in the synthesis; but it can also be an impurity. We define this as transfer because the unpaired electron is effectively transferred to a new species. The new free radical B. can react with monomer and grow into a polymer chain:B. + M ---> B-M. ---> ----> B-Mn-M. and so on.But the effect of the transfer reaction is that growth stops for the R-Mn+1-A species. So transfer reactions have the effect of limiting molecular weight, as do the termination reactions.Use of M for the monomer in the above equations is deceptive. It is important to realize that when an existing polymer molecule reacts with a free radical the reaction does not necessarily occur at the M-M monomer linkage bond. The monomer M is polyatomic and contains a number of bonds: in ethylene we have the central C-C and four C-H bonds, and the free radical may react at any of these as well as at the M-M linkage C-C bonds. Reaction at a C-H is common, so the free radical may take a hydrogen, leaving an unpaired electron on the carbon, which may be other than at the chain end:R-(M)n-CH2-CH2. + R'-Mn''-CH2-CH2-Mn"-R" ---> R-(M)n-CH2-CH3 + R'-Mn''-CH2-.CH-Mn"-R"Here the unpaired electron is on a CH group away from the ends of the chain (this was a CH 2 that lost the hydrogen atom to the original free radical) Reaction with an unreacted ethylene monomer can now occur at this.CH group, resulting in a branched structure. There may also be rearrangement in a linear polymer molecule where the free electron is moved from the last carbon to another back along the chain, so that further addition occurs at that point, resulting in a branch. In free radical polymerization we tend to get branched polymers, and in low density polyethylene (LDPE) there are multiple branches per molecule. The number of branches depend on the probability of reaction with the growing polymer molecules rather than with monomer, and this is controlled by adjusting the temperature and pressure, and in recent years sophisticated catalysts have been developed for this purpose, so as to have a tight control on properties. LDPE is synthesized from ethylene gas using the free radical initiator benzoyl peroxide at high pressures (1000-3000 atm.) and temperatures (50-300°C). Higher pressures and temperatures lead to better yields (more rapid reaction and higher molecular weights) but the density and crystallinity decline progressively due to increasing numbers of branching reactions. The densities are in the range 0.910-0.925 and crystallinities of 50-60%.Remember that branching and lower density may be desirable. High density polyethylene HDPE

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has much less branching: the crystallinity may be as high as 90% and the densities 0.94-0.96 g/cm3. Consequently HDPE and LDPE have very different properties, and different applications. HDPE is produced by coordination polymerization, which will be the subject of the next lecture.

Besides the fact that free radical polymerization tends to produce branched chains, there is also no control of tacticity. This is not a problem with polyethylene of course, but need to be considered when we polymerize propylene and higher alkenes. For propylene:R. + CH2=CH-CH3 ---> R-CH2-CH(CH3). ---> R-(CH2-CH(CH3))n-CH2-CH(CH3).The reaction is such that the CH3 groups are attached to alternate carbons on the polymer chain. We call this head-to-tail linkage of the monomers, rather than head-to-head/tail-to-tail, where we would have some CH3groups on adjacent backbone carbons. But there is random spatial disposition of the CH3 groups, i.e. we have an atactic configuration (as we discussed in an earlier lecture with reference to the structure of polystyrene).4. Means of Polymerization implementing Suspension polymerization: Emulsion polymerization: Water insoluble monomer. Water insoluble monomer. Water insoluble initiator. Water soluble initiator. Suspending agent (optional). Complicated mechanism. Droplets are 100 to 10-3 mm diameter. Droplets are 10-5 to 10-6 mm diameter. "Mini reactors."

Advantages Disadvantages

Suspension

Simple, few ingredients, cheap. Reaction medium is mostly water, which absorbs the hear of polymerization. Produces beads that have technological uses (xerographic toner, catalyst carriers, ion exchange resins, substrates for combinatorial synthesis, etc.)

Autoacceration will still occur. Isolation of the polymer can be laborious if you didn't want beads. May need to purify polymer from suspending agent.

Emulsion

Makes very high MW polymer quickly. Reaction medium is mostly water, which absorbs the hear of polymerization. Creates very tiny particles of polymer that have technological uses (paint, coatings, drug delivery, etc.).

Isolation of the polymer can be laborious if you didn't want viny particles. May need to purify polymer from surfactant.

The mechanism is actually very complicated and continues to be studied to this day. The reaction actually takes place in several stages, but, to a first approximation, the following description suffices: the surfactant molecules surround small amounts of monomer molecules, creating micelles. However, the usual recipe contains much more monomer than can be accomodated in micelles, so there are also large droplets of monomer that are stabilized by small amounts of surfactant. Depending on the monomer, there may also be a small amount of monomer dissolved in the water. Initiator forms free radicals in the water, where they may find a few monomers to react with. In any case, the radicals diffuse into the micelles, where they find lots of monomer but no other growing chains to cause termination (at least, for a while). The growing chain is then protected from termination until a second radical diffuses into the micelle. This is why the MW can be so high in emulsion polymerization without slowing the rate of conversion. No polymerization seems to occur in the large monomer droplets. Why? The explanation lies in simple statistics. Compared to the droplets, there are a large number of micelles, with much higher surface area (estimated 1000 times more). It is simply more likely for a radical to diffuse into a micelle than a droplet.

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QUESTIONS FOR SELF-CONTROL:1. Write out the detailed mechanism for the radical chain polymerization of styrene (vinylbenzene), designating the three stages of the chain mechanism, and giving the repeat structure for the polymer. What is the significance of the subscript "n" in the repeat structure? Why is this an average value? What term is used to describe the extent to which a polymer product contains individual polymer molecules which have a wide or narrow range of molecular weights?2. Explain why the polymers obtained from the radical chain polymerization of vinyl chloride, styrene, or acrylonitrile are unbranched.3. Write out a mechanism for the radical chain polymerization of isoprene (2-methyl-1,3-butadiene). Draw the repeat structures for both natural rubber and the polyisoprene which results from radical polymerization.Then explain how these structures differ and why the Ziegler-Natta catalytic system is able to polymerize isoprene to a polymer which is identical to natural rubber.4. In the radical chain polymerization of ethene, the polyethylene obtained is referred to as "low density" polyethylene (LDPE). Explain, both in mechanistic/chemical terms, including structural depictions, and in solid state/physical structural terms why this polyethylene is "low density". What effect does this have on the physical properties of the polymer?

REFERENCES:1. L. Mandelkern, An lntroduction to Macromolecules, Springer-Verlag, New York, 1992.2. R. G. Treloar, lntroduction to Polymer Science, Springer-Verlag, New York, 1990. An excellent and simple introduction to the relationship of polymer physical properties to structure.3. Шур А.М. Высокомолеклурные соединения, М., 1981г.4. http://research.cm.utexas.edu/nbauld/hmwkpolym.html

Lecture № 6-7. Ion coordination polymerisation.Objective: To become familiar with the mechanism of ion-coordination polymerizationKey questions:1. Ionic polymerization mechanism,2. Cationic polymerization3. Anionic polymerization.

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Summary:1. Ionic polymerization mechanism,Ionic vinyl polymerizations are very similar to free radical vinyl polymerizations. The only difference is the "flow" of the electrons during propagation.Recall that a double bond equals a single bond plus two more electrons.

In free radical vinyl polymerization, the electrons in the pi bond split up. One combines with the unpaired electron in the initiator (or growing chain end) to form the new bond, and the second ends up on the chain end, reproducing the attacking species.

In anionic vinyl polymerization, the electrons in the pi bond more together instead of separately. The initiator (or growing chain end) attacks with a pair of electrons, used to form the new bond. The pi-bond electron pair "flows" away from the attacking species, reproducing the anion at the chain end.Cationic vinyl polymerization is exactly the same mechanism, except that the initiator (or chain end) lacks a pair of electrons. The electron "flow" is simply in the oposite direction, leaving behind a positive charge at the chain end to continue the process. One important difference: ionic polymerizations necessarily carry along a counterion, and their rates are much more sensitive to reaction conditions (e.g., solvent polarity, temperature).2. Cationic polymerizationInitiation and PropagationThe mechanism of cationic polymerization is a kind of repetitive alkylation reaction.

Electron donating groups are needed as the R groups because these can stabilize the propagating species by resonance. Examples:

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Propagation is usually very fast. Therefore, cationic vinyl polymerizations must often be run at low temperatures. Unfortunately, cooling large reactors is difficult and expensive. Also, the reaction can be inhibited by water if present in more than trace amounts, so careful drying of ingredients is necessary (another expense). Cationic Initiators:

Proton acids with unreactive counterions Lewis acid + other reactive compound:

Chain Transfer ReactionsCationic vinyl polymerization is plagued by numerous side reactions, most of which lead to chain transfer. It is difficult to achieve high MW because each initiator can give rise to many separate chains because of chain transfer. These side reactions can be minimized but not eliminated by running the reaction at low temperature. Here are a few examples:

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Examples of Commercial Cationic Polymers

3. Anionic polymerization.In general, we expect that anionic polymerization will be favorable when the monomer carries substituents that will stabilize the anion formed when a basic initiator such as amide ion adds to the double bond of the monomer:

Cyano and alkoxycarbonyl groups are favorable in this respect and propenenitrile and methyl 2-methylpropenoate can be polymerized with sodium amide in liquid ammonia. Ethenylbenzene and 2-methyl- l,3-butadiene undergo anionic polymerization under the influence of organolithium and organosodium compounds, such as butyllithium and phenylsodium. An important development in anionic polymerization has been provided by M. Szwarc's "living polymers." The radical anion, sodium naphthalenide, transfers an electron reversibly to ethenylbenzene to form a new radical anion, 1, in solvents such as 1,2-dimethoxyethane or oxacyclopentane:

Dimerization of the sodium naphthalenide radical anion would result in a loss of aromatic stabilization, but this is not true for 1, which can form a C-C bond and a resonance-stabilized bis-phenylmethyl dianion, 2.

