Anionic polymerization of butyl cyanoacrylate by tetrabutylammonium salts, 2. Propagation rate constants

Anionic polymerizations of butyl cyanoacrylate were initiated in tetrahydrofuran (plus a few experiments in 1,2-dimethoxyethane) by the salts tetrabutylammonium hydroxide, bromide, acetate and three substituted acetates. The hydroxide gives near-ideal ‘living polymerization’ kinetics, with k_p close to 10⁶l·mol^?1. s^?1 at 20°C. The kinetics of the reactions initiated by the acetates and bromide are analysed by the slow-initiation-no-termination theory, using values of the initiation rate constants evaluated in Part 1. The k_p values derived are in the same range as those from the OH-initiated reactions and those of the zwitterionic polymerizations initiated with covalent bases, i.e., tertiary phosphines and amines. A ca. 4-fold variation of k_p with concentration of active species is given a speculative analysis in terms of dissociation from paired to free ions, yielding tentative estimates for k ≈ 10⁵ and k ≈ 10⁷l·mol^?1·s^?1 in THF at 20°C. Molecular weights were all high M _n ≈ 10⁶, with M _w/M _n ≈ 2.