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

Abstract

The total electrostatic free energy change, ΔG el, for poly(4-vinylpyridine) (P4VP) was evaluated from the apparent dissociation constant, p K(α), by means of UV spectra in an aqueous solution of hydrochloric acid (aq. HCl). The intrinsic viscosity ([η]) of P4VP was measured in aqueous solutions of 2 × 10 −3, 4 × 10 −3, 10 −2, 10 −1, 1, 3 and 6 M hydrochloric acid, methanol and N,N-dimethylformamide (DMF) at 25 °C. Linear relations between [η] and weight-average molecular weights ( M w ) 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 ∞, in these solutions of HCl are larger than those in organic solvents. However, in 2 × 10 −3, 4 × 10 −3 and 10 −2 M HCl, the double logarithmic plots of [η] 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 × 10 −3, 4 × 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 [η] experimentally obtained and calculated by means of the Yamakawa-Fujii-Yoshizaki theory is satisfactory.