The anionic ends of 2 are equivalent and can add ethenylbenzene molecules to form a long-chain polymer with anionic end groups, 3 :

If moisture and oxygen are rigorously excluded, the anionic groups are stable indefinitely, and if more monomer is added polymerization will continue. Hence the name "living polymer," in contrast to a radical-induced polymerization, which only can be restarted with fresh monomer and fresh initiator, and even then not by growth on the ends of the existing chains. The beauty of the Szwarc procedure is that the chains can be terminated by hydrolysis, oxidation, carboxylation with CO2 and so on, to give

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polymer with the same kind of groups on each end of the chain. Also, it is possible to form chains in which different monomers are present in blocks. The only requirements are that the different monomers polymerize well by the anion mechanism and contain no groups or impurities that will destroy the active ends. Thus one can start with ethenylbenzene (S), and when the reaction is complete, add methyl 2-methylpropenoate (M) to obtain a block copolymer of the type

QUESTIONS FOR SELF-CONTROL:1. Write an equation for the dimerization of sodium naphthalenide analogous to dimerization of the ethenylbenzene radical anion 1 to give 2. Show why you may expect that this dimerization would not be as energetically favorable as the dimerization of 1.2. Formulate the complete mechanism of the anionic polymerization of styrene using sec-BuLi as the initiator and water as the quenching reagent3. Compare the anionic polymerization of styrene, 2-vinyl pyridine, and methyl methacrylate by drawing the active species at the chain end! Which one is more reactive and why?

REFERENCES:1. L. Mandelkern, An lntroduction to Macromolecules, Springer-Verlag, New York, 1992.2. R. G. Treloar, lntroduction to Polymer Science, Springer-Verlag, New York, 1990. An excellent and simple introduction to the relationship of polymer physical properties to structure.3. Шур А.М. Высокомолеклурные соединения, М., 1981г.4. http :// chem . chem . rochester . edu /~ chem 421/ classes . htm

Lecture # 8. Polycondensation.Objective: To become familiar with the mechanism of polycondensationKey questions:1. Polycondensation mechanism2. Conditions of process3. Hardware design of process

Summary:1. Polycondensation mechanismIn condensation reaction (or step-growth polymerization), two reactants with degree of polymerization, m and n, combine to form their respective polymer. Step-Growth Polymerization applies to monomers with functional groups such as -COOH, -COOR, -COOOC-, -COCl, -OH, -NH2, -CHO, -NCO, epoxy. Polymers such as polyamides and polyesters can be prepared by condensation polymerization where small molecules are eliminated as polymer chains are formed. Condensation polymerization of this type is called polycondensation polymerization. General formula are shown below.m (X-A-X) + n (Y-B-Y) = -[A-B]-m+n + 2nXYFunctionality2 = Linear molecule: thermoplastics >2 = Crosslinkable: gel, thermosetsCharacteristics Repeat unit often not same as monomer structure Release of small molecules (H2O, HCl, etc) Gradual growth of molecular weight. The step-growth reaction proceeds through formation of dimers, trimers, tetramers, etc, by reactions that are identical in rate and mechanism. Successive condensation reactions,”coupling” Relatively slow reactions. Since these reactions are equilibrium reactions, high molecular weight polymer chains will be obtained if the equilibrium is displaced towards the formation of products. This

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can be achieved by stripping through distillation the low molecular weight condensation products that may form during the reaction (H2O, CH3OH, etc.).Stoichiometric concerns. W.H. Carothers determined a relationship between xn the number average chain length (number of repeat units) and the extent of reaction, p for step-growth polymerization reactions. Consider the polymerization of A-X-B, assuming N0 molecules at t = 0, then the extent of reaction at time t is defined by: p = (N0-N)/ N0, where N is the number of molecules at time t.Since xn is given by xn = N0/N (number of monomers per molecule), then the Carother’s equation is

written as: xn = 1/(1-p) and Mn = M0 xn. In step-growth polymerization, a linear chain results from the stepwise condensation or

addition of reactive groups of bifunctional monomers.

• Polyesters: D = -COOA, = -COOH, -COCl, -COOR, -COOOC- and B = -OH• Polyamides: D = -CONHA, = -COOH, -COCl, -COOR, -COOOC- and B = -NH2• Polyurethanes: D = -NHCOOA, = -NCO and B = -OHThermosetting Polymers: one of the monomers has a functionality higher than 2.

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QUESTIONS FOR SELF-CONTROL:1. Specify features of the polymerization reaction:

а) substitution reaction;

e) step-stage process;

b) elimination reaction; f) different elemental composition of the polymer and monomer;

c) addition reaction; g) the same elemental composition of the polymer and monomer.d) chain process;

2. What type of reactions is polycondensation related? 3. Select compounds that can be used as monomers in the polymerization:

а) HOOC-CH=CH-COOH

d) C2H5-C6H4-COOHb) CH2=CCl2 e) H2N-(CH2)5-COOHc) HO-CH2CH2-OH f) HO-CH2CH2CH2-COOH

4. Select compounds that can be used as monomers in the polycondensation:а) CH3(CH2)3COOH d) CH2=CH-COOH

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b) NH2(CH2)2COOH e) HOOC-CH=CH-COOHc) HO(CH2)3COOH f) HOCH2CH2OH

5. What is the monomer used to produce the polymer:

6. What is the formula of the monomer, if at its polymerization formed macromolecule has following structure: ...-CH2-CCl=CH-CH2-CH2-CCl=CH-CH2-... ?7. What is the formula corresponding Capron?

REFERENCES:1. L. Mandelkern, An lntroduction to Macromolecules, Springer-Verlag, New York, 1992.2. R. G. Treloar, lntroduction to Polymer Science, Springer-Verlag, New York, 1990. An excellent and simple introduction to the relationship of polymer physical properties to structure.3. Some features of non-equilibrium polycondensation, V.V. Korshak, Institute of Element-Organic Comppounds4. Шур А.М. Высокомолеклурные соединения, М., 1981г.

Lecture № 9-12. The structure and properties of polymersObjective: To study the features of the structure and properties of macromolecular compoundsKey questions:

1. Block, graft, and ladder polymers2. Naturally occurring polymers

Summary:1. Block, graft, and ladder polymersWhen polymerization occurs in a mixture of monomers there will be competition between the

different kinds of monomers to add to the growing chain and produce a copolymer. Such a polymer will be expected to have physical properties quite different from those of a mixture of the separate homopolymers. Many copolymers, such as GRS, ethene-propene, Viton rubbers, and Vinyon plastics are of considerable commercial importance. The rates of incorporation of various monomers into growing radical chains have been studied in considerable detail. The rates depend markedly on the nature of the monomer being added and on the character of the radical at the end of the chain. Thus a 1-phenylethyl-type radical on the growing chain reacts about twice as readily with methyl 2-methylpropenoate as it does with ethenylbenzene; a methyl 2-methylpropenoate end shows the reverse behavior, being twice as reactive toward ethenylbenzene as toward methyl 2-methylpropenoate. This kind of behavior favors alternation of the monomers in the chain and reaches an extreme in the case of 2-methylpropene and butenedioic anhydride. Neither of these monomers separately will polymerize well with radical initiators. Nonetheless, a mixture polymerizes very well with perfect alternation of the monomer units. It is possible that, in this case, a 1: 1 complex of the two monomers is what polymerizes. In genera1 however, in a mixture of two monomers one is considerably more reactive than the other and the propagation reaction tends to favor incorporation of the more reactive monomer, although there usually is some bias toward alternation. Ethenylbenzene and 2-methyl-1,3-butadiene mixtures are almost unique in having a considerable bias toward forming the separate homopolymers.One of the more amazing copolymerizations is that of ethenylbenzene and oxygen gas, which at one atmosphere oxygen pressure gives a peroxide with an average molecular weight of 3000 to 4000 and a composition approaching C8H802:

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When heated rapidly in small portions the product undergoes a mild explosion and gives high yields (80% to 95%) of methanai and benzenecarbaldehyde. The mechanism may be a kind of unzipping process, starting from a break in the chain and spreading toward each end:

A variation on the usual variety of copolymerization is the preparation of polymer chains made of rather long blocks of different kinds of monomers. A number of ingenious systems have been devised for making such polymers. Another scheme, which will work with monomers that polymerize well by radical chains but not with anion chains, is to irradiate a stream of a particular monomer, flowing through a glass tube, with sufficient light to get polymerization well underway. The stream then is run into a dark flask containing a large excess of a second monomer. The growing chains started in the light-induced polymerization then add the second monomer to give a two-block polymer if termination is by disproportionation, or a three-block polymer if by combination. Thus, with A and B being the two different monomers,

Block polymers also can be made easily by condensation reactions. Thus block polymers can be made by esterification:

