Chain transfer reactions limit the molecular weight of polyglycidol prepared via alkali metal based initiating systems

Anionic polymerization of EEGE with alkali metal based initiators has been shown to yield polyglycidol with low polydispersity indices for molecular weights up to Mn ≈ 30,000. Higher molecular weights have not been obtained due to the occurrence of a chain transfer reaction to the monomer. Chain transfer to the monomer leads to P(EEGE) with an alcohol end group and an allylic alcoholate, which reinitiates the polymerization of EEGE. In the present study, the influence of temperature (in a range from 20 °C to 120 °C) and of different initiating systems, such as 3-phenylpropanol/potassium 3-phenylpropanolate, potassium tert-butoxide and sec-butyllithium/phosphazene base, on the chain transfer reaction is investigated. In all cases, the basicity of the alkoxide at the propagating chain end induces chain transfer. The formation of allylic end groups was evidenced by 1H NMR spectroscopy.