Determination of propagation rate coefficients for an α-substituted acrylic ester: pulsed laser polymerization of dimethyl itaconate

Pulsed laser polymerization experiments have been performed on the bulk polymerization of dimethyl itaconate over the temperature range 20-50°C. The activation energy and frequency factor were calculated as 24.9 kJ/mol^-1 and 2.15 × 10⁵ L/mol^-1s^-1, respectively. The activation energy is comparable with the methacrylate series of monomers. The frequency factor is relatively small and reflects steric hindrance in the transition state caused by the bulky 1,1, disubstitution in the monomer (and consequently the radical). The Mark-Houwink-Kuhn-Sakurada constants were also determined for poly(dimethyl itaconate) in tetrahydrofuran, these are reported as 46 × 10^-5 dL/g (K) and 0.51 (α). The influence of penultimate units (γ-substituents) on homopropagation reactions is discussed particularly for polymerizations leading to significant 1,3 interactions in the resultant polymer.