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

Aggregation behavior of Triton X-114 and Tween 80 at various temperatures and concentrations studied by density and viscosity measurements

“…The increase in T of the sample liquid results in the volume expansion causing more spacing between the molecules of the surfactant leading to a less ordered structure due to the decrease in the cohesive force between the molecules of the samples [14]. For this reason, the density (q) of aqueous solutions of the studied surfactants, Triton X-114 (TX114) and Tween 80, decreases with the rise in T ( Fig.…”

Thermodynamic Parameters and their Dependence on Temperature in the Range 298–353 K for Ethoxylated Sorbitan Ester Tween 20, 40, 60 and 80 Surfactants

“…The thermodynamic parameters evaluated here and some other parameters not computed here, together help to estimate P i , 'a', 'b' and 'r' important parameters through which, structural details and temperature effect can be studied [11]. The V a values estimated here are larger than the corresponding Schaaf's V a values calculated by Ultrasonic technique [21]. In present approach, shape of the molecule matters much in the estimation of V a .…”

“…This means IMF gets strengthened at lower T, thereby bringing molecules of a tween closer in each liquid. At each temperature, V(Tw [21]. From these observations, only possible prediction is that IMF, hence CF strengths in different tween materials are different because, the magnitude of CF is also dependent on internal pressure (IP), which is different in different liquids [11].…”

“…From these observation it is inferred that the expansion of liquids results in loosening of the molecular packing and increase in the intermolecular spacing. Due to this, each sample becomes more and more compressible with rise in T. The compressibility in each sample depends on two factors namely, effect of T on compressibility of hydrocarbon tail part of the surfactants and the interaction among head groups of the neighbouring molecules, as the head of each molecule is polar in nature [21]. As T increases, the cohesive force between the neighbouring molecules in a liquid decreases making molecular bond relatively less strong.…”

“…Thermodynamic parameters are very sensitive to the volume expansivity a. Hence, to calculate a, molar volumes computed up to higher decimal places than the one reported [21] are required. Therefore, re-evaluated molar volumes (V) at different temperatures (T) are employed to depict the nature of variation of V against T. The distribution of points on the V v/s T plot for each sample is fitted to the linear equation of the form.…”