Towards the synthesis of daisy chain polymers
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Mechanically-interlocked molecules have intrigued synthetic chemists due to their unique architectures and properties. Template-directed synthesis serves as a powerful tool for the preparation of these molecules. Molecular daisy chains are a special class of mechanically-interlocked and self-entangled molecules. Daisy chain polymers, which lack a continuous covalently-bonded backbone, have unexplored properties and may have potential value in applications. Entropy-driven ring-opening metathesis polymerization (ED-ROMP) displays some advantages for the preparation of mechanically-interlocked molecules, and thus may be applied for the synthesis of daisy chain polymers. In this thesis, the monomers designed for an ED-ROMP strategy were a type of 1,10-phenanthroline-copper-based complex rotaxane. The structural analyses of these monomers are discussed and the synthetic procedures for a specific monomer are described. In addition, acyclic diene metathesis (ADMET) of a pseudorotaxane, which is the precursor of the corresponding rotaxane, served as an alternative starting material for the preparation of daisy chain polymers. Grubbs’ II and the Grubbs-Hoveyda II catalysts were utilized separately in the ADMET processes; however, no high molecular weight polymers were obtained from GPC analysis. 1H NMR spectra of the crude from the ADMET reaction showed the complete disappearance of the terminal olefin signals, which is consistent with the formation of cyclic oligomers.