Peter H. Elworthy
Bio: Peter H. Elworthy is an academic researcher from University of Southern California. The author has contributed to research in topics: Micelle & Pulmonary surfactant. The author has an hindex of 1, co-authored 1 publications receiving 303 citations.
TL;DR: In this article, a modified equilibrium Wilhelmy method was used to obtain accurate and precise surface tension measurements of surfactant solutions above the c.m.c. This finding places a definite limit upon the validity of the approximation represented by the phase separation theory of micelle formation.
TL;DR: Influence of different parameters such as molecular structure, temperature, salt concentration, and salt concentration that are very important in surfactant adsorption are reviewed here.
TL;DR: In this paper, a review of equilibrium and dynamic aspects of surface tension and adsorption, primarily of single nonmicellar or premiceller surfactants at the air/water interface, is presented.
TL;DR: In this article, the specular reflection of neutrons has been applied to the study of surface and interfaces, and a range of recent experimental results in surface chemistry, solid films and surface magnetism are discussed.
Abstract: The application of the specular reflection of neutrons to the study of surface and interfaces is described. The theoretical and experimental background to the technique is presented. A range of recent experimental results in surface chemistry, solid films and surface magnetism is discussed. In surface chemistry the results include adsorption of surfactants at the air-solution interface, insoluble monolayers and polymers at the air-liquid interface, soap films and adsorption at the liquid-solid and liquid-liquid interfaces. In solid films results on Langmuir-Blodgett films, hard carbon films, polymer films and some semiconductor layers are discussed. In surface magnetism experimental data which illustrate the nature of magnetism in magnetic multilayers and ferromagnetic films, and which describe flux penetration in superconductors, are presented.
TL;DR: The phase behavior of several medium-chain and long-chain fatty acids in water was examined as a function of the ionization state of the carboxyl group to provide insights into the physical states of fatty acid in biological systems.
Abstract: The phase behavior of several medium-chain (10- and 12-carbon) and long-chain (18-carbon) fatty acids in water was examined as a function of the ionization state of the carboxyl group. Equilibrium titration curves were generated above and below fatty acid and acid-soap chain melting temperatures and critical micelle concentrations, and the phases formed were characterized by X-ray diffraction, 13C NMR spectroscopy, and phase-contrast and polarized light microscopy. The resulting titration curves were divided into five regions: (i) at pH values less than 7, a two-phase region containing oil or fatty acid crystals and an aqueous phase; (ii) at pH approximately 7, a three-phase region containing oil, lamellar, and aqueous (or fatty acid crystals, 1:1 acid-soap crystals, and aqueous) phases; (iii) between pH 7 and 9, a two-phase region containing a lamellar fatty acid/soap (or crystalline 1:1 acid-soap) phase in an aqueous phase; (iv) at pH approximately 9, a three-phase region containing lamellar fatty acid-soap (or crystalline 1:1 acid-soap), micellar, and aqueous phases; and (v) at pH values greater than 9, a two-phase region containing micellar and aqueous phases. Interpretation of the results using the Gibbs phase rule indicated that, for oleic acid/potassium oleate, the composition of the lamellar fatty acid/soap phase varied from approximately 1:1 to 1:3 un-ionized to ionized fatty acid species. In addition, constant pH regions observed in titration curves were a result of thermodynamic invariance (zero degrees of freedom) rather than buffering capacity. The results provide insights into the physical states of fatty acids in biological systems.(ABSTRACT TRUNCATED AT 250 WORDS)