从聚合物分子量评价自由基聚合的链终止反应

EVALUATION OF CHAIN TERMINATION IN RADICAL POLYMERIZATION BASED ON THE MOLECULAR WEIGHTS OF POLYMERS

本文从聚合物的聚合度与反应速度关系论述了自由基聚合过程中链终止方式,并由此估价自由基聚合机理。令各反应物起始浓度比例固定并同步改变,于是各链转移速度与链增长速度之比(R_(tr)/R_p)_i为常,由此得直线方程: 1/_n=R_t/R_p+K 在稳态条件下,链终止方式可从下述各直线方程估价。双基终止 1/_n=k_t/K_p^2·R_p/(c^2(M))+K 单基终止 1/_n=k_(t)/k_p·1/(c(M))+K 初级自由基终止 1/_n=k_(prt)/k_p·c(R·)/c(M)+K 转移终止 1/_n=K 苦双基终止、单基终止和初级自由基终止反应同时并存,则 1/_n=k_t/k_p^2·R_p/(c^2(M))+k_t/k_p·1/(c(M))+fk_d k_(prt)/k_i·k_p·c(I)/(c^2(M))+K 本实验设计和数据处理方法用以研究自由基聚合的链终止过程,与实验结果和动力学推导十分一政。

This paper deals with the chain termination in radical polymerization based on the relation between the degree of polymerization and the rate of reactions. Let the initial concentrations of all the reactants to vary on a fixed proportion in a series of polymerization runs, than the ratio of the transfer rate to the propagation rate of the growing radicals (R_(tr)/R_p)will be a constant. As a result, a linear equation 1/_n=R_t/R_p+K was obtained. If it is assumed that the steady state conditions are applicable, the termination reaction may be estimated according to the following equations: (1) Termination by bimolecular reaction: 1/_n=k_t/k^2_P·R_p/(c^2(M))+K (2) Termination by single—radical process 1/_n=k_1/k_p·1/(c(M))+k (3) Termination by combination with primary radical 1/_n=k_(prt)/k_p·c(R·)/c(M)+K=fk_d/K_t·k_(prt)/K_p·c(I)/(c^2(M))+K (4) Termination by transfer 1/_n=K If the growing chains are terminated simutaneously by bimolecular reaction, unimolecular process, and combination with a primary radical, we obtained. 1/_n=k_t/(k^2_p)·R_p/(c^2(M))+k_t/k_p·1/(c(M))+fk_d k_(prt)/(k_i·k_p)·c(I)/(c^2(M))+K The method of the experimental design and the data treament proposed by us to estimate the mechanism of chain termination was found to be fine agree with the results obtained by experiments and derivated from the polymerization kinetics.