Regensburg 2016 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 6: Colloids and Complex Fluids II (joint session BP/CPP/DY, organized by CPP)
CPP 6.2: Vortrag
Montag, 7. März 2016, 10:00–10:15, H51
Phase diagram of polydisperse colloidal dispersions — •Pree-cha Kiatkirakajorn1, Joaquim Li1, Bernard Cabane2, Franck Artzner3, Robert Botet4, and Lucas Goehring1 — 1Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Götingen, Germany — 2LCMD, CNRS UMR 8231, ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05, France — 3Institut de Physique, CNRS UMR 6626, Univ Rennes, 35042 Rennes, France — 4Physique des Solides, CNRS UMR 8502, Univ Paris-Sud, F-91405 Orsay, France
Polydisperse colloidal dispersions have been predicted, for over twenty years, to have a rich and complex phase space of colloidal crystals. However, experiments have consistently suggested that such crystals are kinetically inaccessible, as small amounts of polydispersity poison crystal formation. Here, we show a result of small-angle X-ray scattering experiment of highly polydisperse (yet monomodal) colloidal dispersions in a range of sizes (average size from 8 to 50 nm), with soft, charge-mediated interactions. These dispersions were dialysed and compressed by aqueous solutions of poly(ethylene glycol) to reach 15% to 30% of volume fraction, and crystallize. Their phase diagrams, structure factors and crystal peaks were analysed by the x-ray scattering patterns. We found coexistences of complex crystal structures (two BCC structures and Laves AB2) for the small particle size, and BCC and FCC crystals for the larger particle size. These results show a fractionation among the particles. We further show how this is possible through numerical simulations, which explain how the fractionation occurs and how the particles distribute among the different coexisting phases.