Polar effects in radical polymerization of vinyl monomers; radical copolymerization of several p‐substituted vinyl benzoates

The mutual radical copolymerizations of several p‐substituted vinyl benzoates such as vinyl p‐methoxy‐, p‐methyl‐, p‐chloro‐, p‐bromo‐, and p‐cyanobenzoate and vinyl benzoate were carried out at 60°C. The monomer reactivity ratios were determined by the method of FINEMAN and ROSS. The relative reaction rates of p‐substituted vinyl benzoates to a given poly‐vinyl‐p‐substituted benzoate radical plotted against HAMMETT'S σ‐values gave straight lines. The linear relationships and small ρ‐values show in contrary to p‐substituted styrenes that p‐substituents in this case have only a little polar effect on the vinyl group and on the polymer radical which are separated from the aromatic ring through the carboxyl‐group, and on the exaltation of resonance stabilization of polymerizing species at transition state. The observed σ‐values were correlated with the ρ‐values of p‐substituents on the polymer radicals. Polymers and copolymers of these monomers were hydrolysed to give polyvinyl alcohol.