丁基镁阻滞苯乙烯负离子聚合研究

Butyl-magnesium as a retarder for the retarded anionic polymerization of styrene

以环己烷为溶剂,丁基镁为阻滞剂,丁基锂为引发剂,研究了Mg/Li摩尔比和聚合温度对苯乙烯阻滞负离子聚合反应的影响规律。研究结果表明:在较低转化率下,丁基镁/丁基锂体系阻滞苯乙烯聚合反应速率对单体浓度为一级动力学关系。随着Mg/Li摩尔比增加,苯乙烯聚合速率急剧下降,50℃下Mg/Li摩尔比分别为1、2和4,对应的表观聚合速率分别为丁基锂聚合体系的1/30、1/80和1/800;温度对苯乙烯阻滞聚合速率影响显著,温度升高,阻滞效果下降。Mg/Li摩尔比为1,聚合温度为80℃,其表观聚合速率是50℃的5倍;以丁基镁/丁基锂为引发体系的苯乙烯聚合反应中,随着苯乙烯转化率上升,聚合物数均分子量定量线性增加,表明该聚合反应为活性聚合。

The influences of Mg/Li molar ratio and polymerization temperature on the retarded anionic polymerization were studied with cyclohexane as solvent,butyl-magnesium as retarder and butyl-lithium as initiator.The result shows that the polymerization rate of styrene initiated by butyl-magnesium and butyl-lithium is first-order kinetics with monomer concentration when the conversion of styrene is relatively low.The polymerization rate of styrene decreases dramatically with the increase of Mg/Li molar ratio.The apparent polymerization rate of styrene at 50℃initiated by butyl-magnesium and butyl-lithium is 1/30,1/80 and 1/800 compared with styrene initiated by butyl-lithium while the Mg/Li molar ratio is 1,2 and 4 respectively.The polymerization temperature has a significant effect on the polymerization rate of retarded anionic polymerization initiated by butyl-magnesium and butyl-lithium.The retardation effect becomes worse with the increase of temperature and polymerization rate.The apparent polymerization rate at 80℃is 5 times higher than that of 50℃when the Mg/Li molar ratio is 1.The average molecular weight of the polymer increases linearly and quantitatively with the increase of styrene conversion in the process of retarded anionic polymerization initiated by butyl-magnesium and butyl-lithium,indicating that the polymerization is living polymerization.