双官能度引发剂引发苯乙烯聚合微观动力学

采用 2 ,5 二甲基 2 ,5 二己酰基过氧化己烷 (DMDEHPH)为引发剂 ,在 5 5～ 80℃下引发苯乙烯聚合 .通过研究影响聚合速率的各种因素 ,得出了聚合速率对单体浓度和引发剂浓度的级数分别为 1 0和 0 5次、聚合活化能为 92 0kJ mol、引发效率为 0 5 5± 0 0 3.温度一定 ,引发效率随引发剂浓度的增加而减小 .求得 6 0和70℃下DMDEHPH向引发剂的链转移常数分别为 0 0 37和 0 0 4 8、向单体的链转移常数分别为 0 5 9× 10 - 4和0 75× 10 - 4.

KINETICS OF STYRENE POLYMERIZATION INITIATED BY DIFUNCTIONAL INITIATOR

Compared with the conventional monofunctional initiators,the multifunctional initiators can increase the polymerization rate and polymer molecular weight simultaneously.As a novel initiator,the decomposition rate constant,initiator efficiency and chain transfer constant to the initiator are its basic parameters.However,these basic parameters have rarely been determined,and the mechanism and the kinetics have not been studied.In the present paper,a new kind radical initiator,2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane (DMDEHPH),has been utilized to initiate styrene polymerization in the temperature range of 55～80℃ and DMDEHPH concentration range of 0.01～0.10 mol/L.The effects of initiator concentration,monomer concentration and reaction temperature on the polymerization rate were investigated in details.The increase of monomer concentration,initiator concentration and reaction temperature all can increase the polymerization rate.The relationship of polymerization rate and the corresponding concentration shows that the orders of polymerization rate to active group of initiator concentration and monomer concentration are 0.5 and 1.0,respectively,which validates the correctness of kinetic model presented from the mechanism of polymerization.The activity energy obtained from the polymerization rate constants at various temperatures is 92.0 kJ/mol.The initiator efficiency is in the range of 0.55±0.03 under the experiment conditions, and the initiator efficiency decreases with the increase of initiator concentration.Considering the decomposition degree of O—O bonds during the polymerization,the chain transfer constants to DMDEHPH and monomer are 0.037 and 0.59×10~(-4) at 60℃,and 0.048 and 0.75×10~(-4) at 70℃,respectively.