Vinyl polymerization. 235. Free radicals in the polymerization of vinyl monomers initiated by GOMBERG's and its relatad reactions

Abstract

AbstractFree radicals derived from the GOMBERG's reaction of arylmethyl halides such as benzyldiphenylmethyl‐, and tritylbromide and chloride, with silver powder or mercury can initiate the radical polymerization and copolymerization of styrene, methyl methacrylate, acrylonitrile, vinyl chloride, and vinyl acetate. The orders of initiating abilities of halides in the polymerization of styrene and methyl methacrylate were as follows; for bromides, benzyl‐ > diphenylmethyl‐ > trityl‐, and for chlorides, diphenylmethyl‐ > benzyl‐ > trityl‐, when silver was used as metal component, while the order for the both halides is diphenylmethyl‐ > benzyl‐ > trityl‐ with mercury. These results were understood by the competition of the reactivities of halides to metal with those of the derived radicals to monomer. The over‐all polymerization rate of the system styrene/silver/benzyl bromide was proportional to monomer concentration, square root of halide concentration, and square root of the amount of added but insoluble silver powder.The radical‐like composition curves of styrene‐methyl methacrylate copolymers and the inhibition of polymerization by verdazyl, a stable free radical, show that these polymerization systems include radical propagation step. Hexaphenylethane and 1.1.2.2‐tetraphenylethane were isolated from the reaction systems, trityl halide/silver and diphenylmethyl chloride/silver or mercury, respectively. Recombination products of verdazyl with diphenylmethyl radical and benzyl radical were also isolated, but not N‐trityl‐verdazyl. Tracer study with benzyl bromide‐7−14C showed the incorporation of benzyl fragments in the obtained polymer.