Download or read book Influence of Confinement on Relaxation of Director Orientational Fluctuations in Nematic Liquid Crystal written by Edwin X. Arroyo Félix and published by . This book was released on 2009 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Dielectric Relaxation on Director Dynamics in Uniaxial Nematic Liquid Crystals written by Mingxia Gu and published by . This book was released on 2009 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Director reorientation dynamics is essential to most of today's liquid crystal technologies. Advances in research have allowed one to reduce the response times from millisecond to microsecond and even to nanoseconds. For these small time scales, the description of the director dynamics requires a proper account of the dielectric dispersion effects. However, the first analysis of the role of dielectric dispersion in the director dynamics has been performed only very recently. Previous investigations were limited to dual frequency nematic liquid crystals, and considered only a single dielectric relaxation process. In this thesis, we lift these limitations and propose a model that accounts for multiple processes of dielectric relaxations in both parallel and perpendicular dielectric permittivities. The model yields a number of counterintuitive predictions such as the polar contribution to the dielectric coupling between the field and the nematic liquid crystal. The most important results are summarized below: First, we developed a general model to describe the director orientation dynamics of nematic liquid crystals under an applied electric field that accounts for multiple dielectric relaxations in both parallel and perpendicular dielectric permittivities. This model presents the contribution of dielectric relaxation as a "memory" effect; the director dynamics depends not only on the present electric and director fields, but also on their pre-histories. Second, we discovered an unusual contribution to the dielectric torque as a result of dielectric memory effect. This torque is linear in the present applied electric field and is thus sensitive to its polarity. The phenomenon is accompanied by a spectacular but counter-intuitive effect: the director relaxation during the "switch-off" stage can be accelerated if instead of an abrupt vertical back edge of the voltage pulse, we apply a pulse with a non-instantaneously vanishing back edge. Third, we demonstrate the director dynamics under different "shapes" of the front edge of the voltage pulses, taking into account the dielectric relaxation. Our model allows us to optimize the front edge of the pulse to improve switching efficiency. Finally, we studied the dynamics of electrically induced isotropic-nematic (I-N) phase transition by accounting for the finite rate of the polarization dynamics, which has previously been considered an instantaneous process in the classic theory. Consequently the electrically induced nematic order parameter does not interact directly with the applied electric field, but is mediated by the dynamics of polarization. We present a model based on the Langevin equation that describes the dynamics of two crucial parameters: the polar and non-polar order parameters during the electrically induced I-N phase transition.
Download or read book Spin lattice Relaxation by Fluctuations in the Nematic Liquid Crystal Director written by Merton Adelbert Nickerson and published by . This book was released on 1976 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamics in Small Confining Systems written by and published by . This book was released on 2005 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Liquid Crystal Colloids written by Igor Muševič and published by Springer. This book was released on 2017-05-14 with total page 313 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book brings together the many concepts and discoveries in liquid crystal colloids contributed over the last twenty years and scattered across numerous articles and book chapters. It provides both a historical overview of the development of the field and a clear perspective on the future applications in photonics. The book covers all phenomena observed in liquid crystal colloids with an emphasis on experimental tools and applications of topology in condensed matter, as well as practical micro-photonics applications. It includes a number of spectacular manifestations of new topological phenomena not found or difficult to observe in other systems. Starting from the early works on nematic colloids, it explains the basics of topological defects in ordered media, charge and winding, and the elastic forces between colloidal particles in nematics. Following a detailed description of experimental methods, such as optical tweezing and particle tracking, the book eases the reader into the theoretical part, which deals with elastic deformation of nematic liquid crystals due to inclusions and surface alignment. This is discussed in the context of basic mean field Landau-de Gennes Q-tensor theory, with a brief explanation of the free-energy minimization numerical methods. There then follows an excursion into the topology of complex nematic colloidal structures, colloidal entanglement, knotting and linking. Nematic droplets, shells, handlebodies and chiral topological structures are addressed in separate chapters. The book concludes with an extensive chapter on the photonic properties of nematic dispersions, presenting the concept of integrated soft matter photonics and discussing the concepts of nematic and chiral nematic microlasers, surface-sensitive photonic devices and smectic microfibers. The text is complemented by a large bibliography, explanatory sketches and beautiful micrographs.
