Synthesis and Characterization of Chitosan <i>N</i>-Betainates Having Various Degrees of Substitution

Abstract

An efficient five-step synthetic route was developed for full N-substitution of chitosan with a quaternary betaine moiety. The developed synthetic procedure can also be controlled to produce chitosan N-betainates having lesser degrees of substitution. 6-O-Triphenylmethylchitosan, which is highly soluble in organic solvents, was used as an intermediate for N-acylation reactions. Intermediate products were characterized by 13C CP/MAS NMR, FT-IR, and elemental analysis. The water-soluble quaternary chitosan N-betainates were thoroughly characterized by 1H NMR and 13C NMR and by 2D 1H−1H COSY NMR and 13H−1H HSQC NMR. Degrees of substitution were determined from the 1H NMR spectra. A significant degradation of the polysaccharide backbone during the synthetic procedure was determined by GPC with a light scattering detector.