Thin wetting film from aqueous solution of polyoxyalkylated DETA (Diethylenetriamine) polymeric surfactant

Thin wetting films from aqueous solutions of the polymeric surfactant polyoxyalkylated diethylenetriamine (DETA), have been studied on hydrophilic SiO2-glass surface. The wetting (receding) contact angles θr of the solution on the glass surface have been measured, using the sessile drop method. Also the contact angle θaq of a drop of doubly distilled water on the same glass surface pre-treated with DETA polymeric surfactant solution has been measured. The receding contact angles θr versus polymeric surfactant concentration Cs curves showed a maximum at θr ≈ 22° in the concentration range of 10−6–2 × 10−5 mol dm−3 DETA. The equilibrium thickness h of wetting films from DETA aqueous solution on hydrophilic SiO2-glass surface, pre-treated with surfactant solution, has been measured using the micro-interferometric method at various concentrations, Cs. At very low Cs (between 10−11 and 10−8 mol dm−3) the h-values are almost constant, then they increase with increasing Cs reaching a maximum at 1.5 × 10−6 mol dm−3, after which they decrease with further increase in Cs. Both θr and h exhibit largest values in the concentration range between 2 × 10−6 and 2 × 10−5 mol dm−3 DETA. The analysis of the results obtained shows that the stability of the wetting films from aqueous solutions of DETA is determined by the electrostatic, steric, and hydrophobic components of disjoining pressure, respectively by the adsorption and orientation of the polymeric DETA molecules on the SiO2-glass surface.