Insights into the volumetric properties, conductive property, and interaction behaviors of two nitrile functionalized ionic liquids mixture systems with γ-butyrolactone

•Two nitrile-functionalized ionic liquids mixture systems with γ–butyrolactone were prepared.•The densities and conductivities of two mixture systems were measured.•The excess molar volumes (VE) and apparent molar volumes (Vϕ), were calculated from the density data.•The behaviors of intermolecular interactions were explained by the volumetric properties changes, DSC analysis, IR spectrum shifts, and DFT calculations.