Fullerene Polymers

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FULLERENE POLMERS A SEMINAR UNDER THE GUIDENCE OF Dr. S. SAMI KANNU (Reader in chemistry) Presented by k.vijay benadict raj 19-03-07

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Transcript of Fullerene Polymers

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FULLERENE POLMERS

A SEMINAR

UNDER THE GUIDENCE OFDr. S. SAMI KANNU

(Reader in chemistry)

Presented byk.vijay benadict raj

19-03-07

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BackgroundFullerene- The fullerene is a spheroidal or polyhedra shaped carbon molecule.The Fullerene was discovered in 1984 by Harry Kroto at Rice University. For many years diamond and graphite were believed to be the only carbon allotropes. Kroto and his colleagues were studying carbon clusters and came upon some heavier molecules that added up to exactly 60 carbon atoms. The discovery was called a buckminsterfullerene. It was called this because of the resemblance to the polyhedra structures that Buckminster Fuller had known so well in architecture. The carbon molecule very closely resembles the soccer ball shape.

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View of the molecule

60C

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Laser vaporizationThe graphite is hit with a laser and extreme temperatures are created.

The carbon breaks apart and reforms into fullerenes and other carbon molecules when blasted with inert gasses to cool it.

When the graphite is impregnated with metal atoms endohedral fullerenes form.

Endohedral fullerenes are fullerenes filled with an atom of another element. They are also termed dopyballs.

  

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DISCOVERY

Fullerene is a third allotrope of carbon.The first fullerene was discovered in 1985 richard smalley and robert curl of the united states and harold kroto of the united kingdom.The fullerene thus obtained is composed of 60 carbon atoms are joined to together by single or double bonds to form a hollow sphere.They contain 12 pentagonal and 20 hexagonal faces a design that resembles a soccer ball.Fullerene derive their name from the american architect r. buckminister fuller, whose geodesic dome design is similar to the molecular structure of C60. .

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CLASSIFICATION

One or more metal or noble gas atoms can be trapped inside the molecules its called exohedral fullerenes.

One or more metal or noble gas atoms can be trapped outside the molecules its called endohedral fullerenes.

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PROPERTIES

C60 is not “superaromatic “.

C60 behaves like an electron deficient alkene,and react readily with electron rich spices.

The C60 molecule is known to rotate very rapidly at room temperature while it is in the solid state. This presents a liquid like behavior that is very strange for a solid.

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SOLUBLITYS

fullerene are sparingly soluble in many solvents.Commen solvents for the fullerenes include toluene and carbon di sulphide.Some fullerenes are not soluble.

Fullerenes dissolved in non-polar solvents create unique colors like a red-wine color to deep purple for C60 and C70 molecules in benzene.

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More Uses for FullerenesAntioxidantsFullerenes are powerful antioxidants, reacting readily and at a high rate with free radicals, which are often the cause of cell damage or death. Fullerenes hold great promise in health and personal care applications where prevention of oxidative cell damage or death is desirable, as well as in non-physiological applications where oxidation and radical processes are destructive (food spoilage, plastics deterioration, metal corrosion).

BiopharmaceuticalsMajor pharmaceutical companies are exploring the use of fullerenes in controlling the neurological damage of such diseases as Alzheimer’s disease and Lou Gehrig's disease (ALS), which are a result of radical damage. Drugs for atherosclerosis, photodynamic therapy, and anti-viral agents are also in development. They can be used for recognition of HIVP.

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Polymer Electronics and Bulk PolymersFullerenes are chemically reactive and can be added to polymer structures to create new copolymers with specific physical and mechanical properties. They can also be added to make composites. Much work has been done on the use of fullerenes as polymer additives to modify physical properties and performance characteristics. Currently, the record efficiency for a polymer solar cell is a fullerene/polymer blend, where the fullerene acts as the n-type semiconductor. Polymer transistors and photodetectors have also been developed using the n-type semiconducting properties of fullerenes.

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Fullerene polymers

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Cllassification

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1.Sidechain fullerene polymer

The first fullerene side chain fullerene polymer was prepared by WUDL.

They first prepared a low molecular weight bi hydroxy functional fullerene derivative and then obtained the c60 containing polyester or polyurethane by polycondensation.

GECKLER AND HIRSH prepared the first true side chain fullerene polymer..

 

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Inorder to overcome the influence of the fullerene of steric hinderence of the c60 moiety on the oilymer molecular weight, they prepared the aminopolymer first,and then reacted with fullerene to tbtain the side chain fullerene polymer(4)

 HAWKER prepared a linear polymer with pendent c60 moieties by nitrogen bridging (5)In this reaction azide groupe can control the reaction..For example , using group transfer polymerization allyl methacrylate and methyl acrylate copolymeras were synthesized; then the pendent allyl groups in copolymer were hydrobrominated, followed by reaction with NaN3And finally with fullerene by addtion reaction(6)..

