Reaction, chain, copolymer esters

Hazer [20,25] reported on the reaction of a po]y(eth-ylene g]ycol)-based azoester with methacryloyl chloride in the presence of (CH3CH2)3N. In this reaction double bonds were attached to the chain ends of the poly(ester) thus obtaining a macroinimer. Being used for the thermal polymerization of styrene, the material formed an insoluble gel [20]. Probably, both the C=C double bonds and the azo bonds reacted in the course of the thermal treatment. The macroninimer in a later work [25] was used for thermally polymerizing poly(butadiene) thus leading to poly(ethylene glycol-/ -butadiene) block copolymers. 

Phase mixing can be attributed partly to the irregularity of the copolymer chain. In the case of poly(ester ether) copolymers synthesized by normal step polymerization reactions, the hard segment has a... 

We make polyethylene resins using two basic types of chain growth reaction free radical polymerization and coordination catalysis. We use free radical polymerization to make low density polyethylene, ethylene-vinyl ester copolymers, and the ethylene-acrylic acid copolymer precursors for ethylene ionomers. We employ coordination catalysts to make high density polyethylene, linear low density polyethylene, and very low density polyethylene. 

The industrial production of copolymers of trioxane with ethylene oxide or di-oxolane (1-5%) is conducted as a bulk polymerization in special equipment. The incorporation of small amounts of C-C bonds into the C-0 chain has a remarkable effect on the thermal and chemical stability. In homopolymers the thermal decomposition starts at the semiacetal end groups ( unzipping ) and leads to a complete destruction of the polymer chain, whereas this reaction stops in copolymers already at the first C-C bond. A thermally stable OH end group is thus formed which, in addition, contributes to a much better alkali resistance compared to ester group-terminated homopolymers (see Examples 3-40 and 5-13). 

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. 

The co-monomers such as vinyl acetate, acrylate esters, or carbon monoxide are fed together with ethylene, or introduced by liquid pumps, into the suction of the secondary compressor. The concentration in the feed of the co-monomer which is required to achieve a certain level of the co-monomer in the resulting polymer depends on the reactivity ratios, ri and r2, which are the ratios of rate constants of chain-propagation reactions [5]. The values for the co-monomers used in the high-pressure process are presented in Table 5.1-3. In the case of vinyl acetate, both reactivity ratios are identical and therefore the composition of the copolymer is the same as that of the feed. The concentration of vinyl acetate, for example, in... 

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