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Issue 36, 2010
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Phase transitions in nanoconfined binary mixtures of highly oriented colloidal rods

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Abstract

We analyse a binary mixture of colloidal parallel hard cylindrical particles with identical diameters but dissimilar lengths L1 and L2, with s = L2/L1 = 3, confined by two parallel hard walls in a planar slit-pore geometry, using a fundamental–measure density functional theory. This model presents nematic (N) and two types of smectic (S) phases, with first- and second-order N–S bulk transitions and S–S demixing, and surface behaviour at a single hard wall which includes complete wetting by the S phase mediated (or not) by an infinite number of surface-induced layering (SIL) transitions. In the present paper the effects of confinement on this model colloidal fluid mixture are studied. Confinement brings about profound changes in the phase diagram, resulting from competition between the three relevant length scales: pore width h, smectic period d and length ratio s. Four main effects are identified: (i) second-order bulk N–S transitions are suppressed; (ii) demixing transitions are weakly affected, with small shifts in the μ1μ2 (chemical potentials) plane; (iii) confinement-induced layering (CIL) transitions occurring in the two confined one-component fluids in some cases merge with the demixing transition; (iv) surface-induced layering (SIL) transitions occurring at a single surface as coexistence conditions are approached are also shifted in the confined fluid. The trends with pore size are analysed by means of complete μ1μ2 and p[x with combining macron] (pressure-mean pore composition) phase diagrams for particular values of pore size. This work, which is the first one to address the behaviour of liquid–crystalline mixtures under confinement, could be relevant as a first step to understand the self-assembling properties of mixtures of metallic nanoparticles under external fields in restricted geometry.

Graphical abstract: Phase transitions in nanoconfined binary mixtures of highly oriented colloidal rods

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Publication details

The article was received on 23 Feb 2010, accepted on 12 May 2010 and first published on 23 Jul 2010


Article type: Paper
DOI: 10.1039/C003448G
Citation: Phys. Chem. Chem. Phys., 2010,12, 10831-10841
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    Phase transitions in nanoconfined binary mixtures of highly oriented colloidal rods

    D. D. L. Heras, Y. Martínez-Ratón and E. Velasco, Phys. Chem. Chem. Phys., 2010, 12, 10831
    DOI: 10.1039/C003448G

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