Influence of molecular weight on critical concentration of chitosan/formic acid liquid crystalline solution

Abstract

Chitosan samples with viscosity average molar mass M̄v from 1 × 104 to 58 × 104 were prepared by depolymerization using nitrous acid. In higher molar mass region, critical concentrations to form liquid crystal phase in formic acid corresponded with the predicted values of Flory theory. Significant increase of the critical concentration was observed with decrease of molar mass, especially in the lower molar mass region. The results are qualitatively consistent with the calculated values of Khokhlov-Semenov theory, but deviate from calculated values higher at low molar mass region. This was explained by the inaccuracy of the second Virial approximation basic to this theory at higher concentrations for chains with small persistence length q. A linear relationship between the critical volume fraction V′2 and log M̄v was found for this system.