Vinyl polymerization. 120. Mutual copolymerization of <i>p</i>‐substituted styrenes through radical mechanism

Abstract

Abstract The radical mutual copolymerization of p ‐substituted styrenes, such as p ‐methoxy‐, p ‐chloro‐, p ‐bromo‐, p ‐cyanostyrene, and styrene was carried out with one another at 30°C. in the dark. As initiator, azobisisobutyronitrile was used. The plots of the copolymerization rates against H AMMETT 's σ values showed no linear relationships and the concave curves were obtained therefrom. The relative reactivities of p ‐substituted styrenes with a definite p ‐substituted polystyryl radical, which were shown by the reciprocal of monomer reactivity ratio r 1 , were plotted against σ values and concave curves were also obtained. The relative reactivities of p ‐substituted polystyryl radicals with p ‐substituted styrene were calculated from the ratios r 2 and the propagation rate constants in homopolymerization. the plots of them against σ values gave straight lines with different ρ values, according to the polarity of substituents. These results suggest that polar structures in transition state affected markedly the copolymerization rates. The effect of substituents on resonance stabilization was also quantitatively estimated.