Supramolecular Structuring of Hydrogels and Transient Polymer Networks

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9808433 Moore The proposal outlines an experimental and theoretical study on the structure and behavior of synthetic amphiphilic polymers. The research plan calls for the design, synthesis, and characterization of macromolecular architectures containing oligomeric segments that adopt a well-defined secondary structure. These folded segments expose information-rich surfaces that can self-organize into higher-order forms. Five different types of amphiphilic polymer architectures are proposed. Three of these will involve sequence-specific phenylene ethynylene oligomers, either attached as grafts or end- groups to water-soluble polymers, or, chain-extended with a hydrophilic comonomer to produce a multiblock main-chain architecture. Two others contain conformationally restricted phenylacetylene macrocyclic segments, which will either be grafted as pendant groups onto a hydrophilic polymer or attached to the ends of a water-soluble chain. The architectures containing macrocyclic segments are predisposed toward nano- tubular organizations that result from face-to-face hydrophobic association between planar rings. In contrast to the macrocyclic systems, architectures that incorporate oligomeric segments can exist in either conformationally ordered or disordered states. Thus it should be possible to design sequences that fold or unfold in response to an external stimulus. This may lead to transient networks and gels that reversibly assemble or disassemble in a prescribed fashion. %%% The proposed research is being performed to better understand the structure and properties of amphiphilic macromolecules. Amphiphilic polymers are used in many commercial applications (e.g., detergents and waterborne coatings), and they show considerable promise in a variety of medical applications and as stimuli-responsive materials. From a fundamental standpoint, it is interesting to consider that proteins too, are amphiphilic macromolecules. Given the versatile functions perf ormaed by protein molecules, it is a worthwhile endeavor to mimic their behavior with synthetic substances. ***