dimethylsilanol] and its copolymers with styrene were synthesized by an oxygen atom insertion into the Si-H bond via reaction with dimethyldioxirane. Spectroscopic investigations demonstrated that the conversion of silanes to silanob was almost quantitative. The (4-vinylphenyl)dimethylsilanol polymer and its copolymers with styrene obtained in situ were stable in acetone solution at room temperature. The self-association of silanol groups through hydrogen bonding and the spontaneous condensation of these groups leading to cross-linking and insolubilization were investigated by spectroscopy and differential scanning calorimetry as well as thermogravimetry.
Keywords: silanol-containing polymers poly ( 4-vinylphenylmethylphenylsilanol ) oxyfunctionalization of silane hydrogen bonding glass transition temperature FT-IR In an earlier publication,' we reported the synthesis of a novel polymer, 4-vinylphenyldimethylsilanol polymer, and its styrene copolymers from their silane precursors by the oxygen atom insertion into the Si -H bond via reaction with dimethyldioxirane. The oxyfunctionalization of the silane was found to be efficient and quantitative. In the course of our study, we found that poly (styrene-co-4-vinylphenyldimethylsilanol) ( ST-VPDMS ) was prone to undergo self-condensation to form siloxane cross linkages in the solid state when the copolymer contained more than 18 mol % 4-vinylphenyldimethylsilanol (VPDMS) . From the point of view of molecular structure, the chemical stability of these novel silanol-containing polymers should depend on both electronegativity and steric effects introduced by substituents bound directly to Si atom? Accordingly, a phenyl substituent was chosen to replace a methyl group for the purpose of increasing the stability of the silanol-containing polymers. In this communication, we report the synthesis and characterization of stable 4-vinylphenylmethylphenylsilanol polymer and its styrene copolymers.4-Vinylphenylmethylphenylsilane ( VPMPSAN ) monomer was first synthesized through the reaction of 4-vinylphenylmagnesium chloride and methylphenylchlorosilane similar to that previously described.' The monomer was collected by distillation a t 84-85OC/O.O1 mm Hg with 59% yield. The polymerization of the monomer and the copolymerization of the monomer with styrene were carried out in sealed ampules under an argon atmosphere in the presence of a free radical initiator, 2,2'-azobisisobutyronitrile ( AIBN) , a t 60°C (Scheme 1). The polymer was precipitated from methylene chloride solution into methanol and dried under vacuum at 4OoC for 6 h. Purification of polymers was performed by dissolving polymers in methylene chloride and reprecipitating into methanol followed by vacuum drying at 40°C for 48 h. The results were presented in Table I. The yield of copolymerization was controlled near 10 w t % and the reactivity ratios of monomer and styrene were calculated' to be rVpMpsAN = 0.01 and rstrrene = 0.52. We speculated that the lower reactivity ratio of styrene ( < 1 ) may be caused partly by the insignificance of the steric hindrance between a styrene attacking radical and a VPMPSAN monomer and partly by the resonance stabilization of the phenyl substituent bound to the Si atom. The steric hindrance between a VPMPSAN attacking radical and a VPMPSAN monomer may responsible for the reluctance of VPMPSAN to homopolymerize during the copolymerization with styrene.4-Vinylphenylmethylphenylsilanol polymer ( VPMPS ) and its styrene copolymers (ST-VPMPS) were then syn- thesized from their silane precursors through the reaction with dimethyldioxirane'*3 (Scheme 1). Despite the generally low reactivity of the side groups of synthetic high polyme...
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