Synthesis, characterization, and in vitro degradation of star-shaped P(ε-caprolactone)-b-poly(L-lactide)-b-poly(D,L-lactide-co-glycolide) from hexakis [p-(hydroxymethyl)phenoxy]cyclotriphosphazene initiator

Hexaarmed star-shaped hydroxyl-terminated poly(epsilon-caprolactone) (PCL) was successfully synthesized via the ring-opening polymerization of E-caprolactone (CL) with hexakis[p-(hydroxymethyl)phenoxy]cyclotriphosphazene initiator and stannous octoate catalyst in bulk. The star-shaped PCL with hydroxy end groups could be used as a macroinitiator for block copolymerization with L-lactide (L-LA). The star-shaped triblock copolymer was synthesized by above-mentioned hydroxyl-terminated star-shaped diblock PCL-b-PLLA, D,L-lactide (D,L-LA), and glycolide (GA). IR, H-1 NMR, and GPC analysis showed that the star-shaped block copolymers were successfully synthesized and the molecular weights and the unit composition of the star-shaped block copolymers were controlled by the molar ratios of monomer to initiator. The triblock copolymer presented a three-phase structure, namely, PCL crystalline, PLLA crystalline, and D,L-PLAGA amorphous domains, which made the triblock copolymer different from the diblock copolymer and star-shaped PCL in crystallizability and thermal behaviors. Then, the in vitro degradation behaviors of the copolymers were investigated. (c) 2007 Wiley Periodicals, Inc.