alpha,alpha-Dibromotoluene 1 was found to be polymerized by the reaction with excess Mg to give poly(phenylmethylene)s 2, whose main chains were partially dehydrogenated to carbon-carbon double bonds (C=C). The C=Cs in 2 can be brominated by treatment with Br-2. The polymerization mechanism was presumed to include the formation of Grignard reagents of various species with benzylic C-Br bonds and the nucleophilic attacks of the Grignard reagents to various compounds with benzylic C-Br bonds. Copolymerization of 1 with dichlorodimethylsilane successfully proceeded. Mg/Cu-mediated copolycondensation of 1 with 1,6-dibromohexane proceeded to give polymers that have similar compositions to those of random copolymers of ethylene and styrene. (c) 2006 Wiley Periodicals, Inc.