阻滞阴离子聚合法合成星型聚苯乙烯的动力学研究

Kinetics of Retarded Anionic Polymerization of Styrene to Star-Like Polystyrene

采用阻滞阴离子聚合法,以自制多锂(m-Li)为引发剂、三异丁基铝(TIBA)为阻滞剂、环己烷为溶剂,合成了一系列星型聚苯乙烯。考察了不同聚合条件下苯乙烯的聚合动力学行为,并求出相应的假一级表观增长速率常数和表观增长反应活化能(E″);考察了阻滞剂用量对聚苯乙烯相对分子质量及其分布的影响。实验结果表明,不同聚合条件下苯乙烯的聚合反应为一级反应;在一定聚合温度下,随n(TIBA):n(m-Li)的增大,苯乙烯聚合速率显著降低,当n(TIBA):n(m-Li)≥1时,聚合被完全阻滞;降低聚合温度亦能降低聚合反应速率,但n(TIBA):n(m-Li)的变化对聚合速率的影响更明显;随n(TIBA)∶n(m-Li)的增大,E″增大,聚苯乙烯相对分子质量分布加宽。

A series of star-like polystyrenes were synthesized through retarded anionic polymerization with self-made multi-lithium （m-Li） as initiator, i-Bu3Al （TIBA） as retarder and cyclohexane as solvent. Kinetics of the styrene polymerization was studied. The pseudo first order apparent propagation rate constants and the apparent propagation activation energies （E＂） were obtained by calculation. Influences of TIBA dosage on the polystyrene relative molecular mass and its distribution were investigated. The results showed that the kinetics curve was first order and linear under different polymerization conditions. At a certain polymerization temperature, the polymerization rate dropped with increase of n（TIBA） ： n（m-Li） significantly; when n（TIBA） ： n（m-Li） was more than 1, the polymerization completely stopped. Lowering the polymerization temperature could also reduce the polymerization rate, but the influence of n（TIBA） ： n（m-Li） on the polymerization rate is more obvious. With increase of n （TIBA） ： n （ m-Li）, E＂ rose gradually and relative molecular mass distribution of the synthesized polystyrene widened little by little.