正丁基锂-丁二烯-苯阴离子聚合体系的动力学研究

以苯为溶剂,正丁基锂为引发剂,在充氮条件下,利用膨胀计进行了丁二烯聚合增长反应动力学研究。结果表明,增长反应速度对单体浓度呈一级关系;对引发剂浓度的反应级数(β)小1,并随聚合反应温度的上升而增加,其关系式为β=0.0285+5.292×10~(-3)t;求得表观反应速率常数的通式为k_(1.4)=6.898×10~(15)·e~(-24280/rRt),生成1,4和1,2-结构的表观分速率常数通式分别为k_(1.4)=3.565×10~(15)·e~(-23830/RT)和k_(1.2)2=2.083×10~(16)·e~(-26460/RT);此外,根据解离平衡常数K和温度t的关系,求得上述体系的解缔热△H=26.09kJ/mol,从而计算出真实活化能E=75.52kJ/mol;在苯溶剂中丁二烯聚合的1,2-结构含量,即B.与温度的关系式为:B_v=8.692+0.0223t。

Kinetics of Anionic Polymerization of n-BuLi-Butadiene-Benzene System

The kinetics of anionic polymerization of butadiene initiated by n-BuLi in benzene solvent was investigated. The propagation reaction rate is found to be of first order with respect to monomer concentration with an apparent activation energy of 101.6kJ/mol and a frequency factor of 6.898×10~(15)(l·mol~(-1))~β·min~(-1). However, the propagation rate order of butadiene polymerization relative to the concentration of active species is less than 1, and the values increase with increasing temperature. According to the butadiene polymerization mechanism proposed by us, the apparent activation energy of corresponding reaction rate constants to form 1,4- and 1,2-structures can be obtained, i.e. E'=99.70kJ/mol, A'_(1,4)=3.565×10~(15)(l·mol(-1))~β· min~(-1); E'_(1,2)=110.7kJ/mol, A'_(1,2)=2.083×10~(16)(l·mol~(-1))~β·min~(-1). Based on the equilibrium constant of dimer and monomeric species and the experimentally determined propagation rate order, the dissociation energy, △H=6.09kJ/mol, can be calculated; then the real activation energy(E=E'-△H=75.52kJ/mol) is obtained. Besides, the relationship between vinyl content of polybutadiene and reaction temperature in benzene solvent is established as B_V=8.962+0.0223t.