Supramolecular Gels from Sulfonic Acid-Containing Two-Component Gelators: Molecular Dynamics Simulation, Dye Absorption and Multianalyte Sensing Studies.

We investigated the design and gelation behavior of some two-component supramolecular gels formed from two sulfonic acids, i.e., naphthalene-2-sulfonic acid and (1R)-(-)-10-camphorsulfonic acid paired with various organic amines. This study utilized experimental characterizations, functional studies and molecular dynamics (MD) simulations to study the gelation process. Remarkably, many of these two-component gelators successfully gelled multiple organic solvents and water, while the sulfonic acids or the amines did not individually. This underscores the critical synergistic role that both components play in gel formation. We conducted comprehensive FTIR, XRD, SEM, and rheological characterizations of the hydrogel and some organogels. MD simulations were also performed to evaluate the gels' RDF, CN, H-bonding, and partial density and explore gelation dynamics. A good correlation was observed between the predicted aggregation behavior from both experimental characterization and MD simulation. The findings confirm that gel formation is driven by secondary interactions, including H-bonding, ionic interactions, π-π stacking, and solvophobic forces, which promote gelator aggregation and supramolecular organization. Remarkably, naphthalene-2-sulfonic acid and 1-naphthylamine formed hydrogels across an extensive pH range of 0.2 to 12, which is uncommon among other gelators. The morphologies of these hydrogels exhibited pH dependence, indicating the presence of varying aggregation mechanisms. Furthermore, we have demonstrated several applications for this hydrogel. It effectively removed two water-soluble dyes, methylene blue and crystal violet, from their aqueous solutions. Moreover, the hydrogel can detect a variety of analytes. Upon exposure to volatile organic amine vapors, hydrogel films rapidly melt, providing a straightforward method for detecting amines without the necessity for sophisticated instruments. Trifluoroacetic acid and methanol were also detected similarly, albeit with longer response times. Overall, this work highlights the efficient preparation of multifunctional two-component gels using simple and commercially available sulfonic acids, thus eliminating the need for the tedious and time-consuming synthesis of gelators.