Ester interchange polymerization

LC polymers of the ester type have been the most widely synthesized because they can be prepared by low temperature solution polymerization methods and melt transesterification reactions from available or readily attainable monomers. High temperature ester interchange polymerization, however, is somewhat limited in usefulness because it often leads to polymer structures of poorly defined sequence... 

The addition of alcohols to form the 3-alkoxypropionates is readily carried out with strongly basic catalyst (25). If the alcohol groups are different, ester interchange gives a mixture of products. Anionic polymerization to oligomeric acrylate esters can be obtained with appropriate control of reaction conditions. The 3-aIkoxypropionates can be cleaved in the presence of acid catalysts to generate acrylates (26). Development of transition-metal catalysts for carbonylation of olefins provides routes to both 3-aIkoxypropionates and 3-acryl-oxypropionates (27,28). Hence these are potential intermediates to acrylates from ethylene and carbon monoxide. 

The polymerization of a ring compound usually proceeds by an interchange reaction, induced either catalytically or by the presence of small amounts of end-group-producing substances. For example, the polymerization of lactide, the cyclic dimer of lactic acid, is accelerated by small amounts of water. The water undoubtedly hydrolyzes the lactide to lactyllactic acid, which may then react with other lactide molecules by ester interchange. This reaction scheme can be represented as follows ... 

The counterpart of reaction (III) in polyesters, i.e., ester-ester interchange, probably does not take place to any appreciable degree. Polymeric polysulfide rubbers ( Thiokor type)... 

If the fractional conversion in an ester interchange reaction is 0.99999, what would be the average degree of polymerization of the polyester produced ... 

Polymerization is a two-stage process (Fig. 1) in which the monomer is first prepared either by an ester interchange between dimethyl terephthalate and ethylene glycol, or by direct esterification of terephthalic acid. 

The condensation polymer made by reacting ethylene glycol with 1,4-benzene dicarboxylic acid (terephthalic acid) produces a polymer that is almost exclusively converted into the fiber Dacron. The polymerization is run as an ester interchange reaction using the methyl ester of terephthalic acid ... 

During polymerization, ester interchange between the vinyl ester and a glycol-terminated molecule eliminates acetaldehyde, the stable keto-form of the vinyl ester function. Activation energies for the thermal degradation of PET range [39] between 32 and 62 kcal mole . ... 

Catalysts are also required in many stepwise polymerizations. For example, reaction of polycarboxylic acids and polyols (Reaction 7) is catalyzed by acids ester interchange, by metal compounds such as titanium alkoxides. On the other hand, polyurea synthesis (Reaction 6) generally does not require a catalyst. Metallic compounds are also useful in oxidative polymerization of phenols to give poly(phenylene oxides), illustrated in Reaction 14. 

Introduction of these photocrosslinkable structures in macro-molecular chains can be performed by esterification of hydroxyla-ted polymers with cinnamoyl chloride. Cellulose Q).condensation products (4, ) and mainly poly(vinyl alcohol) have Been treated( by this method. Other chemical modifications have been studied as ester interchange of poly(vinyl acetate) 7) and Knoevenagel reaction on polyesters (8). Very few results on the synthesis of such photocrosslinkable polymers by polymerization have been reported. Therefore free radical polymerization of cinnamic acid vinyl derivatives did not lead to the expected polymers, but to insolubilization reactions. Howewer cationic procedure can be a good way in some cases since Kato et al. could polymerize by this way with high yields p-vinyl phenylcinnamate (9) and B-vinyloxyethyl cinnamate (10). 

Polyester Fibers Reaction. Ester interchange of ethylene glycol with dimethyl terephthalate is followed by condensation polymerization of the intermediate ... 

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