Experiment 10:Polymers

History• The first synthetic polymers was Bakelite, a

phenol-formaldehyde polymer.• Bakelite was commercially introduced in 1909. It

was developed as a synthetic substitute for shellac.• Used at first to make billiard balls but later used for

molded insulation, valve parts, knobs, etc.• Rayon, the first synthetic fiber• Precursors of Rayon– 1884 – developed as artificial silk from collodion

• Marketed in 1891 but was short-lived

– Viscoid – 1892, a cellulose polymer– Rayon – 1926, regenerated cellulose

Polymers

• Definition – A polymer is a molecule with a very high molecular weight which is composed of repeating simple structural units called monomers. Often referred to as macromolecules.– Homopolymer – single recurring monomer– Heteropolymer or Copolymer – at least 2 different

monomer subunits

Polymers

• There are natural polymers and synthetic polymers.

• Natural polymers– DNA, proteins, starches

• Synthetic polymers –– Polyurethanes, Styrofoam

Methods of ProductionTwo major methods depending on the nature of the subunits…

1. Chain-reaction polymers (aka addition polymers)• Monomers are attached to each other by a chain-reaction. The

reaction may have either a radical, an anion, or a cation as an intermediate.

- Polypropene from propene, used in luggage and carpeting- Polystyrene formed from styrene, used in packaging- Polymethyl methacrylate formed from methyl methacrylate, also known

as Lucite or Plexiglass2. Step-Growth Polymerization (aka condensation polymers)• Monomers have functional groups at both ends. When these

ends react, the result is the polymer w/the loss of a small molecule such as water or HCl.

- Usually natural polymers are formed in this way- Monomer units can be different

Homopolymers vs. Copolymers

• Homopolymer – polymer comprised of a single type of monomer unit

• Copolymer (also called a heteropolymer) – contains two ore more distinct momomers

Chain-reaction polymersPolystyrene is a simple polymer made from repeating units of styrene.

CH=CH2R . CH-CH2-R

.

CH=CH2

.CH-CH2-CHCH2-R

(R . is an initiator)

Note : Most stable intermediate will always be benzyl. The dimer shown would continue the same steps growing by one styrene each time.

Formation of “Slime”• Tautomers of vinyl

alcohol• PVA is not made from

vinyl alcohol because aldehyde tautomer favored.

• It is made from Polyvinyl acetate with saponification to the alcohol.

O

O

n

Polyvinyl Acetate

Saponif icationO

n

Polyvinyl Alcohol

H

+O

OH

+ H2O

Step-growth polymerization – Release of water

O

CH

CH2

CH2

O

HC

H2C

H2C

HC

B

O

O

CH2

Na

H2C

n

+ 4 H2O

Recycling Codes

TODAY

• The properties of 3 polymers will be investigated.

1. SOLUBILITY OF POLYSTYRENE

H2C CH

Styrene monomerPhenyl ethene

HC

H2C

n

Polystyrene or styrofoam

2. HOW MUCH WATER CAN IT HOLD?

• http://www.cmu.edu/gelfand/k12-teachers/polymers/polymer-and-absorption/super-absorb-powder.html

3. CROSS-LINKED POLYMER“SLIME”

O

OH

Acrylic Acid

Na+C

CHH2C

O

O-

n+ Na + OH

sodium polyacrylate

Initiator

O

CH

CH2

CH2

O

HC

H2C

H2C

HC

B

O

O

CH2

Na

H2C

n

Waste

• Put your waste from each experiment into the corresponding waste container….– Experiment “A” goes into “A” waste container– Experiment “B” goes into “B” waste container– Experiment “C” goes into “C” waste container

• You may keep your SLIME! … just don’t eat it.