淀粉乙酸酯的阴离子接枝己内酯聚合研究

STUDY ON THE ANIONIC GRAFT POLYMERIZATION OF ε-CAPROLACTONE ONTO STARCH ACETATE

将淀粉在二甲基甲酰胺、吡啶存在下 ,以乙酸酐进行部分乙酰化 ,制备取代度为 0 7～ 1 9的淀粉乙酸酯 (St Ac) .以萘钠与淀粉乙酸酯中残余的羟基反应 ,将羟基转化为醇盐 (ONa) ,引发己内酯进行阴离子开环接枝聚合 ,合成了淀粉 聚己内酯接枝共聚物 (St g PCL) .采用凝胶渗透色谱法 (GPC)研究了接枝前后聚合物分子量的变化情况 ,并以接枝率、单体转化率对接枝反应进行了表征 .研究了接枝条件如温度、溶剂、引发剂和单体的用量对接枝率及单体转化率的影响 .研究发现随着反应温度升高 ,接枝率、单体转化率呈S曲线变化 ,单体浓度、引发剂浓度的增大有利于接枝反应的进行 .

Starch was partially acetylated by acetic anhydride in the presence of pyridine and N,N dimethylformide (DMF), which was used as an activator, and starch acetate (St Ac) with substituting degree ( DS ) about 0 7～1 9 was obtained. The effect of the solvating time by DMF and quantity of acetic anhydride on DS was studied. Graft polymerization of ε caprolactone ( ε CL) onto starch acetate was carried out through anionic ring opening polymerization of ε CL in diethylene glycol dimethyl ether solution. The graft polymerization was initiated by ONa groups which were formed through the reaction of the remained OH groups in St Ac with naphthalene sodium (NS). The grafting reaction was characterized by grafting percentage, monomer conversion, as well as gel permeation chromatography (GPC) through comparison of the M n, M w and M w/ M n of St Ac with that of the grafted copolymer, starch grafted polycaprolactone (St g PCL). The influence of the reaction temperature, monomer and NS concentrations on the grafting percentage and the monomer conversion was discussed. The results showed that the grafting percentage and the monomer conversion vary in a way of S curves as grafting temperature increased from 50℃ to 150℃, but increase with the increasing of the monomer concentration and NS concentration.