(342h) Probing Self-Assembly and Mechanical Properties of a Self-Assembled Molecular Gel

Molecular gels are of significant interest because of their potential applications in drug delivery, tissue engineering, materials for sensors, etc. Here, we consider a molecular gel formed by self-assembly of a low molecular weight gelator, di-Fmoc-l-lysine, in various water-organic solvent mixtures through solvent-triggered approach. Di-Fmoc-L-lysine has two aromatic moieties and multiple hydrogen bond donors and acceptors. Association of this complex gelator molecule during the early stage of gelation has been captured by molecular dynamics simulation. FTIR technique was used to track the change in chemical fingerprints during the gelation process. AFM and SEM results indicate fibrous structure in these gels and these long fibers topologically interact to form a gel-like material. The elastic modulus (G’) was found to be a function of gelator volume fraction (f) and we obtained G’~f^1.8, having similarities with entangled polymer networks. The stress-relaxation behavior of these gels has been captured using the stretched-exponential function. The large stress-relaxation time for these gels has been attributed to the long fiber dimensions, and the stretching exponent value of 1/3 indicates polydispersity in fiber dimensions. Cavitation rheology experiments capture fracture-like behavior of these gels with critical energy release rate of ~0.1 J/m², an order of magnitude lower than that reported for polymer gels.