Reactive polymers incorporating silyl enol ether groups. 3 - Incorporation of alpha,beta-bis(siloxy)vinylene units into the backbone of vinyl polymers by free-radical (co)polymerization of 2,3-bis(trialkylsiloxy)butadienes

2,3-Bis(trimethylsiloxy)butadiene (1) and 2,3-bis(tert-butyldimethylsiloxy)butadiene (2) have been homopolymerized and copolymerized with styrene (St) and methyl methacrylate (MMA) under free-radical conditions. Comparison of initial rates and molecular weights with polymerizations conducted under identical experimental conditions on monosubstituted analogs, 2-trimethysiloxybutadiene (3) and 2-(tert-butyldimethylsiloxy)butadiene (4), demonstrated that the second substituent does not decrease the polymerizability significantly despite the additional steric hindrance introduced in the monomer. Extensive H-1 and C-13 NMR characterization of the polymers demonstrated that the main incorporation mode is of the 1,4-type, allowing more than 95% of the butadienyl subunit to be incorporated in the main chain as an alpha,beta-bis(trialkylsiloxy)vinylene functional group. Monomer reactivity ratios r(1) and r(2) at 60 degrees C were determined from copolymer composition curves obtained at low conversions and are compared with values obtained for other 1,2-butadienyl systems.