The catalytic effects of the poly(vinylpyridine)‐ligand in the oxidative polymerization of phenols

In order to study the catalytic effects of the polymer‐ligand, copper‐poly(vinylpyridine) (Cu‐PVP) complexes were used as catalyst for the oxidative polymerization of phenols. The catalysis was discussed. The rate of the 2,6‐dimethylphenol (XOH) polymerization catalyzed by the Cu‐PVP complex was slower than that catalyzed by a Cu‐pyridine complex. By the measurement of the kinetic constants, it was suggested that a bulky PVP ligand obstructed the coordination‐step of the monomer and the electron‐transfer‐step from the coordinated monomer to the cupric ion. The polymerization of the mixture of XOH and o‐cresol with Cu‐PVP as catalyst was saturated at a higher conversion, and the yield and the molecular weight of the polymer obtained were larger than in the cases where the Cu‐pyridine or the Cu‐γ‐picoline complex systems were used as catalysts. XOH is preferentially activated by the Cu‐PVP catalyst because its oxidation potential is lower, thus the effect of the PVP ligand may be observed. XOH was polymerized by the swelled Cu‐PVP complex as a heterogeneous catalyst in benzene or a benzene containing mixture of solvents. The catalyst was recovered by filtration in a high yield and re‐used repeatedly. Cu‐PVP complexes are relatively stable toward alkali because of their chelate structure. The polymerization was accelerated 3 to 5 times in alkaline solution, and the side‐reaction was suppressed.