Effect of gabapentin on solution surface properties and micellization behavior of betaine-based surfactant ionic liquids

Abstract

This study investigates the surface properties, micellization, and electrical conductivity of betaine-based ionic liquids (ILs) composed of [R-bet][Br] where R represents the C4, C6 and C8 (specifically [C4bet][Br], [C6bet][Br], and [C8bet][Br]) in aqueous gabapentin solutions at concentrations of (0.0000, 0.0100, 0.0300, and 0.0500) mol kg−1 at 298.15 K. The surface tension measurements revealed that increasing gabapentin concentration and alkyl chain length decrease surface tension, indicating significant hydrophobic and hydrophilic interactions. The related thermophysical micellization parameters, including critical micelle concentration (CMC) and minimum surface area per molecule (Amin), exhibited improved micellization and interfacial efficiency with longer alkyl chains. Thermodynamic analysis confirm the spontaneous nature of micelle formation, with more negative Gibbs free energy values for SAILs with longer alkyl chains. The electrical conductivity studies indicate lower limiting molar conductivity (Λ0) at higher gabapentin concentrations, due to increased viscosity and ion-ion interactions. Ion association constants (KA) and DFT-COSMO calculations support stronger hydrophobic interactions and molecular packing influenced by alkyl chain length and gabapentin.