The very widely used polyurethane foams can be considered to be either block polymers or copolymers. The essential ingredients are a diisocyanate and a diol. The diisocyanate most used is 2,4-diisocyano-1-methylbenzene and the diol can be a polyether or a polyester with hydroxyl end groups. The isocyano-groups react with the hydroxyl end groups to form initially an addition polymer, which has polycarbamate (polyurethane) links, and isocyano end groups:

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A foam is formed by addition of the proper amount of water. The water reacts with the isocyanate end groups to form carbamic acids which decarboxylate to give amine groups:

The carbon dioxide evolved is the foaming agent, and the amino groups formed at the same time extend the polymer chains by reacting with the residual isocyano end groups to form urea linkages:

Graft polymers can be made in great profusion by attaching chains of one kind of polymer to the middle of another. A particularly simple but uncontrollable way of doing this is to knock groups off a polymer chain with x-ray or y radiation in the presence of a monomer. The polymer radicals so produced then can grow side chains made of the new monomer. A more elegant procedure is to use a photochemical reaction to dissociate groups from the polymer chains and form radicals capable of polymerization with an added monomer. Modern technology has many uses for very strong and very heat-resistant polymers. The logical approach to preparing such polymers is to increase the rigidity of the chains, the strengths of the bonds in the chains, and the intermolecular forces. All of these should be possible if one were to make the polymer molecules in the form of a rigid ribbon rather than a more or less flexible chain. Many so-called ladder polymers with basic structures of the following type have been prepared for this purpose:

A With the proper structures, such polymers can be very rigid and have strong intermolecular interactions. Appropriate syntheses of true ladder polymers in high yield usually employ difficultly obtainable starting materials. An example is

Although there seem to be no true ladder polymers in large-scale commercial production, several semi-ladder polymers that have rather rigid structures are employed where high-temperature strength is important. Among these are

2. Naturally occurring polymers

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There are a number of naturally occurring polymeric substances that have a high degree of technical importance. Some of these, such as natural rubber, cellulose, and starch, have regular structures and can be regarded as being made up of single monomer units. Others, such as wool, silk, and deoxyribonucleic acid are copolymers. The difference between the properties of the cis- and trans-isomers is apparent for naturally-occurring polyisoprenes

Gutta Percha(trans-1,4-polyisoprene) NaturalRubber(cis-1,4-polyisoprene)

Cellulose is a long chain of linked sugar molecules that gives wood its remarkable strength. It is the main component of plant cell walls, and the basic building block for many textiles and for paper. Cotton is the purest natural form of cellulose. In the laboratory, ashless filter paper is a source of nearly pure cellulose. Cellulose is a natural polymer, a long chain made by the linking of smaller molecules. The links in the cellulose chain are a type of sugar: ß-D-glucose. Two unlinked molecules of ß-D-glucose are pictured at right. The sugar units are linked when water is eliminated by combining the -OH group and H highlighted in gray. Linking just two of these sugars produces a disaccharide called cellobiose. Cellulose is a polysaccharide produced by linking additional sugars in exactly the same way. The length of the chain varies greatly, from a few hundred sugar units in wood

pulp to over 6000 for cotton.

The cellulose chain bristles with polar -OH groups. These groups form many hydrogen bonds with OH groups on adjacent chains, bundling the chains together. The chains also pack regularly in places to form hard, stable crystalline regions that give the bundled chains even more stability and strength. Cellulose is a major component of wood. Cellulose fibers in wood are bound in lignin, a complex polymer. Paper-making involves treating wood pulp with alkalis or bisulfites to disintegrate the lignin, and then pressing the pulp to matte the cellulose fibers together. Cellulose is found in large amounts in nearly all plants, and is potentially a major food source.

Plants store glucose as the polysaccharide starch. The cereal grains (wheat, rice, corn, oats, barley) as well as tubers such as potatoes are rich in starch. Starch can be separated into two fractions-amylose and amylopectin. Natural starches are mixtures of amylose (10-20%) and amylopectin (80-90%).

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Amylose forms a colloidal dispersion in hot water whereas amylopectin is completely insoluble.

The structure of amylose consists of long polymer chains of glucose units connected by an alpha acetal linkage. The graphic on the left shows a very small portion of an amylose chain. All of the monomer units are alpha -D-glucose, and all the alpha acetal links connect C1 of one glucose to C4 of the next glucose. As a result of the bond angles in the alpha acetal linkage, amylose actually forms a spiral much like a coiled spring. Amylose is responsible for the formation of a deep blue color in the presence of iodine. The iodine molecule slips inside of the amylose coil. The graphic shows very small portion of an amylopectin-type structure showing two branch points [drawn closer together than they should be]. The acetal linkages are alpha connecting C1 of one glucose to C4 of the next glucose. The branches are formed by linking C1 to a C6 through an acetal linkages. Amylopectin has 12-20 glucose units between the branches. Natural starches are mixtures of amylose and amylopectin. In glycogen, the branches occur at intervals of 8-10 glucose units, while in amylopectin the branches are separated by 10-12 glucose units.

Spider silk is composed of complex protein molecules. This, coupled with the isolation stemming from the spider's predatory nature, has made the study and replication of the substance quite challenging. In 2005, independent researchers in the University of Wyoming (Tian and Lewis), University of the Pacific (Hu and Vierra), the University of California at Riverside (Garb and Hayashi) and Shinshu University (Zhao and Nakagaki) have uncovered the molecular structure of the gene for the protein that various female spider species use to make their silken egg cases. Although different species of spider, and different types of silk, have different protein sequences, a general trend in spider silk structure is a sequence of aminoacids (usually alternating glycine and alanine, or alanine alone) that self-assemble into a beta sheet conformation. These "Ala rich" blocks are separated by segments of amino acids with bulky side-groups. The beta sheets stack to form crystals, whereas the other segments form amorphous domains. It is the interplay between the hard crystalline segments, and the elastic semi amorphous regions, that gives spider silk its extraordinary properties.The Structure and Function of deoxyribonucleic acid (DNA)

Biologists in the 1940s had difficulty in accepting DNA as the genetic material because of the apparent simplicity of its chemistry. DNA was known to be a long polymer composed of only four types of subunits, which resemble one another chemically. Early in the 1950s, DNA was first examined by x-ray diffraction analysis, a technique for determining the three-dimensional atomic structure of a molecule . The early x-ray diffraction results indicated that DNA was composed of two strands of the polymer wound into a helix. The observation that DNA was double-stranded was of crucial significance and provided one of the major clues that led to the Watson-Crick structure of DNA. Only when this model was proposed did DNA's potential for replication and information encoding become apparent. A DNA molecule consists of two long polynucleotide

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chains composed of four types of nucleotide subunits. Each of these chains is known as a DNA chain, or a DNA strand. Hydrogen bonds between the base portions of the nucleotides hold the two chains together. Nucleotides are composed of a five-carbon sugar to which are attached one or more phosphate groups and a nitrogen-containing base. In the case of the nucleotides in DNA, the sugar is deoxyribose attached to a single phosphate group (hence the name deoxyribonucleic acid), and the base may be either adenine (A), cytosine (C), guanine (G), or thymine (T). The nucleotides are covalently linked together in a chain through the sugars and phosphates, which thus form a “backbone” of alternating sugar-phosphate-sugar-phosphate.

Because only the base differs in each of the four types of subunits, each polynucleotide chain in DNA is analogous to a necklace (the backbone) strung with four types of beads (the four bases A, C, G, and T). These same symbols (A, C, G, and T) are also commonly used to denote the four different nucleotides—that is, the bases with their attached sugar and phosphate groups. The way in which the nucleotide subunits are lined together gives a DNA strand a chemical polarity. If we think of each sugar as a block with a protruding knob (the 5′ phosphate) on one side and a hole (the 3′ hydroxyl) on the other, each completed chain, formed by interlocking knobs with holes, will have all of its subunits lined up in the same orientation. Moreover, the two ends of the chain will be easily distinguishable, as one has a hole (the 3′ hydroxyl) and the other a knob (the 5′ phosphate) at its terminus. This polarity in a DNA chain is indicated by referring to one end as the 3′ end and the other as the 5′ end. The three-dimensional structure of DNA—the double helix—arises from the chemical and structural features of its two polynucleotide chains. Because these two chains are held together by hydrogen bonding between the bases on the different strands, all the bases are on the inside of the double helix, and the sugar-phosphate backbones are on the outside. In each case, a bulkier two-ring base (a purine) is paired with a single-ring base (a pyrimidine); A always pairs with T, and G with C. This complementary base-pairing enables the base pairs to be packed in the energetically most favorable arrangement in the interior of the double helix. In this arrangement, each base pair is of similar width, thus holding the sugar-phosphate backbones an equal distance apart along the DNA molecule. To maximize the efficiency of base-pair packing, the two sugar-phosphate backbones wind around each other to form a double helix, with one complete turn every ten base.

Because we already have considered the chemistry of most of these substances, we shall confine our attention here to wool and collagen, which have properties related to topics discussed previously in this chapter. The structure of wool is more complicated than that of silk fibroin because wool, like insulin and lysozyme, contains a considerable quantity of cystine, which provides -S-S- (disulfide) cross-links between the peptide chains. These disulfide linkages play an important part in determining the mechanical properties of wool fibers because if the disulfide linkages are reduced, as with ammonium mercaptoethanoate solution, the fibers become much more pliable. Advantage is taken of this reaction in the curling of hair, the reduction and curling being followed by restoration of the disulfide linkages through treatment with a mild oxidizing agent.

