Highly toughened and heat-resistant poly(l-lactide) materials through interfacial interaction control via chemical structure of biodegradable elastomer

Abstract

Three biodegradable elastomers with different chemical structures, i.e., polyurethane (PU), poly(l-lactide)-b-polyurethane-b-poly(l-lactide) (LPUL) and poly(d-lactide)-b-polyurethane-b-poly(d-lactide) (DPUD) triblock copolymers were prepared to blend with commercial poly(l-lactide) (PLLA) to provide weak, medium and strong interfacial interactions through weak van der Walls, interfacial chain entanglement and interfacial stereocomplex (SC) crystallization, respectively. Morphology analysis indicated that the size of dispersed phase in the amorphous PLLA matrix decreased with increasing PLLA or PDLA content of the biodegradable elastomers and agglomeration of dispersed particles occurred obviously during matrix crystallization for PLLA/PU and PLLA/LPUL blends due to the relatively weak interfacial interactions, while agglomeration did not occur apparently for PLLA/DPUD blends due to the strong interfacial interaction arisen from the interfacial SC crystallites. With well-tuned and stabilized phase morphology, PLLA/DPUD exhibited the best toughening efficiency for both the amorphous and highly crystalline PLLA matrix. Moreover, the PLLA/DPUD showed the highest mechanical strength and crystallization rate, attributing to the presence of interfacial SC crystallites, which could reinforce the mechanical strength and work as efficient nucleating agents for crystallization of PLLA matrix. In addition, PLLA/DPUD blends showed superior heat resistance over PLLA/PU and PLLA/LPUL blends by processing on conventional machine. All the excellent performances were attributed to the special interfacial interaction originated from interfacial SC crystallites of PLLA/DPUD blends.