Effects of Palmitic Acid - Silica Nanoparticle Complexes on Liquid Interfaces (Abstract/Comunicazione in atti di convegno)

Type
Label
  • Effects of Palmitic Acid - Silica Nanoparticle Complexes on Liquid Interfaces (Abstract/Comunicazione in atti di convegno) (literal)
Anno
  • 2012-01-01T00:00:00+01:00 (literal)
Alternative label
  • Libero Liggieri, Eduardo Guzmán, Michele Ferrari, Eva Santini, Francesca Ravera (2012)
    Effects of Palmitic Acid - Silica Nanoparticle Complexes on Liquid Interfaces
    in 19th International Symposium on Surfactants in Solution (SIS2012), Edmonton, Alberta, Canada
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Libero Liggieri, Eduardo Guzmán, Michele Ferrari, Eva Santini, Francesca Ravera (literal)
Note
  • Comunicazione (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • CNR - Istituto per l'Energetica e le Interfasi, Genova , Italy (literal)
Titolo
  • Effects of Palmitic Acid - Silica Nanoparticle Complexes on Liquid Interfaces (literal)
Abstract
  • Surfactants are commonly utilised to modify the hydrophilic/hydrophobic character of solid particles in liquid environments. The utilisation of surfactants associated to particles for the modification of the surface properties of liquids is instead a new and little investigated topic that can bring to innovative concepts in relation to several practical applications. We have recently investigated the properties and the structure of different types of interfacial layers obtained from aqueous dispersions of nanometric silica and Palmitic acid (PA) - PA monolayers spread on the silica dispersions, interfacial layers of silica dispersions added with PA, liquid-liquid interfacial layer of silica dispersions and PA solutions in oil - have been investigated. A pool of complementary measurement methods and diagnostics have been used, in order to elucidate the role of the PA interaction with the particles, to investigate the surface-activity of the originated silica-PA complexes and their behaviour at the water-air and water-oil interfaces. A Langmuir trough was used to obtain compression isotherms of the mixed PA+silica surface layers and to measure the dilational viscoelasticity, providing information about the their phase behavior. The structure of these layers was directly investigated by Brewster Angle Microscopy and Ellipsometry. Drop Shape tensiometry was utilized to measure the dynamic surface and the interfacial tension and dilational viscoelasticity of the silica dispersions added by PA. In spite of the different conditions in which the PA and particles were interacting, combining the analysis of above results provided simple interpretations for the variety of observed behaviours, based on the adsorption of PA at the particle surface. In all cases, in fact, a threshold in the PA adsorption at the particles can be identified, above which the resulting nanoparticle-PA complexes abruptly change from hydrophilic to partially hydrophobic, promoting their incorporation into the interfacial layer. The tensiometric studies evidence a large surface-activity of these partially hydrophobic nanoparticle+PA complexes for the aqueous surface, comparable with the most efficient technical surfactant blends. It is remarkable in addition that the above threshold correspond to a very low fraction - about 0.005 - of the PA monolayer saturation. These features can be particularly attractive for practical purposes. On the contrary, the same complexes are only little surface active for the water-oil interface, where they break due to the large oleophilic character of PA, which transfer into the oil phase, while the naked particles return in the dispersion. (literal)
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