Radical Polymerization of Isotactic and Syndiotactic PMMA Macromonomers

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Highly isotactic (iso-) and syndiotactic (syn-) poly (methyl methacrylate) (PMMA) macromonomers having a styrene group were prepared by the reaction of the corresponding PMMA living anions with p-vinylbenzyl bromide and their polymerizations were examined by using radical initiator. The rate of polymerization (R_p) of iso-PMMA macromonomer was slightly higher than that of syn-macromonomer. A similar tacticity dependence of the reactivity was also observed in the radical copolymerization with styrene. Termination rate constant (k_t) could be directly determined from the decay of ESR signals of propagating radicals. To determine the number of initiator fragment in a polymacromonomer chain (N) and initiator efficiency (f), polymacromonomers obtained with perdeuterated were AIBN analyzed by ^2H NMR spectroscopy. Propagation rate constant (k_p was estimated from R_p, k_t and f. Both the k_t and k_p values were much smaller than those for styrene polymerization, and the decrease of k_t of th … More e macromonomer was much more evident than the decrease of k_p. The k_p and k_t values for iso-macromonomer were larger than the corresponding values for the syn-one. The result suggests that the higher segmental mobility of iso-PMMA chain than that of syn-PMMA chain brings about the larger k_p and k_t values.Copolymerization of iso-and syn-macromonmers in chloroform, toluene and dimethyl sulfoxide (DMSO) also confirmed higher reactivity of the iso-macromonomer. However, R_p and the relative reactivity of the iso-macromonomer to syn-one decreased depending on the solvent in the order of chloroform > toluene > DMSO, which is the same as the order of decrease in capability of stereocomplex formation, suggesting that some specific interaction lowers mobility of macromonomer and diminishes the difference in their reactivities.Poly (iso-macromonomer) was found to have larger volume in chloroform than poly (syn-macromonomer) as determined by GPC-LALLS, similarly to the case of linear PMMAs. Stereocomplex formation between stereoregular polymacromonomers and linear PMMAs in solid was also examined. Copolymers of iso-and syn-macromonomers from stereocomplex effectively though a mixture of the homopolymers of these macromonomers did not. Less