Equation of State and Structure of Electrostatic Colloidal Crystals: Osmotic Pressure and Scattering Study - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal de Physique II Année : 1997

Equation of State and Structure of Electrostatic Colloidal Crystals: Osmotic Pressure and Scattering Study

V. Reus
  • Fonction : Auteur
L. Belloni
  • Fonction : Auteur
Thomas Zemb
N. Lutterbach
  • Fonction : Auteur
H. Versmold
  • Fonction : Auteur

Résumé

Electrostatically stabilized aqueous suspensions of bromopolystyrene particles have been studied by scattering and osmotic pressure measurements. We investigated their structure and the interparticle interactions as a function of the volume fraction at very low salinity of the order of micromole/l. At slow crystallization speed we observe perfect crystals, body centrered cubic crystals by light scattering for volume fractions between 0.04 and 0.7% and face centrered cubic crystals by Ultra Small Angle X–ray Scattering (USAXS) for higher volume fractions (2–12%). After shear the crystal displays other structures. At low volume fractions (0.1–0.3%), some reflexions disappear by light scattering whereas a strong diffuse “prepeak" appears before the first Bragg peak for higher concentrations (2–12%) evidenced by USAXS. This “prepeak" can be attributed to defects in the crystal. Osmotic pressures have been measured by difference between the hydrostatic pressure in the solution and in the reservoir separated by an hemipermeable membrane. The experimental data are very well reproduced by the Poisson Boltzmann Cell (PBC) theory which shows that the interaction between particles is purely repulsive. No attractive contribution has been experimentally detected. By calculating the mean square displacement of a particle inside its cage from the eccentric PBC model, we have verified that the Lindemann criterion for the existence of crystals (against melting) is satisfied. This study has allowed to determine the equation of state of an electrostatical colloidal crystal and is equivalent to an ultraprecise force/distance measurement between latex particles since the measured forces are of the order of 10-12 N for distances of the order of 4000 Å.

Domaines

Articles anciens
Fichier principal
Vignette du fichier
ajp-jp2v7p603.pdf (1.36 Mo) Télécharger le fichier
Origine : Accord explicite pour ce dépôt

Dates et versions

jpa-00248466 , version 1 (04-02-2008)

Identifiants

Citer

V. Reus, L. Belloni, Thomas Zemb, N. Lutterbach, H. Versmold. Equation of State and Structure of Electrostatic Colloidal Crystals: Osmotic Pressure and Scattering Study. Journal de Physique II, 1997, 7 (4), pp.603-626. ⟨10.1051/jp2:1997142⟩. ⟨jpa-00248466⟩

Collections

AJP
131 Consultations
151 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More