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 UVvis 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 degrees C) and Fe2+-Mebip (ca. 180 degrees 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.