Preparation Of Organic Composite Films With Chitosan/Poly (?-Glutamic Acid) And Study On Its Properties

Organic composite films have been extensively applied in the fields such as water treatment,food processing,pharmaceuticals,separation and purification.As people pay more and more attention to environmental protection,the use of natural polymer materials in functional film preparation has become a research hotspot.Wherein,chitosan(CS)and poly(?-glutamic acid)(?-PGA)have been regarded as excellent raw materials for film preparation due to their advantages including antibacterial performance,water absorption,moisture retention,and biocompatibility.In view of the application in biomedicine,protein purification,food processing,water treatment,and etc.,the films made with CS and ?-PGA are attracting more and more attention?Presently,most methods of CS/?-PGA film preparation need some organic additives as activators or linkers,which can weaken biocompatibility,mechanical properties and antimicrobial property.To this end,phase transformation method and liophilization method were applied to make a new CS/?-PGA film in this work,and the preparation process was further optimized.As a result,a novel green process for film preparation was constructed.Based on this,the relationship between micro-structure and macro-performance of the film was analyzed.The detail results were shown as following:1.Research on film preparation: The effects of reaction solution,matrix ratio and concentration,and film formation mode on the film in its structure were studied.The micro-morphology,intermolecular forces,and crystallization of film were analyzed by SEM,IR,and XRD,respectively.The results show:(1)Acetic acid is the best additive for film formation;(2)The optimal matrix ratio(?-PGA:CS)and their optimal concentration were 1:3 and 2%,respectively;(3)The film made by the phase transformation method has a dense surface,but the lyophilized one has uniform and larger pores.This indicates that film-formed mode obviously affects film structure.Meanwhile,CS has a good compatibility to ?-PGA,but there is an interaction between them during film preparation.Some basic characteristics of the film such as water absorption,water retention and swelling were investigated and the results indicate:(1)The water absorption and retention capacity of the composite film are better than them of the pure chitosan film.(2)The lyophilized film is better than phase transformation film in the swell ability,and the lyophilized film needs a shorter swelling time relative to the phase transformation film.The results show that the structure of film has a great influence on the water absorption and water retention.In addition,the hydrophilic carboxyl group in ?-PGA can contribute to improving the swell ability of the composite film.2.Study on film adsorption: The effects of matrix ratio,solution p H,adsorption time and initial concentration of protein on film adsorption of bovine serum albumin were studied.The results show that:(1)The film gets a maximum adsorption of 950 mg/g under the optimum condition of mass ratio of ?-PGA/CS 1:3,p H 4.8,initial protein concentration 3.0 mg/m L,and adsorption equilibrium time 60 hr.From this,it is found that the matrix ratio and p H of protein solution have a significant effect on the adsorption performance.It can be due to that the carboxyl groups of ?-PGA do not only directly affect film adsorption,but also change the structure of film which indirectly affects film adsorption.(2)The adsorption behavior of film meets the Freundlich model.This indicates that the film has both physical adsorption and chemical adsorption of BSA.3.Study on antibacterial performance of film: The effects of chitosan concentration,film matrix solution and film on the antibacterial properties were studied.The results show that both CS and ?-PGA have a certain antibacterial function,and the antibacterial ability of film increases with the increment of CS concentration.Wherein,the film can inhibit Staphylococcus aureus better than Escherichia coli.In this work,the film preparation process was improved.The novel green method for film preparation can greatly improve the water retention,moisture retention,and adsorption performance of the organic composite film of CS/?-PGA.This work will give a good reference for preparing relative composite film,and the film will be potentially applied in the food,medicine and cosmetology.