Studies on chitin-based liquid crystalline polymers - V. Integrated influence of number and length of substituent on hydroxyethyl chitosan
- 化学化工－已发表论文 
A novel liquid crystalline polymer-hydroxyethyl chitosan(HECS) was synthesized in alkali system. The degree of molar etherification(DME) of HECS was controlled by both the amounts of ethylene oxide and the reaction time. DME of HECS specimens was from 0.2 to 5.4 measured by element analysis and NMR. All specimens formed typical cholesteric texture-fingerprint texture while dissolved in formic acid. HECS with DME >1.9 was water soluble, and the HECS aqueous solution also formed cholesteric phase with typical texture. The mesophase texture was detected both by polarized optical microscopy and scanning electron microscopy. Samples for SEM studies were treated by permanganic etching in order to increase the contrast. The studies were focused on the effect of DME on the critical concentration (c*) of mesophase formation for HECS/formic acid solutions. The results indicated that c* sharply increased with DME at first, and became independent as DME varied from 0.2 to 1.9. After that (DME>1.9), it regain obvious rise as DME continuously heightened. These results were explained by the variation of both persistence length q and molecular diameter d in Flory's semi-experience equation c* approximate to 8 q/x (x = 2q/d). The variation of DME of HECS related with two structural factors, i.e. the number and length of the substituent, the former affected c* slightly, but the latter affected c* evidently.