TEMPERATURE-DEPENDENCE OF VISCOSITIES AND POTENTIOMETRIC TITRATION BEHAVIOR OF POLY(N-VINYLIMIDAZOLE) IN AQUEOUS SALT-SOLUTIONS

The potentiometric titration behavior has been studied for the aqueous solutions of poly(N-vinylimidazole) (PVI) in the presence of various supporting electrolytes, NaCl, NaBr, NaNO3, NaI, NaSCN, and NaClO4 at 5, 25, and 45-degrees-C. At low degree of neutralization alpha', an inflection on the titration curve and turbidity of solution have been observed for the systems containing NaNO3, NaI, NaSCN, or NaClO4 with appropriate concentration. The viscosities of aqueous NaBr solutions of PVI have been measured at 5, 25, and 45-degrees-C as a function of alpha'. The solution viscosities increase with temperature throughout the whole range of alpha'. The intrinsic viscosity-alpha' curves pass through a minimum followed by normal increase with the increase in neutralization. The initial contraction of the polymer chain may be attributed to the formation of intramolecular chelate-like bridge between protonated and unprotonated imidazole rings.