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The principal protein sf skin and connective tissue is called collagen and is primarily constituted of glycine, proline, and hydroxyproline. Collagen is made up of tropocollagen, a substance with very long and thin molecules (14 x 2900 A, MW about 300,000). Each tropocollagen molecule consists of three twisted polypeptide strands. When collagen is boiled with water, the strands come apart and the product is ordinary cooking gelatin. Connective tissue and skin are made up of fibrils, 200 A to 1000 A wide, which are indicated by x-ray diffraction photographs to be composed of tropocollagen molecules running parallel to the long axis. Electron micrographs show regular bands, 640 A apart, across the fibrils, and it is believed that these correspond to tropocollagen molecules, all heading in the same direction but regularly staggered by about a fourth of their length. The conversion of collagen fibrils to leather presumably involves formation of cross-links between the tropocollagen molecules. Various substances can be used for the purpose, but chromium salts act particularly rapidly.

QUESTIONS FOR SELF-CONTROL:1. If you make a block copolymer from isoprene, methyl methacrylate, and styrene, in which

order do you have to add the monomers (and what is the obtained block copolymer)?2. How would you make: (i) poly(styrene-block-isoprene‐block-vinyl pyridine); (ii) poly(vinyl

pyridine‐block-styrene-block-vinyl pyridine); (iii) poly(styrene-block‐vinyl pyridine-‐block‐styrene)?

3. What would be the expected structure of a copolymer of ethenylbenzene and propene made by a Ziegler catalyst if the growing chain is transferred to the monomer as a radical? As an anion?

4. Devise a synthesis of a block polymer with poly-1,2-ethanediol and nylon 66 segments. What kind of physical properties would you expect such a polymer to have?

5. Suppose one were to synthesize two block copolymers with the following structures:

What difference in physical properties would you expect for these two materials?

REFERENCES:1. Alberts B, Johnson A, Lewis J, et al., Molecular Biology of the Cell. 4th edition, New York: Garland Science; 2002.2. L. Mandelkern, An lntroduction to Macromolecules, Springer-Verlag, New York, 1992.3. R. G. Treloar, lntroduction to Polymer Science, Springer-Verlag, New York, 1990. An excellent and simple introduction to the relationship of polymer physical properties to structure.4. Шур А.М. Высокомолеклурные соединения, М., 1981г.

Lecture № 13-15. Processing of polymersObjective: To learn the basic methods of processing materials in productsKey questions:1. Classification of methods of polymer processing2. Crystallization, melting and glass transition3. Mechanical behavior of polymers4. Characteristics and typical applications of few plastic materials.

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Summary: 1. Classification of methods of polymer processing. Polymers play a very important role in human life. In fact, our body is made of lot of polymers,

e.g. Proteins, enzymes, etc. Other naturally occurring polymers like wood, rubber, leather and silk are serving the humankind for many centuries now. Modern scientific tools revolutionized the processing of polymers thus available synthetic polymers like useful plastics, rubbers and fiber materials. As with other engineering materials (metals and ceramics), the properties of polymers are related their constituent structural elements and their arrangement. Polymers are classified in several ways – by how the molecules are synthesized, by their molecular structure, or by their chemical family. For example, linear polymers consist of long molecular chains, while the branched polymers consist of primary long chains and secondary chains that stem from these main chains. However, linear does not mean straight lines. The better way to classify polymers is according to their mechanical and thermal behavior. Industrially polymers are classified into two main classes – plastics and elastomers. Plastics are moldable organic resins. These are either natural or synthetic, and are processed by forming or molding into shapes. Plastics are important engineering materials for many reasons. They have a wide range of properties, some of which are unattainable from any other materials, and in most cases they are relatively low in cost. Following is the brief list of properties of plastics: light weight, wide range of colors, low thermal and electrical conductivity, less brittle, good toughness, good resistance to acids, bases and moisture, high dielectric strength (use in electrical insulation), etc. Plastics are again classified in two groups depending on their mechanical and thermal behavior as thermoplasts (thermoplastic polymers) and thermosets (thermosetting polymers). Thermoplasts: These plastics soften when heated and harden when cooled – processes that are totally reversible and may be repeated. These materials are normally fabricated by the simultaneous application of heat and pressure. They are linear polymers without any cross-linking in structure where long molecular chains are bonded to each other by secondary bonds and/or inter-wined. They have the property of increasing plasticity with increasing temperature which breaks the secondary bonds between individual chains. Common thermoplasts are: acrylics, PVC, nylons, polypropylene, polystyrene, polymethyl methacrylate (plastic lenses or perspex), etc. Thermosets: These plastics require heat and pressure to mold them into shape. They are formed into a permanent shape and cured or ‘set’ by chemical reactions such as extensive cross-linking. They cannot be re-melted or reformed into another shape but decompose upon being heated to too high a temperature. Thus thermosets cannot be recycled, whereas thermoplasts can be recycled. The term thermoset implies that heat is required to permanently set the plastic. Most thermosets composed of long chains that are strongly cross-linked (and/or covalently bonded) to one another to form 3-D network structures to form a rigid solid. Thermosets are generally stronger, but more brittle than thermoplasts. Advantages of thermosets for engineering design applications include one or more of the following: high thermal stability, high dimensional stability, high rigidity, light weight, high electrical and thermal insulating properties and resistance to creep and deformation under load. There are two methods whereby cross-linking reaction can be initiated – cross-linking can be accomplished by heating the resin in a suitable mold (e.g. bakelite), or resins such as epoxies (araldite) are cured at low temperature by the addition of a suitable cross-linking agent, an amine. Epoxies, vulcanized rubbers, phenolics, unsaturated polyester resins, and amino resins (ureas and melamines) are examples of thermosets. Elastomers: Also known as rubbers, these are polymers which can undergo large elongations under load, at room temperature, and return to their original shape when the load is released. There are number of man-made elastomers in addition to natural rubber. These consist of coil-like polymer chains those can reversibly stretch by applying a force.

Processing of polymers mainly involves preparing a particular polymer by synthesis of available raw materials, followed by forming into various shapes. Raw materials for polymerization are usually derived from coal and petroleum products. The large molecules of many commercially useful polymers must be synthesized from substances having smaller molecules. The synthesis of the large molecule polymers is known as polymerization in which monomer units are joined over and over to become a large molecule. More upon, properties of a polymer can be enhanced or modified with the addition of special materials. This is followed by forming operation. Addition polymerization and

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condensation polymerization are the two main ways of polymerization. Most of polymer properties are intrinsic i.e. characteristic of a specific polymer. Foreign substances called additives are intentionally introduced to enhance or modify these properties. These include – fillers, plasticizers, stabilizers, colorants, and flame retardants. Fillers are used to improve tensile and compressive strength, abrasion resistance, dimensional stability etc. wood flour, sand, clay, talc etc are example for fillers. Plasticizers aid in improving flexibility, ductility and toughness of polymers by lowering glass transition temperature of a polymer. These are generally liquids of low molecular weight. Stabilizers are additives which counteract deteriorative processes such as oxidation, radiation, and environmental deterioration. Colorants impart a specific color to a polymer, added in form of either dyes (dissolves) or pigments (remains as a separate phase). Flame retardants are used to enhance flammability resistance of combustible polymers. They serve the purpose by interfering with the combustion through the gas phase or chemical reaction.Polymeric materials are formed by quite many different techniques depending on (a) whether the material is thermoplast or thermoset, (b) melting/degradation temperature, (c) atmospheric stability, and (d) shape and intricacy of the product. Polymers are often formed at elevated temperatures under pressure. Thermoplasts are formed above their glass transition temperatures while applied pressure ensures that the product retain its shape. Thermosets are formed in two stages – making liquid polymer, then molding it. Different molding techniques are employed in fabrication of polymers. Compression molding involves placing appropriate amount of polymer with additives between heated male and female mold parts. After pouring polymer, mold is closed, and heat and pressure are applied, causing viscous plastic to attain the mold shape. Figure shows a typical mould employed for compression molding.

Transfer molding differs from compression molding in how the materials is introduced into the mold cavities. In transfer molding the plastic resin is not fed directly into the mold cavity but into a chamber outside the mold cavities. When the mold is closed, a plunger forces the plastic resin into the mold cavities, where and molded material cures. In injection molding, palletized materials is fed with use of hopper into a cylinder where charge is pushed towards heating chamber where plastic material melts, and then molten plastic is impelled through nozzle into the enclosed mold cavity where product attains its shape. Most outstanding characteristic of this process is the cycle time which is very short. The schematic diagram of injection-molding machine is shown in figure.

