Using the metal-ligand interaction to construct complex supramolecular polymer architectures.

摘要

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 processibility of a polymer. This thesis reports the preparation and investigation of a series of metallo-supramolecular polymers prepared from different (macro) monomer units, which consist of flexible alkyl and alkyl ether cores. Attached to either end of these flexible 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 solution casting these solutions. A series of studies (including DSC, DMA, TGA and WAXD) were carried out in order to examine the solid state properties of films. The metallo-supramolecular polymers which have large poly(tetrahydrofuran) cores form thermoplastic elastomeric films in which the ionic blocks and soft poly(tetrahydrofuran) segments are phase separated. It was also possible to prepare gel-like metallo-supramolecular polymers from one of the monomer units mixed with a lanthanoid metal (e.g. La(III), Eu(III)) and a transition metal ion (e.g. Co(II) or Zn(II)). Such materials show dramatic reversible responses to a variety of stimuli, including thermal, mechanical, chemical and light. The nature of the response can be controlled by the nature of the combination of transition metal ion and lanthanoid metal ion used. These metal-ligand studies influenced the development of ligand-containing cyclic precursors that could be functionalized for reversible cyclization using imine and metathesis chemistry. This laid the groundwork for future preparations of interwoven and/or interlocked polymer systems.