Poly‐2‐ and poly‐4‐vinylpiperidine

Poly‐2‐vinylpiperidine and poly‐4‐vinylpiperidine were prepared from poly‐2‐vinylpyridine and poly‐4‐vinylpyridine, respectively, by catalytic hydrogenation at a hydrogen pressure of 3500 p.s.i. and a temperature of 220–250°C., using a palladium catalyst. The hydrochlorides, acetyl derivatives, and phenyl thioureates of the new polymers could also be obtained. The molecular weights of the polymers were estimated by light scattering and viscosity in chloroform and methanol solution and were found to lie in the range of 10,000 to 35,000. The electrochemical properties were investigated by potentiometric titration and electrophoresis. From the character of the titration curves it was concluded that no appreciable nearest neighbor interaction exists in polyvinylpiperidine. By an analysis of the combined potentiometric‐electrophoretic data an intrinsic acid dissociation constant p K 0 = 10.08 ± 0.07 was calculated. The discrepancy between this value and the value of the dissociation constants of monomeric piperidines, p K ≈ 11, has been further investigated by thermochemical measurements.