title: Switchable supramolecular polymers from the self-assembly of a small monomer with two orthogonal binding interactions.
abstract: The low molecular weight heteroditopic monomer 1 forms supramolecular polymers in polar solution as shown, for example, by infrared laser-based dynamic light scattering (DLS), small-angle neutron scattering (SANS), electron microscopy (TEM, cryo-TEM), and viscosity measurements. Self-assembly of 1 is based on two orthogonal binding interactions, the formation of a Fe(II)-terpyridine 1:2 metal-ligand complex and the dimerization of a self-complementary guanidiniocarbonyl pyrrole carboxylate zwitterion. Both binding interactions have a sufficient stability in polar (DMSO) and even aqueous solutions to ensure formation of linear polymers of considerable length (up to 100 nm). The supramolecular polymerization follows a ring-chain mechanism causing a significant increase in the viscosity of the solutions at millimolar concentrations and above. The linear polymers then further aggregate in solution into larger globular aggregates with a densely packed core and a loose shell. Both binding interactions can be furthermore switched on and off either by adding a competing ligand to remove the metal ion and subsequent readdition of Fe(II) or by reversible protonation and deprotonation of the zwitterion upon addition of acid or base. The self-assembly of 1 can therefore be switched back and forth between four different states, the monomer, a metal-complexed dimer or an ion paired dimer, and finally the polymer.
authors.affiliation: Institut für Organische Chemie, Universität Duisburg-Essen, Universitätsstrasse 7, 45141 Essen, Germany.
authors.forename: Gerd
authors.initials: G
authors.lastname: Gröger
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Meyer-Zaika
authors.forename: Christoph
authors.initials: C
authors.lastname: Böttcher
authors.forename: Franziska
authors.initials: F
authors.lastname: Gröhn
authors.forename: Christian
authors.initials: C
authors.lastname: Ruthard
authors.forename: Carsten
authors.initials: C
authors.lastname: Schmuck
mesh_terms: D006863:Hydrogen-Ion Concentration; D008027:Light; D008670:Metals / Q000737:chemistry; D008854:Microscopy, Electron; D008958:Models, Molecular; D008968:Molecular Conformation; D033363:Neutron Diffraction; D011108:Polymers / Q000737:chemistry*; D053838:Scattering, Small Angle; D014783:Viscosity
chemical_list: D008670:Metals; D011108:Polymers