Propagation rate coefficients of 2-(dimethylamino)ethyl methacrylate radical polymerization in bulk, alcohols and alcohol/water solutions determined by PLP-SEC

Abstract

The pulsed laser polymerization – size exclusion chromatography (PLP-SEC) technique is used to investigate the radical polymerization propagation kinetics of 2-(dimethylamino)ethyl methacrylate (DMAEMA) in n-butanol and ethanol (EtOH), as well as EtOH/water mixtures, with SEC analysis conducted in three different eluent systems. The measured propagation rate coefficient, k_p, in bulk is characterized by an activation energy (E_A) of 20.8 kJ mol⁻¹, with the 607 L mol⁻¹ s⁻¹ at 25 °C in good agreement with previous literature. The k_p and E_A values measured for 50 wt% DMAEMA in n-butanol and ethanol (EtOH) do not differ significantly from bulk. However, the k_p value increases and E_A decreases as monomer content in EtOH is lowered below 20 wt%, with k_p also increasing by 80% for 50 wt% DMAEMA as water fraction in an EtOH/H₂O solvent mixture increased from 0 to 75%. The mixed solvent system provides a route to synthesize DMAEMA polymers in an aqueous environment, as the extent of DMAEMA monomer solvolysis is greatly reduced compared to that in pure water.