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.

Equilibria of a nematic liquid crystal confined between two eccentric cylinders are studied within a purely director approach. A planar equilibrium configuration competes against a three-dimensional one. A stability diagram is obtained in terms of both the ratio between the radii of the bounding cylinders and the distance between their axes. It turns out that the nonplanar minimizer has a structure more complex than that envisaged in the tensorial approach employed by McKay and Virga [Phys. Rev. E 71, 041702 (2005)] and that the planar configuration cannot be the absolute minimizer when the outer cylinder becomes a plane wall. The mechanical actions transmitted by the nematic liquid crystal on both bounding cylinders are computed and compared with other results available in the literature.

Elastic actions exchanged by eccentric cylinders in liquid crystals.

We analyze the impact of extrinsic and intrinsic curvature on positions of topological defects (TDs) in two-dimensional (2D) nematic films. We demonstrate that both these curvature contributions are commonly present and are expected to be weighted by comparable elastic constants. A simple Landau-de Gennes approach in terms of tensor nematic order parameter is used to numerically demonstrate impact of the curvatures on position of TDs on 2D ellipsoidal nematic shells. In particular, in oblate ellipsoids the extrinsic and intrinsic elastic terms enforce conflicting tendencies to positions of TDs.

https://iopscience.iop.org/article/10.1088/1742-6596/780/1/012015/pdf

Impact of curvature on topological defects

We summarize recent findings and advances in cancer diagnostics in relation to extracellular vesicles (EVs) and emerging therapeutic options of nanomaterials. We revise the common mechanism for EV inception, vesiculation, through a physical model of the liquid mosaic membrane with laterally mobile membrane rafts that determine local spontaneous curvature. If such in-plane orientational ordering is present, we show that spatial non-homogeneities may trigger energetically favourable membrane vesiculation. In addition, we revise a novel technique of cancer therapy using multifunctional titanium nanobeads (NBs) that form a fully biocompatible system used for optical imaging, magnetic resonance imaging and selective reactive oxygen species photo-generation. We study the encapsulation of these functional NBs theoretically with Monte Carlo (MC) simulations and find that the wrapping transition depends on the strength of mobile charges, giving insight into future functional optimization for maximum therapeutic benefit.

The role of membrane vesiculation and encapsulation in cancer diagnosis and therapy

We study numerically curvature and electric field driven domain formation and reorientations in two-dimensional nematic liquid crystals within square confinement. We use the Landau-de Genne...

Topological defect enabled formation of nematic domains

We study numerically external electric or magnetic field driven switching between percolated and non-percolated configuration of nanoparticles in soft matter ternary systems. The system consists of nematic liquid crystal, impurities and elongated nanoparticles. We use the Lebwohl–Lasher lattice − type modeling to determine the orientational order of nanoparticles and consequently the Metropolis algorithm to find the percolation threshold. In our model the external field acts directly only on the liquid crystal component, which in turn tends to reorient nanoparticles. We determine regimes where an external field relatively robustly switches between percolated and non-percolated states. The main variable physical parameters are volume concentration and length-to-width ratio of nanoparticles, concentration of impurities and temperature. We have revealed that impurities imposing static orientational disorder are a significant part of the system. A possible application is also proposed.

Samo Kralj

Papers

Elastic actions exchanged by eccentric cylinders in liquid crystals.

Impact of curvature on topological defects

The role of membrane vesiculation and encapsulation in cancer diagnosis and therapy

Topological defect enabled formation of nematic domains

Field percolation-switching in soft ternary anisotropic system