Preparation of Elastic and Antibacterial Chitosan–Citric Membranes with High Oxygen Barrier Ability by in Situ Cross-Linking

Chitosan–citric biomembranes Ch-CA-Gx (x = 0–3) were prepared by a simple cross-linking. The dependence of mechanical property, water-resisting capacity, microstructural characteristic, oxygen barrier ability, and thermal properties of membranes on the content of glycerin was investigated. The results revealed that vacuum drying at 80 °C can lead to low-yield amidation and the Maillard reaction, thus affecting the thermal stability and water resistance of biomembranes. Owing to the ionic cross-linking and amidation, the chitosan–citrate complex showed weaker compatibility when the glycerin content increased, thereby leading to discontinuity of microstructure in the Ch-CA-Gx (x = 1–3) membranes, which was in line with the weaker mechanical properties and water-resisting abilities of membranes, compared to Ch-CA-G0. Chitosan membranes showed interestingly high oxygen barrier capabilities under 40 and 80% relative humidity (RH) conditions, probably attributed to the increased diffusion length arising from th...