Review of solution methods and certain other methods of polymer fractionation

Discrimination in terms of solubility differences forms the basis of the most widely applicable methods of polymer fractional ion. These include fractional precipitation and extraction on a batch scale; the rapid column methods, namely, the elution method and precipitation chromatography; and turbidimetric titration, which is strictly an analytical procedure. The principles of solution fractionation are reviewed as applied to batch fractionation and to the column methods, and certain essential differences are pointed out between these two approaches. The importance of proper solvent selection in the several methods is considered, and examples are presented of fractionation on the basis of chemical and structural differences as well as in terms of molecular weight. A brief summary is also presented on the present status of certain other methods, including thermal diffusion, none refining, and adsorption chromatography, which utilize different physical principles as the basis of separation.