Preparation Of Antibacterial Ploylactic Acid/Graphene Oxide Composite Films And Study On Its Properties

Poly?L-lactic acid??PLLA?is a biocompatible polyester derived from renewable sources.It is desirable to reduce its brittleness and introduce antibacterial activity for biomedical applications by using grapheme oxide?GO?as a structural and antibacterial agent.However,commonly used polymer/GO composite synthesis methods,such as physical mixing and covalent functionalization,either cause phase segregation or compromise the intrinsic properties of GO.In this paper,we report a novel method for synthesizing PLLA/GO nanocomposite films.First,perylene bisimides-containing PLLA?PBI-PLLA?was synthesized via ring-opening polymerization of L-lactide using a hydroxyl-derivate of perylene bisimides?PBI-OH?as the initiator.Next,PBI-PLLA was conjugated with GO via?-?stacking to form PLLA-conjugated-GO?PLLA-c-GO?.Last,PLLA/GO films were fabricated by simple solution casting of commercial PLLA and PLLA-c-GO dissolved in chloroform.The exhaustive characterizations reveal that GO retained the original morphology and functional groups after the formation of PLLA-c-GO,which provided the blended film with the antibacterial properties of GO.The starting thermal degradation temperature of PLLA/GO films in N₂ increases to 313?comparing to commercial PLLA films at 293?.Their surface is more hydrophilic with the water contact angle of 53°.Their elongation at break improves significantly from 3%to 30%compared to commercial PLLA films,demonstrating much better flexibility.Most importantly,the PLLA/GO films show good antibacterial activity towards Escherichia coli?E.coli?,Bacillus subtiliscells?B.subtilis?and Staphylococcus aureus?S.aureus?cells with the bacterial colony number reduction by 80%.At the same time,they show low toxicity towards mammalian cells,such as L929 and macrophage cells.Overall,the novel PLLA/GO films will be a competitive material in food and drug packaging fields.