Structure-Function Relationships of Self-Assembled Fibrillar Gels

Abstract

Fibrillar gels represent an important class of materials with commercially relevant applications in the cosmetics and pharmeceutical industries and biological significance as the underlying structural component in many soft tissues. In this work we study two distinct fibrillar gels that are different in terms of constituent molecules, solvent, gelation mechanism and mechanical properties. Fibrin is a naturally occuring protein that forms covalently crosslinked hydrogels and is responsible for the strain hardening of blood clots. In contrast, P3HT is a synthetic conjugated polymer that forms a thermoreversible physical gel in organic solvents and is utilized as an active component in organic solar cells. A combination of small angle scattering techniques is used to characterize the morphology of these gels, both the individual fibers and the network structure, over large length scales between 1 nm and 10 µm. Furthermore, the combined rheological and structural characterization of these gels is used to develop relationships between the structural and mechanical properties of these systems. In fibrin gels the structural origin of strain hardening is investigated by directly probing the structure of hydrated gels as they are strained. Additionally, rheoSANS measurements have been utilized to investigate the gelation and dissolution of P3HT gels. By exploring systems with very different mechanical and physical properties we have developed a framework for analysis that can be applied to a variety of fibrillar systems.