Studies on critical behavior of liquid crystalline butyryl chitosan
- 化学化工－已发表论文 
O-butyryl chitosan which was prepared from chitosan demonstrated lyotropic liquid crystalline behavior in various solvents, for example, water, methanol, formic acid, acetic acid, dichloroacetic acid(DCA), trifluoroacetic acid, dimethyl sulfoxide, acrylic acid, m-cresol, foramide, N,N-dimethyl acetamide. The typical fingerprint texture of cholesteric phase can be observed. Critical concentrations of butyryl chitosan in four acidic solvents were determined using polarized microscopy. All critical concentration values(calculated by v/v%) were 16 similar to 17%, independent of the acdity of solvent. This result was similar to that of chitosan. Since the protonation of amine with acid is easy even though the acid is weak, the rigidity of chain(therefore the critical concentration) did not depend on acidity of solvents. Critical temperature of butyrul chitosan/DCA system was measured by DSC. The phase diagram was drawn. Critical temperature reached maximum values of 39 degrees C when concentration was 60% (w/w%). Because butyryl chitosan would degrade in DCA, the enthapy of transition calculated from DSC traces started to decrease at 48h after the solution was prepared. So the best staying time of solution before DSC determination is 48h. The dependence of butyrylation degree on critical concentration was studied. Two butyryl chitosan samples with relatively different degree of butyrylation which was measured by IR had the same critical concentration values in DCA.