Poly(lactide)‐based supramolecular polymers driven by self‐complementary quadruple hydrogen bonds: construction, crystallization and mechanical properties

A series of poly(lactide) (PLA)-based supramolecular polymers based on linear PLLA-b-PCL-b-PLLA triblock copolymers (PLLA, poly(l-lactide); PCL, poly(epsilon-caprolactone)) or/and three-arm star (PCL-b-PDLA)(3) block copolymers (PDLA, poly(d-lactide)) were synthesized. The effects of the structure and composition on crystal structure, crystallization behavior, spherulite morphology and mechanical properties of the synthesized supramolecular polymers were investigated. The results of DSC and polarized optical microscopy indicated that the supramolecular polymer exhibited poor crystallization ability with respect to PCL/PLA block copolymer, and the crystallinity of the supramolecular polymer with alternating PCL/PLA multiblock structure was stronger than that with similar crosslinked network structure. The presence of molten PCL blocks disturbed the orientation of lamellae, forming spherulites with feather-like dendrites, and ring-banded spherulites were observed as the molecular weight of the PLA blocks increased. The results of tensile tests demonstrated that supramolecular polymers with larger molecular weight of PLA blocks showed the pronounced ductile fracture. On this basis, stereocomplexed supramolecular polymers were also synthesized, and it was found that the stereocomplex crystals had a significant impact on the crystallization and mechanical properties of the supramolecular polymers. Therefore, in this work a novel technique for manufacturing toughened PLA-based material and tuning its performances is proposed, which may promote the application of PLA-based materials in more fields. (c) 2022 Society of Industrial Chemistry.