Dilational rheological properties of gemini surfactant 1,2-ethane bis(dimethyl dodecyl ammonium bromide) at air/water interface

Abstract

The dilational rheological properties of 1,2-ethane bis(dimethyl dodecyl ammonium bromide) (C 12C 2C 12·2Br) at air/water interface were investigated using oscillating barriers method at low frequency (0.005–0.1 Hz). The dilational modulus of C 12C 2C 12·2Br is higher than that of dodecyltrimethyl ammonium bromide (DTAB), indicating the strength against perturbation of interfacial layer of the former is greater. This phenomenon is explained by molecular dynamics simulation. Many factors have great effect on the dilational rheology such as bulk concentration, temperature and NaBr. The results reveal that the dilational modulus passes through a maximum value with C 12C 2C 12·2Br concentration increasing. It is also found that the maximum value of the dilational viscous component appears at different concentration with the dilational frequency increasing. And the higher the dilational frequency is, the higher the concentration corresponding to the maximum value of the dilational viscous component is. When temperature rises, the dilational modulus decreases gradually. Moreover, the addition of NaBr can increase the dilational modulus of C 12C 2C 12·2Br.