Phase Separation of Mixtures of Colloidal Boehmite Rods and Flexible Polymer

Buitenhuis, Johan; Donselaar, Liesbeth N.; Buining, Paul A.; Stroobants, A.; Lekkerkerker, H. N. W.

doi:10.1006/jcis.1995.1427

Cited by 85 publications

(92 citation statements)

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“…In this figure also the binodal of the isotropic phase as determined by Buitenhuis 8 is given. The composition of the samples and the observed morphological development are summarized in Table 2.…”

Section: 1mentioning

confidence: 97%

“…4 Attractive interactions in dispersions of rodlike particles and macromolecules easily bring about aggregation and gelation. [5][6][7][8] These metastable states often obscure large parts of the equilibrium phase diagram. In this paper we present experiments on model dispersions of hard rods in which the attractive interactions are switched on by adding nonadsorbing polymer.…”

Section: Introductionmentioning

confidence: 99%

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Tunable Attractions Directing Nonequilibrium States in Dispersions of Hard Rods

Bruggen

Lekkerkerker

2000

Macromolecules

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The effect of attractive interactions on the phase behavior of colloidal hard rods has been studied by the addition of nonadsorbing polymer. In these rod-polymer mixtures, four pathways of phase separation can be distinguished: nucleation and growth, spinodal decomposition, aggregation, and gelation. The first three mechanisms give rise to macroscopic phase separation, whereas for the latter mechanism this is not necessarily the case. The observed phenomena are explained on the basis of an interplay between the position of both the spinodal line and the glass line, the overall composition of the sample, and the range of the potential.

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Section: 1mentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Tunable Attractions Directing Nonequilibrium States in Dispersions of Hard Rods

Bruggen

Lekkerkerker

2000

Macromolecules

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“…There have been previous experiments on the influence of polymer on the I-N phase transition in mixtures of boehmite rods and polystyrene polymers and mixtures of cellulose nanocrystals and Dextran polymers [18,19,20]. Other studies related to our work have focused on the condensation of rod-like polymers due to the presence of polymer and/or multivalent cations [21,22].…”

Section: Introductionmentioning

confidence: 97%

Isotropic-nematic phase transition in suspensions of filamentous virus and the neutral polymer Dextran

et al. 2004

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We present an experimental study of the isotropic-nematic phase transition in an aqueous mixture of charged semi-flexible rods (fd virus) and neutral polymer (Dextran). A complete phase diagram is measured as a function of ionic strength and polymer molecular weight. At high ionic strength we find that adding polymer widens the isotropic-nematic coexistence region with polymers preferentially partitioning into the isotropic phase, while at low ionic strength the added polymer has no effect on the phase transition. The nematic order parameter is determined from birefringence measurements and is found to be independent of polymer concentration (or equivalently the strength of attraction). The experimental results are compared with the existing theoretical predictions for the isotropic-nematic transition in rods with attractive interactions.

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“…11 The effect of the depletion interactions in mixtures of rodlike colloidal particles has been investigated experimentally using a flexible nonadsorbing polymer; demixing between isotropic as well as nematic phases has been observed. 12,13 A mixture of spherical colloidal particles with a rodlike polymer component has also been studied. 14 The phase equilibria can become quite complex; for example, three and four phase coexistence of isotropic, nematic, and columnar phases has been observed experimentally in a mixture of platelike colloidal particles and nonadsorbing polymers.…”

Section: Introductionmentioning

confidence: 99%

Global fluid phase behavior in binary mixtures of rodlike and platelike molecules

Varga

Galindo

Jackson

2002

The Journal of Chemical Physics

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The phase behavior of a liquid-crystal forming model colloidal system containing hard rodlike and platelike particles is studied using the Parsons-Lee scaling ͓J. D. Parsons, Phys. Rev. A 19, 1225 ͑1979͒; S. D. Lee, J. Chem. Phys. 87, 4972 ͑1987͔͒ of the Onsager theory. The rod and plate molecules are both modeled as hard cylinders. All of the mixtures considered correspond to cases in which the volume of the plate is orders of magnitude larger that the volume of the rod, so that an equivalence can be made where the plates are colloidal particles while the rods play the role of a depleting agent. A combined analysis of the isotropic-nematic bifurcation transition and spinodal demixing is carried out to determine the geometrical requirements for the stabilization of a demixing transition involving two isotropic phases. Global phase diagrams are presented in which the boundaries of isotropic phase demixing are indicated as functions of the molecular parameters. Using a parameter z which corresponds to the product of the rod and plate aspect ratios, it is shown that the isotropic phase is unstable relative to a demixed state for a wide range of molecular parameters of the constituting particles due to the large excluded volume associated with the mixing of the unlike particles. However, the stability analysis indicates that for certain aspect ratios, the isotropic-nematic phase equilibria always preempts the demixing of the isotropic phase, irrespective of the diameters of the particles. When isotropic-isotropic demixing is found, there is an upper bound at large size ratios ͑Asakura and Oosawa limit͒, and a lower bound at small size ratios ͑Onsager limit͒ beyond which the system exhibits a miscible isotropic phase. It is very gratifying to find both of these limits within a single theoretical framework. We test the validity of the stability analysis proposed by calculating a number of phase diagrams of the mixture for selected molecular parameters. As the hard rod particles promote an effective attractive interaction between the hard-plate colloidal particles, the isotropic-isotropic demixing usually takes place between two rod-rich fluids. As far as the isotropic-nematic transition is concerned, a stabilization as well as a destabilization of the nematic phase relative to the isotropic phase is seen for varying rod-plate size ratios. Moreover, isotropic-nematic azeotropes and re-entrant phenomena are also observed in most of the mixtures studied. We draw comparisons between the predicted regions of stability for isotropic demixing and recent experimental observations.

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Phase Separation of Mixtures of Colloidal Boehmite Rods and Flexible Polymer

Cited by 85 publications

References 0 publications

Tunable Attractions Directing Nonequilibrium States in Dispersions of Hard Rods

Tunable Attractions Directing Nonequilibrium States in Dispersions of Hard Rods

Isotropic-nematic phase transition in suspensions of filamentous virus and the neutral polymer Dextran

Global fluid phase behavior in binary mixtures of rodlike and platelike molecules

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