Abstract
Highly isotactic (iso-) and syndiotactic (syn-) poly(methyl methacrylate) (PMMA) macromonomers having styrene end group were prepared by the reaction of the corresponding PMMA living anions with p-vinylbenzyl bromide and their polymerizations were studied in toluene using 2,2′-azobisisobutyronitrile as an initiator. The rate of polymerization (Rp) 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 of the macromonomers with styrene. Propagation rate constant (kp) for the homopolymerization of macromonomers was estimated from Rp, termination rate constant (kt) determined by ESR spectroscopy [K. Hatada et al., Makromol. Chem., Rapid Commun., 11, 101 (1990)] and initiator efficiency (f) determined from end group analysis of polymacromonomer by means of NMR spectroscopy [T. Kitayama et al., Polym. Bull., 25, 205 (1991)]. Both the kt and kp values were much smaller than those for styrene polymerization, and the decrease of kt of the macromonomer was much more evident than the decrease of kp. The kp and kt values for iso-macromonomer were much larger than the corresponding values for the syn- one. The results suggest that the higher segmental mobility of iso-PMMA chain than that of syn-PMMA chain brings about the larger rate constants for propagation and termination reactions.
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