Download or read book Dielectric Relaxation and Electrooptical Effects in Nematic Liquid Crystals written by Ye Yin and published by . This book was released on 2007 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orientational dynamics of the nematic director in the applied electric field is a fundamental physical phenomenon that is at the heart of numerous modern technologies. Dielectric reorientation of the director is caused by a torque that depends on both the electric field and electric displacement. The finite rate of dielectric relaxation causes a time lag of the electric displacement as compared to the instantaneous value of the electric field. This effect which has been previously ignored is the subject of this review. We show that it causes profound effects when the characteristic time of the field changes is close to the dielectric relaxation time. Depending on the type of the nematic material, the characteristic relaxation times range from milliseconds (dual-frequency materials) to nanoseconds ("regular" materials such as pentylcyanobiphenyl). From the fundamental viewpoint, the problem is to determine the dielectric torque as a function of not only the present values of the electric field and director (as in the current theory), but of the previous values of these variables. As the modern industry demands nematic devices capable of switching within 1 ms or less, the issue of finite rate of dielectric relaxation becomes also of practical importance. We review recent experimental and theoretical works that link the phenomenon of dielectric relaxation in nematic liquid crystals to their fast electro-optical switching and also to the problem of dielectric heating. We discuss the theoretical model that allows one to relate director reorientation to the "history" of the electric field and the experimental verification of its validity. We analyze the effect of dielectric heating that is especially profound at the frequencies corresponding to dielectric relaxation. One of the important new results here is that the temperature raise depends on the state of director orientation. We also reported on a thermodielectric bistability in DFNs caused by the anisotropic nature of dielectric heating and director reorientation in an electric field. The bistability is a result of the positive feedback loop: director reorientation -> anisotropic dielectric heating -> dielectric anisotropy -> director reorientation. We demonstrate both experimentally and theoretically that two states with different temperature and director orientation, namely, a cold planar state and a hot homeotropic state coexist in a LC cell for a certain frequency and amplitude range of the applied voltage.
Download or read book Influence of Flexoelectric Effect on Director Alignment of Nematic Liquid Crystals in Axial Arrangement Cylindrical Cells written by and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : A positive nematic liquid crystal (5CB) sample is confined in cylindrical cells under strong or weak axial anchoring boundary conditions when a radial nonuniform low-frequency electric field is applied and the flexoelectric effect is taken into account. Based on the Frank elastic free energy, the surface energy of the Rapini–Papoular approximation, the polarization free energy and the flexoelectric free energy caused by electric field, we obtain the free energy density of the nematic and solve the corresponding Euler–Lagrange equation numerically. We investigate the director distribution, the critical voltage and the critical exponent of nematic liquid crystal in cylindrical cells. It follows that the critical exponent is the classical one. It is also shown that the critical voltage in the system is affected by the flexoelectric effect, the geometric effect and radial weak anchoring effect on the cylindrical surfaces. A new type of director transition caused by the flexoelectric effect, the dielectric coupling effect and the radial weak anchoring effect is found.
Download or read book Liquid Crystals written by and published by . This book was released on 2001 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NMR of Ordered Liquids written by E.E. Burnell and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 465 pages. Available in PDF, EPUB and Kindle. Book excerpt: NMR of Ordered Liquids gives a unique overview of the scope and limitations of the NMR of oriented liquids, based on contributions from acknowledged experts in the field. The book consists of four sections: -detailed general introduction which covers the basic principles and sophisticated experimental techniques; -wide variety of applications ranging from NMR studies of small atoms and molecules in anisotropic liquids to the utilization of residual dipolar couplings for structure determination of biological molecules; -summary of the sophisticated theoretical treatments, computer simulations, and phenomenological models for anisotropic intermolecular interactions that are widely used in the analysis of experimental results; -overview of the dynamical aspects and relaxation processes relevant for orientationally ordered molecules.
Download or read book Annual Reports on NMR Spectroscopy written by and published by Academic Press. This book was released on 2016-01-09 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annual Reports on NMR Spectroscopy provides a thorough and in-depth accounting of the progress made in nuclear magnetic resonance (NMR) spectroscopy and its many applications. Nuclear magnetic resonance (NMR) is an analytical tool used by chemists and physicists to study the structure and dynamics of molecules. In recent years, no other technique has gained as much significance as NMR spectroscopy. It is used in all branches of science in which precise structural determination is required, and in which the nature of interactions and reactions in solution is being studied. Annual Reports on NMR Spectroscopy has established itself as a premier resource for both specialists and non-specialists alike who want to become familiar with the new techniques and applications of NMR spectroscopy. Serves as the premier resource for learning the new techniques and applications of NMR spectroscopy Provides a key reference for chemists and physicists using NMR spectroscopy to study the structure and dynamics of molecules
Download or read book Modern Topics in Liquid Crystals written by Agnes Buka and published by World Scientific. This book was released on 1993 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains 19 review articles, written by leading experts in the field of neutron scattering, NMR, dielectric spectroscopy, ferroelectricity, liquid crystal polymers as well as related subjects. The articles cover a broad range of topics which are currently the center of focus and interest in this field. The book will be useful for experienced researchers as well as students and those who want to enter the field. Apart from the fact that such a publication covers a gap in the literature, there is also a personal actuality. This volume will be devoted to Professor L Bata, who started the liquid crystal research in Hungary some 25 years ago and who is still head of the department at KFKI today. He initiated a lot of new subjects in the field and supported many young scientists during these years. He is celebrating his 60th birthday this year.
