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From capillary condensation to interface localization transitions in colloid-polymer mixtures confined in thin-film geometry

De Virgiliis, Andres und Vink, Richard L. C. und Horbach, Jürgen und Binder, Kurt (2008) From capillary condensation to interface localization transitions in colloid-polymer mixtures confined in thin-film geometry. Physical Review E, 78, . DOI: 10.1103/PhysRevE.78.041604.

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Kurzfassung

Monte Carlo simulations of the Asakura-Oosawa model for colloid-polymer mixtures confined between two parallel repulsive structureless walls are presented and analyzed in the light of current theories on capillary condensation and interface localization transitions. Choosing a polymer-to-colloid size ratio of q=0.8 and studying ultrathin films in the range of D=3 to D=10 colloid diameters thickness, grand canonical Monte Carlo methods are used; phase transitions are analyzed via finite size scaling, as in previous work on bulk systems and under confinement between identical types of walls. Unlike the latter work, inequivalent walls are used here: While the left wall has a hard-core repulsion for both polymers and colloids, at the right-hand wall an additional square-well repulsion of variable strength acting only on the colloids is present. We study how the phase separation into colloid-rich and colloid-poor phases occurring already in the bulk is modified by such a confinement. When the asymmetry of the wall-colloid interaction increases, the character of the transition smoothly changes from capillary condensation type to interface localization type. For very thin films (i.e., for D=3) and a suitable choice of the wall-colloid interactions, evidence is found that the critical behavior falls in the universality class of the two-dimensional Ising model. Otherwise, we observe crossover scaling between different universality classes (namely, the crossover from the three-dimensional to the two-dimensional Ising model universality class). The colloid and polymer density profiles across the film in the various phases are discussed, as well as the correlation of interfacial fluctuations in the direction parallel to the confining walls. The broadening of the interface between the coexisting colloid-rich and polymer-rich phases (located parallel to the confining walls) is understood in terms of capillary wave fluctuations. The experimental observability of all these phenomena is briefly discussed.

Dokumentart:Zeitschriftenbeitrag
Titel: From capillary condensation to interface localization transitions in colloid-polymer mixtures confined in thin-film geometry
Autoren:
AutorenInstitution oder E-Mail-Adresse der Autoren
De Virgiliis, AndresUNLP-CONICET, La Plata, Argentina
Vink, Richard L. C.Universität Göttingen
Horbach, JürgenNICHT SPEZIFIZIERT
Binder, KurtUniversität Mainz
Datum:9 Oktober 2008
Erschienen in:Physical Review E
Referierte Publikation:Ja
In ISI Web of Science:Ja
Band:78
DOI :10.1103/PhysRevE.78.041604
Seitenbereich:
Status:veröffentlicht
Stichwörter:demixing transition in confinement, colloid-polymer mixtures, Monte-Carlo simulation
HGF - Forschungsbereich:Verkehr und Weltraum (alt)
HGF - Programm:Weltraum (alt)
HGF - Programmthema:W FR - Forschung unter Weltraumbedingungen (alt)
DLR - Schwerpunkt:Weltraum
DLR - Forschungsgebiet:W FR - Forschung unter Weltraumbedingungen
DLR - Teilgebiet (Projekt, Vorhaben):W - Vorhaben Materialwissenschaftliche Forschung (alt)
Standort: Köln-Porz
Institute & Einrichtungen:Institut für Materialphysik im Weltraum
Hinterlegt von: Dr.rer.nat. Jürgen Horbach
Hinterlegt am:20 Okt 2008
Letzte Änderung:27 Apr 2009 15:17

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