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Biomass-derived poly(lactic acid) and poly(3-methyl-1,5-pentanediol sebacate) alternating multiblock copolymers with improved marine biodegradability and mechanical properties
Summary
Researchers synthesized biomass-derived alternating multiblock copolymers combining poly(lactic acid) and poly(3-methyl-1,5-pentanediol sebacate), finding that the regular block arrangement allows tunable thermal and mechanical properties — including up to 518% elongation at break — while also enabling biodegradation in both compost and seawater, addressing PLA's brittleness and limited marine biodegradability.
• Biomass-derived PLA and PMPDSe alternating multiblock copolymers were synthesized. • Adjusting PLA length controls thermal properties, making the copolymer versatile. • Alternating multiblock copolymers showed higher elongation at break and toughness. • Alternating multiblock copolymers showed biodegradability in compost and seawater. • Introducing sebacic acid may enhance biodegradability, requiring further research. The reliance on fossil resources and the mismanagement of waste owing to the rapid increase in plastic production have led to serious environmental problems, particularly global marine pollution. In recent years, poly(lactic acid) (PLA) has been widely used as a biomass plastic to replace petroleum-based materials. However, the biodegradation of PLA is limited to composting environments and its brittle nature limits its application. This study aimed to synthesize a biomass-based PLA and poly(3-methyl-1,5-pentanediol sebacic acid) (PMPDSe)-diol copolymer and evaluate its marine biodegradability and mechanical properties. PLA was copolymerized with PMPDSe-diol to obtain the triblock copolymer PLA-PMPDSe-PLA, which was then chain-extended with hexamethylene diisocyanate to form an alternating multiblock (PLA- alt -PMPDSe) copolymer. Because of their regular arrangement, the thermal and mechanical properties could be controlled by varying the length of the PLA chains, compared with random multiblock (PLA- ran -PMPDSe) copolymers. In particular, when 61% or 71% PLA was included, the films had higher elongation at break (331%–518%) and toughness than PLA and PLA- ran -PMPDSe copolymers. Biodegradability was the highest when 54% PLA was used, and the films disintegrated in compost and seawater. In seawater, the molecular weight decreased to 45% in three months, and the biodegradability was confirmed to be more than 17% in two months. Furthermore, the PLA- alt -PMPDSe copolymer exhibited a contact angle of over 83°, which is equivalent to that of PLA and could be used as a film. This polymer has a wide range of applications and will contribute to the development of sustainable bioplastics and address plastic waste.