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2D-LC/SEC-(MALDI-TOF)-MS Characterization of Symmetric and Nonsymmetric Biocompatible PEOm–PIB–PEOn Block Copolymers

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journal contribution
posted on 08.10.2013 by Haitham Barqawi, Matthias Schulz, Adekunele Olubummo, Volker Saurland, Wolfgang H. Binder
Complex copolymer mixtures can be directly analyzed via multidimensional chromatographic techniques after successful synthesis. High-performance liquid chromatography coupled to size exclusion chromatography (LC/SEC) revealed detailed information on the chemical composition, polymeric structure, and molar mass distribution of copolymer mixtures, in particular of symmetric and nonsymmetric α-TEO-ω-PEO telechelic PIB copolymers. A series of azide/alkyne “click” reactions after living polymerization reactions were used to prepare the either symmetric or nonsymmetric PIB–PEO-based triblock copolymers of the general structure (PEOn–PIB–PEOm BCPs (with n = 3; m = 3, 12, or 17)). In order to demonstrate the efficiency of the “click” reaction and thus the purity of the final triblock copolymers, the critical conditions of the PIB-homopolymers (Mn = 3–30 kg mol–1) in the isocratic elution mode (LCCC) were investigated. Thus, it was possible to separate the final polymers from their intermediates using a reversed-phase Atlantis-RP C18 column as stationary phase and a mixture of methyl-tert-butyl ether/methanol (85.34/14.66 (w/w)) as mobile phase. On the basis of the PEO segment length and overall hydrophobicity of the BCPs, we observed a complete separation of the stepwise “click” products. Finally, direct coupling of the 2D-LC/SEC to (MALDI-TOF) mass spectrometric techniques allowed a clear identification of all reaction steps proving the structure of the final symmetric and nonsymmetric triblock copolymers.