Enhancement of crystallization and adjustment properties for biocompatible poly(lactide)-based thermoplastic polyurethane via stereocomplexation

A novel biocompatible poly(lactide)-based thermoplastic polyurethane based on poly(lactide)-b-poly(hexylene succinate)-b-poly(lactide) triblock copolymers was synthesized via polycondensation, ring-opening polymerization and chain extension reactions. The chemical structure and molecular weight of poly(lactide)-based thermoplastic polyurethane were characterized by FT-IR, 1H NMR and GPC, and the results revealed that the synthesized polyurethane with multi-block structure exhibited a larger molecular weight with respect to the corresponding triblock precursor. XRD and DSC results indicated that thermoplastic polyurethane exhibited poor crystallization ability, which may be attributed to the restriction imposed by the multi-block structure of the resulting polyurethane. The occurrence of stereocomplexation significantly improved the crystallization ability of poly(lactide)-based polyurethane. The measurement of mechanical, shape memory, hydrophilicity and biodegradation properties of the resulting materials were conducted, and the results were discussed to correlate the varying compositions and the formation of stereocomplex crystals to these properties. It was identified that the increased stereocomplex crystallinity reduced the hydrophilicity and degradation rate of poly(lactide)-based thermoplastic polyurethane. The synthesized materials were also evaluated for their biocompatibility by in vitro hemolysis and cytotoxicity experiments which renders them as potential biomedical materials.