Influence of degree of molar etherification on critical liquid crystal behavior of hydroxypropyl chitosan

Hydroxypropyl chitosan (HPCS) with different degree of molar etherification (DME, from 0.6 to 6.0) were synthesized and characterized by FTIR, (1)H-NMR and elemental analysis. The effect of DME on critical concentration forming lyotropic liquid crystal(C*) was investigated in three solvents (formic acid, dichloroacetic acid and water). C* increased as DME raised but presented a platform at low DME (less than about 2.6), which was explained based on both the amount and the size of flexible substituents. HPCS with DME greater than or equal to 3.2 were water soluble. C* of HPCS aqueous solutions were evidently lower than those of formic acid or dichloroacetic acid solutions. Typical cholesteric texture appeared in HPCS solutions of all three solvents at proper concentrations. (C) 2001 Elsevier Science Ltd. All rights reserved.