Hierarchy and architecture - tailoring physical associations toward functional networks and gels*

Taking cues from biological systems, we are interested in understanding how physical associations may be utilized in the design of functional materials: (1) supramolecular networks and elastomers, and (2) peptide-polymer hybrids.

Supramolecular interactions may hold the key to the development of elastomers with a tailored elastic response and improved mechanics, such as observed in the muscle protein titin. We have developed supramolecular elastomers and interpenetrating network systems that probe the interplay of non-covalent and covalent interactions in structural organization and mechanical response. In this research, concepts of interfacial control of self-assembly, composition, and dynamics as it relates to mechanical behavior are examined. Variations in non-covalent interaction strength and network regularity are also highlighted as handles to tune dynamic response and morphology.

The underlying structural blocks of nature’s high-performance materials are polypeptides, which exhibit secondary structures that contribute to the high degree of molecular order observed in biohybrid materials. Polymeric hybrids with a focus on ‘soft’ domain ordering have been designed using a dynamic elastomeric polyurethane/urea framework with poly(dimethyl siloxane) (PDMS) and poly(ethylene glycol) (PEG) soft segments. We explored the impact of peptide chain length/fraction, and secondary structure on mechanics in chain-extended and non-chain extended systems. Extending this work to an overlay of covalent and non-covalent architectures influenced peptide hydrogen bonding and hierarchy. Tailored physical associations between the hard and soft domains yielded functional responses with applications as injectable hydrogels and actuating materials.