Dynamic surface properties of aqueous media imparted by a sugar-modified organosiloxane surfactant

Abstract

A novel tetrasiloxane-tailed surfactant bearing oligo(ethylene oxide) methyl ether and sugar moieties (TGA-2) has been evaluated. The dynamic surface tension (DST) and spreading properties imparted to water by TGA-2 have been investigated. DST parameters, namely effective diffusion coefficient, activation barrier, and contact angle have been calculated and analyzed. A general diffusion mechanism of surfactant TGA-2 has been delineated. DST analyses yielded significantly different long-term (D_L) and short-term (D_S) diffusion coefficients, implying that the adsorption process involves a mixed diffusion-kinetic mechanism. Adsorption activation energies (E_a) of the surfactant TGA-2 have been measured as 9.14 kJ/mol at 4 × 10⁻⁵ M and 19.37 kJ/mol at 4 × 10⁻⁴ M. These small E_a values suggest that the tetrasiloxane group is favorable for adsorption. A polytetrafluoroethylene (PTFE) membrane was chosen as a solid substrate to demonstrate the spreading ability imparted by TGA-2. At a TGA-2 concentration of 0.5% in water, the contact angle decreased from 57° to 7.8° in 60 s, such that the droplets became almost flat.

GRAPHICAL ABSTRACT

Keywords:

• Dynamic surface tension
• Organosiloxane surfactants
• Diffusion coefficients
• Activation barrier
• Spreading ability

Additional information

Funding

The work was financially supported by Natural Science Foundation of Shanxi (No. 201801D121051), Doctoral Scientific Research Foundation of Taiyuan University of Science and Technology No. 20162015 and No. 20162023), Shanxi Scholarship Council of China (Grant No. 2017-086), Science and technology innovation project of colleges and universities in Shanxi (Grant No. 2017158).