Effect of branched chain and polyoxyethylene group on surface dilational rheology of cationic surfactants

The measurements of dynamic surface tensions and surface dilational rheological properties were carried out for four cationic surfactants aqueous solutions, hexadecanol glycidyl ether ammonium chloride (C16PC), guerbet alcohol hexadecyl glycidyl ether ammonium chloride (C(16)GPC), hexadecanol polyoxyethylene(3) glycidyl ether ammonium chloride(C-16(EO)(3)PC) and guerbet alcohol hexadecyl polyoxyethylene(3) glycidyl ether ammonium chloride (C(16)G(EO)(3)PC), using the oscillating bubble method. The influences of surface ageing time, surface pressure, dilational frequency and bulk concentration on surface rheological properties have been expounded. It is found that diffusion-exchange process plays the crucial role for C16PC film at all experimental concentrations. On the other hand, the relaxation process in-surface dominates the properties of film at low and high bulk concentration for branched cationic surfactants and C-16(EO)(3)PC respectively. The branched hydrophobic chain will enhanced the molecular interactions at the surface and improve the value of modulus maximum. The introducing of EO group will produce new relaxation process, such as the variation of orientation of EO group at the surface, which enhances the contributions of viscous nature of film. Moreover, the coexistence of branched chain and EO group will produce oriented variations of film structure and result in the maximum modulus at dynamic curve.