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.

A deuteron NMR study of the 8CB liquid crystal confined to the controlled pore glass matrix is presented. The theoretical analysis based on the phenomenological Landau - de Gennes type description predicts a strong influence of the pore curvature on the confined 8CB smectic ordering and almost none on its nematic ordering, in good agreement with experiment.

Deuteron NMR study of an 8CB liquid crystal confined to porous glass

The annihilation of defect is studied theoretically in liquid crystals (LCs). We consider the annihilation of point disclinations in nematic and line edge dislocations in smectic A LC phase, respectively. We stress qualitative similarities in these processes. The whole annihilation regime is taken into account, consisting of the pre-collision, collision, and post-collision stage.

Annihilation of defects in liquid crystals

Music can be viewed as a structure formed by notes. Different structures in music have potential to yield enormously rich diversity of different melodies. Music is a typical example where a structure defines a property. Similar concepts could be also exploited in education, in presented case in nano-sciences, which are typical representatives of soft materials the structure of which can be strongly manipulated with local geometry and presence of appropriate nanoparticles. The objects of study, named also LC shells, will be exploited as basic unit elements for future soft colloidal crystals. A different arrangement of colloids within the crystal would result in different physical properties in a similar way as different packing of atoms results in different crystals made of real atoms. In presented research will be demonstrated, how relevant basic mechanisms in thin films of nematic liquid crystals could be explained in a classroom and used as a case study, also for explanation of many other physical properties. This research topic is still in its infancy. At this stage only various defect structures in relatively simple geometries (spherical and elliptical) will be analyzed. There is a need to find simple ways to control sensitively the valence of LC shells and in particular to develop strategies to assemble them in crystal structures of desired symmetry. This would allow tailoring specific optical dispersion relations or other physical property of interest and make new ways to teach different physical properties on the »music« based approach.

https://oaji.net/articles/2015/457-1422203894.pdf

Interplay between art and science in education: "music" based approach in nanosciences

We study the effects of nanoparticles (NPs) on thermotropic nematic liquid crystals (LCs) in relatively dilute NP–LC mixtures. We are interested in the fundamental generic mechanisms that quantitatively and qualitatively affect the phase behavior of LCs. A simple molecular field analysis shows that a phase transition will likely occur upon entry into the ordered phase. Moreover, the interaction between nematogenic NPs and LCs could force a sergeant–soldier-like behavior, in which only the phase behavior of one component is affected despite the symmetric appearance of the coupling term. When NPs are anisotropic, their influence on LC phase behavior can be qualitatively different depending on the anchoring, even in the absence of the disorder. We illustrate numerically that a random-field-type disorder might impose either short-range, quasi-long-range, or even long-range order, which might survive.

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Phase behavior of nematic-nanoparticle mixtures

We perform a numerical study of the annihilation of nematic radial and hyperbolic point defect. Both the pre-collision and post-collision stages are taken into account. Initially a pair of defects is induced at the axis of the cylindrical capillary. A semi-microscopic interaction potential and the Brownian molecular dynamics are used. In the early stage the cores of defects are negligibly mutually influenced. Their relative velocity is inversely proportional to the separation d between defects. As d becomes comparable to the nematic correlation length, the cores significantly deform. During the collision the defects merge and become indistinguishable. In the post-collision regime the order parameter at the collision site gradually recovers the equilibrium configuration.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Samo Kralj

Papers

Deuteron NMR study of an 8CB liquid crystal confined to porous glass

Annihilation of defects in liquid crystals

Interplay between art and science in education: "music" based approach in nanosciences

Phase behavior of nematic-nanoparticle mixtures

Nematic point defect annihilation in a cylindrical capillary