Radical (co)polymerization behavior of alkoxyvinylsilanes [tri(isobutoxy)vinylsilane 1, triethoxyvinylsilane 2, di(isobutoxy)-methylvinylsilane 3, di(isobutoxy)phenylvinylsilane 4, diethoxymethylvinylsilane 5, and diethoxyphenylvinylsilane 6] was systematically investigated. Homopolymerization and copolymerization with styrene of these alkoxyvinylsilanes were performed under various conditions in order to find appropriate initiating systems for the radical polymerizations. Transformation of some of the copolymers into poly[(vinyl alcohol)-co-styrene]s was examined via oxidative cleavage of the Si-C bonds in the alkoxyvinylsilane repeating units.KEY WORDS: Radical Polymerization / Copolymerization / Poly(alkoxyvinylsilane) / Polystyrene / Polymer Reaction / Radical polymerization of vinylsilanes followed by oxidative cleavage of C-Si bonds in the resulting repeating units could be a useful method for preparing poly(vinyl alcohol) (PVA) and its derivatives. The strategy, which was for the first time proposed by T. E. Hogen-Esch, et al. in 1996, 1 had not been realized until we recently demonstrated that copolymers of di(isobutoxy)methylvinylsilane 3 and styrene prepared by radical copolymerization can be transformed into poly[(vinyl alcohol)-co-styrene]s (Scheme 1).2 In fact, that is the first example of the synthesis of poly[(vinyl alcohol)-co-styrene]. Although the copolymer should be prepared by hydrolysis of poly[(vinyl acetate)-co-styrene], the synthesis of the precursor copolymer via radical copolymerization is not practical due to the large difference of the monomer reactivity ratios [r 1 (styrene) = 56, r 2 (vinyl acetate) = 0.01].3 On the other hand, the oxidation of the homopolymer poly3 afforded an insoluble product, whose elemental analysis agreed well with the composition of PVA. 2Although the results are highly promising for further development, the problem with the process is that the copolymerization initiated by 1,1 0 -azobis(cyclohexane-1-carbonitrile) (VAZO) at 130 C did not proceed efficiently, giving rather low molecular weight copolymers in low yields (M n < 8600, yield < 35%). Accordingly, in order to establish this strategy as a practical synthetic method for polymeric materials containing vinyl alcohol (VA) repeating units, we should find more efficient conditions for the polymerization of 3 or other vinylsilanes, which can be polymerized to give higher molecular weight (co)polymers and can provide an appropriate C-Si bond for the following oxidative cleavage.According to the literatures, 4 the requirement for the oxidative cleavage to successfully proceed is the presence of at least one -OR or -NR 2 group on Si. Thus, as for alkoxyvinylsilanes, because we have found that the repeating unit of a monoalkoxyvinylsilane [dimethyl(isobutoxy)vinylsilane] in the copolymer with styrene could not be efficiently transformed into VA repeating unit after oxidation, 2 we have trialkoxyvinylsilane and dialkoxyvinylsilane as candidates. Whereas there have been some reports and patents describing polym...