AbstractIntrinsic viscosities [η], sedimentation coefficients s, radii of gyration Rgand second virial coefficients A2, refractive index increments and apparent specific volumes were determined in aqueous solution in theta solvents and over a wide range of concentrations msof a supporting electrolyte KCl, for five samples of potassium polystyrene sulfonate prepared by sulfonation of narrow molecular weight distribution polystyrenes. Coil expansion coefficientsαas well as the Flory coefficient Φ relating [η] to coil dimensions were evaluated. Following a theory of Alexandrowicz,α2was found to be a linear function of M1/4m−1/3S; Φ appears to decrease with increase inα.The low values of Φ, characteristic for polyelectrolyte solutions, are consistent with the value determined for the Mandelkern‐Flory paramete