We review the current state of knowledge of phase separation and phase equilibria in porous materials. Our emphasis is on fundamental studies of simple fluids (composed of small, neutral molecules) and well-characterized materials. While theoretical and molecular simulation studies are stressed, we also survey experimental investigations that are fundamental in nature. Following a brief survey of the most useful theoretical and simulation methods, we describe the nature of gas‐liquid (capillary condensation), layering, liquid‐liquid and freezing/melting transitions. In each case studies for simple pore geometries, and also more complex ones where available, are discussed. While a reasonably good understanding is available for phase equilibria of pure adsorbates in simple pore geometries, there is a need to extend the models to more complex pore geometries that include effects of chemical and geometrical heterogeneity and connectivity. In addition, with the exception of liquid‐liquid equilibria, little work has been done so far on phase separation for mixtures in porous media.

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Phase separation in confined systems

Advanced Mathematical Methods for Scientists and Engineers

Aspects of Scientific Explanation: and Other Essays in the Philosophy of Science

We present a review of experimental, theoretical, and molecular simulation studies of confinement effects on freezing and melting We consider both simple and more complex adsorbates that are confined in various environments (slit or cylindrical pores and also disordered porous materials) The most commonly used molecular simulation, theoretical and experimental methods are first presented We also provide a brief description of the most widely used porous materials The current state of knowledge on the effects of confinement on structure and freezing temperature, and the appearance of new surface-driven and confinement-driven phases are then discussed We also address how confinement affects the glass transition

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Effects of confinement on freezing and melting.

With the maturation of the information display field, liquid-crystal materials research is undergoing a modern-day renaissance. Devices and configurations based on liquid-crystal materials are being developed for spectroscopy, imaging and microscopy, leading to new techniques for optically probing biological systems. Biosensors fabricated with liquid-crystal materials can allow label-free observations of biological phenomena. Liquid-crystal polymers are starting to be used in biomimicking colour-producing structures, lenses and muscle-like actuators. New areas of application in the realms of biology and medicine are stimulating innovation in basic and applied research into these materials.

Liquid-crystal materials find a new order in biomedical applications.

We introduce the slave-master mechanism in the phase behavior of two-component systems where both components could exhibit some kind of (quasi) long-range order. The key feature of the mechanism is that one component strongly influences the other while the reverse influence is negligible. To illustrate the effect, we consider systems where each isolated component exhibits an order-disorder phase transition on varying a control parameter (e.g., temperature) to which we refer as the generalized temperature. We present a minimal model that shows robust slave-master behavior. As exemplary systems, we present thermotropic liquid crystals (LCs) exhibiting nematic and smectic A phase order, focusing on the interaction strength between orientational and translational order. Mixtures of nematic LC molecules and anisotropic nanoparticles are also presented. We show that qualitatively different behaviors could emerge via the specific nature of the inter-component interaction. Mastering this mechanism could lead to various applications based on phase tunable properties. 

Slave-master mechanism of thermotropic liquid crystal phase transitional behavior

The classical methods of solid mechanics assume that the homeomorphism of deformation sometimes does not provide an adequate description of the theological behaviour and fracture of real materials, while irreversible macro deformation and the fracture of solids are predetermined by material behaviour in nanoscale. When we talk about crack propagation, we must talk at least about four phenomena, namely about crack incubation, initiation, and crack propagation must be sleeted in two parts, to growth of short crack and to growth of linear elastic or long crack.

Principle of Universality in Crack Incubation and Propagation

We studied the impact of the cell thickness on configurations of line disclinations within a plane-parallel nematic cell. The Lebwohl-Lasher semimicroscopic approach was used and (meta)stable nematic configurations were calculated using Brownian molecular dynamics. Defect patterns were enforced topologically via boundary conditions. We imposed periodic circular nematic surface fields at each confining surface. The resulting structures exhibit line defects which either connect the facing plates or remain confined within the layers near confining plates. The first structure is stable in relatively thin cells and the latter one in thick cells. We focused on structures at the threshold regime where both structures compete. We demonstrated that “history” of samples could have strong impact on resulting nematic configurations.

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Thickness Induced Line-Defect Reconfigurations in Thin Nematic Cell

Closed biological membranes were considered within the spontaneous curvature model. Ground state membrane shapes were compared with Monte Carlo simulations in the thermal equilibrium, where membranes are subject to thermal uctuations. The results of the two approaches correspond well with each other. The oblate discocyte membrane shapes are obtained in the ground state but can become metastable when thermal uctuations are taken into account. The nematic ordering in oblate and stomatocyte vesicle membranes was also studied. It was conrmed

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Modeling of closed membrane shapes

We study the impact of random bond-type disorder on two-dimensional (2D) orientational ordering of nematic liquid crystal (LC) configurations. The lattice Lebwohl–Lasher pseudospin model is used to model orientational ordering perturbed by frozen-in rod-like impurities of concentration p exhibiting the isotropic orientational probability distribution. The impurities are either (i) randomly spatially distributed or (ii) form diffusion limited aggregation (DLA)-type patterns characterized by the fractal dimensions d f , where we consider cases d f ∼ 1.7 and d f ∼ 1.9 . The degree of orientational ordering is quantified in terms of the orientational pair correlation function G ( r ) . Simulations reveal that the DLA pattern imposed disorder has a significantly weaker impact for a given concentration of impurities. Furthermore, if samples are quenched from the isotropic LC phase, then the fractal dimension is relatively strongly imprinted on quantitative characteristics of G ( r ) .

Samo Kralj

Papers

Slave-master mechanism of thermotropic liquid crystal phase transitional behavior

Principle of Universality in Crack Incubation and Propagation

Thickness Induced Line-Defect Reconfigurations in Thin Nematic Cell

Modeling of closed membrane shapes

Impact of diffusion limited aggregates of impurities on nematic ordering