两步加碱法制备N,O-羧甲基壳聚糖—反应条件对取代度的影响

Preparation of N,O-Carboxymethyl Chitosan by the Approach of Two-step Alkalization—Reaction Conditions Influencing the Degree of Substitution

利用两步加碱法制备羧甲基壳聚糖,并采用等电点沉降法对其精制。结果表明,在m(壳聚糖)∶m(氯乙酸)∶m(氢氧化钠)=1∶4 8∶4 8,反应时间6h,温度60℃,异丙醇用量50mL,水用量22mL的较适宜反应条件下,制得的羧甲基壳聚糖取代度高达1 7,与传统方法制得的产物取代度最大1 1相比,有较大幅度的提高。同时,对影响产物取代度因素的研究表明:碱量、氯乙酸用量和反应温度是影响产物取代度的关键因素;产物取代度随碱量的增加而增加,随氯乙酸用量和反应温度的提高,呈现先增后减的规律。最后,对产物进行的红外光谱分析表明,产物为N,O 羧甲基壳聚糖,且主要是氧位取代。

Carboxymethyl chitosan (CMC) was prepared by a two-step alkalization and refined by deposition at isoelectric point.The results showed that the degree of substitution (DS) of CMC prepared under the reaction conditions,such as m(chitosan)∶m(monochloroacetic acid)∶m(alkali)=(1∶4.8∶4.8),reaction time 6 h,temperature 60 ℃,isopropyl alcohol 50 mL and water 22 mL,reached as high as 1.7,indicating a drastic increase in the DS values in comparison with that (<1.1) of CMC prepared by the conventional methods.Investigation of the factors influencing the DS indicated that the amounts of alkali and chloroacetic acid and the reaction temperature were the key factors influencing the DS.The DS increased with the increase in the amount of alkali,while increased at first and then decreased with increasing amount of monochloroacetic acid and rise in temperature.The IR spectra of CMC showed that the product was N,O-CMC and the carboxymethylation mainly occurred on the oxygen position.