Supramolecular Polymers with Orthogonal Functionality

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.