Download or read book Flowing Matter written by Federico Toschi and published by Springer Nature. This book was released on 2019-09-25 with total page 309 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book, published in the Soft and Biological Matter series, presents an introduction to selected research topics in the broad field of flowing matter, including the dynamics of fluids with a complex internal structure -from nematic fluids to soft glasses- as well as active matter and turbulent phenomena. Flowing matter is a subject at the crossroads between physics, mathematics, chemistry, engineering, biology and earth sciences, and relies on a multidisciplinary approach to describe the emergence of the macroscopic behaviours in a system from the coordinated dynamics of its microscopic constituents. Depending on the microscopic interactions, an assembly of molecules or of mesoscopic particles can flow like a simple Newtonian fluid, deform elastically like a solid or behave in a complex manner. When the internal constituents are active, as for biological entities, one generally observes complex large-scale collective motions. Phenomenology is further complicated by the invariable tendency of fluids to display chaos at the large scales or when stirred strongly enough. This volume presents several research topics that address these phenomena encompassing the traditional micro-, meso-, and macro-scales descriptions, and contributes to our understanding of the fundamentals of flowing matter. This book is the legacy of the COST Action MP1305 “Flowing Matter”.
Download or read book Liquid Crystalline Polymers written by Vijay Kumar Thakur and published by Springer. This book was released on 2015-11-16 with total page 627 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces anisotropic innovations in liquid crystalline polymers as well as new nanocomposite materials and testing techniques. The authors detail the newest discoveries of material properties, material types and phases, and material characterization. This interdisciplinary work creates valuable links that strengthen the approach to the evolving field of liquid crystalline polymers/ materials.
Download or read book Dynamics in Small Confining Systems III Volume 464 written by J. M. Drake and published by . This book was released on 1997-06-03 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interfacial science has rapidly expanded beyond the original realm of chemistry to include physics, mechanical and chemical engineering, biology, materials science, and other specialized subfields. This book in a series from MRS emphasizes the effects of confinement on the physical and chemical properties of equilibrium and nonequilibrium systems. Of particular interest is the question of how nearby surfaces or ultra-small geometries can force a system to behave in ways significantly different than it behaves in bulk. Theoretical, experimental and computational evidence of the effects of confinement on gaseous, liquid and solid systems is presented. Topics include: probing confined systems; structure and dynamics of liquids at interfaces; nanorheology and tribology; adsorption; diffusion in porous systems and reaction dynamics.
Download or read book Nuclear Relaxation and Molecular Dynamics of Selectively Deuterated Para diethynylbenzenes in Nematic Liquid Crystal Phase 5 written by W. Harry Dickerson and published by . This book was released on 1982 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physical Review written by and published by . This book was released on 1999-05 with total page 1552 pages. Available in PDF, EPUB and Kindle. Book excerpt: Publishes papers that report results of research in statistical physics, plasmas, fluids, and related interdisciplinary topics. There are sections on (1) methods of statistical physics, (2) classical fluids, (3) liquid crystals, (4) diffusion-limited aggregation, and dendritic growth, (5) biological physics, (6) plasma physics, (7) physics of beams, (8) classical physics, including nonlinear media, and (9) computational physics.
Download or read book Time Resolved Spectroscopy in Complex Liquids written by Renato Torre and published by Springer Science & Business Media. This book was released on 2007-11-27 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: Time-Resolved Spectroscopy in Complex Liquids is intended to introduce the experimental researchers to state-of-the-art techniques in the study of the dynamics of complex liquids. The contributors concentrate on time-resolved optical spectroscopy, which recently produced many relevant results and new information about complex liquids. This is an emerging topic of soft-matter science and this book provides the most up-to-date account of new development.
