Poly( I -[4-(2-~hloroethyl)phenyl]ethylene](3) was synthesized by bulk polymerization of 4-(2-chloroethy1)styrene (6) in two steps from commercial products. The polymer was characterized by means of GPC (weight-average molecular weight a,, = 85000 and number-average molecular weight M , = 63500), ' H NMR and I3C NMR spectroscopy. The first stage of thermal degradation begins at 290°C and ends at about 410°C. The overall activation energy was calculated to be 43 kcal . mol-' (180 kJ . mol-I). The solid residue was crosslinked and insoluble. The volatile products, identified by gas chromatography-mass spectroscopy (GC-MS), were chiefly hydrogen chloride, dichloromethane and monomer. In a slrongly basic medium, nucleophilic substitution of chlorine was achieved without elimination.