Controlled radical polymerization of a trialkylsilyl methacrylate by reversible addition-fragmentation chain transfer polymerization

The reversible addition-fragmentation chain transfer (RAFT) polymerization of a hydrolyzable monomer (tent-butyldimethylsilyl methacrylate) with cumyl dithiobenzoate and 2-cyanoprop-2-yl dithiobenzoate as chain-transfer agents was studied in toluene solutions at 70 C. The resulting homopolymers had low polydispersity (polydispersity index < 1.3) up to 96% monomer conversion with molecular weights at high conversions close to the theoretical prediction. The profiles of the number-average molecular weight versus the conversion revealed controlled polymerization features with chain-transfer constants expected between 1.0 and 10. A series of poly (tent-butyldimethylsilyl methacrylate)s were synthesized over the molecular weight range of 1.0 x 10(4) to 3.0 x 10(4), as determined by size exclusion chromatography. As strong differences of hydrodynamic volumes in tetrahydrofuran between poly(methyl methacrylate), polystyrene standards, and poly(tert-butyldimethylsilyl methacrylate) were observed, true molecular weights were obtained from a light scattering detector equipped in a triple-detector size exclusion chromatograph. The Mark-Houwink-Sakurada parameters for poly(tert-butyldimethylsilyl methacrylate) were assessed to obtain directly true molecular weight values from size exclusion chromatography with universal calibration. In addition, a RAFT agent efficiency above 94% was confirmed at high conversions by both light scattering detection and H-1 NMR spectroscopy. (c) 2005 Wiley Periodicals, Inc.