对用马来酸酐在N,N-二甲基甲酰胺溶剂中酰化壳聚糖的反应条件作了改进,选择反应温度为90 ℃,反应时间为9 h,对所得马来酰化壳聚糖进行红外光谱分析和热分析。从其红外光谱图可见,马来酸酐的两个共轭羰基的吸收峰已消失,而在1 714.7 cm-1处可见不饱和羧酸的羰基C=O伸缩振动峰,在1 650.3 cm-1处可见由酰胺键的羰基C=O和共轭烯烃的C=C双键叠加的吸收峰,由此说明马来酸酐与壳聚糖发生酰化反应生成了马来酰化壳聚糖。红外光谱分析结果表明:壳聚糖与马来酸酐两者的物质的量之比为1比1.8时酰化度最高。由热重分析的结果可知:马来酰化壳聚糖的热稳定性比壳聚糖差,推断其原因是由于在多聚糖结构中引入了C=O,C=C及-OH等取代基后破坏了壳聚糖的晶体结构所致。

Conditions for acylation of chitosan (CTS) with maleic anhydride in DMF to give maleoyl chitasan (MLCTS) were improved, and the temperature and time of 90 ℃ and 9 h were chosen respectively for the reaction. The reaction product of MLCTS was studied by IRS and TG. It was shown in the IR spectrum that 2 absorption peaks of the conjugated crabonyl groups of maleic anhydride were disappeared, while stretching vibrational peak due to the C=O group of unsaturated carboxylic acid at 1 714.7 cm-1, and absorption peak due to duplicating of C=O of acetamido group and C=C of conjugated alkene at 1 650.3 cm-1 were observed. On the base of these facts, it was deduced that acylation of CTS by maleic anhydride was set giving the acylate MLCTS. It was shown by the results of IRS study, optimum acylation was attained by keeping the ratio of amount of substances (n) of CTS and maleic anhydride at 1 to 1.8. It was found by the results of TG analysis, that the thermostability of MLCTS was lower that CTS, which was deduced as a result of destruction of its crystalline structure due to introduction of C=O, C=C and OH groups into the CTS molecule.