Probing Gelation and Rheological Behavior of a Self-Assembled Molecular Gel

Molecular gels have been investigated over the last few decades; however, mechanical behavior of these self assembled gels is not Well understood, particularly how these materials fail at large strain. Here, we report the gelation and rheological,behavior of a molecular gel formed, by self-assembly of a loW molecular weight gelator (LMWG), di-Fmoc-L-lysine, in 1-propancil/water Mixture. Gels were prepared by solvent triggered technique; and gelation was tracked using Fourier transform infrared (FTIR) spectroscopy and shear rheology. FTIR spectroscopy Captures the formation of hydrogen bonding between the gelator molecules; and the change in I. spectra during the gelation process correlates with the gelation kinetics results captured by rheology. Self-assembly of gelator molecules leads to a fiber-like structure, and these long fibers topologically interact to form a gel-like material. Stretched-exponential function can capture the stress-relaxation data. Stress-relaxation time for these gels have been found to be long owing to long :fiber dimensions, and the stretching exponent value of 1/3 indicates polydispersity in fiber dimensions. Cavitation rheology captures fracture-like behavior of these gels, and critical energy release rate has; been estimated to be of the order 0.1 J/m(2). Our results provide new understanding of the rheological behavior of molecular gels and their structural origin.