Olefin Metathesis for the Synthesis of Supramolecular Structures

The research presented in this thesis combines the versatility of olefin metathesis with the concept of supramolecular chemistry. Several supramolecular architectures, such as liquid crystalline polymers, catenanes, and self-assembled monolayers were designed with olefin metathesis. Chapter 1 introduces several ABA triblock copolymers synthesized by welldefined, bimetallic catalysts and norbomene-based monomers. Sequential addition of these monomers yielded the triblock copolymers with low polydispersities and controlled molecular weight. One objective of this thesis is the synthesis of side-chain liquid crystalline material via ROMP. Therefore the synthesis and polymerization of a number of norbomene and cyclobutene-based monomers bearing nitrostilbene side-chains is presented. The liquid crystalline behavior was determined by differential scanning calorimetry (DSC) and optical polarized microscopy. The poly(norbomene)s show nematic mesophase behavior whereas the poly(cyclobutene)s display enantiotropic smectic A mesomorphism. A 1:1 diblock copolymer also shows enantiotropic smectic A mesomorphism. This difference in mesophase behavior was attributed to varying degrees of backbone rigidity. As an extension of the work described above, Chapter 3 describes the synthesis and characterization of discotic liquid crystalline material for their use as hole transport materials. Norbornene- and cyclobutene monomers containing triphenylenes were synthesized introducing a newly developed strategy for the synthesis of the triphenylene-based side-chain. The mesomorphic behavior of the polymers was investigated by DSC and powder diffraction X-ray scattering and was identified as discotic liquid crystalline. In an effort to synthesize a variety of supramolecular structures via RCM, Chapter 4 illustrates a new strategy for obtaining self-assembled interlocked and intertwined architectures. Three different self-assembly approaches based on metal templating, hydrogen bonding, and π-π interactions followed by RCM to yield catenane or rotaxane structures are introduced. The final chapter presents a new strategy to polymerize directly from surfaces through ROMP. Using a two-step self-assembly approach, a 'molecular wire' molecule containing norbornene and thiol was anchored to gold surfaces pretreated with dodecanethiol. Addition of a ruthenium catalyst to the functionalized surface followed by addition of monomer resulted in the synthesis of polymer brushes on the surface. The polymer brushes were characterized by scanning tunneling microscopy, atomic force microscopy, and scanning electron microscopy.