Phase behaviour of oleanolic acid/stearyl stearate binary mixtures in bulk and at the air-water interface.
Chem Phys Lipids
; 160(1): 45-57, 2009 Jul.
Article
en En
| MEDLINE
| ID: mdl-19394318
The solid-liquid phase behaviour of oleanolic acid (OLA)/stearyl stearate (SS) was investigated by differential scanning calorimetry and polarizing optical microscopy. A eutectic type diagram, with the eutectic composition close to pure SS was obtained. Complementary studies by NMR, X-ray diffraction (XRD) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy were performed. A mutual influence was detected in mixtures: the low melting form of SS is favoured at low OLA molar fractions (X(OLA)) and spherulitic structures appear at high X(OLA) and high temperature. Additionally, H-bonding between OLA carbonyl groups increases in the presence of SS. The study of OLA/SS by the Langmuir method and Brewster angle microscopy revealed the organization at the air-water interface: OLA interacts with water in the first layer, while SS is completely segregated to the upper layer for X(OLA)>0.3, and it distributes in the first and upper layers for X(OLA)<0.3.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Ácido Oleanólico
/
Estearatos
/
Ceras
/
Agua
/
Aire
Idioma:
En
Revista:
Chem Phys Lipids
Año:
2009
Tipo del documento:
Article
País de afiliación:
Portugal
Pais de publicación:
Irlanda