Effect of Addition of Zinc Chloride on the Radical Copolymerization of Styrene with 3-Methyl-3-buten-2-one

Abstract

Copolymerization of styrene with 3-m"ethy1-3-buten-2-one was studied in the presence of zinc chloride. Zinc chloride easily coordinates with 3-methyl-3-buten-2-one and its double bond stretchings and n-x* absorption shift toward lower energy side.By the addition of styrene to the coordinated compound, the binary complex ([MIPKSt]) and the ternary complex ([ZnCl₂MIPK₂St₂]) are formed. The ternary complex is C-T complex. Formation constants of the binary and the ternary complexs are 0.16 and about 0.21 at 25°C in chloroform, respectively. AIBN initiated copolymerization of styrene with 3-methy1-3-buten-2-one in the presence of: zinc chloride brings about styrene-3-methyl-3-buten-2-one 1: 1 copolymer and polystyrene. The alternating tendency of copolymer composition increases with increasing amount of initial zinc chloride and styrene., Yields of copolymer and polystyrene increase with increasing concentration of the ternary coMplex. The copolymer is 1: 1 alternating copolymer' on the basis of the composition curve of this system and the measurement of NMR spectrum of polymer itself. These results showed that this polymerization is the homopolymerization of the ternary complex and a part of ionic dissociation of the ternary complex brings about the cationic polymerization of styrene.