Adsorption and aggregation behavior of aliphatic alcohol polyoxyethylene ether phosphate with different ethylene oxide addition numbers

Aliphatic alcohol polyoxyethylene ether phosphate (AEP) is an excellent surfactant, and thus the relationship between the ethylene oxide addition number of AEP and properties of AEP should be systematically described to improve the application efficiency of this surfactant. In this paper, the static surface tension, dynamic surface tension and wetting properties of AEP with different ethylene oxide (EO) addition numbers were measured to study the effect of the EO addition number on the adsorption performance. The aggregation behavior of AEP in different phases was observed using polarizing microscope (POM), small angle X-ray scattering (SAXS) and steady-state fluorescence quenching methods. An increase in the EO addition number increases the CMC and the maximum adsorption of reduced AEP. However, the surface activity efficiency increases concomitantly with the increase in the EO addition number. The linear relationship between the number of PC20 and EO addition numbers was determined. An increase in the EO addition number results in a faster rate of surface tension reduction and faster film formation, which is controlled by a mixed diffusion-kinetic adsorption mechanism. As the concentration of AEP increases, AEP with different EO addition numbers is present as a lamellar phase liquid crystal, but an increase in the EO addition number decreases the order of the liquid crystal. An intuitive relation between the EO addition number and AEP micelle aggregation behavior was not observed in the surfactant solution.