丁酸壳聚糖液晶的临界行为研究

STUDIES ON CRITICAL BEHAVIOR OF LIQUIDCRYSTALLINE BUTYRYL CHITOSAN

用偏光显微镜法测定了丁酸壳聚糖在四种酸性溶剂中的临界浓度值．发现临界浓度值（ｖ／ｖ％）与溶剂的酸性无关，都是１６％～１７％．在以二氯乙酸为溶剂时，不同丁酰化程度的丁酸壳聚糖有相同的临界浓度．用ＤＳＣ法测定了丁酸壳聚糖／二氯乙酸体系的临界温度，并绘制了相图．结果表明，浓度达６０％（ｗ／ｗ％）后，临界温度基本不再变化，稳定在３９℃左右．

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 16～17%,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 butyryl chitosan/DCA system was measured by DSC.The phase diagram was drawn.Critical temperature reached maximum values of 39℃ 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.