Solution properties of polyvinylpyridine in acid .2. Solution properties of poly(4-vinylpyridine) in aqueous solution of hydrochloric acid

The total electrostatic free energy change, Delta(el), for poly(4-vinylpyridine) (P4VP) was evaluated from the apparent dissociation constant, pK(alpha), by means of UV spectra in an aqueous solution of hydrochloric acid (aq. HCl). The intrinsic viscosity ([eta]) of P4VP was measured in aqueous solutions of 2 x 10(-3), 4 x 10(-3), 10(-2), 10(-1), 1, 3 and 6 M hydrochloric acid, methanol and N,N-dimethylformamide (DMF) at 25 degrees C. Linear relations between [eta] and weight-average molecular weights (M,) were observed in 10(-1), 1, 3 and 6 M HCl, methanol and DMF. It was found that the unperturbed dimension of P4VP evaluated from the Stockmayer-Fixman plot was dependent on the concentration of HCl. The characteristic ratios, C infinity, in these solutions of HCl are larger than those in organic solvents. However, in 2 x 10(-3)), 4 x 10(-3) and 10(-2) M HCl, the double logarithmic plots of [eta] and M-w show a concave-downward curvature. The persistence length (q) and the molar mass per contour length (M-L) were evaluated from viscosity data in 2 x 10(-3), 4 x 10(-3) and 10(-2) M HCl according to the theory of the worm-like chain model. When the diameter of the cylinder (d) was assumed to be 1.0 nm, the agreement between [eta] experimentally obtained and calculated by means of the Yamakawa-Fujii-Yoshizaki theory is satisfactory. (C) 1997 Elsevier Science Ltd.