Temperature effect on the adsorption and micelle formation of pentaethylene glycol monoalkyl ethers

The temperature effect on the adsorption at air/water interface and micelle formation of poly(ethylene glycol) monoalkyl ether (CiEj) nonionic surfact ant was investigated on the basis of the thermodynamic strategy. From the r esults of surface tension experiments and after applying the thermodynamic treatment, surface density and thermodynamic quantity changes associated wi th the adsorption and micelle formation were obtained. It has been found th at the entropy of adsorption from monomeric state of CiEj is positive and d epend on both concentration and temperature in the same trend; the entropy increases with increasing adsorption of surfactant and increasing temperatu re. This phenomenon is against that of ionic surfactant. The difference was analyzed in term of the competition between the dehydration effect and the orientation effect. For CiEj nonionic surfactant systems, the large amount of dehydration at high temperature dominates the controversial results of surface density and entropy changes. Moreover, the effect of hydrophobic ch ain length on the surface adsorption and micelle formation was included in this study using three CiE5'S with i = 8, 10, and 12. Those gave outstandin g aspects with respect to the thermodynamic property changes.