Strengthening the Shape Memory Behaviors of l-Lactide-ased Copolymers via Its Stereocomplexation Effect with Poly(d-Lactide)

Abstract

Biodegradable shape memory polymers (SMPs) have great application prospects in biomedical fields, particularly, those SMPs with the transition temperature of ∼37 °C have attracted keen interests. In this study, poly­(d-lactide) (PDLA) of different molecular weights (5000 or 20 000) was introduced into poly­(l-lactide-co-glycolide) (PLGA) or poly­(l-lactide-co-ε-caprolactone) (PLCL) copolymers at different amounts (5, 10, 15 wt%) to investigate the effect of PLLA/PDLA stereocomplexation (SC-PLA) on the shape memory performance of the blends. The tested copolymers were in different chemical compositions to adjust the lengths of PLLA segments and the glass transition temperatures (T g). Characterizations on crystallization, mechanical properties, shape fixing, and recovery ratios of the blends were conducted, and the results were discussed to correlate the formation of SC-PLA crystals to the shape memory performances of corresponding blends. It was identified that SC-PLA crystals would act as cross-links and had strengthened the stationary phase within the matrixes, which could significantly improve the shape memory performances of PLGA/PDLA and PLCL/PDLA blends if more SC-PLA crystals had formed. Based on the findings, a kind of porous scaffold was prepared using the PLCL(75:25)/PDLA (5k, 10 wt%) blend, which displayed excellent and reproducible compression and recovery behaviors under 37 °C, showing potentials as body temperature triggered SMPs for in vivo applications such as implantable template to facilitate tissue regeneration.