Molar mass characterization of hydrophilic copolymers, 1 Size exclusion chromatography of neutral and anionic (meth)acrylate copolymers

Abstract

A robust and reproducible method for the molar mass analysis of neutral and anionic copolymers based on methacrylic acid and different (meth)acrylates has been developed. Size exclusion chromatography (SEC) using a novel polyester- based packing as the stationary phase and dimethylacetamide (DMAC) as the mobile phase yields highly accurate results for copolymers with a methacrylic acid content up to 50 wt.-%. To suppress the different polar and ionic interactions between the sample molecules, the stationary phase and the eluent, DMAC was modified with LiBr and acetic acid. Calibrating the SEC system with poly(methyl methacrylate) of narrow polydispersity, molar masses were obtained that are in good agreement with data obtained by SEC-MALLS (multi-angle laser light scattering) and SEC measurements of methylated samples. The reproducibility and the robustness of the novel method were proven by running similar samples in three different laboratories and for an extended period of two weeks.