Adsorption Kinetics of Brij 97 at the Air/Solution Interface

Abstract

Dynamic surface tension and surface adsorption kinetics at the air/aqueous solution interface of polyoxyethylene‐10‐oleyl ether (Brij^®97, C₁₈H₃₅O(CH₂CH₂O)₁₀H), for application in a drug delivery system, were investigated at different bulk surfactant concentrations and different temperatures. Apparent diffusion coefficients D _a , activation barrier ϵ _a , and the adsorption kinetic parameters n and t* were obtained from the extended Ward and Tordai approach and Rosen's empirical model, respectively. It is shown that Brij 97 solutions follow a mixed diffusion‐activation adsorption mechanism. Results evaluated by the extended Ward and Tordai approach are consistent with those obtained from Rosen's empirical model. With increase in bulk concentration from 0.125 to 12.5 CMC, ϵ _a increases from 0.151 to 11.0 kJ/mol, and parameter n decreases from 1.57 to 0.711. Increase in temperature results in a decrease in activation barrier ϵ _a . This indicates that the diffusion tendency decreases with increase of the interaction between surfactant molecules and the thermo‐motion of molecules favors surface adsorption.

Keywords:

• Dynamic surface tension
• adsorption kinetics
• surfactant
• Brij 97

Acknowledgment

Support of this work by the Natural Science Fund Foundation of China (Grant No. 30370945) and the Fund Foundation of Guizhou Provincial Governor (Qian, No. 2001‐6) are gratefully acknowledged.