Development of Micro-Crosslinked Poly(L-Lactic Acid) With Flexible, Anti-Aging, and Barrier Properties by In Situ Polymerization of Graphene Oxide

Although poly(L-lactic acid) (PLLA) is biocompatible and degradable, its inherent brittleness, susceptibility to aging, low ultraviolet light (UV) resistance, and moderate gas barrier properties limit its diverse applications. In this study, graphene oxide (GO) was used as an initiator, unsaturated poly (butylene itaconate) (PBI) was used as a flexible chain segment, and GO-grafted P(LA-g-BI) (GO-g-PLBI) copolymer was synthesized by in situ melt polycondensation of lactic acid. Nuclear magnetic resonance, Fourier transform infrared, and X-ray photoelectron spectroscopy results confirmed the successful synthesis of GO-g-PLBI and the formation of a multi-branched structure. The GO-g-PLBI film demonstrated excellent ductility and oxygen barrier properties, with elongation at break increased by 73.8 times compared with PLLA, while oxygen permeability (OP) decreased by 40.3%. The incorporation of PBI facilitated micro-crosslinking within the copolymer, thereby enhancing its thermal stability. More gg and gt conformations were formed in the copolymer, while the crystallization of the copolymer induced by aging was inhibited, thus showing excellent anti-aging properties. Interestingly, the OP value of this micro-crosslinked GO-g-PLBI film decreased by 60.9% after physical aging, demonstrating extremely high oxygen barrier properties. This study offers a viable approach to developing PLLA/graphene nanocomposites that exhibit adjustable flexibility, enhanced oxygen barrier, heat and UV resistance, anti-aging properties, and high transparency.