Acetylation and molecular mass effects on barrier and mechanical properties of shortfin squid chitosan membranes

Chitosan samples with different N-deacetylation levels were obtained from β-chitin under heterogeneous alkali conditions. Oxidative depolymerisation was performed to attain low-acetylated chitosan samples with different molecular mass. Water vapour permeability, membrane swelling and tensile mechanical properties were analysed in plasticized self-supporting chitosan membranes. The main purpose was to describe unambigously the effect of the biopolymer molecular mass and acetylation degree on these properties. Commercially available chitosan samples derived from α-chitin were also studied for comparison. The equilibrium degree of swelling in water and the water vapour permeability increase by increasing the molecular mass or the degree of acetylation. Regarding the effect on the mechanical properties, generally harder and tougher membranes were obtained for chitosans with higher molecular mass or lower acetylation degree. These observations are tentatively explained based on the different structural characteristics of the polymer and can lead to a better understanding of the tools necessary to tailor a specific type of chitosan membrane.