Dilute Solution Properties of Linear Polystyrene in Θ-Solvent Media

Abstract

Dilute solution parameters descriptive of polymer coil size and segment—solvent interaction have been evaluated for each of three polystyrene—solvent systems at various temperatures in the vicinity of the Θ value characteristic of a given pair. The pure solvents selected for these studies were diethyl malonate, cyclohexane, and 1—chloro—n—undecane, which with polystyrene display Θ temperatures of 35.9°, 34.8°, and 32.8°C, respectively, as ascertained from analyses of second virial coefficient—temperature relationships. A single polymer sample of narrow molecular weight distribution was employed in all investigations. Parameters interpolated for each polystyrene—solvent pair at the Θ temperature of the system are examined from the point of view of the specific influence of the medium on coil characteristics. Differences are observed, for example, among the intrinsic viscosity values. Accurate, relative comparison of such solution properties is facilitated through use of the common polymer sample and intentional selection of pure solvents displaying Θ temperatures in proximity. The complicating effects of variable molecular weight, molecular weight distribution, and temperature per se are thus conveniently eliminated. Intrinsic viscosity and second virial coefficient data obtained for each pair at various temperatures near Θ are examined in accordance with the formal functional interdependence predicted by certain theoretical treatments, applicable to weakly interacting systems of the kind here investigated.