Kinetic and ESR studies on radical polymerization. Radical polymerization behavior of N‐octadecylmaleimide in benzene

The polymerization of N ‐octadecylmaleimide ( 1 ) initiated with azodiisobutyronitrile ( 2 ) was investigated kinetically in benzene. The overall activation energy of the polymerization was calculated to be 94,2 kJ·mol −1 . The polymerization rate ( R p ) at 50°C is expressed by the equation, R p = k [ 2 ] 0,6 [ 1 ] 1,7 . The homogeneous polymerization system involves ESR‐detectable propagating polymer radicals. Using R p and the polymer radical concentration determined by ESR, the rate constants of propagation ( k p ) and termination ( k t ) were evaluated at 50°C. k p (33 L · mol −1 · s −1 on the average) is substantially independent of the monomer concentration. On the other hand, k t (0,3 · 10 4 – 1,0 · 10 4 L · mol −1 · s −1 ) is fairly dependent on the monomer concentration, which is ascribable to a high dependence of k t on the chain length of rigid poly( 1 ). This is the predominant factor for the high order with respect to the monomer concentration in the rate equation. In the copolymerization of 1 (M 1 ) and St (M 2 ) with 2 in benzene at 50°C, the following copolymerization parameters were obtained: r 1 = 0,11, r 2 = 0,09, Q 1 = 2,1, and e 1 = +1,4.