Structured Rigid Rod Framework Gels from Clickable Synthetic Polypeptides

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TECHNICAL SUMMARY:Classical polymer networks, in particular hydrated and solvated crosslinked gels, are typically derived from random covalently crosslinked polymer backbones. Most systematic studies of such systems involve the generation of structures with an effective mesh size that is molecular in nature in a traditional chemically crosslinked system, and defined by random crosslink chemistry. This project involves the construction of highly controlled polymeric networks consisting of rigid rod alpha-helical polypeptides functionalized with short functional groups or oligomeric groups that impart solubility, charge, chelating or ligand groups, and responsive behavior to the network system with modular levels of control. The systems, which utilize a versatile click chemistry for functionalization, can be designed with random crosslinks that link the helical rod-like polypeptide chains to the network, or alternatively, the rods can be linked together at their endgroups through multi-arm linkers to provide highly defined network structures whose mesh size is determined by the extended chain length of the polymer, and mechanical properties influenced by the rigidity of the backbone. Unlike the networks formed from traditional random coil polymers, the high persistence length and rod-like rigidity of the helical structure can provide an open mesh structure. By appending different functional groups to the backbone, it should be possible to create unique gel structures that can present solvated, reactive or chelating groups within the interior of the mesh structures and exhibit controlled mechanical properties. The intellectual merit of this work involves the implementation of fundamental chemistry and physics to explore the control of these novel gel/network architectures with the freedom to modify side groups to manipulate other gel properties, and manipulation of architecture and structure to gain isolation of function and key architectural aspects of the gel system such as mesh size and water hydration. The specific aims of this project are to: 1) develop and extend the synthetic approaches to clickable synthetic polypeptides; 2) investigate new polypeptide conformationally controlled structured framework hydrogels; 3) investigate responsive mesh framework gel systems for which the full responsive behavior is due to the changes in conformation of oligomeric side chains within the rigid framework and 4) demonstrate the incorporation of unique functionality to achieve novel properties for applications such as ion selective membranes or electrolytes and three dimensional matrices for biomaterials with unique decoupled mechanical, transport, and ligand properties.NON-TECHNICAL SUMMARY:New types of polymeric networks will be generated using chemical synthetic methods to create polymer hydrogels in which relatively rigid segments that mimic the behavior of some natural biomolecules are used to strengthen gels while maintaining open mesh structures for molecular transport. The gels will be functionalized with a range of responsive chemical groups, enabling unique properties such as selective transport of ions, sequestration of specific molecules, reactivity, and temperature or pH responsive gating behavior. By exploring this new concept in the generation of molecular rigid rod gel systems, opportunities exist for development of new biomimetic hydrogels for tissue regeneration, drug releasing systems, water separation membranes, and solid state electrolytes for solar, battery and other electrochemical energy and storage applications. Mentoring and outreach to high school age students as well as future faculty development activities will also be a key part of the proposed program, including participation of the PI in outreach programs that engage high school students and undergraduate students. The PI is also a co-Investigator in the NSF funded Open Chemistry Collaborative in Diversity Equity (OXIDE) and National Diversity Equity Workshop (NDEW) for addressing diversity representation in the chemical science faculties, as well as the Future Faculty Workshop for Materials Chemistry.