Anionic polymerization of p-methoxystyrene in tetrahydrofuran

Kinetics of homopropagation of living poly-p-methoxystyrene has been investigated in tetra-hydrofuran at 25°C in the presence and absence of an electric field. The rate constants of ion pairs were evaluated to be 40, 40 and 15 M^–1 s^–1 for sodium, potassium and caesium salts, respectively, being smaller than those for the corresponding salts of living polystryene. The rate constant of free anion was 4.0 × 10⁴ M^–1 s^–1, and was also smaller than that for styrene. The difference between the rate constants of these two monomers was attributed to the difference of the reactivities of the monomers due to and electron-donating effect of the methoxy group. The dissociation constants were also smaller than those of the living polystyrene. This is due to the interaction between the active end and gegenion becoming larger as a result of an increase of the electron density at the active end by the methoxy group. The substituent effect was notable especially for the dissociation behaviour of ion pairs containing gegenions of small ionic radius. The comparatively large field effect was observed at lower field intensities than for styrene previously studied.