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在超临界二氧化碳流体中用辛酸亚锡作催化剂,用左旋丙交酯开环聚合成功地合成了相对分子质量大于80000,分散指数为2.5的聚左旋乳酸。深入研究了聚合温度、时间、压力、单体浓度、催化剂用量及超临界二氧化碳纯度等各种因素对聚左旋乳酸相对分子质量及其分布的影响,对聚合物的相对分子质量和分布采用凝胶渗析色谱、1HNMR谱、13CNMR谱、红外光谱和差式扫描量热器等进行表征。结果表明:聚合温度、单体对催化剂的浓度比和超临界二氧化碳纯度是关键因素,最佳聚合条件为温度85～90℃,c(LA)/c(SnOct2)为500～1000,聚合时间48h;辛酸亚锡是高效催化剂,但催化效率随影响因素而变;超临界二氧化碳流体中的聚合机理为配位插入聚合。
In the supercritical carbon dioxide fluid with stannous octoate as a catalyst, L-lactide ring-opening polymerization was successfully synthesized with a relative molecular mass of more than 80,000, a dispersion index of 2.5 Poly-L-lactic acid. The influences of various factors such as polymerization temperature, time, pressure, monomer concentration, catalyst dosage and supercritical carbon dioxide purity on the relative molecular mass and distribution of poly-L-lactic acid were studied in detail. The relative molecular mass and distribution of polymer Dialysis chromatography, 1HNMR spectroscopy, 13CNMR spectroscopy, infrared spectroscopy and differential scanning calorimetry. The results showed that the polymerization temperature, the concentration of monomer to catalyst and the purity of supercritical carbon dioxide were the key factors. The optimum polymerization conditions were temperature 85-90 ℃, cO (LA) / c (SnOct2) 500-1000 and polymerization time 48h ; Stannous octoate is an efficient catalyst, but the catalytic efficiency changes with the influencing factors; and the polymerization mechanism in supercritical carbon dioxide fluid is coordination insertion polymerization.