在微波辅助下,以辛酸亚锡为催化剂、壳聚糖(CS)为大分子引发剂引发消旋丙交酯(D,L-LA)本体开环聚合制备了壳聚糖接枝聚乳酸共聚物. 通过正交试验确定了最佳合成条件:微波功率10 W,反应温度120 ℃,反应时间15 min,催化剂用量:n(丙交酯):n(辛酸亚锡)=1 000:1. 通过红外光谱、元素分析、核磁共振氢谱、X射线衍射和热分析测试技术对接枝共聚物的结构与性能进行了表征和测试. 结果表明,在微波条件下,能快速、有效地合成壳聚糖接枝聚乳酸共聚物,单位糖环上聚乳酸支链的平均乳酰单元数大于17.46;聚乳酸支链的引入有效削弱了壳聚糖分子间和分子内较强的氢键作用,与壳聚糖相比较,共聚物的结晶性能下降,热分解发生在246 ℃,低于壳聚糖的253 ℃;随n(D,L-LA)/n(CS糖环数)值增大,共聚物中平均乳酰单元数逐渐增大,共聚物的结晶性能、起始分解温度逐渐下降.
Chitosan-graft-poly(D,L-lactide)(CS-g-PLA) copolymers were obtained by means of microwave-irradiation and graft copolymerization via ring opening polymerization using stannous octoat(Sn(oct)_2) as catalyst without any organic solvent. Through orthogonality experiment the best synthesis conditions were optimized as follows:reaction power 10 W, reaction temperature 120 ℃, reaction time 15 min, the amount of catalyst n(lactide)∶ n(Sn(oct)_2)=1 000∶ 1. The products were characterized by FTIR, ~1H NMR, XRD and DTG. These results show that microwave-assisted ring-opening polymerization can produce a CS-g-PLA copolymer successfully and rapidly. The average degree of polymerization of polylactide branch chains in the graft copolymer was 17.46. Compared with CS, the grafting destroyed the original crystallinity of chitosan, and the onset temperature of degradation and thermal stability of the products descended. The feed ratio n(D,L-LA)/n(aminoglucoside) had a strong influence on the structure and properties of the CS-g-PLA copolymer, and higher feed ratio led to the copolymer with a higher average degree of polymerization of polylactide branch chains, and a lower crystallinity and an onset temperature(246 ℃) of degradation, lower than that of CS of 253 ℃.
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