稀土Schiff碱配合物催化烷基异氰酸酯室温聚合

利用Schiff碱稀土配合物Ln（H2Salen）2Cl3·2C2H5OH与AI（i—Bu）3组成的催化体系催化烷基异氰酸酯室温聚合，详细考察了催化剂组成以及聚合条件等对烷基异氰酸酯聚合的影响，并研究了己基异氰酸酯的聚合动力学．以La、Nd、Sm和Gd四种稀土元素为代表，合成了相应的Schiff碱配合物，结果表明轻稀土体系比重稀土体系好，La的聚合活性最高．在-40℃-40℃很宽的聚合温度范围内，可以得到分子量分布窄（MWD=1．50～2．40）的高分子量聚异氰酸酯，20℃为最佳的聚合温度．己基异氰酸酯的最佳聚合条件为：AI]／La]=30（摩尔比），n-HexNCO]／La]=100，n—HexNCO]=3．43mol／L，甲苯溶液中20℃聚合12h，聚合物收率74．0％，聚合物黏均分子量高达73．5×10^4，数均分子量40．2×10^4，MWD=1．79．聚合动力学研究表明己基异氰酸酯聚合反应对单体浓度和催化剂浓度都是一级关系，聚合反应活化能为43．64kJ／mol．

Room temperature polymerization of alkyl-isocyanates catalyzed by rare earth Schiff base complexes

The polymerization of alkyl isocyanates catalyzed by rare earth chloride salen complexes/triisobutyl aluminum （Ln（H2salen）zCl3·2C2HTOH/Al（i-Bu）3） at room temperature was investigated. The influences of ligand structure, catalyst composition, polymerization temperature, polymerization time, the concentration of catalyst and monomer, and the polymerization solvent on the polymerization of isocyanates were studied. It was found that under the polymerization conditions examined La（H2salenA）2C13·2C2H7OH/AI（i-Bu）3 （H2salenA= N,N＇-disalicylideneethylene diamine） is a fairly high efficient catalyst for the polymerization of n-hexyl isocyanate （n-HexNCO） preparing high molecular weight poly（n-hexyl isocyanate） （PHNCO） with narrower molecular weight distribution at room temperature. PHNCO could be prepared with yield of 74.0%, number-average molecular weight （Mn） of 40.20×10^4 and MWD of 1.79 under the following optimum conditions： Al]/La]=30（molar ratio）, n-HexNCO]/La]=100（molar ratio）, n-HexNCO]=3.43mol/L polymerization at 20℃ for 12 h in toluene. In the same polymerization conditions, poly （n-octyl isocyanate） （PONCO） with yield of 67.3%, and poly （n-butyl isocyanate） （PBNCO） with yield of 45.5% could be prepared respectively. The kinetics of the polymerization of n-HexNCO was also investigated and found to be first-order with respect to both monomer and catalyst concentrations.