Characterization of Poly(methyl methacrylate)- and Polystyrene-Based Block Copolymers by Liquid Chromatography under Limiting Conditions of Desorption Gradient

Size exclusion chromatography-gradient (SEC-Gradient) is a powerful technique to separate polymers by their chemical composition. The stationary phase is first conditioned with a gradient from adsorli to desorli, and polymer samples are injected after the gradient in SEC conditions. Since its first description in 2011 by Schollenberger and Radke, it has never been applied to block copolymers. Liquid chromatography under limiting conditions of desorption (LC LCD), developed in the 2000s by Berek, allows the separation of block copolymers from their parent homopolymers by injecting some barriers of appropriately chosen solvents at specific injection delays before sample injection. In this work, we propose a new technique close to the LC LCD elution mechanism but applying column conditioning with a global gradient before sample injection, as in SEC-Gradient experiments, namely, liquid chromatography under limiting conditions of desorption gradient (LC LCDG). Using this LC LCDG technique, we managed to baseline separate poly(methyl methacrylate) (PMMA)- and polystyrene (PS)-based block copolymers from their PMMA and PS parent homopolymers. The chromatographic method development to achieve an optimal separation and identify a low molar mass limit is particularly described.