Kinetic and ESR studies on the radical polymerization. radical‐initiated copolymerization of the diethyl itaconate‐SnCl4 complex and styrene

Abstract

AbstractThe copolymerization of diethyl itaconate(1) (M1) and styrene (2) (M2) with dimethyl 2,2′‐azoisobutyrate (3) was performed in benzene at 50°C, and the following copolymerization parameters were obtained: r1 = 0,34, r2 = 0,35, Q1 = 0,93 and el = +0,66. The copolymerization system was found to involve ESR1Electron spin resonance. ‐observed propagating polymer radicals at low monomer feed composition (f2) of 2. The apparent rate constant of termination increased rapidly with f2. The ESR‐determined values of the apparent propagation rate constant of the copolymerization were lower than those calculated on the basis of the Mayo‐Lewis model, suggesting a significant penultimate effect in the copolymerization. On the other hand, the copolymerization of the 1‐SnCl4 complex (M1) and 2 (M2) at 50°C yielded a nearly alternating copolymer independently of the monomer feed composition. The propagating polymer radicals were ESR‐observable even up to f2 = 0,8. The ESR‐determined apparent rate constant (kp) of propagation showed a maximum near f2 = 0,5. From the relationship between kp and f2, the rate constants of cross‐propagations of the present alternating copolymerization were evaluated as k12 = 483 and k21 = 510 L. mol−1 · s−1. Comparison of the k21 value and the reported propagation rate constant (209 L · mol−1 · s−1) of homopolymerization of 2 leads to the conclusion that the alternating copolymerization via free‐monomer propagation mechanism originates from a pronounced penultimate effect suppressing homopropagation of 2, but not from enhanced cross‐propagation.