Molecular characterization of block copolymers by means of liquid chromatography: I. Potential and limitations of full adsorption–desorption procedure in separation of block copolymers

Abstract

The full adsorption–desorption (FAD) procedure was applied to the selected model di- and tri-block copolymers. The dynamic integral desorption isotherms were measured for various homo- and block-copolymers of poly(methyl methacrylate) and poly(glycidyl methacrylate) in a system of non-porous silica–dichloroethane adsorli–tetrahydrofuran desorli. The aim was to evaluate separation selectivity of the FAD approach toward molar mass and chemical composition of macromolecules. It was demonstrated that under optimum conditions the FAD procedure can discriminate parent homopolymers from di-block copolymers, as well as di-block from tri-block copolymers when the adsorptivities of blocks differ sufficiently. The molar mass of both kinds of polymer chains affected the course of their desorption in present system of adsorbent–adsorli/desorli. Consequently the block copolymers studied could not be effectively fractionated according to their composition by a single FAD procedure. A combined method, full adsorption–desorption plus size exclusion chromatography was proposed for the species with selectively adsorbing blocks to provide a two dimensional fractionation of block copolymers.