Ultrasonic study of thermo-acoustic parameters of the polysorbate 20, 40, 60 and 80 liquid surfactants at different temperatures

Ultrasonic velocities (u) and densities (rho) have been measured at different temperatures ranging from 298 K to 353 K for non-ionic (NIC) surfactants like polyoxyethylene (20) sorbitan monolaurate (Tween-20), polyoxyethylene (20) sorbitan palmitate (Tween-40), polyoxyethylene (20) sorbitan monostearate (Tween-60) and polyoxyethylene (20) sorbitan monooleate (Tween-80). From these isentropic compressibility (beta), intermolecular free length (L-f), acoustic impedance (Z), molar volume (V), available volume (V-a), molar sound velocity (R-a) and molar compressibility (W) have been calculated. The focuses on the review of the chemical structure of polysorbates and the influence of the temperature on acoustical parameters have been employed to discuss molecular packing, molecular movement, structure alterations and molecular interactions. (c) 2014 Elsevier B.V. All rights reserved.