ORGN 407 |
| Supramolecular polymers are the ordered chains of small molecules, which are held together through non-covalent interactions. The size and configuration of the supramolecular polymers depend on the concentration, solvent polarity and temperature, which lead to unusual rheological properties. We have previously shown that bis-urea macrocycles can be constructed from rigid spacers and ureas. The monomers predictably assemble into tubular structures in the solid-state through hydrogen bonding interactions. We set out to explore the limits of this structural motif by testing whether the macrocyclic framework could have flexible chains. We synthesized a series of unsymmetrical bis-urea macrocycles from rigid diisocyanates and flexible diamines (Figure 1). Figure 1. Synthesis of unsymmetrical bis-urea macrocycles. Unsymmetrical bis-urea macrocycles were synthesized from rigid C-spacers and flexible poly ethylene glycol chains to form unsymmetrical bis-urea macrocycles. Our hypothesis is that the rigid macrocycles are more likely to adopt tubular assemblies. The unsymmetrical molecules stack in an alternating manner to form tubular structures via hydrogen bonding interactions. Additionally, intramolecular hydrogen bonding is possible when more flexible side chains are present since oxygen atoms can function as an intramolecular acceptor which results in the collapse of the ring structures. We will report the characterization of these monomers and their further self-assembly into ordered supramolecular structures in solid state and in organic solutions. Rigid macrocycles form tubular structures in solid state and limited association in solutions. More flexible macrocycles form the ring collapsed structures and stronger association in solutions.
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Heterocycles and Aromatics, Molecular Recognition and Self Assembly
8:00 PM-10:00 PM, Tuesday, April 8, 2008 Morial Convention Center -- Hall A, Poster
Division of Organic Chemistry |
