Construction of Fully Biodegradable Poly(L-Lactide-Co-Caprolactone) Random Copolymer/Poly(D-Lactide) Blend: Crystallization, Toughness, and Biodegradability

In this work, poly(L-lactide-co-ε-caprolactone) (PLCL) copolymers with varying ε-caprolactone (ε-CL) contents that ranged from 0% to 10% were synthesized via ring-opening polymerization of L-lactide and ε-CL at 170°C for 1 h. Fully biodegradable PLCL/poly(D-lactide) (PDLA) blends with stereocomplex (SC) crystallites were fabricated through a solution blending approach. The effects of ε-CL content in PLCL on the crystallization behavior, thermal properties, mechanical performance, and degradation behavior of PLCL/PDLA blends were systematically investigated. The successful synthesis of PLCL was confirmed by 1 H NMR and FTIR analyses. The melting peaks observed in the high-temperature region and the characteristic diffractions in WAXD patterns provided evidence for the formation of SC crystallites in PLCL/PDLA blends. Compared with PLCL, the incorporation of PDLA significantly enhanced the crystallization rate, due to the nucleation function of SC crystallites. With increasing ε-CL content in the copolymer system, the T g and crystallinity of PLCL gradually reduced, and the melting peaks of HC and SC crystals shifted toward lower temperatures due to the reduced sequence regularity. A pronounced improvement in deformability was achieved by the presence of ε-CL segments. As the ε-CL content increased from 1.5% to 10%, the elongation at break rose from 12% to 192%, with the morphology of elongated fibrils. Higher ε-CL contents accelerated enzymatic degradation, with mass loss exceeding 75% after 7 days at 10% ε-CL, because the increased chain mobility may facilitate the penetration of water and Proteinase K into the blend, thereby promoting enzymatic erosion. Overall, high-performance PLA-based composites with excellent biodegradability were achieved via SC crystallization and modulation of ε-CL comonomer content. Summary PLCL copolymers with tunable ε-CL content were prepared and characterized. SC crystallization regulated the crystallization and thermal behavior. ε-CL segments enhance chain mobility and improve blend deformability. Enzymatic degradation kinetics were accelerated as ε-CL content increased.