H_2O/TiCl_4/Py体系引发苯乙烯正离子聚合  

CARBOCATIONIC POLYMERIZATION OF STYRENE BY H_2O/TiCl_4/Py INITIATING SYSTEM

作　　者：冉奋[1] 吴一弦[1] 邱迎昕[1] 黄丽[1] 武冠英[1] 

机构地区：[1]北京化工大学化工资源有效利用国家重点实验室,北京100029

出　　处：《高分子学报》2006年第3期391-396,共6页Acta Polymerica Sinica

基　　金：国家自然科学基金(基金号20474006)资助项目

摘　　要：研究了在少量吡啶(Py)存在下由水(H2O)四氯化钛(TiCl4)体系引发苯乙烯于二氯甲烷正己烷中进行碳正离子聚合,分别考察[Py]、[H2O]和[TiCl4]对聚合速率、产物分子量与分子量分布的影响.实验结果表明,少量亲核试剂吡啶(Py)对聚合反应起着重要作用,可有效地降低聚合速率和使分子量分布变窄;随着[H2O]和[Py]降低或[TiCl4]增加,聚合产物的分子量增加,而分子量分布指数(Mw Mn)基本维持在1.8左右;随着[Py]增加,聚合速率降低;随着[H2O]和[TiCl4]增加,聚合速率提高.聚合速率对单体浓度呈一级动力学关系,对Py、H2O和TiCl4的反应级数分别为-0.72、0.72和1.86.聚合速率对TiCl4浓度呈接近二级动力学关系,这可能与体系中TiCl4主要以二聚体形式存在有关.聚合转化率和产物分子量均随着反应时间延长而逐渐增大,PS的数均分子量与转化率呈线性增加关系.The carbocationic polymerization of styrene （St） initiated by using H2 O/TiCl4 was conducted at - 60℃ in dichlommethane （CH2 Cl2）/hexane （n-Hex） （40/60, V/V） in the presence of pyridine （Py） . The effect of Py, H2O and TICl4 concentrations on the polymerization rate, molecular weight and molecular weight distribution （MWD or Mw/Mn ） of polystyrene （PS） were investigated in detail. The results show that a desirable polymerization process with a relatively slow polymerization rate and PS products with relatively narrow molecular weight distribution （MWD,Mw/Mn≈ 1.8） were obtained in the presence of a small amount of Py. The polymerization rate and molecular weight of PS obviously decreased while MWD maintained almost unchanged （Mw/M,≈ 1.8） with the increase of Py concentration.The kinetic order with respect to Py concentration was calculated to be - 0.72 on the basis of first-order dependence of polymerization rate on monomer concentration. The polymerization rate increased, but the molecular weight of PS products decreased with increasing H2O concentration in the polymerization system. The kinetic order with respect to H2O concentration was calculated to be 0.72 on the basis of first-order dependence of polymerization rate on monomer concentration. Both the polymerization rate and the molecular weight of PS products increased greatly with the increase of TICl4 concentration and a near second-order （β = 1.86） dependence on TICl4 concentration was observed, which may he attributed to the dimer formation of TICl4. The experimental results also showed that the monomer conversion as well as the molecular weight of polymer products increased, but MWD almost kept unchanged with the polymerization time. The number-average molecular weight of polymers increased linearly with monomer conversion.

关 键 词：正离子聚合 动力学 苯乙烯 聚苯乙烯 

分 类 号：O631.3[理学—高分子化学]