Solid‐state polymerization of vinylpyridine coordination compounds

A survey of the solid‐state polymerizability of 2‐ and 4‐vinylpyridine (Vpy) complexes of divalent cobalt, nickel, copper, and zinc chlorides has been carried out. The influence of metal ion, ligand, coordination stereochemistry, and crystal structure is discussed. The tetrahedral modification of the complex Co(4‐Vpy)2Cl2 has been found to undergo a particularly facile thermal polymerization below its melting point to yield high molecular weight poly‐4‐vinylpyridine. The polymer is shown to be conventional atactic head‐to‐tail poly‐4‐vinylpyridine. Thermogravimetric methods and optical microscopy have been used to study the thermal polymerization of single crystals of the complex. Results indicate a diffusion‐controlled mechanism in which defective regions in the crystal act as nuclei for the polymerization.