Unperturbed dimensions of polystyrene in mixed solvents at high temperature

At 371.5 K, which is the θ-temperature for polystyrene (PS) in 3-methyl cyclohexanol (MC), intrinsic viscosities η] have been measured for PS samples of different relative molar mass M in mixtures of MC with a thermodynamically good solvent 1,2,3,4-tetrahydronaphthalene over the whole range of solvent composition. Eleven graphical procedures have been utilised and assessed in deriving the unperturbed polymer dimensions expressed as K_θ (in the relation $\text{η] = K}{}_{\mathrm{\theta }}\text{M}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{α}{}^3$ where α is the expansion factor). For those procedures concluded to be the most reliable, there was no influence of binary solvent composition: the value of K_θ = 78 (±1) × 10^?3 dm³ kg^?1 was the same as that obtained directly under θ-conditions.