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.

Molar mass characterization of hydrophilic copolymers, 2 Size exclusion chromatography of cationic (meth)acrylate copolymers

“…In ref. [13] it was shown that anionic copolymers can be separated by SEC using a novel polyester-based packing (GRAM) as the stationary phase and dimethylacetamide (DMAC) as the mobile phase. The mobile phase was modified with LiBr and acetic acid to screen polar and ionic interactions.…”

“…In the first part of this publication we described a robust and reproducible method for the molar mass analysis of neutral and anionic copolymers based on methacrylic acid and different (meth)acrylates [13]. These copolymers are produced by Röhm, Germany, under the trade name EUDRAGIT ® .…”

“…Different from the anionic copolymers investigated in ref. [13] the refractive index increments of the cationic copolymers are very low resulting in very noisy light scattering curves, which cannot be used for the calculation of molar mass distributions.…”

High‐Resolution Separation of Oligo(acrylic acid) by Capillary Zone Electrophoresis

“…[2] However, the free radical polymerization of AA is very complex [3,4] and the characterization of AA-based polymers is difficult. [5] Nevertheless, some researchers have been able to control molar masses in the free radical polymerization of AA using RAFT agents [6] and nitroxides, [7] which have led to welldefined (although not uniform, i.e. not ''truly monodisperse'') poly-or oligo(acrylic acid) (oligoAA) chains.…”

“…The separation assumed to be based on size exclusion proves to be strongly disturbed by adsorption phenomena, [5] and there is some controversy about the SEC of PAA. Aqueous SEC of PAA and SEC of methylated PAA in tetrahydrofuran yield significantly different molar mass Summary: Oligo(acrylic acid)s, produced by RAFT polymerization, have been separated and analyzed for the first time by capillary zone electrophoresis.…”