Absence of Lateral Phase Segregation in Fatty Acid-Based Catanionic Mixtures

• Tipo: Artigo em Revista Científica Internacional
• Data: 2010

Autores

Youlia Michina (Autor) Outra; David Carriere (Autor) Outra; Thibault Charpentier (Autor) Outra; Rodrigo Brito (Autor) FCUP; Eduardo F Marques (Autor) FCUP; Jean Paul Douliez (Autor) Outra; Thomas Zemb (Autor) Outra

Revista

Título: Journal of Physical Chemistry B

Vol. 114 Nº 5

Páginas: 1932-1938

ISSN: 1520-6106

Editora: American Chemical Society

Indexação

ISI Web of Knowledge - 27 Citações

Scopus - 27 Citações

Classificação Científica

FOS: Ciências exactas e naturais > Química

CORDIS: Ciências Físicas > Química > Química física > Química das superfícies ; Ciências Físicas > Física > Termodinâmica > Termodinâmica aplicada

Outras Informações

ID Authenticus: P-003-956

DOI: 10.1021/jp910267v

Abstract (EN): Mixtures of ionic surfactants of opposite charge ("catanionic" mixtures) show strongly nonideal behaviors, for example, in terms of evolution of surface tension, critical micelle concentration, or morphology with respect to composition in each surfactant. In several catanionic systems, it has been proposed that the interaction between both surfactants is so strong that lateral phase segregation occurs within bilayers, with crystallites of preferential composition demixing from the excess of the other surfactant. Here, we investigate the temperature-composition phase diagram of the myristic acid/cetyltrimethylammonium mixtures. Combining microcalorimetry, X-ray diffusion, and solid-state deuterium NMR, we demonstrate that no separation is observed in the gel (L(beta)) state. The catanionic mixtures therefore behave like two-dimensional solid solutions with a negative azeotrope: the existence of a composition at which a maximum in melting temperature is observed does not imply the existence of a preferential crystal of this composition, but results from the preferential attraction between unlike amphiphilic molecules. Additionally, this study reveals the presence of a so-called intermediate phase, that is, a phase that shows dynamic properties intermediate between that of the L(beta) and the L(alpha) phases.

Idioma: Inglês

Tipo (Avaliação Docente): Científica