Kinetic and EPR studies on radical polymerization. Radical polymerization of di-2[2-(2-methoxyethoxy)ethoxy]ethyl itaconate

Abstract

The polymerization of di-2[2-(2-methoxyethoxy)ethoxy]ethyl itaconate (1) with dimethyl 2,2′-azobisisobutyrate (2) was studied, in benzene, kinetically and spectroscopically with the electron paramagnetic resonance (EPR) method. The polymerization rate (R _p) at 50°C is given by the equation:R _p=k[2]^0.48 [1]^2.4. The overall activation energy of polymerization was calculated to be 34 kJ·mol⁻¹. From an EPR study, the polymerization system was found to involve EPR-observable propagating polymer radicals of 1 under the actual polymerization conditions. Using the polymer radical concentration, the rate constants of propagation (k _p) and termination (k _t) were determined. With increasing monomer concentration,k _p(1.5∼4.3 L·mol⁻¹·s⁻¹ at 50°C) increases andk _t (1.0·10⁴∼4.2·10⁴ L·mol⁻¹·s⁻¹ at 50°C) decreases, which seems responsible for the high dependence ofR _p on the monomer concentration. The activation energies of propagation and termination were calculated to be 11 kJ·mol⁻¹ and 84 kJ·mol⁻¹, respectively. For the copolymerization of 1(M ₁) and styrene (M ₂) at 50°C in benzene the following copolymerization parameters were found:r ₁=0.2,r ₂=0.53, Q₁=0.57, ande ₁=+0.7.