Inverse gas chromatography and partial solvation parameters

Abstract

Inverse gas chromatography (IGC) is widely used for the characterization of polymers and surfaces. The present work describes a novel method for this characterization through the recently introduced partial solvation parameters (PSPs). PSPs are molecular descriptors that combine elements from Quantum Mechanics with the QSPR/LSER/solvatochromic and solubility parameter approaches. A simple coherent thermodynamic framework is presented, through which IGC experimental measurements are used to determine the dispersion, polarizability, and Lewis acid/base interactions of the studied polymers and surfaces. The role or usefulness of various classes of probes for this characterization is critically examined. Emphasis is given on the hydrogen-bonding features of polymers and on the way IGC may be used to extract reliable information on hydrogen-bond formation constants and on the related energy-, entropy-, and free-energy changes. The new method has been used for the characterization of a number of common polymers and one hyperbranched structure. Extension to materials surface characterization, determination of partial surface tensions, and other perspectives of the new method are discussed. The new approach establishes a thermodynamically consistent, coherent, and straightforward method for the integral characterization of polymers as regards their cohesion (partial solubility parameters), solvation (partial solvation parameters), and surface (partial surface tensions) features.