The interaction of poly-2-vinylpyridine 1-oxide and poly-4-vinylpyridine 1-oxide with monosilicic acid

Abstract

Poly-2-vinylpyridine 1-oxide of molecular weight greater than 50,000 inhibits fibrogenesis normally associated with the presence of quartz in the lungs of animals and the cytotoxic actions of silica in cultures of phagocytic cells. Poly-4-vinylpyridine 1-oxide has little effect. Since the pathogenic effects of silica may be due to monosilicic acid produced in the cells, a study has been made of the interaction of monosilicic acid and each of these polymers. The interaction of each polymer and monosilicic acid is evidenced by a shift in the ultraviolet absorption peaks and a change in the viscosity of polymer solutions. The complex formed by the 2-isomer is stable up to 60°, as is shown by the viscosity–temperature curve, but that formed by the 4-isomer decomposes when warmed. From its ultraviolet absorption, poly-2-vinylpyridine 1-oxide is thought to be a compact structure with stacked pyridine rings and closely packed oxygen atoms along one side of the polymer chain. This allows bonding of the silicic acid by three hydroxy-groups. Silicic acid probably forms loose interchain cross-links with poly-4-vinylpyridine oxide.