Kinetic and electron paramagnetic resonance studies on radical polymerization. Radical‐initiated polymerization of methyl N‐phenylitaconamate in N,N‐dimethylformamide

The polymerization of methyl N ‐phenylitaconamate(methyl 2‐methylenesuccinanilate ( 1 )) with dimethyl 2,2′‐azodiisobutyrate ( 2 ) was studied in N , N ‐dimethylformamide (DMF) kinetically and by means of electron paramagnetic resonance (EPR) spectroscopy. The polymerization rate ( R p ) at 55°C is given by the equation: R p = k [ 2 ] 0,58 · [ 1 ] 1,6 . The overall activation energy of the polymerization was calculated to be 54,2 kJ/mol. The number‐average molecular weight of poly( 1 ) was in the range between 5000 and 17000. From an EPR study, the polymerization system was found to involve the EPR‐detectable propagating polymer radical of 1 at practical polymerization conditions. Using the concentration of polymer radicals, the rate constants of propagation ( k p ) and termination ( k t ) were determined for 55°C. The rate constant of propagation k p (between 8,4 and 12 L · mol −1 · s −1 ) tends to somehow increase with increasing monomer concentration. On the other hand, k t (between 1,9. 10 −5 L · mol −1 · s −1 ) increases with decreasing monomer concentration, which results from a considerable dependence of k t on the polymer‐chain length. Such monomer‐concentration‐dependent k p and k t values are responsible for the high dependence of R p on the monomer concentration. Thermogravimetric results showed that thermal degradation of poly( 1 ) occurs rapidly at temperatures higher than 200°C and the residue at 500°C amounts to 26% of the initial polymer. For the copolymerization of 1 (M 1 ) with styrene (M 2 ) at 55°C in DMF the following copolymerization parameters were found: r 1 = 0,52, r 2 = 0,31, and Q , e values Q 1 = 1,09 and e 1 = +0,55.