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

Abstract

AbstractThe 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 (Rp) at 55°C is given by the equation: Rp = 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 (kp) and termination (kt) were determined for 55°C. The rate constant of propagation kp (between 8,4 and 12 L · mol−1 · s−1) tends to somehow increase with increasing monomer concentration. On the other hand, kt (between 1,9. 10−5 L · mol−1 · s−1) increases with decreasing monomer concentration, which results from a considerable dependence of kt on the polymer‐chain length. Such monomer‐concentration‐dependent kp and kt values are responsible for the high dependence of Rp 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 (M1) with styrene (M2) at 55°C in DMF the following copolymerization parameters were found: r1 = 0,52, r2 = 0,31, and Q, e values Q1 = 1,09 and e1 = +0,55.