稀土化合物催化内酯开环聚合　Ⅱ．异丙氧基稀土催化D．L－丙交酯开环聚合

RING-OPENING POLYMERIZATION OF LACTONE BY RARE EARTH COMPOUNDS Ⅱ. SYNTHESIS OF POLY(D. L-LACTIDE) CATALYZED WITH RARE EARTH ISOPROPOXIDES

系统地研究了异丙氧基稀土催化Ｄ．Ｌ－两交酯（ＬＡ）开环聚合的规律．实验表明：在甲苯溶剂中，异丙氧基稀土对Ｄ．Ｌ－丙交酯聚合有较高的催化活性，可获得较高的分子量（Ｍη＝４．０×１０４）不同稀土元素的活性次序如下：Ｌａ＞Ｎｄ＞Ｄｙ＞Ｙ．异丙氧基稀土催化Ｄ·Ｌ－两支酯聚合的合适条件为：［ＬＡ］＝１．９５ｍｏｌ／ｌ，［Ｌｎ（Ｏ－ｉ－Ｐｒ）３］＝６．５×１０－３ｍｏｌ／ｌ，甲苯，９０℃，聚合反应速度与单体和催化剂浓度均成一级关系，聚合反应表现活化能为着６７．７ｋＪ／ｍｏｌ．

Ring-opening polymerization of D. L-lactide (D.L-LA) have been successfully carried out by using rare earth isopropoxides as catalyst for the first time.The effects of different rare earth isopropoxides different solvents LA/Ln molar ratio time and polymerization temperature on the polymerization reaction were investigated. It was found that the catalytic activity of different rare earth isopropoxides is as follows: La> M>Nd>Dy>Y, and the optium conditions of the ring-opening polymerization of D. L--LA were: [LA]: 1.95mol/l, [Ln(Oipr)3]:6.5 × 10-3mol/l,90℃, toluene. A kinetic study has shown that the polymerization is firstorder in both monomer and catalyst. The apparent activation energy of the polymerization of D.L--LA with La(Oipr)3 is 67.7KJ/mol.