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Main chain fullerene polymer

The first main chain fullerene was prepared by beni nori via electrochemical polymerization.

 a well defined main chain fullerene polymer was prepared by “OLEAMURA”.

 They heated PsTEMPO, which was prepared by nitroxyl-mediated ‘living’ radical polymerization at 1450C.

 

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The C60 derivatives thus obtained 60-80% yield were found to be predominately A1,,D1, dipolystyryl dihydro fullerenes.

 

It is retained the redox properties of original C60.

 Another reactive fullerene polymer allowed the incorporation of fullerene units into the polymer backbone of polysiloxanes. (scheme 17)

 

Similarly, C60 pearl-necklace polymer, poly(4, 49, carbonyl bisphenylene-trans 2-fullerenobiscaetamide) was synthesized by direct poly condensation of trans fullerene bisacetic acid with 4, 49, diaminobenzophenone in the presence of large excess of triphenyl phosphate and pyridine. (scheme(18)).

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Fullereo dendrimer

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Wooleyet al prepared dendritic fullerene by attachment of poly(aryl ether) based dendrimer to phenol functionalized fullerenes(scheme-20).The benzylic bromide moiety of the fourth generation dendrimer reacts with rhe phenolic groups attached to fullerene , and thus two dendrimer building blocks copule with one fullerene to give the fullerene based dendrimer.Using cycloaddtion reaction of azides with fullerenes, wooley et al prepared a new type of fullerene dendrimer based on the benzylic bromid moiety of the fourth generation dendrimer.The final products contained mono and bi addtion products.But no higher addition products.

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The failure to obtain tri or multisubstitution may be due to steric hindrence around the c60.Nucleus and unfavourable electronic conditions after the biaddtion .Rio et al used a m poly(aryl ether) dendrimerTo obtain a series of fullerodendrimers. Systametic changes in yhe photophysical properties properties in thre series suggest increasing interaction betwee n the poly(aryl ether) dendritic wedges and the cntral chromophore from yhe exterior.Rio et al areincorporated there fullero dendrimers in to mesoporous silica glasses , and showed that there matrials posses efficient optical limiting properties.

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Star shaped fullerene polymer

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Star shaped fullerene polymers

1. Many papers have been published on radical polymerization of the presence of C60.

2.  Chen and Lin gave a detail description.3.  They conducted radical polymerizations of styrene in the

presence of C60 at 900C in benzene using benzoyl peroxide (BPO) as the initiator.

4. However, the number of polystyrene chains added to C60 increases with polymerization time. Scheme2.

5. They polymerization process was followed by monitoring BPO concentration, C60 content and polymerization time. It was found that C60 acts like a radical absorber, which multiply absorbs primary radicals of BPO and the propagating polymer radicals. At be beginning of the reaction, chain propagation is restricted by the radical absorbing effect of C60.

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Direct fulleranation of polycarbonate (PC), a commercially important optical polymer, can yield. Star shaped fullerene polymers.

By simply irradiating a solution of PC and C60 at room temperature using a conventional Ar lamp, or by warming a C60/PC solution to 600C in the presence of AIBN, tangetdl star shaped fullerene PC polymers.

Living free radical technique (iniferter) He etal. Scheme 31 synthesised starlike C60 bonding polymers.

The used C60 with pendent N,N diethyldithiocarbanate groups (C60-SR) as a polyfunctional photoiniferter.

Photopolymerization proceeded by living radical mechanism and gave soluble polyfunctional polymers.

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Fullerene endcapped polymers

The first fullerene c60 end capped polystyrene were prepared by reaction of amino terminated polystyrene with c60.

 GU prepared mono c60 end capped oligovinylene (scheme33)

 Mono and bi c60 end capped poly ethylene oxide were prepared using the reaction with azide group with c60.

 They are exhibiting good photo conductivity.. 

   CLOUTEL reported here c60 end capped star polymer(scheme-35)

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Cross linked fullerene polymers

Photochemical addition of c60 to furan derivatives has been used to prepare crosslinked furan containing polymer.Poly(2hydroxy ethylmethacrylate) with 2- furoic chloride an d then 1122 tetra cholora ethana solution polymer was exposed to visible light in the presence of c60.Thje solution turned to gel after 10h and solidified completely. Ethylene diene norborene with c60 was prepared by jiang.A highly uniform photo condutive film can be obtained from the solution..(scheme 37)Polymer derivatives of fullerene.

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All fullerene polymers

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All fullerene polymers.

Fullerene cages are directly connected covalently. 

I n 1993 rao et al first reported that solid c60 film undergoes a phototransformation when exposed to visible or uv light yield toluene insoluble species , which were characterized as all fullerene polymer4s formed by2+2 cycloaddtion between neighbouring c60 molecules. 

Ma and co wor4kers synthesized high molecular weight. Plyfullerenes by fullerene by photochemical reactions of c60.

