Long-alkane-chain modified N-phthaloyl chitosan membranes with controlled permeability

A series of N-phthaloyl acylated chitosan membranes with controlled permeability were synthesized by the regioselective protection of the chitosan amino groups as the corresponding phthalimides followed by reaction with the long-chain dodecanoyl chloride. Fourier transform infrared (FT-IR) and 1H nuclear magnetic resonance (1H NMR) analysis suggested that the degree of substitution (DS) ranged from 2.8 to 3.6. Contact angles, water retention values and mechanical examinations demonstrated that the hydrophobicity and mechanical properties of the membranes were all improved significantly following the modifications, together with their solubility in many organic solvents. Thermal weight change analysis demonstrated that a higher DS provided enhanced thermal properties. The controlled permeability of the membranes was determined by measuring the diffusion of urea, and the amount of urea released decreased significantly with increasing DS. The comprehensive properties of the membranes could be tuned by regulating their DS values as required.