N,O-羧甲基壳聚糖的合成和性质研究

采用多段升温法将壳聚糖改性,合成了取代度为1.84、平均分子量为3.08×105、等电点为7.28的N,O-羧甲基壳聚糖(CMC),分别用紫外光谱、红外光谱、荧光光谱对其结构进行了表征,并对其水溶液的Zeta电位、电导率、表面张力以及水分散体系中羧甲基壳聚糖微粒的粒径分布进行了研究.结果表明, N,O-羧甲基壳聚糖具有表面活性;介质的pH值和浓度对羧甲基壳聚糖溶液的稳定性有很大的影响.

Synthesis and Studies on Properties of N,O-Carboxymethylchitosan

N,O-Carboxymethylchitosan(CMC) beginningwith chitosan and chloracetic acid bystepwisely increasingtemperature methodwas synthesized. Carboxymethylation substitutive degree is 1.84, average molecularweight is 3.08×105 and instrinsic viscosity (25±0.5)℃is 180 L/g. Itwas characterized by ultraviolet spectrum, infrared spectrum, fluorescence spectrum. Its ultraviolet characteristic absorption peak is at 206 nm arising fromn→πelectron transition. However, the ultraviolet characteristic absorption peakof chitosan is at195 nm. One of stretchingvibration absorption peak of CMC infrared spectrum is at 1635 cm-1which results from stretching vibration of -C=O(-COOH) bond. But at 1635cm-1there is no stretchingvibration peakof C=O in the chitosan infrared spectrum. In fluorescence spectrum, the excitation wavelength of CMC is 330 nm and its emissionwavelength is 407 nm. The excitationwavelength of Chitosan is 320nm and its emissionwavelength is 391 nm. Synthesized CMC is soluable in the aqueous solution. It is a macromolecular surface-active agent. CMC surface tension linearly decreases with the increasing of CMC concentration in aqueous solution. But its conductivity linearly increases with the increasing of CMC concentration in the aqueous solution. The CMC aggregate behaviors in CMC aqueous solution is also studied, which shows that there is a some degree aggregation in the aqueous solution of synthesized carboxymethylchitosan. Meanwhile, the Zeta potential of CMC aqueous solution is studied. It demonstrates that Zeta potential value decreaseswith the decreasing of the concentration of CMC. The study indicates CMC is an amphoteric macromecleular electrolyte and its isoelectronic point is 7.28. Therefore, the pHvalue and concentration of CMC have great influence on the stability of CMC aqueous solution.