caa a22 4500 475764307 CHVBK 20180406123600.0 cr unu---uuuuu 170329e20001001xx s 000 0 eng 10.1007/s003960000338 doi (NATIONALLICENCE)springer-10.1007/s003960000338 A simple adsorption model for ionic surfactants [Elektronische Daten] [A. Semmler, H.-H. Kohler] In the past, few theoretical attempts have been made to describe quantitatively the adsorption of ionic surfactants at liquid interfaces. Well-known adsorption isotherms due to Frumkin or Hill-de Boer cannot respond to the specific electrostatic and geometric properties of the surfactant molecules. Our approach is based on a combination of the Gouy-Chapman theory with a modified Frumkin isotherm. The modification implies that the system is free to choose an optimal head group area and an optimal arrangement of the surfactant molecules in the interface as a function of bulk concentration. Interaction energies between neighbouring adsorbed surfactant molecules and between surfactant and water molecules are taken into consideration. The minimum of the Gibbs free energy of the system is equivalent to a minimal interfacial tension. Thus, the thermodynamically stable isotherm can be obtained as the lower envelope of the family of σ versus ln c isotherms resulting from different choices of the model parameters, including the area per molecule. According to the Gibbs equation, the Γ versus ln c adsorption isotherm is obtained as the derivative of this envelope. By variation of the model parameters, the envelope of the calculated adsorption isotherms can be fitted to experimental data of the interfacial tension versus bulk concentration. A computer program is used to calculate the σ versus c and the Γ versus ln c curves as well as to fit the parameters. Springer-Verlag Berlin Heidelberg, 2000 Key words Ionic surfactants nationallicence Adsorption nationallicence Model nationallicence Isotherm nationallicence Surface tension nationallicence Semmler A. University of Regensburg Institute of Analytical Chemistry Chemo- and Biosensors Physical Chemistry of Surfaces and Structures 93040 Regensburg, Germany e-mail: hans-helmut.kohler@chemie.uni-regensburg.de, DE aut Kohler H.-H University of Regensburg Institute of Analytical Chemistry Chemo- and Biosensors Physical Chemistry of Surfaces and Structures 93040 Regensburg, Germany e-mail: hans-helmut.kohler@chemie.uni-regensburg.de, DE aut https://doi.org/10.1007/s003960000338 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s003960000338 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Semmler A. University of Regensburg Institute of Analytical Chemistry Chemo- and Biosensors Physical Chemistry of Surfaces and Structures 93040 Regensburg, Germany e-mail: hans-helmut.kohler@chemie.uni-regensburg.de, DE aut NATIONALLICENCE 700 1- Kohler H.-H University of Regensburg Institute of Analytical Chemistry Chemo- and Biosensors Physical Chemistry of Surfaces and Structures 93040 Regensburg, Germany e-mail: hans-helmut.kohler@chemie.uni-regensburg.de, DE aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer