Preparation,Characterization,and Enhancement Of Chitosan Hydrogel Membrane Based On Alkali Solvent

As world’s second-largest natural polysaccharide, chitosan has a broad application prospects. In recent years, the theory of polysaccharides alkaline solvent system has brought a major breakthrough for chitosan’s scientific research, production and processing, which can improve the materials’mechanical properties, and solve energy consumption problem. This article will focus on property of chitosan hydrogel membrane prepared in the new method, such as hydrogel mechanical strength, crystallinity, microscopic aperture structure, etc., and to evaluate the possibility of its use in the medical material and potential value. Polysaccharide components blended and ion-enhancement are proposed to further improve the performance of the chitosan hydrogel membrane.(1) Propose a new method for preparing high strength chitosan hydrogel membrane--- dissolve chitosan in LiOH/ urea alkaline system, and precipitate to hydrogel membrane in alcohol and acid bath. This method does not require any external crosslinker, no need complex chemical reaction, which is easy and non-toxic. Compared with traditional chitosan hydrogel membrane made by dissolving in acid then perticipate in alkali, chitosan hydrogel membrane made by the new method is excellent in mechanical properties.4% pure chitosan hydrogel’s tensile strength is 1.98MPa, elongation at break was 297%, nearly 20 times than the former. The experiments show that the mechanical properties of the high strength chitosan hydrogel membrane is In proportion to the chitosan concentration. In the range of 2%-4%,4% concentration is the best. SEM results show that the micro-pore structure of the chitosan gel obtained by the two systems have significant differences. alkali The high strength hydrogel membrane have uniform and dense micro-pore structure, and the 4% chitosan hydrogel membrane has pore size distribution of 50 to 200 nm. Pores and connections between them are tight and uniform, while pore size distribution of the traditional hydrogel membrane is about 200 μm. Pore sizes increase when concentration reduce.(2) Prepare chitosan/sodium alginate (CS/SA) complex hydrogel membrane. The mechanical strength of 4%CS/1%SA is excellent, with tensile strength of 1.82 MPa and elongation-at-break of 412% which increased by 39%. SEM results show that the more proportion with chitosan the smaller pore size:2% CS/3% SA with 40 to 60 μm, 3%CS/2%SA with 10 to 30 μm, and 4%CS4/1%SA with 5 to 20um. Chitosan sodium alginate can adjust the the microscopic aperture, while keeping the exellent strength.(3) Mechanical properties of composite chitosan hydrogel membrane by metal ions are greatly improved. Under condition of Amino and ion molar ratio is 2/3, CS hydrogel membrane with Zn2+ has tensile strength of 3.06 MPa, and elongation-at-break of 418%,55% and 41% increased respectively, compared with the uncomplexed hydrogel. The tensile strength of Composite chitosan hydrogel membrane with Cu2+ and Mg2+ can improve by at least 36%. XRD characterization show that after composited with metal ions, chitosan hydrogel membrane’s crystalline structure is closer to its natural state, thus affecting its mechanical properties.