STEREOCHEMICAL KINETICS OF POLYMERIZATION OF METHYL-METHACRYLATE UNDER GROUP-TRANSFER POLYMERIZATION CONDITIONS - C-13 NMR ANALYSIS OF POLY(METHYL METHACRYLATE) TERMINATED WITH LABELED END-GROUPS

The stereochemistry of the chain end of poly(methyl methacrylate) prep ared under group-transfer polymerization conditions and terminated wit h (CH3I)-C-13 in the presence of tris(dimethylamino)sulfonium difluoro trimethylsiliconate (TASSiMe3F2) is determined by C-13 NMR and compare d with the tacticity of the chain. The propagation statistics reveal c onsistency with a Bernoullian process for the entire temperature range studied (-96 to +45-degrees-C), confirming previous reports based on main-chain triad tacticity alone. The results suggest that the E and Z stereoisomers demonstrated for these systems propagate with identical stereochemistry and show that a comparison of the stereochemistry of the end group and the main chain is a valuable method for analyzing th e stereochemical statistics of vinyl polymerization.