Preparation Of The Degradable Free-standing Polylactic Acid/chitosan Based Films

The potential applications of non-petroleum-based degradable materials are promoted by the increasingly severe white pollution.Polylactic acid?PLA?,as a prime candidate biodegradable material to replace traditional petroleum-based plastics,has amazing bio-compatibility,non-toxicity and transparency.However,the application of PLA is restricted by its hydrophobicity and uncontrollable degradation rate.Here,a series of polylactic acid/chitosan?PLA/CS?based free-standing degradable films are prepared with non-solvent induce phase separation?NIPS?method.The degradation rates of the composite films are mainly explored with different optimization parameters and surface modifications.The main contributions are as follows:1)According to the hydrophilicity and transparency of PLA-based films prepared with different methods and solvent-non-solvent systems,the combination of NIPS method and chloroform/DMF-water system is established as the optimized preparation system of PLA/CS-based self-supporting degradable films.The transmittance of the obtained antibacterial PLA/CS porous films is more than 95%,the water contact angle is decreased from 80°to 72°,the degradation weight loss after 12 weeks is increased from 17%to 24%.2)With the increasing ratio of CS solution in the PLA/CS blend solution,the pore sizes of PLA/CS composite films are decreased from 8/1?V/V?to 6/1?V/V?,and then increased from 6/1?V/V?to 3/1?V/V?.Meanwhile,the degradation rate is closely related to the pore size,the larger the pore size,the faster the hydrolysis rate.When PLA solution and CS solution are blended with ratio of 6/1?V/V?,the pore size is the smallest and the degradation rate is the lowest among all PLA/CS composite films.In addition,CS plays a main role in the antibacterial activity of PLA/CS composite films.The antibacterial rates increase with the CS contents.Moreover,PLA/CS composite films modified with F127 can significantly improve the uniformity of pore sizes,whereas the transmittances reduce from 95%to 65%.And PLA/CS composite films modified by plasma treatment have remarkably enhanced antibacterial activities and increased degradation rates from 24%to 42%after 12 weeks.3)PLA/CS/MoS₂ composite films are prepared by adding photosensitive molybdenum disulfide?MoS₂?nanosheets to PLA/CS films in order to make it photodegradable under visible light.When exposed to visible light,MoS₂ can enhance the composite film's ability of absorbing light to generate free radicals.It makes PLA/CS/MoS₂ composite films photocatalytical degradable under visible light and develops a new potential photodegradable and biodegradable material.The photodegradation process can be controlled by changing MoS₂ contents.The weight loss of the composite film with 10%?W/W?MoS₂ is the highest?²2%?,after exposed to visible light for 8 days.The above results indicate that the prepared free-standing PLA/CS based composite films have advantages of highly transparency,controllable degradation rates and amazing antibacterial activity,which can be used as excellent biomedical and packaging materials.Besides the green preparation method can save costs and produce films on a large scale.