Metal/ligand-induced formation of metallo-supramolecular polymers

The use of metal-ligand binding as the driving force for the self-assembly polymerizations of a ditopic ligand offers a facile route to the preparation of organic/inorganic hybrid materials. Such metallo-supramolecular polymers potentially offer the functionality of the metal ion along with the processability of a polymer. We report, herein, the preparation and investigation of a series of metallo-supramolecular polymers prepared from three different (macro)monomer units. One monomer has a penta-(ethylene glycol) core while the other two consist of poly(tetrahydrofuran) cores of different molecular weights (M _n = 2000 or 4800 g mol ^-1). Attached to either end of these polyether chains is the terdentate ligand 2,6-bis(benzimidazolyl)-4-oxypyridine. Addition of a metal ion (e.g., Fe(II), Co(II), Zn(II), or Cd-(II)), which can bind to the ligand in 1:2 ratio, to a solution of the (macro) monomer results in the self-assembly of linear supramolecular polymers. Viscosity studies demonstrate the formation of self-assembling aggregates and mechanically stable films can be obtained by casting from solution. A series of studies (including DSC, DMA, TGA, and WAXD) were carried out in order to examine the solid-state properties of the films. The metallo-supramolecular polymers, which have the largest poly(tetrahydrofuran) core, form thermoplastic elastomeric films in which the ionic blocks and soft poly(tetrahydrofuran) segments are phase separated.