Supramolecular Hydrogel Derived from a Simple Organic Salt Capable of Proton Conduction

Exploiting supramolecular synthon approach based on a Cambridge Structural Database (CSD) analysis, a series of easily accessible primary ammonium sulfonates have been synthesized as potential supramolecular gelators. Single crystal X-ray diffraction (SXRD) structures of majority of the sulfonates reported herein revealed the existence of both 1D and 2D supramolecular synthons which are known to play crucial role in gelation. One such salt namely 1-naphthylmethyl ammonium naphthalene-2-sulfonate (N2SNm) produced hydrogel that displayed proton conduction (1.2x10-4 S cm-1) as revealed by Nyquist plot whereas both the xerogel and the as synthesized bulk solid of N2SNm failed to show any measurable conductivity indicating plausible role of water molecules as proton source in hydrogel state. Based on powder X-ray diffraction (PXRD) patterns (simulated from SXRD data of N2SNm and experimental PXRD of the hydrogel), we hypothesized that the water molecules must be the part of the crystal lattice of the hydrogel network to act as proton source.