A modified Grignard metathesis (GRIM) polymerization has been used for the synthesis of various end-group functionalized poly(3-alkylthiophene)s (PAT)s. Subsequent reactions have been performed to transform these polymers into novel telechelic polythiophenes with reactive ends. The resultant polymers can be used as building blocks for the synthesis of block copolymers using several approaches: ATRP, living polymerization and "click" chemistry.