Download or read book Study of Nanoparticle Liquid Crystal Dispersions Using Optical Microscopy and Solid State NMR written by Jonathan Milette and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of Zirconia Nanoparticles with Mixed Ligand Shells by Solid state NMR Methods and Dispersions of Polymer Functionalized Gold Nanoparticles in Nematic Liquid Crystals written by Safiya Allie and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: " This thesis concerns the characterization of nanoparticles and liquid crystal nanocomposites. Two types of nanoparticles were prepared: zirconia nanoparticles were functionalized with different ratios of dodecyl- and phenyl- phosphonic acids as a model system for developing a NMR-based characterization method to determine the spatial distribution of the ligands. This study was motivated by the finding that successful dispersions of nanoparticles in liquid crystals often requires mixed ligand shells and it assumed that there is a homogeneous distribution of the two ligands. Secondly, more readily prepared polymer functionalized gold nanoparticles were tested as an alternative to mixed ligand shells of low molar mass mesogenic ligands to achieve stable dispersions in a nematic liquid crystal. Spin diffusion NMR experiments developed for heterogeneous polymeric materials were used as a novel surface characterization method for nanoparticles with mixed ligand shells. 1D solid-state 31P and 1H NMR spectroscopy, respectively used to characterize the surface binding and ligand shell composition, showed that the compositions of the strongly bound ligand shells matched the reaction ratios. The spatial proximities of the dodecyl and phenyl groups were probed by 2D 1H-13C Heteronuclear Correlation (HETCOR) and 1H Double Quantum (DQ) NMR experiments. The HETCOR and 1H DQ NMR experiments indicate a significant population of dodecyl- and phenyl- phosphonic acids are nearest neighbors which would be consistent with molecular level mixing on the nanoparticle surface. However the proton spin diffusion experiments indicate the presence of some type of phase separation. This finding is significant since previous studies of mixed phosphonic acid monolayers in the literature assume a homogeneous distribution. The analysis of the spin diffusion build up curves yielded domain sizes on the order of ~ 4-5 nm which appear to be too large given the nanoparticle dimensions. Control experiments point towards an overestimate of the spin diffusion coefficients since these experiments were originally developed for the extended proton-proton dipolar coupling networks found in polymers. Gold nanoparticles, AuNPs, functionalized with 2000 MW thiolated poly(ethylene oxide), PEO-SH, were dispersed in a common nematic liquid crystal, 4-cyano-4'-pentylbiphenyl (5CB). Dispersions of free PEO, 2000 MW, in 5CB were also prepared. The two types of blends were characterized by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). Relatively high concentrations of 10 wt. %, 20 wt. % and 50 wt. % AuNPs-PEO in 5CB were investigated. The dispersions were all characterized by POM by cooling from the isotropic state to erase all thermal history. Both the AuNP-PEOs and PEO alone are completely miscible in isotropic 5CB to very high concentrations. Whereas the free PEO significantly lowers the isotropic to nematic (I-N) phase transition temperature of 5CB, the AuNP-PEOs only cause a small change, similar to previously studied AuNPs with mesogenic ligands. Below the I-N transition, both the polymer and AuNP dispersions display a biphasic state over a wide temperature range. For higher concentrations (> 10 wt. % PEO), PEO spherulite crystallization nucleates the nematic phase of 5CB. At lower PEO concentrations, the I-N transition of 5CB precedes PEO crystallization which shows a dendritic morphology. The AuNP-PEOs form a cellular network which shares similarities with that formed by AuNPs with mesogenic ligands. Differences in the network morphologies are attributed to the stronger disordering effect of the polymer ligands on the nematic structure as compared to the mesogenic ligands. " --

Download or read book Liquid Crystals With Nano And Microparticles In 2 Volumes written by Jan P F Lagerwall and published by World Scientific. This book was released on 2016-10-10 with total page 944 pages. Available in PDF, EPUB and Kindle. Book excerpt: 'The overall book content is excellently coordinated to form a synchronised story, interesting to a broad scientific audience … The book summarises the present knowledge in the field, introduces fundamental concepts to the beginners, describes key measuring methods and presents several different typical demonstrative systems, some of them exhibiting an extraordinary rich spectrum of structures and superstructures. I am sure that with time the book will become an attractor to a broad audience (physicists, chemists, material scientists, engineers, etc.), ranging from students, beginners in the field to experienced researchers. To summarise, this is the book that I have been missing on my bookshelf.'Liquid Crystals TodayWhile liquid crystals are today widely known for their successful application in flat panel displays (LCDs), academic liquid crystal research is more and more targeting situations where these anisotropic fluids are put to completely different use, in varying contexts. A particularly strong focus is on colloidal liquid crystals, where particles, bubbles or drops are dispersed in a liquid crystal phase. The liquid crystal can act as a host phase, with the inclusions constituting foreign guests that disturb the local order in interesting ways, often resulting in large-scale positional arrangement and/or uniform alignment of the guests. But it may also be formed by solid particles themselves, if these are of nanoscale dimensions and of disc- or rod-shape, and if they are suspended in an isotropic liquid host at sufficient concentration.This book aims to cover both the modern research tracks, gathering pioneering researchers of the different subfields to give a concise overview of the basis as well as the prospects of their respective specialties. The scope spans from curiosity-driven fundamental scientific research to applied sciences. Over the course of the next decade, the former is likely to generate new tracks of the latter type, considering the exploratory and productive phase of this young research field.

