Retention Behavior of Linear, Branched, and Hyperbranched Polyesters in Interaction Liquid Chromatography

Abstract

The retention behavior of aromatic polyesters possessing different degrees of branching was studied in gradient liquid adsorption chromatography (gradient chromatography), liquid adsorption chromatography (LAC), and liquid chromatography at the critical conditions (LCCC). The chromatographic experiments revealed that retention of linear and branched polyesters is influenced by the degree of branching as well as the molar mass of the polymer samples in all enthalpy-dominated chromatographic modes such as LAC, LCCC, and gradient chromatography. At critical conditions of the linear polymer, the corresponding branched structures elute in the adsorption mode, indicating a stronger adsorptive interaction between the stationary phase and the branched polymer molecule. In gradient chromatography, polymer samples with higher degrees of branching are retarded longer on the stationary phase. A clear dependence between the degree of branching and the elution volume was found in both chromatographic modes, which clearly demonstrates a pronounced effect of topology on retention behavior. The results suggest the use of gradient chromatography as a first separation step for a two-dimensional characterization method of branched polymers in order to separate by both degree of branching and molar mass.