Binary diamondoid molecular gels

We demonstrate the formation of gels composed of saturated carbon cage, diamondoid molecules that are rendered attractive through acid-base, non-covalent interactions (hydrogen bonding either with or without proton transfer). The gels are formed by mixing dimethyl sulfoxide (DMSO) solutions of 1-adamantanecarboxylic acid (A1C) with 1-adamantylamine (A1N). Upon mixing at vanishing concentrations, these diamondoid molecules rapidly aggregate. At approximately 3% by weight, the resulting suspension forms a percolated network. These resulting gels have elastic moduli of 10^2-10^4Pa at diamondoid concentrations in the 3-7wt% range. With increasing applied stress these gels yield and shear thin. Upon cessation of the applied stress, the gels recover their quiescent properties and demonstrate reversibility. At 1:1 mole ratio of 1-adamantanecarboxylic acid (A1C) and 1-adamantylamine (A1N), the gel’s elastic modulus increases as ϕx with x~4. Transmission Electron Microscope (TEM) images indicate that the gels are formed from a network of interwoven and branched fibers. In combination, the flow properties and TEM images indicate that the fibers can be broken down under shear and reform in the absence of shear. Both Wide-angle and Small-angle X-ray Scattering (WAXS and SAXS) are used to investigate the gel’s microstructure. Particular attention is paid to determine the applicability of models for colloidal gelation to these molecular gels