The characterization of N-methyl, N-ethyl, N-propyl, N-butyl and N-hexyl chitosans, novel film-forming polymers

Abstract

The N-alkyl chitosans in the title were prepared from chitosan ( Euphausia superba) by aldimine formation and hydrogenation at room temperature in aqueous media. They are white powders with a certain degree of crystallinity; their substitution degrees are: acetamido 36%, secondary amine 23-33%, primary amine 31-41%. The chelating ability of N-alkyl chitosans is specific for certain cations such as Cu 2+, Hg 2+ and Pb 2+ for which the capacities are in the range 2-6% by weight, depending on conditions and choice of N-alkyl chitosan. In the N-alkyl chitosans, the hydrogen bonds are weakened by the presence of substituents and therefore they swell in water. Membranes are easily cast from acetic acid solutions. Circular dichroism and ultraviolet spectrometry measurements indicate that the chelation of metal ions depresses the acetamido group bands and introduces new spectral bands due to the chelates. Circular dichroism spectra also reveal the hydration state of the membranes. Applications are foreseen in the pharmaceutical, cosmetic and textile industries