Chain transfer to solvent in two-state anionic polymerization, 1. Fast exchange between propagating species

✍ Scribed by Galina I. Litvinenko; Alexander A. Arest-Yakubovich

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 372 KB
• Volume: 4
• Category: Article
• ISSN: 1022-1344
• DOI: 10.1002/mats.1995.040040209

✦ Synopsis

Abstract

A theoretical consideration of molecular weights and molecular weight distribution (MWD) of polymers formed in anionic polymerization proceeding via active centres of two different types under conditions of chain transfer to solvent with a fast exchange between propagating species is presented. Analytical expressions for number‐and weight‐average degrees of polymerization are obtained. Expressions for P~n~ and P~w~ are shown to be the same as in a one‐centre process with the apparent intensity of chain transfer proportional to the weight fraction of the polymer formed via “transferring” centres. The polymers formed possess a moderately wide unimodal MWD. The dependence of the polydispersity index on the effective intensity of chain transfer goes through a maximum; for M~0~/I~0~ = 10^3^ the maximum value of P~w~/P~n~ is ca. 4,6. The method is suggested for the estimation of the relative reactivity in chain propagation of two active centres from the dependence of molecular weight on initiator mixture composition. The effects of association of active centres on the average molecular weights are analyzed. The case when one of the centres is dormant is also considered.