Preparation And Characterization Of Antibacterial Cellulose/chitosan Films

With the rapid consumption of non-renewable resources, preparation offunctional membranes using natural polymers instead of petrochemical productscomes to attract more and more membrane scientists’ attention. Among naturalpolymers, cellulose and chitosan are mostly used due to their unique properties.Membranes based on the combination of cellulose and chitosan can be widely used inthe fileds of water treatment, food packaging and biomedical materials et al. The mostcommon cellulose/chitosan based films are cellulose/chitosan blend film. However, incurrent time, there are some problems existed in cellulose/chitosan blend films, suchas poor miscibility between cellulose and chitosan, inferior mechanical andantibacterial properties, et al. In this work, the performances of several ILs wereinvestigated for co-dissolving cellulose and chitosan. Based on the experimentalresults, one of ILs was selected as a co-solvent to prepare cellulose/chitosan blendfilms with good miscibility and performance. On the other hand, chitosan-gratedoxycellulose films were also prepared through the reaction between chitosan andoxycelllose in ILs in this study, which is a new way to prepare cellulose/chitosanbased films.First of all, the dissolution of cellulose in1-butyl-3-methylimidazolium chloride(BmimCl),1-allyl-3-methylimidazolium chloride (AmimCl) and1-ethyl-3-methylimidazolium acetate (EmimAc) ionic liquids (ILs) was studied in thiswork. The results suggested that among three ILs, EmimAc shows the best ability todissolve cellulose. The solubility of cellulose in these ILs was increased with theincrease of dissolution temperature and time, but the degree of polymerization (DP) ofregenerated cellulose was decreased with the increase. Within45min, the solubility ofcellulose in EmimAc is8.3%at90°C, and the DP and crystallinity of celluloseregenerated from it is375and50.2%, respectively.Secondly, the dissolution of chitosan in1-butyl-3-methylimidazoliumchloride/1-hydrogen-3-methylimidazolium chloride (BmimCl/HmimCl),1-allyl-3-methylimidazolium chloride/1-hydrogen-3-methylimidazolium chloride (AmimCl/HmimCl) and1-ethyl-3-methylimidazolium acetate (EmimAc) ionic liquids(ILs) was studied. It was found that the solubility of chitosan in EmimAc is far morebetter than BmimCl/HmimCl and AmimCl/HmimCl. The solubility of chitosan inEmimAc, BmimCl/HmimCl and AmimCl/HmimCl was8.3%,0.5%and1%at90°Cwithin60min, respectively. In addition, the apparent viscosity of6%chitosan/EmimAc solution is lower than1%chitosan/BmimCl/HmimCl and1%chitosan/AmimCl/HmimCl solution.Based on the study of the performance of several ILs for dissolving cellulose andchitosan, EmimAc was selected as the solvent to co-dissolve cellulose and chitosanblends. The resulted solution has been used to prepare blend films and these filmswere further characterized. The results indicated that the films contained more ratio ofchitosan exhibited more effective antimicrobial ability against E. coli. and S. aureus.However, with the increase of chitosan content, the mechanical properties of the blendfilms decreased. The FTIR and XRD results suggested the high miscibility betweencellulose and chitosan in blend films. Due to the hydrogen bonding between celluloseand chitosan, the blend films exhibited superior thermal stability than regeneratedcellulose or chitosan film. The tensile strength and elongation at break of the blendfilm contained50%chitosan are43.1MPa and6.0%respectively, and its onsetdegradation and maximum degradation rate temperature are236.4°C and263.8°CrespectivelyMoreover, chitosan-grafted oxycellulose films were prepared and characterizedin this work. The effects of reaction conditions on the nitrogen contents andmechanical properties of chitosan-grafted oxycellulose films were investigated. Theresults revealed that the ideal SmimHSO4dosage and reaction time are5%and2hrespectively. Under this condition, the nitrogen and chitosan contents inchitosan-grafted oxycellulose films are0.69%and8.3%respectively, its tensilestrength and elongation at break are12.3MPa and12.3%respectively, and its onsetdegradation and maximum degradation rate temperature are215.7°C and259.1°Crespectively. The C=N stretching vibration peak at1643cm-1in FTIR spectra of chitosan-grafted oxycellulose film along with the C=N peak at400.0eV in its XPSspectra certify the Schiff Base reaction between oxycellulose and chitosan.Additionally, chitosan-grafted oxycellulose film has a highly inhibitory effect on thebacteria of E. coli. and S. aureus.