Polymerisation via macrozwitterions, 1. Ethyl and butyl cyanoacrylates polymerised by triethyl and triphenylphosphines

Anionic polymerisation of ethyl and butyl cyanoacrylates in THF initiated by triethyl and triphenylphosphines were followed by adiabatic calorimetry at temperatures between 20 and −95°C. The polymers showed UV absorptions characteristic of phosphonium and cyanoacrylate carbanion end groups, indicating that the growing chains were macrozwitterions. Monomer conversion was quantitative and of 1st order in both monomer and initiator. Other criteria of ‘living’ polymerisation were satisfied, e.g. molecular weights corresponded to one chain per initiator molecule, and indicated that monomer added subsequently was incorporated on to previously formed chains. Assuming the overall rate to be that of propagation yielded values of kp = 1 – 3 · 105 dm3 · mol−1 · s−1 at −78°C, with very low activation energies, i.e. 2,2 and 5,5 kJ · mol−1 for ECA and BCA, respectively. Of a range of inert salts only LiBr significantly reduced the rate of polymerisation.