Imidazole-based surface-active gelator: Thermo responsive gel-to-gel transition of 1-hexadecyl-3-methyl imidazolium salicylate for multidimensional applications

Abstract

Surfactant based low molecular weight gelators with stimuli responsive properties are advantageous in designing new age smart materials for multipurpose applications. In our efforts towards developing the smart surface active gelators, herein we report synthesis of the 1-hexadecyl-3-methyl imidazolium salicylate (C16MeImSal) with better surface activity than its precursor surfactant and exhibited thermo-reversible gel-to-gel transition, from transparent fibrous, wormlike gel to opaque lamellar gel phase. The thermo-reversible gel-to-gel transition is due to hydrogen-bonding, hydrophobic- and van der Waals interactions. The gel phase behavior was observed visually, by vial inversion and dilution with water, by Uv–Vis (solution turbidity) and FT-IR spectroscopy (shift of νO-H, νC-H, νCO2- band frequencies). Small angle neutron scattering was used to investigate the shape and size of the aggregates responsible for the phase transition. The gelator was used to construct the hybrid pharmaceutical ionogel by successfully encapsulating the chemotherapeutic drug imatinibmesylate and diclofenac sodium drug within the ionogel matrix. Further, the ionogel was used to absorbs heavy-metal ions (25.67 % Cu2 + and 23.42 % Co2 + ) and ionic dyes (45.07% methyl orange and 32.53% crystal violet) from aqueous medium opening up new avenues in the field of low cost and highly efficientsmart gelators with multitasking abilities.