Studies on lyotropic and thermotropic liquid crystalline behavior of cyanoethyl hydroxypropyl chitosan

Cyanoethylhydroxypropyl chitosan was synthesized by hydroxypropylation of chitosan followed by cyanoethylation. The degree of hydroxypropylation and cyanoethylation was 3, 2 and 1. 0 respectively. Both cyanoethylhydroxypropyl chitosan(CNHPCS) and hydroxypropyl chitosan(HPCS) demonstrated lyotropic liquid crystalline behaviors, and fingerprint texture was observed in their concentrated solutions implying the presence of cholesteric phase. The critical concentration of HPCS in DCA(29%) is higher than CNHPCS's(17%), owing to the enhanced chain rigidity contributed by the introduction of cyanoethyl group, In the case of CNHPCS, cholesteric thermotropic mesophase could be observed between its melting point 193 degrees C and decomposition temperature 220 degrees C measured by both DSC and polarized light microscope. SALS was employed to determine the pitch of cholesteric phase in CNHPCS as received film. The results were consistent with those of PLM.