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Supramolecular Polymers with Orthogonal Functionality

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journal contribution
posted on 23.12.2014, 00:00 by Souleymane Coulibaly, Christian Heinzmann, Frederick L. Beyer, Sandor Balog, Christoph Weder, Gina L. Fiore
Supramolecular polymers with orthogonal interactions are of broad interest, and reports on such materials with multifunctional stimuli-responsive behavior are rare. Polymer blends based on a poly­(ethylene-co-butylene) core (PEB) terminated with either 2-ureido-4­[1H]-pyrimidinone (UPy) hydrogen-bonding motifs (UPy-PEB-UPy) or 2,6-bis­(1′-methylbenzimidazolyl)­pyridine (Mebip) ligands coordinated to metal ions ([M­(Mebip-PEB-Mebip)]2+ (M = Zn, Fe)) were prepared. The degree of orthogonality of the supramolecular polymer blends was explored by UV–vis spectroscopy, small-angle X-ray scattering, and dynamic mechanical thermal analysis (DMTA). Polymer blends of [Zn­(Mebip-PEB-Mebip)]­(NTf2)2 and UPy-PEB-UPy resulted in a statistical mixture of noncovalent interactions, whereas blends with [Fe­(Mebip-PEB-Mebip)]­(ClO4)2 and UPy-PEB-UPy assembled in an orthogonal fashion. Additionally, the DMTA showed two transitions for the disassembly of UPy (ca. 60 °C) and Fe2+-Mebip (ca. 180 °C) phases. The Fe2+-Mebip interactions were selectively disrupted by the addition of a competitive ligand, demonstrating that each supramolecular motif can be targeted with either a thermal or chemical stimulus.