Aggregation of cetyltrimethylammonium bromide with hydrolyzed polyacrylamide at the paraffin oil/water interface: Interfacial rheological behavior study

Aggregation behavior of cetyltrimethylammonium bromide (CTAB) and hydrolyzed polyacrylamide (HPAM) at the paraffin oil/water interface has been studied with the method of dilational rheology. The dilational modulus increases with increasing oscillating frequency and decreases with increasing CTAB concentration. For the CTAB–HPAM mixture, the dilational modulus increases with increasing HPAM concentration. This is attributed to the high active complex of CTAB–HPAM formed at the interface, which is confirmed via the surface and interfacial tension measurements. Because of the strong hydrophobic interaction between oil molecules and surfactants, the amount of adsorption of CTAB and the dilational modulus at oil/water interface are smaller than the corresponding ones obtained at the air/water interface. The variations of Gibbs elasticity and dilational modulus of CTAB with the concentration at interface show different profiles.