Solid–Liquid Phase Transition in the Octadecanoic Acid Film Adsorbed on the Toluene–Water Interface
- Autores: Tikhonov A.M.1,2
-
Afiliações:
- Kapitza Institute for Physical Problems, Russian Academy of Sciences
- Institute of Solid State Physics, Russian Academy of Sciences
- Edição: Volume 127, Nº 4 (2018)
- Páginas: 797-802
- Seção: Statistical, Nonlinear, and Soft Matter Physics
- URL: https://journals.rcsi.science/1063-7761/article/view/193748
- DOI: https://doi.org/10.1134/S1063776118100102
- ID: 193748
Citar
Resumo
The structure of the soluble protonated (pH = 2) octadecanoic acid film adsorbed on the saturated hydrocarbon (n-hexane)–water and aromatic hydrocarbon (toluene)–water interfaces is studied by X-ray reflectometry using synchrotron radiation. The experimental data demonstrate that a solid phase of a Gibbs monolayer 26 ± 1 Å thick, in which aliphatic tails are perpendicular to the surface and the area per molecule is A = 18 ± 2 Å2, is formed in the film at the n-hexane–water interface. The solid monolayer on the toluene–water interface in the adsorbed film melts when temperature increases, and this transition is caused by disordering of the hydrocarbon tails of the acid. During the solid–liquid transition, the Gibbs monolayer thickness remains almost the same, 22 ± 1 Å. In the solid phase, we have A = 20 ± 2 Å2, and the angle of deviation of the molecular tails from the normal to the surface is about 30°. The density of the liquid monolayer phase with A = 24 ± 2 Å2 corresponds to liquid n-octadecane.
Sobre autores
A. Tikhonov
Kapitza Institute for Physical Problems, Russian Academy of Sciences; Institute of Solid State Physics, Russian Academy of Sciences
Autor responsável pela correspondência
Email: tikhonov@kapitza.ras.ru
Rússia, Moscow, 119334; Chernogolovka, Moscow oblast, 142432
Arquivos suplementares