Extrusion is another kind of injection molding, in which a thermoplastic material is forced through a die orifice, similar to the extrusion of metals. This technique is especially adapted to produce continuous

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lengths with constant cross-section. The schematic diagram of a simple extrusion machine is shown in figure:

Blow molding of plastics is similar to blowing of glass bottles. Polymeric materials may be cast similar to metals and ceramics.2. Crystallization, melting and glass transition

Polymers are known by their high sensitivity of mechanical and/or thermal properties. This section explains their thermal behavior. During processing of polymers, they are cooled with/without presence of presence from liquid state to form final product. During cooling, an ordered solid phase may be formed having a highly random molecular structure. This process is called crystallization. The melting occurs when a polymer is heated. If the polymer during cooling retains amorphous or non-crystalline state i.e. disordered molecular structure, rigid solid may be considered as frozen liquid resulting from glass transition. Thus, enhancement of either mechanical and/or thermal properties needs to consider crystallization, melting, and the glass transition. Crystallization and the mechanism involved play an important role as it influences the properties of plastics. As in solidification of metals, polymer crystallization involves nucleation and growth. Near to solidification temperature at favorable places, nuclei forms, and then nuclei grow by the continued ordering and alignment of additional molecular segments. Extent of crystallization is measured by volume change as there will be a considerable change in volume during solidification of a polymer. Crystallization rate is dependent on crystallization temperature and also on the molecular weight of the polymer. Crystallization rate decreases with increasing molecular weight. Melting of polymer involves transformation of solid polymer to viscous liquid upon heating at melting temperature, Tm. Polymer melting is distinctive from that of metals in many respects – melting takes place over a temperature range; melting behavior depends on history of the polymer; melting behavior is a function of rate of heating, where increasing rate results in an elevation of melting temperature. During melting there occurs rearrangement of the molecules from ordered state to disordered state. This is influenced by molecular chemistry and structure (degree of branching) along with chain stiffness and molecular weight. Glass transition occurs in amorphous and semi-crystalline polymers. Upon cooling, this transformation corresponds to gradual change of liquid to rubbery material, and then rigid solid. The temperature range at which the transition from rubbery to rigid state occurs is termed as glass transition temperature, Tg. This temperature has its significance as abrupt changes in other physical properties occur at this temperature. Glass transition temperature is also influenced by molecular weight, with increase of which glass transition temperature increases. Degree of cross-linking also influences the glass transition such that polymers with very high degree of cross-linking do not experience a glass transition. The glass transition temperature is typically 0.5 to 0.75 times the absolute melting temperature. Above the glass transition, non-crystalline polymers show viscous behavior, and below the glass transition they show glass-brittle behavior (as chain motion is very restricted), hence the name glass transition. Melting involves breaking of the inter-chain bonds, so the glass- and melting- temperatures depend on: • chain stiffness (e.g., single vs. double bonds) • size, shape of side groups • size of molecule • side branches, defects • cross-linking

3. Mechanical behavior of polymers

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Polymer mechanical properties can be specified with many of the same parameters that are used for metals such as modulus of elasticity, tensile/impact/fatigue strengths, etc. However, polymers are, in many respects, mechanically dissimilar to metals. To a much greater extent than either metals or ceramics, both thermal and mechanical properties of polymers show a marked dependence on parameters namely temperature, strain rate, and morphology. In addition, molecular weight and temperature relative to the glass transition play an important role that are absent for other type of materials. A simple stress- strain curve can describe different mechanical behavior of various polymers. As shown in figure – 11.4, the stress-strain behavior can be brittle, plastic and highly elastic (elastomeric or rubber-like). Mechanical properties of polymers change dramatically with temperature, going from glass-like brittle behavior at low temperatures to a rubber-like behavior at high temperatures. Highly crystalline polymers behave in a brittle manner, whereas amorphous polymers can exhibit plastic deformation. These phenomena are highly temperature dependent, even more so with polymers than they are with metals and ceramics. Due to unique structures of cross-linked polymers, recoverable deformations up to very high strains / point of rupture are also observed with polymers (elastomers). Tensile modulus (modulus) and tensile strengths are orders of magnitude smaller than those of metals, but elongation can be up to 1000 % in some cases. The tensile strength is defined at the fracture point and can be lower than the yield strength.

As the temperature increases, both the rigidity and the yield strength decrease, while the elongation increases. Thus, if high rigidity and toughness are the requirements, the temperature consideration is important. In general, decreasing the strain rate has the same influence on the strain-strength characteristics as increasing the temperature: the material becomes softer and more ductile. Despite the similarities in yield behavior with temperature and strain rate between polymers, metals, and ceramics, the mechanisms are quite different. Specifically, the necking of polymers is affected by two physical factors that are not significant in metals: dissipation of mechanical energy as heat, causing softening magnitude of which increases with strain rate; deformation resistance of the neck, resulting in strain-rate dependence of yield strength. The relative importance of these two factors depends on materials, specimen dimensions and strain rate. The effect of temperature relative to the glass transition is depicted in terms of decline in modulus values. Shallow decline of modulus is attributed to thermal expansion, whereas abrupt changes are attributable to viscoelastic relaxation processes. Together molecular weight and crystallinity influence a great number of mechanical properties of polymers including hardness, fatigue resistance, elongation at neck, and even impact strength. The chance of brittle failure is reduced by raising molecular weight, which increases brittle strength, and by reducing crystallinity. As the degree of crystallinity decreases with temperature close to melting point, stiffness, hardness and yield strength decrease. These factors often set limits on the temperature at which a polymer is useful for mechanical purposes. Elastomers, however, exhibit some unique mechanical behavior when compared to conventional plastics. The most notable characteristics are the low modulus and high deformations as elastomers exhibit large, reversible elongations under small applied stresses. Elastomers exhibit this behavior due to their unique, cross-linked structure. Elastic modulus of elastomers (resistance to the uncoiling of randomly orientated chains) increases as with increase in temperature. Unlike non-cross-linked polymers, elastomers exhibit an increase inelastic modulus with cross-link density.

4. Characteristics and typical applications of few plastic materials.a) Thermo plastics

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1. Acrylonitrile-butadiene-styrene (ABS): Characteristics: Outstanding strength and toughness, resistance to heat distortion; good electrical properties; flammable and soluble in some organic solvents. Application: Refrigerator lining, lawn and garden equipment, toys, highway safety devices. 2. Acrylics (poly-methyl-methacrylate) Characteristics: Outstanding light transmission and resistance to weathering; only fair mechanical properties. Application: Lenses, transparent aircraft enclosures, drafting equipment, outdoor signs 3. Fluorocarbons (PTFE or TFE) Characteristics: Chemically inert in almost all environments, excellent electrical properties; low coefficient of friction; may be used to 260o C; relatively weak and poor cold-flow properties. Application: Anticorrosive seals, chemical pipes and valves, bearings, anti adhesive coatings, high temperature electronic parts. 4. Polyamides (nylons) Characteristics: Good mechanical strength, abrasion resistance, and toughness; low coefficient of friction; absorbs water and some other liquids. Application: Bearings, gears, cams, bushings, handles, and jacketing for wires and cables 5. Polycarbonates Characteristics: Dimensionally stable: low water absorption; transparent; very good impact resistance and ductility. Application: Safety helmets, lenses light globes, base for photographic film 6. Polyethylene Characteristics: Chemically resistant and electrically insulating; tough and relatively low coefficient of friction; low strength and poor resistance to weathering. Application: Flexible bottles, toys, tumblers, battery parts, ice trays, film wrapping materials. 7. Polypropylene Characteristics: Resistant to heat distortion; excellent electrical properties and fatigue strength; chemically inert; relatively inexpensive; poor resistance to UV light. Application: Sterilizable bottles, packaging film, TV cabinets, luggage 8. Polystyrene Characteristics: Excellent electrical properties and optical clarity; good thermal and dimensional stability; relatively inexpensive Application: Wall tile, battery cases, toys, indoor lighting panels, appliance housings. 9. Polyester (PET or PETE) Characteristics: One of the toughest of plastic films; excellent fatigue and tear strength, and resistance to humidity acids, greases, oils and solvents Application: Magnetic recording tapes, clothing, automotive tire cords, beverage containers. b) Thermo setting polymers 1. Epoxies Characteristics: Excellent combination of mechanical properties and corrosion resistance; dimensionally stable; good adhesion; relatively inexpensive; good electrical properties. Application: Electrical moldings, sinks, adhesives, protective coatings, used with fiberglass laminates. 2. Phenolics Characteristics: Excellent thermal stability to over 150o C; may be compounded with a large number of resins, fillers, etc.; inexpensive. Application: Motor housing, telephones, auto distributors, electrical fixtures.

QUESTIONS FOR SELF-CONTROL:1. Determine the geometric shape of the macromolecule:

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2. What is the geometric shape of the macromolecules of polymers A and B?

3. During the processing of polymers in products often are used method of casting a polymer melt into the prepared mold. Which polymers may be used at this stage of processing? 4. What signs are distinguished polymers from low molecular compounds:

a) poor solubility; f) flexibleness;b) swelling during dissolution; g) low friability;c) low viscosity of solutions; h) thermoplasticity;d) high viscosity of solutions; i) thermoset;e) inability to crystallize; j) conductivity?

5. Compare the flexibility of macromolecules:А. [-СО-(CH2)5-NН-]n; B. [-CH2-CH(CH3)-]n.

REFERENCES:1. V. R. Gowariker, N. V. Viswanathan, and Jayadev Sreedhar, Polymer Science, New Age International (P) Limited publishers, Bangalore, 2001 2. C. A. Harper, Handbook of Plastics Elastomers and Composites, Third Edition, McGrawHill Professional Book Group, New York, 1996. 3. William D. Callister, Jr, Materials Science and Engineering – An introduction, sixth edition, John Wiley & Sons, Inc. 2004.

