Polymer chain dimensions in mixed solvents

Abstract

Abstract An extension of the Shultz‐Flory theory of polymer chain dimensions in mixed solvents is proposed. It is based on solution thermodynamics with z , the lattice coordination number, finite rather than effectively infinite. Intrinsic viscosities of polyisobutylene in cyclohexane–benzene solutions have been obtained over the range of compositions and theoretical values compared with them. Those with z ∼ 4 give the best fit. A similar analysis has been performed for published intrinsic values of polystyrene in the same mixture, giving z ∼ 3. The z values compare well with those found for polyisobutylene–benzene and polystyrene–benzene by other methods, and this low value may be due to backcoiling of the polymer molecules.