Effect of substituents on the radical copolymerization of ring‐substitutedtrans‐cinnamonitriles with vinyl monomers

摘要

AbstractRadical copolymerizations of ring‐substitutedtrans‐cinnamonitriles with olefins such as styrene and acrylonitrile were studied at 60°C. The copolymerization parameters of cinnamonitriles (M1) in the copolymerizations with styrene (M2) were determined to ber1= 0,01 to 0,30,r2= 0,45 to 4,25,Q1= 0,06 to 0,70, ande1= −0,52 to 1,35. The relative reactivity, log(1/r2), showed a tendency to increase with increasing Hammett constant σ and was higher in conjugated cinnamonitriles than in less conjugated nitriles. Forp‐substituted cinnamonitriles, ρ and γ values in the equation of log(1/r2) = ρ · σ + γ ·ERwere estimated to be 0,48 and 2,0, respectively, whereERis a resonance constant. The relative reactivity was also increased with increasing13C NMR chemical shift of the olefinic β‐carbon of cinnamonitriles and decreasing polarity of the solvents used. In addition, the relative reactivity towards a poly(acrylonitrile) radical is higher in cinnamonitrile than in cinnamic esters. The structure of the radical generated by the attack of the 2‐methyl‐2‐propyl radical at the cinnamonitrile was examined by means of electron paramagnetic res