Probing the temperature- and concentration-dependent nonlinear thermodynamic parameters of 5CB–ZnO–dodecane mixtures

The effects of temperature and zinc oxide nanoparticle (ZnONP) concentration on the nonlinear thermodynamic parameters of 4′-pentyl-4-biphenylcarbonitrile (5CB) were systematically investigated. Five 5CB– x ZnO–dodecane mixtures ( x = 0, 0.25, 0.5, 1.0 and 2.0 wt%) were prepared, and their density was measured over the temperature range 293.15–311.15 K. From the measured density data at different temperature, various nonlinear parameters including Moelwyn–Hughes parameter ( C 1 ), Beyer’s nonlinearity parameter ( B/A ), isothermal, isobaric and isochoric acoustical parameter ( K ith , K iba , K ich ), isothermal Gruneisen parameter (Γ), Anderson–Gruneisen parameter ( δ ), Sharma parameter ( S o ), Lennard-Jones repulsive exponent ( n ), fractional free volume ( f ), Huggins parameter ( F ) and related acoustical parameters were evaluated. C 1 and Γ decreased modestly with temperature, signalling a gradual reduction in vibrational anharmonicity and molecular ordering, whereas f increased, reflecting enhanced molecular mobility and weak molecular packing. Across all compositions these parameters were largely insensitive to ZnONP loading, indicating weak host–guest perturbation of the 5CB matrix. The empirical relation C 1 ≈ δ + 1 held throughout, and the S o remained invariant with both temperature and concentration. The findings establish that temperature, rather than nanoparticle concentration, predominantly governs the anharmonic and free-volume behaviour of these liquid-crystal mixtures.