Abstract
Measurements of the surface tension of aqueous solutions of polysorbates (Tween 20, Tween 60 and Tween 80) at 293, 303 and 313 K were made. On the basis of the obtained results the Gibbs surface excess concentration of the Tweens at the water–air interface and critical micelle concentrations were determined. Knowing the Gibbs surface excess concentration and taking into account the difference between the limiting area occupied by water and Tween molecules at the water–air interface, the fraction occupied by Tween molecules was established. The limiting area occupied by the Tween molecule was calculated by applying the Joos equation. The area determined in such a way was confirmed by the calculations of cross section of Tween molecules based on the bond lengths and the angles between them as well as the average distance between the molecules, taking into account their different conformations. This area was used for calculation of the standard Gibbs energy of adsorption using the Langmuir equation. The standard Gibbs energy of Tweens adsorption at the water–air interface was also calculated from the hydrophobic part of Tween molecule–water interface tension and that of hydrophobic part. Using the determined values of standard Gibbs energy of adsorption at different temperatures, the standard enthalpy and entropy values were deduced. The standard thermodynamic functions of micellization were also determined and compared to the Gibbs energy of Tween molecules interactions through the water phase.
Highlights
Polysorbates, among others are applied in the food, cosmetic and pharmaceutical industries because of their nontoxicity, availability, emulsification, solubilization and other advantages [1,2,3,4,5,6,7]
In most cases the surfactant adsorption at the water–air interface is determined using the Gibbs isotherm equation, which is based on the surface tension measurements of aqueous solutions of surfactants
(iii) The packing of the molecules of each Tween depends on the temperature. (iv) The standard Gibbs energy of Tween adsorption depends on the kind of Tween and temperature
Summary
Polysorbates, among others are applied in the food, cosmetic and pharmaceutical industries because of their nontoxicity, availability, emulsification, solubilization and other advantages [1,2,3,4,5,6,7]. T80 is widely used in drug dosage forms to control wetting, stability and solubilization of hydrophobic drugs [3, 4, 6, 7] Their wide practical applications are not completely explained, taking into account their adsorption and aggregation properties in the aqueous media. The purpose of our studies was to determine the adsorption of Tweens at the water–air interface and their CMCs based on the surface tension of the hydrophobic (tail) and hydrophilic (head) parts of the Tweens For this purpose, the surface tensions of the aqueous solutions of T20, T60 and T80 at 293, 303 and 313 K were measured. On the basis of the obtained values of surface tension, the thermodynamic analysis of the adsorption and micellization processes of Tweens was performed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
