Supramolecular gels: using an amide-functionalized imidazolium-based surfactant

Abstract

Studies on supramolecular gel aggregates via supramolecular interactions are very fascinating and impressive. The interactions of gelator with solvent and inorganic salt can functionalize, activate, or control the properties of supramolecular gels. A lot of work on this area has been done, but all these contributions are only at an early stage. In this work, we tuned the gel formation conditions and properties by using low-molecular-weight gelator (LMWGs), amide-functionalized imidazolium-based surfactant, viz., N-cetyl-N′-acetamido imidazolium bromide ([N-C16, N′-CONH2-Im]Br), in different solvents and with inorganic salt additives. Under chemical (Cu2+/H2O2) and physical (temperature) stimuli, gel-sol phase transition occurred in the gel formed from 2 wt% [N-C16, N′-CONH2-Im]Br in the solvent formamide (FM). Accompanied with increased mechanical strength of the gels, morphology alternation from initial straight stripe-shaped structures to curly belt-like textures was observed in the addition of CuBr2. From Small-angle X-ray scattering (SAXS) measurements, bilayer units with interdigitated hydrocarbon tails of the gelator were testified to appear in the gels. Comparative experiments demonstrate that the π-π interaction, H-bonding, and hydrophobic interaction between the gelator molecules are the main driving forces for the gelation. The low-cost gelator, facile preparation, and coordination-driven assembly process make the robust gel a good candidate in various applications, such as material templates and drug deliveries.