The synthesis of poly(p-phenylene methylene) (PPM)-based block copolymers such as poly(p-phenylene methylene)-b-poly(epsilon-caprolactone) and poly(p-phenylene methylene)-b-polytetrahydrofuran by mechanistic transformation was described. First, precursor PPM was synthesized by acid-catalyzed polymerization of tribenzylborate at 16 degrees C. Then, this polymer was used as macroinitiators in either ring-opening polymerization of epsilon-caprolactone or cationic ring-opening polymerization of tetrahydrofuran to yield respective block copolymers. The structures of the prepolymer and block copolymers were characterized by GPC and (1)H NMR investigations. The composition of block copolymers as determined by (1)H NMR and TGA analysis was found to be in very good agreement. The thermal behavior and surface morphology of the copolymers were also investigated, respectively, by differential scanning calorimetry and atomic force microscopy measurements, and the contribution of the major soft segment has been observed. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4021-4026, 2011