Interfacial dilational properties of model oil and chemical flooding systems by relaxation measurements

In the present work, the influences of a model organic acid (oleic acid) on the interfacial dilational properties of different types of surfactants (anionic surfactant sodium 4,5-diheptyl-2-propylbenzene sulfonate 377 and asymmetrical anionic Gemini surfactant C12COONa-p-C9SO3Na) and polymers (HPAM and HMPAM) systems were studied at decane–water interface, respectively, by means of interfacial tension relaxation measurements. The decay curves of interfacial tension were fitted by the summation of a number of exponential functions. The dilational elasticity and dilational viscosity component were calculated by Fourier transform and displayed as Cole–Cole plots (plotting ɛi or ɛi/ɛ0 as a function of ɛr or ɛr/ɛ0, respectively). The experimental results show that the interfacial behaviors of both surfactants are part conformance with a diffusion-controlled process and part conformance with a reorientation controlled process. In the case of partly hydrolyzed polyacrylamide Mo-4000, the nature of mixed film is controlled mainly by interaction between polymer chains and surfactant molecules in the interface. As for hydrophobically modified polyacrylamide, the film properties are controlled by the formation of mixed surfactant-hydrophobic block associations in the interface and the reorientation process resulted from exchange of associations between different regions of interface. Under our experimental conditions, the mixed adsorption films formed by oleic acid and surfactant molecules are more compact than pure surfactant films.