The Viscosity of Dilute Solutions of Long-Chain Molecules. V. Dependence on the Solvent

Abstract

Staudinger's relation between ηsp/c and the molecular weight of a chain molecule solute should theoretically apply only if the chain molecules are kinked in a purely random way. With actual solutions, one would expect the kinked chains to be more or less tightly coiled than for purely random kinking, depending on whether the average cohesive energy density between like units (solvent molecules and solute submolecules) is greater or less than that between unlike units. The tighter the coiling, the less is the specific viscosity, for a given solute molecule chain length. This cohesive energy density difference is closely related to μ1, the constant, characteristic of a given solute-solvent system, which enters into the equations recently derived by the author for the activities of the components and for related quantities, such as osmotic pressures, solubilities, and precipitabilities. From this relationship, it has been shown that the ηsp/c values for solutions of a given polymer in different solvents should, in general, be symbatic with the proportion of a poor solvent which is required to produce precipitation of a solid phase. Data from the literature on polystyrene and polybutene solutions are in agreement with this conclusion.