Copolymer interchain

This involves the reaction between two or more polymers to form a copolymer. Interchain copolymer... 

The copolymers are insoluble in water unless they are neutralized to some extent with base. They are soluble, however, in various ratios of alcohol and water, suggesting appHcations where deUvery from hydroalcohoHc solutions (149) but subsequent insolubiUty in water is desired, such as in low volatile organic compound (VOC) hair-fixative formulations or tablet coatings. Unneutralized, their Ts are higher than expected, indicating interchain hydrogen bonding (150). 

The glass transition temperature of a random copolymer usually falls between those of the corresponding homopolymers since the copolymers will tend to have intermediate chain stiffness and interchain attraction. Where these are the only important factors to be considered a linear relationship between Tg and copolymer composition is both reasonable to postulate and experimentally verifiable. One form of this relationship is given by the equation... 

It must be pointed out that deviations from such a simple relationship do occur. For example, since random copolymerisation tends to promote disorder, reduce molecular packing and also reduce the interchain forces of attraction, the Tg of copolymers is often lower than would be predicted by the linear relationship. Examples are also known where the Tg of the copolymer is higher than predicted. This could occur where hydrogen bonding or dipole attraction is possible between dissimilar comonomer residues in the chain but not between similar residues, i.e. special interchain forces exist with the copolymers. 

The regular structure of the alternating copolymer with its absence of side chains enables the polymer to crystallise with close molecular packing and with interchain attraction augmented by the carbonyl groups. As a result these polymers exhibit the following characteristics ... 

In addition to homopolymers of varying molecular and particle structure, copolymers are also available commercially in which vinyl chloride is the principal monomer. Comonomers used eommercially include vinyl acetate, vinylidene chloride, propylene, acrylonitrile, vinyl isobutyl ether, and maleic, fumaric and acrylic esters. Of these the first three only are of importance to the plastics industry. The main function of introducing comonomer is to reduce the regularity of the polymer structure and thus lower the interchain forces. The polymers may therefore be proeessed at much lower temperatures and are useful in the manufacture of gramophone records and flooring compositions. 

As has been mentioned earlier, a number of copolymers such as nylon 66/610/6 are available. Sueh a copolymer has an irregular structure and thus interchain bonding and crystallisation are limited. As a consequence the copolymer is soluble in alcohols and many other common polar solvents. 

Those involving the use of functionalized blend components that produce in situ compatibilizing interchain copolymers some common reactive functionalities include carboxyl, epoxy, isocyanate, and anhydride, etc. 

Nonetheless, one cannot exclude the probability of a successful combination of these prerequisites (as was the case with poly[(NiPAAm-co-GMA)-g-PEO considered above]) that will allow us to obtain, using the chemical colouring approach, the protein-like HP-copolymers with a dense hydrophobic core wrapped by the hydrophilic shell. Such a shell should be capable of efficiently protecting the temperature-responsive macromolecules against pronounced interchain hydrophobic interactions and precipitation at temperatures significantly higher than those at which the copolymers of the same total monomer composition—but with a non-protein-like primary sequence of comonomer units—are in the soluble state. 

Ionomer. Ionomer is the generic name for polymers based on sodium or zinc salts of ethylene-methacrylic acid copolymers in which interchain ionic bonding, occurring randomly between the long-chain polymer molecules, produces solid-state properties. 

The potential for rapid randomizing processes in the copolyesters at elevated temperatures has been demonstrated conclusively by heating a mixture of the two homopolymers of PHBA and PHNA at 450 °C at a pressure of around several hundred psi [40]. Within a few seconds a viscous melt was observed to extrude from the cracks in the mold. Analysis of this material showed a structure consistent with the random 50/50 copolymer of HBA/HNA (see Figs. 18 and 19). We estimate that at this very high temperature the rate of interchain transesterification reactions corresponds to 1000 ester interchanges/chain/10 s. 

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