Dynamic Surface Properties of Eco-Friendly Cationic Saccharide Surfactants at the Water/Air Interface

Abstract

Abstract The equilibrium surface properties and dynamic surface tension (DST) are presented for aqueous solutions of novel eco-friendly cationic saccharide surfactants (CnDGPB) at different concentrations and temperatures. The equilibrium surface tension, the DST, the effective diffusion coefficients and the activation barrier of the surfactants are calculated and analyzed. In addition, the general diffusion mechanism of the surfactants is proposed. The equilibrium surface tension results show that the γCMC and CMC values decrease with increasing temperature. The interactions (repulsion forces) between the hydrophobic groups and water molecules decrease with increasing temperature, which results in increased HLB values. This phenomenon causes a higher Amin and lower Γmax. The DST of CnDGPB below and above the CMC is tested by the maximum bubble pressure method at temperature from 25 °C to 45 °C. The adsorption activation energy of CnDGPB is between 3 kJ/mol and 20 kJ/mol. The results show that the final stages of the DST decays are consistent with the activated diffusion-controlled adsorption mechanism.