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

The dilational theological properties of 1,2-ethane bis(dimethyl dodecyl ammonium bromide) (C12C2C12 center dot 2Br) at air/water interface were investigated using oscillating barriers method at low frequency (0.005-0.1 Hz). The dilational modulus Of C12C2C12 center dot 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 mod ulus passes through a maximum value with C12C2C12 center dot 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 C12C2C12 center dot 2Br. (c) 2006 Elsevier B.V. All rights reserved.