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LABORATORY WORKS

Methodical recommendations for conducting laboratory worksLaboratory studies promotes knowledge of the physical methods of chemical

research, the student develops independence and instills the skills of the experiment. In order to work in the laboratory took place successfully, you must first explore the theoretical material from textbooks, lecture notes and the benefits of chemical workshops. This produces a conscious attitude to the implementation of experimental techniques, the work itself will be understood, and, therefore, and understood. Working in the chemistry lab should strictly observe the safety rules and regulations of the chemical utensils and appliances. We must learn to use chemical agents, chemical equipment, which are listed in the guidelines for the work on the chemical workshop. Guidelines should not be a straitjacket, and to deprive independence, but rather follow the orders of speeds up, prevents possible damage to equipment, glassware and reagents. The success of the experimental work depends not only on the correctness of the choice of working methods, the sequence of measurement, weight measurements, but also on the correct systematic recording of results. By the implementation of the laboratory work allowed students with admission after verification of a teacher of theoretical knowledge on the subject, knowledge of laboratory methods of work and prepared to conduct lab journal entries on the topic. After completing the laboratory work the student must bring order to your workplace and deliver them on duty or technician. After processing the results in the lab book the student must submit the report teacher.

Thematic plan of laboratory work

Name of the theme Number of hours

Manual

Laboratory work № 1-2. Identification of physical and chemical parameters of polymers

2 Methodical instructions

Laboratory work № 3-4. Determination of the molecular weight of the polymer by viscometric method


Laboratory work № 5-6. Determination of the resin and filler in the polymer samples.


Laboratory work № 7-8. Synthesis of the polymer by polycondensation and study of its properties


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Laboratory work № 9-10. Determination of the isoelectric point of the protein


Laboratory work № 11-12. Identification of natural, artificial and synthetic fibers.


Laboratory work № 13-15. Polymeranalogous conversion of polymers


Methodical instructions

Laboratory work № 1-2. Identification of physical and chemical parameters of polymersPurpose: To determine the content of volatile substances and moisture, moisture absorption of the test polymer.1. Determination of moisture and volatiles.Equipment and instruments: weighing bottles, desiccators, analytical balance.Test materials: nylon pelletsStages of the work: Moisture and volatile content is determined by the difference between specific weights of the initial plastic sample before and after drying in a thermostat at the installed temperature and time. In a 40 mm diameter weighing bottle about 5 g of the polymer is weighed up to 0.001 g on the analytical balance and is placed in an incubator. Drying temperature and time of the plastics specified in technological instructions. Then open weighing bottle is cooled in a desiccator, then you must close lid and re-weigh. Volatile content and moisture content are expressed in percentage.

Allowable moisture and volatile components in the powdered phenoplast are 2-4.5% and aminoplast are 3.5 - 4%, in fibrous and layered phenoplast are 0.8-3% and 0.2% in polyamides.Data processing:The content of volatile substances and moisture in percentage (x) is calculated by the formula:

where a2 is the weight of weighing bottle with the sample before drying, g; a1 - the weight of weighing bottle with the sample after drying, g; a - the weight of the empty sample bottle, gFor the calculation you must take the average value between two determinations.2. Determination of water absorption of the polymer materialObjective: To determine the mass of water absorbed by the specimen as a result of their staying in the water for a well established time at a certain temperature.Test materials: 3 Discs of 2 polymeric materials with diameters of 100 mm.Equipment and appliances: drying cupboard, water baths, electric cooker, analytical balances.Stages of the work: A) Determination of water absorption in cold water.Samples is weighed and quickly immersed in distilled water and kept at 232 С during 241 hour. Thereafter, the samples removed from water, wiped with dry and clean cloth or filter paper no more than 1 minute, and weighed.Processing of the results:The mass of water absorbed by the sample is calculated in milligrams according to the formula:Х1 = m2 – m1,, gwhere m1 - mass of the sample before immersion in water, g m2 - mass of the sample after removal of the water, gWeight of water absorbed by the sample per unit of area:

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А — sample surface, mm

Mass fraction of water absorbed by the sample in percentage:

Laboratory work № 3-4. Determination of molecular weight polymers by viscosimetryObjective: To determine the molecular weight.Equipment and devices: Oswald viscosimeter, flasks with ground glass stoppers on 25 ml, 5 ml graduated pipette with scale interval 0.2 ml, stopwatchTest materials: polystyrene solution in benzenePreparing for the determination.Preparing viscometerThe viscometer is thoroughly washed with the chromic mixture, then a large amount of hot water, rinse with distilled water, alcohol, ether and dried.Preparation of polymer solutionThe milled and dried polymer is dissolved in a suitable solvent. A portion of the polymer is selected so that for the initial solution at a measurement temperature ηspecific = 1.5. The solution should not contain particulate matter that can clog the capillary. This solution was filtered through a glass filter number 1 or number 2.Taking measurementsFirst, measure the flow time of the pure solvent. To do this, 10 ml of solvent is poured into the wide knee of viscometer. Through a rubber tube with a blower the solvent is sucked above the upper mark on the ball-shaped extension. Suction is stopped. As soon as the liquid level drops to the upper mark, the stopwatch is started and flow time of the solvent from the top to the bottom mark is noted. When the liquid drops to the bottom mark, turn off the stopwatch and record the result. Flow time is determined at least 5 times and take the average. After determining the flow time (τ0) of the solvent viscometer is removed from the oven, the solvent is poured through the wide knee and viscometer is dried. In a dry viscometer poured with graduated pipette 10 ml of polymer solution and again set viscometer in a thermostat. After incubation during 15 minutes flow time of solution is measured at least 5 times (τ) as described above. Thereafter viscometer is thoroughly washed with solvent and dried. Then 10 ml of solution with another concentration, which obtained by adding 5 ml of pure solvent to the initial solution, is poured into viscometer and it’s flow time is measured. Of all, you must perform at least three dilutions and measurements for dilute solutions. After all measurements viscometer must be washed several times with solvent and dried. Obtained data are recorded in Table 1.Solution volume, ml

Concentration of the solution, g/100 ml

Flow time of solution ( t), s

Processing of the results:The relative viscosity (ηrel) is the ratio of the solution flow time to the solvent flow time:

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Specific viscosity (ηSpecific

) is the ratio of the difference between the solution and the solvent

viscosity to the viscosity of the solvent:

The reduced viscosity (η reduced

) is the ratio of the specific viscosity of the polymer solution to its

concentration:

Intrinsic viscosity [η] is called as the limiting value of ηspecific / C (or ln η relative / C) at a concentration of the solution tends to zero.

To determine the molecular weight, the Mark-Houwink equation, which expresses the dependence of the intrinsic viscosity from the molecular weight, are used.

K = 1,1 • 10-4

α = 0,725

where K and a - constants for the system polymer - solvent at a given temperature.

Polymer Solvent T, K K*10-4

α

polystyrene toluene 25 1.18 0.72

polymethacrylate chloroform 25 0.47 0.78

polymethacrylate acetone 25 0.96 0.69

cellulose acetate acetone 25 1,6 0,82

polyacrylonitrile dimethylformamide 25 3,35 0,72

Polyvinyl alcohol water 25 5,95 0,63

polyvinylpyrrolidone water 25 1,4 0,7Based on the retrieved data, curve is constructed as a function η specific / C from C, after that you

must continue its to intersection with the y-axis and by the point of intersection as the resulting value of [η] determined the value of the molecular weight by taking the value of "K" and "α" from the tables for the corresponding pair "polymer-solvent system".

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Laboratory work № 5-6. Determination of the resin and fillerObjective: To determine the amount of resin and filler in the sample by extraction.Test material: press powder.Reagents, instruments and equipment: Acetone, boxing for taking the sample, the conical flask with refinished stopper to 250 ml, the thermostat.Stages of the work: Press powder of about 5 g is weighed, taken up with 0.01 grams, and placed in a conical flask to 250 ml with stopper. To press powder 40 - 50 ml of acetone is added, flask is closed by stopper and vigorously stirred for about 10 min. Then the slurry is filtered and the residue of filler on the filter is dried in a thermostat at 800C to constant weight.Processing of the results:The amount of filler in the percentage is calculated by the formula:X = (A1 / A) * 100, wherea - the mass of the press powder, ga1 - weight of residue, gThe resin content percentage calculated by the formula:

Х1 = 100 – Х

Laboratory work № 7-8. The synthesis of polymer by polycondensation and studying its propertiesExp 1. Obtaining polyether based on glycerine and phthalic anhydrideReagents: glycerol, phthalic anhydride, acetone, alcoholic solution of potassium hydroxide 0.5N, 1% phenolphthalein solutionEquipment: a porcelain cup (crucible), burette, thermometer to 3500C, 50ml conical flasks, cylinder or graduated tube, analytical balance, stove.Stages of the work: In a porcelain beaker 5.5 g phthalic anhydride and 3.35 g of glycerol are placed and covered by porcelain cup. Mixture is heated to 1800C with maintaining this temperature for one hour. During the synthesis of the polyester, phthalic anhydride is sublimated under heating and crystallized on the cold

ηуд/С

0,10,20,30,40,50,60,70,80,91,01,11,2

0,10,20,30,40,50,60,70,80,91,01,11,21,31,41,51,61,71,81,92,02,12,22,32,40

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walls of the beaker and the cup. It periodically is scraped into a beaker and the reaction mixture is thoroughly stirred. After synthesis the molecular weight of the polymer is determined.Exp 2. Determination molecular weight of polyester

a) Determination of the acid number. In a pre-weighed on an analytical balance flask 0.1-0.3 g of sample with accurate to 0.0002 g is placed, then 5-7ml of acetone is added and after dissolution of sample, solution is titrated with an alkali in the presence of phenolphthalein until the appearance of pink color. Parallel with, control experiment is carried out with the same amount of solvent.

