Poly(epsilon-caprolactone)-poly(fluoroalkylene oxide)-poly(epsilon-caprolactone) block copolymers. 1. Synthesis and molecular characterization

Hydroxyl-terminated telechelic poly(fluoroalkylene oxide)s, (PFPE)s, with m olecular weights ranging from 1100 to 3400 were employed as transfer agents for the ring-opening polymerization of epsilon-caprolactone (CL) in the pr esence of various catalysts/initiators. The highest conversion rate of CL w as observed using Ti(OBu)(4) and Bu2SnO as catalysts/initiators. The polyme rization of CL started only from the hydroxyl groups of PFPE, leading to th e formation of ABA triblock copolymers without formation of homopolymer pol y(epsilon-caprolactone) (PCL). The rate of insertion of the first unit of C L is much faster than the insertion of the other CL units, and the average molecular weight of the ABA copolymers was that expected by the CL/PFPE rat io. The polymerization rate of CL in the presence of PFPE using aluminum al koxides as initiator was very slow, contrary to what is known about the hom opolymerization of CL.