Anionic polymerization of vinyl monomers with condensed aromatic hydrocarbon anions

Abstract

AbstractThe order of catalytic activity of condensed aromatic hydrocarbon radical anions toward polymerization of acrylonitrile, styrene, and isopren is: naphthalene > anthracene > naphthacene > pentacene.Based on the concept that vinylpolymerization with the hydrocarbon radical anions is initiated by electron transfer from the anion to the vinylmonomer, this order of catalytic activity was theoretically confirmed by calculating the equilibrium constant K in the equilibrium: R⊖ + M ⇌ R + M⊖ (R: hydrocarbon; M: vinylmonomer), where K was evaluated from the half‐wave reduction potential of R and M. The same order was also estimated by the lowest vacant orbital energies corresponding to the electron affinities of R and M.From the apparent number of anions consumed per polymer molecule it was inferred that the smaller the equilibrium constant K with respect to the vinylmonomer, the smaller is the proportion of anions participating in the initiation of polymerization. The devious results with acrylonitrile can be explained by the mechanisms of anionic chain end stabilization suggested by some authors.