Acid Number (AN), indicating the number of mg KOH required to neutralize the carboxyl groups contained in 1 g of the analyte, is calculated by the formula:

, mg of KOH/g of polymer

where V1 - volume of 0.1 N solution of alkali, who had gone on a working sample titration, ml; V 2 - volume of 0.1 N solution of alkali, who had gone on a control sample, in ml; F - amendment to the titer of 0.1 N solution of KOH; 0.00561 - titer 0.1N solution of alkali, g / ml; q - the weight of substance, g.

Molecular weight of polyester is calculated by the formula:

Make a conclusion with reaction equations according to the results of experiments.

Laboratory work № 9-10. Determination of the isoelectric point of the proteinState of swelling characterized by the degree of the swelling α, which is defined as the amount

of liquid absorbed per unit mass or volume of the polymer:

Where m0 and V0 - weight and volume of the initial polymer, mt and Vt - weight and volume of the swollen polymer at time t. Thus, the process of swelling can be observed periodically weighing the swelling agent (gravimetric method) or by measuring the volume of liquid remaining after swelling (volumetric method).Reagents - food gelatin, gelatin treated with 40% aqueous formaldehyde, 0.2 M solutions of acetic acid and sodium acetate. Equipment - pipette on 5 and 10 ml, weighing bottles, a glass, a watch glass, a pH meter, analytical scales.

Studying the influence of pH on the swelling of gelatin is carried out in solutions of the following compositions:

Table 1.Volume of 0.2 M acetic acid solution, ml

Volume of 0.2 M sodium acetate solution, ml

Approximate pH Weight of gelatin before swelling, m0, g

Weight of gelatin after swelling, m, g

0 0 7.01 9 5.7

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3 7 5.14 6 4.95 5 4.87 3 4.49 1 3.810 0 2.7

The pH is accurately measured using a pH meter. Weighing gelatine (weighing about 50 mg) is must be bring in the weighing bottles or glasses with a prior prepared solutions. After 60 minutes, removed from the sample bottle gelatin, gently dried between sheets of filter paper and weighed on a watch glass.

Then you must take a small amount of swollen gelatin from each sample, transfer to tubes, pour 5 ml of distilled water and heat on a steam bath until complete dissolution of the polymer in one of the tubes.

Make a conclusion with calculating the degree of swelling of gelatin α and the graph of depending the degree of swelling from the pH value and finding the IEP. Explain differences in the degree of swelling and solubility of usual gelatin and gelatin processed with formalin.

Laboratory work № 11-12. Identification of natural, artificial and synthetic fibers.Exp 1. Behavior of fibers during combustionReagents and equipment: fiber samples, dry fuel or spiritlampReaction of the burning is a preliminary test of textile fibers. Test is carried out in a flame of a spirit lamp or a match. Fiber is pre-rolled in the flagellum with length of 1.5-2 cm and is carefully it introduced with tweezers into the flame. After the start of the combustion fiber is immediately removed from the flame. You should note the behavior of the fiber at the approaching to the flame, introducing into the flame and removing from it; the kind of residue (ash) after burning and smell at the burning of fiber. The results are recorded in the table.Fiber Ability to

igniteColor of the flame

Burning behavior

Smell View of residue

Reaction of steam

By the nature of combustion all the fibers can be divided into four groups:1- At the approaching to fire they do not melt and do not change shape, burn without melting, after removing from the flame they continue to burn without melting; burning residue - light ash-gray color; burning smell is burnt paper (cotton, linen, viscose, copper and ammonia, polynosic fibers). 2- At the approaching to flame they melt and twist in the direction of the opposite to flame, burn slowly with melting, after removing from the flames they damp by themselves; burning residue - fragile black ball or a fluffy black ash; during combustion they emit a smell of burning feathers (silk, wool).3- At the approaching to flame they melt, after removing from the flame they continue to burn with a bright flame; melting residue – is a solid black bead with irregular shape, a certain burning smell is absence (diacetate, triacetate fibers, the fibers of polyacrylonitrile).4- At the approaching to flame they melt, burn slowly with melting, at the combustion they give white smoke (nylon, Anid) or black smoke with soot (polyester), after removing from the flame they damp by themselves (except lavsan), the residue after burning - solid round ball, a certain burning smell is absence (polyamide fibers - nylon, Anid, Enanth, polyester - polyester, perchlorovinyl - chlorine).

Exp 2. Testing solubility in acids.The fibers are boiled with concentrated hydrochloric acid for 5-10 minutes, stirring

occasionally with a glass stick.

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soluble in boiling hydrochloric acid, are not soluble in boiling hydrochloric broken or deformed: natural fibers acid: synthetic fibers, excepting(cotton, linen, wool, silk), synthetic polyamide fiber (polyester, fibers (acetate, copper-ammonia, perchlorovinyl, polyacrylonitrile) viscose), a synthetic polyamide fiber

Determine the reaction of the 1. Benzene at the cold - dissolves decomposition products (perchlorovinyl fiber)(at heating dry fibers in a test tube 2. Insoluble – act with nitric acid strip of pH paper, soaking in water, without heating – dissolves is brought to the outlet of tube and (polyacrylonitrile fiber) the reaction of the vapors of 3. Insoluble – act with nitric aciddecomposition products is noted) at the heating - dissolves

(polyester fiber – lavsan)

A) Acid reaction B) Base reactioncellulose fibers (cotton, linen, protein fibers (wool, silk), polyamide fiber acetate, copper-ammonia, B1 Glacial acetic acid at the heating - viscose staple) dissolves (polyamide fiber)A1 Glacial acetic acid – dissolves B2 Insoluble (wool, silk) - act with

(acetate fiber) concentrated hydrochloric acid A2 Insoluble – act with concentrated without heating – dissolves (silk)hydrochloric acid without heating – B3 Insoluble (wool) act with

dissolves (copper-ammonia, viscose) concentrated sulfuric acid at A3 Insoluble – act with concentrated heating – dissolves rapidly (wool),sulfuric acid without heating – dissolves slowly (protein fibers)dissolves (cotton), insoluble (linen)

Exp 3. Qualitative reactions for textile fibersa) Qualitative reactions for wool, silk

A1 In concentrated nitric acid they swell and stain in yellowA2 With an alkaline solution of lead salts wool gives dark brown colorationA3 At heating with a 1% solution of ninhydrin they are painted in blue color

b) Qualitative reactions for cellulose fibers - copper-ammonia, viscose, acetate fiberB1 At the treatment with concentrated solution of zinc chloride (2-3ml), to which is added 3 drops of a solution of iodine in potassium iodine, the fibers is colored in blueB2 Viscose fiber in concentrated sulfuric acid dissolves with formation a red-brown solution

c) Qualitative reactions for acetate fiber – in 0.5% solution of potassium permanganate they are colored in dark brown, viscose in a dark gray color

d) Qualitative reactions for polyamide fiberD1 At boiling for 1 minute in 0.2% solution of ninhydrin they give a blue colorD2 At boiling for 2-3 minute in a mixed solution of rhodamine C (0.3-0.4g per liter) and cationic blue (0.1-0.2 g per liter), followed by washing with cold water, they are painted in bright reddish-purple color

e) Qualitative reactions for polyacrylonitrile fiber

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E1 At boiling in a concentrated solution of sodium hydroxide they are painted in orange or reddish-brown colorE2 At boiling for 2-3 minute in a mixed solution of rhodamine C (0.3-0.4g per liter) and cationic blue (0.1-0.2 g per liter), followed by washing with cold water, they are painted in bright the blue color

f) Qualitative reactions for chlorine-containing fibers – perchlorovinyl (chlorine), polyvinylchloride)

Fiber sample is placed in a dry tube and heated to decomposition. When plentiful vapors start to allocation you must tray moistened iodine-starch paper to the hole tube. It’s bluish indicates the presence of free chlorine in the vapor. Iodine-starch paper is paper, impregnated with starch solution to which is added potassium iodide.

g) Qualitative reactions for polyester fiber – lavsanG1 At boiling in dry tube to decomposition yellow ring – sublimate of terephthalic acid - is formed on the walls of the tube.G2 At boiling for 2-3 minute in a mixed solution of rhodamine C (0.3-0.4g per liter) and cationic blue (0.1-0.2 g per liter), followed by washing with cold water, they are painted in light pink color

Make a conclusion with reaction equations according to the results of experiments.

Laboratory work № 13-15. Polymer conversionExp 1. Dissolving cellulose in copper-ammonia solution (reagent Schweitzer)Reagents and equipment: copper-ammonia solution (reagent Schweitzer) – (10g

of anhydrous copper sulfate is dissolved in 200ml of water and poured 100ml 2M sodium hydroxide solution. Precipitate of copper hydroxide is washed with water for removing sulfate ions and then sucked through a Buchner funnel. The resulting precipitate is dissolved in 25% ammonia solution. Ammonia is slowly poured under continuous stirring of the flask contents; at the bottom of the flask a little precipitate must remain. The solution is allowed to stand, then it is drained by decantation or filtration. Reactive should be stored in a tightly closed bottle.); Concentrated hydrochloric acid, absorbent cotton wool, tubes, rods.

