Viscometric behavior of polyacrylate ion in concentrated salt solutions

Abstract

Abstract Viscosities of polyacrylate ion in the presence of potassium bromide, sodium bromide, lithium bromide, sodium iodide, sodium hydroxide, and hydrochloride acid in aqueous solution were measured over the approximate ranges 0.0–0.6% polymer and salt up to saturation with respect to polyacrylate or to salt. The general initial effect of added electrolyte is to reduce the ratio η sp / c and to convert the curve characteristic of polyelectrolytes into a straight line, which can be extrapolated to zero polymer concentration to given [η], the intrinsic viscosity of the polymer in the presence of excess salt. Sodium hydroxide and sodium bromide produce minima in plots of [η] against salt concentration. Sodium iodide precipitates polyacrylate at 1.5 N iodide as a translucent gel, which redissolves at 3.0 N and finally reprecipitates at 6 N . In the latter range of concentration, [η] exhibits a maximum. Both by‐ions and counter‐ions have specific effects on the viscosity of the polyion.