(381f) Self-Assembly and Mechanical Properties of Di-Fmoc-L-Lysine Containing Molecular Gels

Molecular gels formed by self-assembly of low molecular weight gelators are of significant interest because of their potential applications in drug delivery, tissue engineering, materials for sensors, etc. Here, we present gelation of a low molecular weight gelator, di-Fmoc-L-lysine, in various water-organic solvent mixtures through solvent-trigger approach. Di-Fmoc-L-lysine has two aromatic moieties and multiple hydrogen bond donors and acceptors making it an interesting material to study. FTIR technique was used to capture change in chemical fingerprints during the gelation process. AFM and SEM results indicate fibrous structure in these gel with the evidence of branching. Association of gelator molecules during the early stage of gelation leading to such structures has also been predicted by molecular dynamics simulation. Shear and cavitation rheology were used to investigate the mechanical properties of these gels. The gels display strain-softening behavior at moderate strain values. Cavitation rheology technique captures the critical pressure for fracture. Critical energy release rate (G_c) was estimated from the critical pressure and the magnitude of G_c was found to be an order of magnitude lower than that reported for the polymer gels indicating different failure mechanism in these gels.