Stages of the work: Into tube 4-5ml cuprammonium solution are poured, then are dipped a small piece of cotton

(cellulose). All mixture thoroughly stirred with wand to completely dissolve. There are formatted a viscous clear solution with bright blue color. To this solution 10-15 drops of concentrated hydrochloric acid is added. Cellulose stands out (compare with the structure of the original). The ability to dissolve cellulose in Schweitzer's reagent is used in the production of cuprammonium artificial silk.

Exp 2. Preparation and properties of cellulose acetateReagents and equipment: sulfuric and acetic acid, concentrated; absorbent

wadding, acetone, 50 ml conical flask, porcelain cup, test tube with a ground glass neck, reflux condenser, a glass slide.

Stages of the work: A small piece of cotton wool is well wetted with water and placed in a 50 ml conical flask,

which is filled before with 5ml glacial acetic acid and 1-2 drops of concentrated sulfuric acid (catalyst). After cooling the mixture is heated in a boiling water bath with constant stirring with a glass rod to dissolve the cellulose. The resulting solution is poured as a thin stream to the glass with 250-300ml of ice water. Precipitated flakes is filtered and dried in a porcelain dish on a boiling water bath. Obtained cellulose acetate is placed into the tube with 1-2 ml of acetone and heated on the steam bath with reflux condenser for 2-3 minutes. The resulting solution is poured onto a glass slide and allowed to acetone evaporating. The resulting film is removed and applied to the flame. You should compare the ability to burn the original cellulose and its acetate.

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Exp 3. Interaction cellulose with the alkali (mercerization)Reagents and equipment: 40% sodium hydroxide solution, 10% hydrochloric acid

solution, the filter paper. Stages of the work: In the glass with concentrated sodium hydroxide strip of filter paper is lowered. In another

glass with distilled water a strip of paper of the same size is dipped (sample for comparison). After 5-7 minutes the paper is extracted from liquid. The sample from the first glass is washed with water, neutralized with 10% hydrochloric acid solution, rinsed again with water and dried between sheets of filter paper. You must compare appearance of the samples, water wetting ability and strength at break.

Exp 4. Reacting cellulose with sulfuric acidReagents and equipment: concentrated sulfuric acid, sulfuric acid solution (in

porcelain cup to 20ml of water is added 30ml of concentrated sulfuric acid, after that the solution should be cool to 5°C), 10% ammonia solution, the filter paper, porcelain cup.

Stages of the work: In porcelain dish with half filled solution of sulfuric acid filtration paper strip with 1 cm of

wide is immersed for 5, 10, 15, 20, 25, and 30 second. There after, the paper is quickly transferred into a large glass of water, to which added a small amount of ammonia solution. After some time the paper strips is removed, dried between sheets of filter paper and then in airing cupboard.

You must compare appearance of the samples, water wetting ability and strength at break.Make a conclusion with reaction equations according to the results of experiments.

4 STUDENT’S SELF-STUDY (SSS)

Guidelines for performing tasks of individual workThe purpose of self-study is to master the fundamental knowledge, skills and

abilities in the field of macromolecular chemistry. Independent student work includes preparation to current lectures and laboratory work, studing material imposed on independent study. This kind of work promotes the development of independence, responsibility and organization of students, the development of creative approach to solving problems on educational and professional levels.

One of the self-study forms is the writing and defensing the essay on one of the suggested topics. The abstract should contain necessary:

1. Title page (you can see the pattern on chair)2. Table of contents - this essay plan in which each section must comply with the

page number on which it is located.3. Introduction - a section of the essay, devoted to justifying the choice of topic

and formulating the problem, which will be presented.4. Main part - part of the essay, which consistently revealed major aspects of

problem in accordance with some logic (chronological, thematic).5. Conclusion - summarizing, a brief analysis - justification of the benefits of that

point of view with which you agree.6. List of literature sources - at least 8-10 literature sources

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Length of an abstract should be no less than 8 and no more than 12 pages. Work must be done with 14 font, sizes of fields - top, bottom, left - 25mm, right - 15mm; line spacing - 1.5. Pages must be numbered. Indention - 1cm.

Thematic plan of the SSS

The kind of work The contents References

Fulfillment period

Quantity of hours

Form of control

The preparing for lectures

Consolidate the obtained knowledge by participating in office hour, studying the scientific and journalistic periodic press

1, 3, 4 1-15 weeks 20 Orally, written tasks

The preparation to laboratory works

Activate self study Consolidate the obtained knowledge by participating in office Hour. Mastering by the elementary techniques of researches of objects

1, 3, 4 1-15weeks

20 Written work

Boundary control Check the obtained knowledge through examinations and tests

7, 15 week 5 Orally

Total 45

Individual tasks for checking progress 3 week

1. Demonstrate a possible mechanism of chain termination in the polymerization of ethylene as a result of disproportionation and recombination.2. Show a scheme of chain polymerization reaction of propylene. Write a radical mechanism of this reaction (three stages) with acetyl peroxide.3. Locate hydrocarbons below in order of increasing lightness to chain polymerization: 1) ethylene, 2) propylene, 3) 2,3-Dimethyl-2-butene, 4) 2-butene.

6 week1. Show the mezanizm of chain polymerization of butene-1 in the presence of benzoyl peroxide.2. Write schemes of chain polymerization for the following compounds: styrene, acrylonitrile, methyl acrylate. Please give a mechanism of cationic polymerization for the styrene in the presence of boron fluoride.

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3. Teflon - highly stable polymer prepared by polymerization of tetrafluoroethylene. Make a chart of the reaction.

10 week1. For produsing viscose silk the cellulose is treated with sodium hydroxide. After this to the formed alkyl cellulose is added carbon disulfide and in this conditions cellulose xanthate (viscose) are obtained. Viscose silk is a hydrolysis product of the cellulose xanthate in an acidic medium. Write the equation of all these reactions. What is cellophane? 2. Write the fragment of xylan molecule formula, if it is known that it consists of residues of β-1,5-D-xylose linked by β-1,4 glycosidic bonds. 3. A.M. Butlerov first realized the dimerization of isobutylene at heating with 60% sulfuric acid. Obtained dimer is a mixture of two isomers: 2,4,4-trimethylpentene-1 and 2,4,4-trimethylpentene-2. Write the reaction of producing diisobutylenes. Explain the mechanism of this reaction, taking into account that it proceeds via carbocation. 4. Make a chart of step polymerization reaction with three molecules of propylene. Explain the mechanism of this reaction (with the formation of carbocations). Call trimers obtained by systematic nomenclature.5. By the polymerization in the presence of sulfuric acid diisobutylene was obtained from 140g. isobutylene. Unreacted isobutylene was evaporated and diisobutylene was mixed with bromine, and 120g of bromine was expended. Determine the percentage yield of diisobutylene.

14 weekTopics of abstract

1. Thermoplastics - the current state of the industry2. Thermosets - the current state of the industry3. Main components of the polymeric compositions4. Rubber and tire5. Polymers of natural origin and their derivatives 6. The structure and general properties of polymers7. Using of polymers in medicine8. Natural fibers9. Synthetic fibers10. Artificial fibers11. Polymer films12. Ion exchange resin13. Plastics based on natural and petroleum asphalts

Criteria for evaluating all forms of Student’s Self-Study

Points/ Criteria

100 90 85 80 75 70 65 60 55 50 <50

The ability to use theoretical knowledge in solving

+ + + + + - - - - - -

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practical tasksLevel of mastering of theoretical material

+ + + + + + + + + + -

Reasonableness and clarity of response

+ + + + + + + - - - -

Quality of reporting material

+ + + + + + + + + + -

Completeness of representations the knowledges and skills by the subject

+ + + + + + + + + + -

Test and Measurement tools

1. Basic concepts of polymer chemistry2. The unique properties of polymers3. Starting materials for synthesis of polymers4. Molecular weight and polydispersity of the polymer molecules5. Differences between low molecular weight substances and macromolecules6. Number average molecular weight characterization and methods of determination.7. Weight average molecular weight characteristics and methods of its determination.8. Curves of the molecular weight distribution9. Chemical method of establishing the molecular weight10. classification of polymers by origin11. Classification of synthetic polymers on the structure of the main chain12. Classification of synthetic polymers by chemical composition13. Classification of carbon-chain polymers14. Classification of hetero polymers15. Thermoplastic and thermosetting polymers16. Structure of polymers17. Classification of polymers in the form of molecules and stereoisomers18. Intermolecular forces in macromolecules - orientation effect, hydrogen bonds, etc.19. Globular and fibrillar structure20. The additive polymerization - main stage21. Mechanisms of chain termination - recombination

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22. Mechanisms of chain termination - disproportionation23. Chain termination mechanisms - transfer to the monomer, the polymer, the solvent24. Polymerization inhibitors or stabilizers25. Cationic polymerization mechanism - the main stage, the conditions of conducting 26. Anionic polymerization mechanism - the main stage, the conditions of conducting27. Coordination polymerization based on ziegler-natta catalysts28. Polycondensation process, the main characteristics29. Functionality of monomer and its value30. Equilibrium polycondensation31. Nonequilibrium polycondensation32. Influence of various factors on the rate of polycondensation and polymer molecular weight33. Modification of polymers without changing the length macrochain34. Modification of polymers with increasing chain length35. Destruction of polymers36. Methods for polymer processing into articles. Forming fibers.37. Methods for polymer processing into articles. Forming films.38. Methods for polymer processing into articles. Plastics molding

Vocabulary

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