Flash photolysis study of initiation step in radical polymerization of Si-containing vinyl monomers: reactivities to arylthiyl radicals

Abstract

The initiation step in radical polymerization of Si-containing vinyl monomers with arylthiyl radicals (ArS.) has been studied by the flash photolysis method. Rate constants for reversible addition reactions of ArS. with various Si-containing vinyl monomers have been determined by the selective radical scavenging method. For each thiyl radical, the reactivities for CH2 CHX increased in the order:X= C(CH3)3 (CH2)3 CH2Si(OCH3)3⩽ CH2Si(CH3)3∼ Si(OCH3)3∼ Si(CH3)3 C6HSi(CH3)3−p∼ C6H4Si(CH3)3−p The reactivity of the C C was increased by the substitution of the Si atom at vinyl and allyl positions. The polar and resonance factors of Si-containing monomers were evaluated from the kinetic data, which were compared with the Alfrey-PriceQ-e scheme obtained from the copolymerization data.