A novel method for obtaining a quaternary salt of chitosan

A novel method for obtaining N,N,N-trimethylchitosan has been developed using dimethylsulfate as the methylant agent. Dimethylsulfate is not only more efficient but is less expensive than other commonly used agents. The resultant chitosan derivatives were characterized by FTIR, 1H NMR, CP-MAS 13C NMR, and a capillary viscometer. Films were processed by casting and then hydrophilic changes were assessed by water contact angle measurements. The highest degree of substitution (DQ¯=52.5%) was obtained after a 6 h long-term reaction at room temperature. The use of higher temperatures helped to provoke polymeric thermal degradation and favor O-methylation over a N-methylation reaction.