Experimental verification of modern theory of molecular weight fractionation based on solubility difference

Abstract

Abstract An attempt was made to verify the modern theory of molecular weight fractionation based on solubility behavior by experiment. Atactic polystyrene (PS) in methylcyclohexane (MCH) and in cyclohexane (CH) were employed for this purpose. The following quantities were determined experimentally and compared with theoretical values calculated with the aid of an electronic computer: The partition coefficient σ, volume ratio of polymer‐lean phase to polymer‐rich phase R , polymer volume fraction in the two phases, v p(1) and v p(2) , weight‐average molecular weight M̄ w and the breadth of the molecular weight distribution (the ratio of weight‐ to number‐average molecular weight, M̄ w /M̄ n and standard deviation σ′) of the polymers in both phases. The experimental data can be well explained in terms of theory if the concentration dependence of the polymer/solvent interaction parameter χ, expressed by p , is reasonably taken into account, i.e., p = 0,7 for PS in MCH and p = 0,6 for PS in CH. It was shown that σ depends slightly on molecular weight.