Shear-Rate Dependence of the Intrinsic Viscosity of Flexible Linear Macromolecules

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Abstract
Shear‐rate dependence of the intrinsic viscosity has been studied on polystyrene in four different solvents by using a Zimm—Crothers rotational viscometer and Ubbelohde viscometers. The former viscometer was employed particularly for measuring zero‐shear intrinsic viscosity [η]0. The results are summarized in terms of the [η]/[η]0 versus generalized rate of shear β=([η]0ηsM/RT)G, where ηs is the solvent viscosity, M the solute molecular weight, G the rate of shear, and others have usual significance. It has been found that, (i) at the values of β below 0.1, [η] is practically independent of rate of shear (or shear stress); (ii) the non‐Newtonian effect does exist even in θ conditions; and (iii) at the values of β below 2, the [η]/[η]0‐vs‐β curves of the systems with different molecular weights and in different solvents give a single composite curve, which fairly well resembles to the curve of a prolate ellipsoid with the axial ratio p=3.