End-group analysis of polymacromonomer formed in the radical polymerization of styrene-type PMMA macromonomers by using 2H NMR spectroscopy

Summary Isotactic (iso-) and syndiotactic (syn-) poly(methyl methacrylate) (PMMA) macromonomers having styrene group as a polymerizable function were polymerized with perdeuterated 2,2-azobisisobutyronitrile in toluene at 60°C. The resultant polymacromonomers were analyzed by ²H NMR spectroscopy to determine the number of initiator fragment in a polymacromonomer chain (N) and initiator efficiency (f). The N values were less than unity (0.500.72), indicating the chain transfer reaction to occur in the radical polymerization of macromonomer. The f values were 0.180.28 and much smaller than that for styrene polymerization (0.50.7). Iso-macromonomer gave larger N and f values than syn- one, suggesting that the tacticity of macromonomer affects the reaction pathway probably owing to the difference in chain mobility between iso- and syn-PMMA chains.