UNPERTURBED DIMENSIONS OF POLYMERS IN BINARY SOLVENT MIXTURES

Intrinsic viscosity measurements were carried out on polystyrene and polyvinylpyridine solutions in various solvents and solvent mixtures. The Stockmayer-Fixman extrapolation was applied to the date: it yields the unperturbed dimensions Kθ of the chain. A unique value of Kθ was found for a given polymer in all pure solvents, as expected; in the case of binary mixtures, the Kθ value is found higher or lower than this unique value, depending upon the thermodynamic parameter x12 characterizing the solvent mixture. According to these results, the properties of θ-solutions (as defined classically for pure solvents) should not be extended to ternary systems, since Kθ does not depend solely on temperature. © 1968.