壳聚糖金属配位控制氧化降解及反应动力学研究——(Ⅰ)壳聚糖金属配位控制氧化降解

METAL-COORDINATING CONTROLLED OXIDATIVE DEGRADATION OF CHITOSAN AND DYNAMICS INVESTIGATION ——(Ⅰ) INVESTIGATION OF METAL-COORDINATION CONTROLLED OXIDATIVE DEGRADATION OF CHITOSAN

将壳聚糖首先转化为壳聚糖金属(Cu()、Mn()、Co()、Zn())配合物,再以H2O2对壳聚糖金属配合物进行氧化降解制取低聚壳聚糖。降解过程中黏度的变化及降解产物分子量分布表明,金属盐种类对反应影响存在以下趋势:Cu2+>Co2+>Mn2+>Zn2+,且随氧化剂用量增加、反应温度升高、pH值升高、O2含量降低,壳聚糖降解速度均会相应增加;产物分子量分布表明在相同降解条件下,壳聚糖配合物的降解速度明显高于壳聚糖,且所得降解产物分子量分布较壳聚糖直接降解窄。脱金属处理后的降解产物不含金属离子。

A new method for chitosan degradation called metal-coordinating controlled degradation was suggested in this paper. Transitional metal ion (Cu(Ⅱ), Mn(Ⅱ), Co(Ⅱ) and Zn(Ⅱ)) was added to chitosan′s acetic acid solution to obtain chitosan-metal complex, and H_2O_2 was used to cut chitosan chain to get low molecular weight chitosan with narrow molecular weight distribution(MWD). Viscosity and molecular weight distribution of degraded products expressed effect of metal type on the degradative speed is as follow: Cu^(2+)>Co^(2+)>Mn^(2+)>Zn^(2+). And with oxidant amount, temperature and pH increasing, O_2 content decreasing, degradative speed of chitosan increases. MWD of degraded chitosan shows with same conditions, degradative velocity of complexes is faster than that of chitosan, and the MWD of the former is much more narrow than that of the latter.