三异丁基铝阻滞苯乙烯负离子聚合动力学

Kinetics of retarded styrene anionic polymerization by triisobutylaluminum

以环己烷为溶剂、三异丁基铝为阻滞剂、丁基锂为引发剂,研究了三异丁基铝与丁基锂摩尔比[n(Al)/n(Li)]和聚合温度对苯乙烯阻滞负离子聚合反应速率和动力学的影响规律,对相应的假一级表观增长速率常数进行了求解。结果表明,采用三异丁基铝/丁基锂体系引发苯乙烯阻滞负离子聚合,在苯乙烯转化率较低(小于60%)时,苯乙烯聚合速率对单体浓度为一级动力学关系;随着n(Al)/n(Li)的增大,苯乙烯聚合速率下降;n(Al)/n(Li)越接近1,阻滞效果越明显。聚合温度对三异丁基铝/丁基锂体系引发苯乙烯阻滞负离子聚合速率有显著影响,随着温度升高,聚合速率上升,阻滞效果变差;温度每升高10℃,苯乙烯聚合速率增大约1倍。聚合温度和n(Al)/n(Li)存在叠加影响,而前者对不同n(Al)/n(Li)引发体系的影响程度存在差异;聚合温度较低时,其变化对聚合速率影响更大。

The influences of molar ratio of triisobutyl aluminum to butyllithium[n(Al)/n(Li)]and polymerization temperature on the reaction rate and kinetics of retarded styrene anionic polymerization were studied with cyclohexane as solvent,triisobutylaluminum as retarder and butyllithium as initiator.The pseudo first order apparent propagation rate constant was calculated.The results showed that retarded styrene anionic polymerization initiated by triisobutyl aluminum and butyllithium was first order kinetics with respect to monomer concentration when conversion of styrene was relatively low(less than 60%).The styrene polymerization rate decreased with increase of n(Al)/n(Li).The closer n(Al)/n(Li)was to 1,the more ob-vious the retardation effect was.The polymerization temperature had a significant effect on the polymerization rate of retarded styrene anionic polymerization in the presence of triisobutylaluminum and butyllithium.The retardation effect became worse with increase of temperature and polymerization rate.The styrene polymerization rate doubled with every 10℃increase of temperature.The polymerization temperature and n(Al)/n(Li)had superposition effects on the styrene polymerization rate initiated by triisobutylaluminum and butyllithium.The effects of polymerization temperature on the retarded styrene anionic polymerization distinguished from one another with different n(Al)/n(Li),its change had a greater effect on the polymerization rate when the polymerization temperature was lower.