Liquid chromatography at the critical point of adsorption - A new technique for polymer characterization

Abstract

Liquid chromatography at the critical point of adsorption (CC) is a versatile method for the determination of different types of molecular heterogeneity in polymers Operating at the transition point of size-exclusion and adsorption modes of liquid chromatography, this method is capable of separating polymers according to their functionality At the critical point of adsorption the polymer chain behaves like an invisible part of the macromolecule and only the heterogeneities (functional groups, blocks, grafts) manifest themselves chromatographically. The application of this method to the determination of the chemical heterogeneity of block copolymers and the composition of polymer blends is demonstrated. Block copolymers can be analysed with respect to the block lengths of the individual blocks A complete description of their molecular heterogeneity is possible using two-dimensional chromatography CC vs. SEC. Binary polymer blends are separated with respect to the components regardless of their individual molar masses under experimental conditions, where one component elutes at the critical point of adsorption.