Structure of N-alkyl chitosan membranes on water-permselectivity for aqueous ethanol solutions

N-Alkyl chitosans with different numbers of carbons and degrees of substitution of the N-alkyl group were prepared. The water-permselectivity for aqueous ethanol solutions through the N-alkyl chitosan membranes in evapomeation were studied. The permeation rate and separation factor for water-permselectivity were significantly influenced by the number of carbons in the N-alkyl group, in particular, one N-alkyl chitosan membrane showed a maximum in the permeation rate and separation factor. The degree of substitution in the N-alkyl group little affected the permeation rate, but significantly changed the separation factor. The characteristics of permeation and separation for an aqueous ethanol solution through the N-alkyl chitosan membranes with different N-alkyl groups and different degrees of substitution of the N-alkyl group an discussed from the viewpoints of physical and chemical structures of their membranes, such as, density, crystallinity, surface free energy and degree of swelling of the membrane.