Using liquid chromatography at the critical point of adsorption the molar mass and the polydispersity of the individual blocks in block copolymers of decyl and methyl methacrylate are determined. In addition, the total molar mass and the chemical composition of the block copolymers are calculated and compared to data from conventional size exclusion chromatography (SEC) and SEC with coupled density-refractive index detection. The agreeement of the data obtained by the different methods is found to be very good.

Block copolymers of decyl and methyl methacrylate were analyzed by liquid chromatography at the critical point of adsorption. The molar mass and the polydispersity of the decyl methacrylate block was determined using chromatographic conditions resulting in a critical mode for poly(methy1 methacrylate). In addition, using the same column system, the total molar mass and polydispersity of the block copolymers were determined, operating at chromatographic conditions insuring a size exclusion mechanism for both components.CCC 0025-1 16X/93/$05.00

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.

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A robust and reproducible method for the molar mass analysis of cationic copolymers based on dimethylaminoethyl methacrylate or trimethylammonioethyl methacrylate 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 an amino comonomer content up to 50 wt.-%. To suppress the different polar and ionic interactions between sample molecules, stationary phase and eluent, DMAC was modified with LiBr and tris(hydroxymethylamino)methane (TRIS). Calibrating the SEC system with poly(methyl methacrylate) of narrow polydispersity, molar masses were obtained that are in good agreement with viscosity data. Reproducibility and robustness of the novel method were proven by running samples for an extended period of two weeks.