超高分子量聚苯乙烯的合成和聚合反应动力学

THE SYNTHESIS OF ULTRA-HIGH MOLECULAR WEIGHT POLYSTYRENE AND POLYMERIZATION KINETICS

杯芳烃钕与Mg(n Bu) 2 、HMPA所组成的三元络合催化剂用于苯乙烯配位聚合能以高收率制得超高分子量聚苯乙烯 .以甲苯为溶剂 ,在一定条件下制成三元配位催化剂 ,当 [Nd]=8× 10 - 4mol L ,[St]=4 .0mol L ,Mg Nd =2 0 .0 (摩尔比 ) ,HMPA Mg =1.0 (摩尔比 ) ,5 0℃聚合 4 5min ,聚合转化率可达到 80 %左右 .所得聚苯乙烯的重均分子量高达 2 10× 10 4 ,分子量分布指数为 1.6 1.间规聚苯乙烯含量为 81% .动力学研究表明 ,聚合反应速率与单体和主催化剂 杯 [6 ]芳烃钕的浓度分别呈 1次方关系 ,聚合反应的表观活化能为 4 1.7kJ

Calix[n]Nd/MgBu2n/HMPA is an effective catalytic system for the synthesis of the ultra-high molecular weight polystyrene (UHMWPS) The catalytic activity of different Calix[n]Nd complex decreases in the following order: Calix[6]Nd > Calix[4]Nd > Calix[8]Nd. It shows that the aging of catalyst plays an important role on catalytic activity. The optimum conditions are as follow: Mg/Nd = 20.0 (molar ratio), HMPA/Mg = 1.0 (molar ratio) and aged 2.5 h under 50degreesC. The study of influence of solvent shows that toluene is a good solvent. The polymerization result shows that the conversion is over 80% at 50degreesC, 45 min. The kinetics of styrene polymerization using Calix[6]Nd-20MgBu(2)(n)-20HMPA in toluene were investigated by weight method. It was found that the rate of polymerization is first order with respect to both monomer (St) and Calix[6]Nd concentrations. According to Arrhenius equation, it was found that polymerization activation energy is 41.7 kJ/mol. GPC characterization of obtained polymer shows: M-w = 21.0 x 10(5), MWD = 1.61. H-1-NMR spectra of UHMWPS shows that the content of syndiotactic triad is 81%.