Formation and mechanics of self-assembled molecular gels

Molecular gels are associated with the formation of space spanning structures produced by aggregation of low molecular weight molecules that associate through hydrogen bonding, π-stacking, acid base or van der Waals interactions. One specific type of gel forming molecule is based on a hydrophobic peptide – fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF). This thesis explores gels formed when water is added to Fmoc-FF dissolved in dimethyl sulfoxide (DMSO). At high water concentrations, gels are formed at concentrations as low as 0.001%. We establish the gel line defining the Fmoc-FF and water concentrations where gels are formed. At fixed water concentration, over a narrow range of Fmoc-FF concentrations, solutions pass from being low viscosity liquids to a rigid material with elastic moduli G’ > 10^5 Pa. Here we characterize the kinetics of gelation and demonstrate that these gels are reversible in the sense that they can be disrupted mechanically and will rebuild strength over time. We attempt to understand the gelation process as arising from increasing strength of attraction between Fmoc-FF molecules with increasing water concentration. Furthermore, an effort is made to describe the underlying changes in strength of attraction leading to gelation and the mechanical behavior of the resulting gels using a dynamic localization theory