Characteristics of PLLA films blended with PEG block copolymers as additives for biodegradable polymer stents

Purpose: Biodegradable poly(L-lactide) (PLLA) has been widely used as stent materials with good biocompatibility and its controllability over biodegradation rate. However, PLLA has several restrictions such as prolonged degradation and limited swelling. In this study, PLLA films blended with poly(ethylene glycol) (PEG)-based block copolymers as additives were fabricated to investigate the effect of PEG based additives. Methods: Various PEG-based di- or tri-block copolymers were synthesized by ring opening polymerization using methoxy PEG (MPEG) and PEG as an initiator. The block copolymers were then blended with PLLA at various mass ratios. Swelling and mechanical properties of the blended PLLA films were characterized and compared with those of control PLLA. Results: It was found that sol-gel phase transition of block copolymers was depended on type and concentrations of the copolymers. PLLA films blended with di- or tri-block copolymer (MPEG-PLLA or PLLA-PEG-PLLA) showed higher degree of swelling than hydrophobic control PLLA. In addition, mechanical properties of block copolymer-blended PLLA films were slightly reduced in comparison to those of control PLLA. Conclusions: PLLA films blended with hydrophilic PEG-based block copolymer as additives demonstrated improved swelling property as well as mechanical properties. This approach is expected to be useful for fabrication of biodegradable and drug releasing polymer stents.