Properties of polyelectrolytes: Maleic acid‐vinylpyrrolidone copolymers. I. Viscometric behavior in dilute solution

The viscometric behavior of maleic acid‐vinylpyrrolidone copolymer systems p(MA–co–VP) were studied in dilute solution. The weight‐average molecular weights of fractionated copolymers were determined by gel permeation chromatography. Viscometric relations were determined in aqueous salt solutions and in organic solvents. Two theta‐conditions were found for p(MA–co–VP): in 0.968 M Na₂SO₄, and in a DMSO/acetone mixture, 35.6/56.4 (v/v) at 25°C. The conformational and thermodynamic parameters K_Θ and B were evaluated from viscosity data in good solvents using the Stockmayer–Fixman and Berry extrapolations. A linear variation of B with the salt concentration was observed. The electrostatic (B_e) and nonelectrostatic (B_o) contributions to B were estimated. It was found that B_e > B_o, and this was attributed to the hydrophylic nature of p(MA–co–VP) copolymers. The latter would reflect a greater influence of the electrostatic interaction on the hydrodynamic behavior of this polymer. The electrostatic (α η3), and the nonelectrostatic lim  C  s →∞(α³ − 1) contributions to the expansion factor α η3 were determined. It was found that α ηe3 is a function of (M̄_w/C_s)^1/2, as is predicted by the Fixman theory.