Clusters in carefully de oxygenated tolune – acetonitrile soultons at room temperature. 

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   Morita etal considered that the strong lattice interaction is the one dimensional system would dramatically modify and distort the conjuctedpolymer system, and thatP+orBP+ formed. Therefore the density of states in the upper energy range of the valence band would be decreased, resulting in suppression of the interband absorption, especially in the lower energy range.Fig 3 which shows that transfer of free electrons between the rigid bands of C60 and PAT is nearly impossible since charge transfer (CT) requires positive energy C,T = 0.1to 0.2ev.

However, charge transfer from polymer to C60 may occur if polaronic effects are taken in to account, both in the polymers. (P+ level approximately 0.2ev while BP+ approximately 0.7ev above the valance band to P) and in C60 molecules.

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In C60 a shape deformation effect will lead to splitting of three fold degenerate LUMO of C60 in the ionic state due to polaronic distortion; in other words john teller distortion will occur.

In latter case, the t1u level should split into three levels of different symmetries as sketched figure 3 and the transferred electron should occupy the lowest split-level. Moreover, it has been reported that in weak doping with slightly positive CT energy, the coulomb attraction of the P+ polaron and the dopant can additionally stabilize the charge transfer due to the creation of polarons P+

in the ground state with C60.

LESR providence evidence that C60 is formed upon photoexitation figure 4 shows two spin signals in which the g approximately equal to 2.000 spin with deltaHFWHM approximately equal to 4 G us assigned to the P3…….. polaron radical (donor cation radical), and the g approximately equal to 1.9935 spin with deltaHFWHM approximately equal to 3.7 G is assigned to C60

- anion radical.

Recently Marumoto etal studied regioregular PAT/ C60 composite is used.

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Application

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Figure 12 C60 doped PMPS (polymethylphenylsilane) has low dark conductivity, and the photo induced discharge is fast and complete.These properties are very important for electron photographic applications.

They found that the C60 moieties were bonded to the pendant benzene ring of PMPS by Friedel-crafts reaction and incorporated into the main chain by direct copolymerization.Doping this compound in to PVK, long etal found much higher photoconductivity than could be obtained by doping with pure C60.

C60 can enhance the photoconductivity of non-conductivity as well as conducting polymers.

Another system is C60 containing styrene acrylamide copolymer in which the maximal C60 content in the polymer is 1.45wt% good conductivity.PVK/MDDA(didecylaminemodified MWNT) blend showed good photoconductivity. However the PVK/MVNT exhibited little photoconductivity (figure 15).Fluorescence studies indicated the MDDA can act as an electron acceptor in either the ground state or excited while PVK is electron donor.

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Photodiodes

Bulk heterojunction polymer photovoltaic devices and photodiodes have been constructed with composite films of semiconducting polymer as electron donors and fullerene derivatives are electron acceptor.NAVA et al prepoared fullerene containing polyester by polycondensation of bifunctional fullerene adducts with tetraethyleneglycol or polyethylene glycol (scheme46a,b)Oligo (p phenyl vinylene) fullerene dyads were prepared by several research groups in order to avoid the incompletely and macrophase separation problem of regular fullerene based photovoltaic devices.WANGet al fabricated a multiplayer organic lightemitting device by mixing together a c60 based poly(phenylvinylene)dyad and an emmisive conjugated polymerPMPV(scheme-49).Their primary study showed that the PPVc60 dyad can improne the light emiting performance..

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Optical limitingOne of the most attractive NLO properties of fullerene is optical limiting.optical limiting occurs when the optical transmission of a material decreases with increasing laser fluence, a property that is desirable for protection sensors and human eyes from intensc laser beam radiation.For laser radiation at 532 nm,C60 and its derivative are among the best material showing optical limiting properties.SUN et al prepared linear polystyrene bound c60 (scheme-50 )in fullerene cages are covalently attached to polystyrene chains, in primarily pendant linkages by a friedel kraft type reaction using alcl3 catalyst.

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These soluble pendant c60 ps polymers have better defind structure than the copolymers reported by KOJIMA et al.  At the optical limiting of the polystyrene bound c60 at 532 nm is not as good as that of pristine c60 in solution.LU et al synthesized copolymers of benzylaminofullerene with methylmethaacrylate by free radical polymerization.These polymers have relatively good solubility in thf.Although benzylamino fullerene homopolymer shows optical limiting of all the copolymersm is much weaker.

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Conclusion The development of fullerene organic chemistry , many low molecular organic reactions can be used ib polymeric modification of fullerene. By controlling the functional groups in polymers and reaction conditions, many welldefined fullerene polymers,such as side chain fullerene polymers, mainchain fullerene polymers,dendritic fullerene polymers, starshaped fullerene polymers, fullerene end capped polymers and so on.At the same time many LIVING POLYMERIZATION method can be introduced.By anionic polymerization, well defined six arm star shapped fullerene polymers can be obtained. 

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