Molecular interactions of sodium dodecyl sulphate with isoniazid at various temperatures: experimental and molecular dynamics simulation approach

Abstract The conductivity, surface tension, viscosity and density of sodium dodecyl sulphate (SDS) solutions at different temperatures are precisely measured in the presence of 0.001 M isoniazid (INH) solution at concentrations ranging from 0.04 to 0.001 M. The critical micelle concentrations (CMC) are calculated. CMC decreases in the presence of INH in SDS and increases with rising temperature. Gibbs free energy change (∆G) is determined by using the dissociation constant (α) and mole fraction of CMC (XCMC) from conductivity methods. The negative and positive values of enthalpy change (∆H) and the entropy change (∆S) are observed, respectively. The maximum surface excess concentration (Γmax), the minimum area occupied by surfactant molecule (Amin) at the air–water interface, packing parameters (P), Gibb’s energy of adsorption (∆Gads), molar Gibb’s energy at CMC at maximum adsorption attained (ΔGm), surface pressure at CMC (πCMC), aggregation number (N), micellar radius (R) and pC20 are calculated from surface tension methods and apparent molar volume (Vᵩ) from density is determined. The Jones–Dole coefficient (B) and the Falkenhagen coefficient (A) are determined by viscosity study. Molecular dynamics simulation studies are also included for some systems to obtain density, viscosity, and surface tensions.