Download or read book Surfaces and Interfaces of Liquid Crystals written by Igor Muševič and published by Springer Science & Business Media. This book was released on 2004-08-11 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the state of the art of our understanding of liquid-crystal interfaces on a molecular level. The interactions of liquid crystal molecules with a surface play an essential role in the operation of liquid crystal displays (LCD's) and other LC devices that are based on the controllable anchoring of LC molecules on polymer coated surfaces. This book addresses the microscopic interaction between a macromolecule (liquid crystal, polymer) and a wall, using state of the art surface and interface-sensitive experimental techniques, such as Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (STM), Linear and Nonlinear Optical Microscopy and (Dynamic) Light Scattering (DLS). These experimental techniques were complemented with computer simulations and supra molecular chemistry methods to develop controllable polymeric surfaces.

Download or read book Liquid Crystal Dispersions written by Paul S. Drzaic and published by World Scientific. This book was released on 1995 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer-dispersed liquid crystal (PDLC) materials are of interest both for their potential in display technology and the fascinating science found in liquid crystals confined to small cavities. Liquid Crystal Dispersions is a comprehensive overview of the science and technology of this new class of materials. Topics covered include formation of PDLC devices, a catalog of droplet structures and transformations, device electro-optical properties, and applications. Liquid Crystal Dispersions will be of value to the nonspecialists keen on gaining an overview of this new field, as well as to specialists interested in a comprehensive review of work in this area.

Download or read book NMR of Liquid Crystal Dendrimers written by Carlos Rodrigues da Cruz and published by CRC Press. This book was released on 2016-12-08 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dendrimers are hyperbranched molecules with well-defined nanometer-scale dimensions. Important technological applications of these systems, both in biomedicine and materials science, have been recently proposed. Liquid crystal dendrimers are fascinating materials that combine the characteristics of dendrimers with the anisotropic physical behaviour and molecular self-organization typical of liquid crystals. This unique association of physical and chemical properties, together with the possibility of multi-selective functionalization put forward by dendrimers, opens new perspectives for applications. Nuclear magnetic resonance (NMR) is a powerful experimental technique applied in materials science and an important tool to the study of molecular organization and dynamics. This book presents an introduction to dendrimers properties with special insight into liquid crystal dendrimers and a detailed description of the NMR theory and experimental techniques used in the investigation of these materials. It also discusses recent NMR research results on liquid crystal dendrimers, with emphasis on molecular order and dynamics studies. This book introduces the properties of dendrimers, with special insight into liquid crystal dendrimers, and a detailed description of NMR theory and experimental techniques used in the investigation of these materials. It also discusses results of recent NMR research on liquid crystal dendrimers, with an emphasis on molecular order and dynamics studies. Advanced undergraduate and graduate students of physics, chemistry, and materials science and researchers in the fields of dendrimers, liquid crystals, and NMR will find the book extremely useful.

Download or read book Optical and Electro optical Properties of Nematic Liquid Crystals with Nanoparticle Additives written by Javad Mirzaei and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liquid crystals (LCs) are an interesting class of materials that are attracting significant attention due to their ever-growing applications in a wide variety of fields such as liquid crystal display (LCD) technology, materials science and bioscience. In recent years, along with the developments of materials at the nanoscale, doping LCs with nanoparticles (NPs) has emerged as a very promising approach for improving LC properties. Nanoparticle additives can introduce novel effects on optical and electro-optical properties of nematic liquid crystals (N-LCs), such as altered molecular alignment, faster response time and increased efficiency. This thesis studies the impacts that the inclusion of metallic NPs made of gold or semiconductor CdSe quantum dots (QDs), have on optical and electro-optical properties of N-LCs. Using polarized optical microscopy and detailed capacitance and transmittance measurements of nematic mixtures in electro-optic test cells, characteristics such as optical texture, phase transition temperatures, switching voltages and dielectric anisotropy are investigated in pure as well as doped samples. Surface ligands in NPs and their chemical functionalization play an important role in the LC-NP interactions, largely by determining the dispersibility of NPs and stability of the nanocomposites. One important objective of this thesis is to investigate and prepare a series of gold nanoparticles (Au NPs) with specially formulated robust coatings that maximizes solubility and stability in LC medium. Silanization of NPs is developed as a method to overcome the stability challenge. The functionalization of silanized NPs with aliphatic ligands or liquid crystalline molecules, provides chemically and thermally stable NPs with hydrophobic and structurally compatible surfaces required for dispersion in N-LCs. After complete characterization the synthesized particles are used to make the new nematic nanocomposites. By analysis of the structure-property relationships governing LC-nanomaterial composites and by comparison of new results and data from previous studies on other types of NPs, this thesis will further reveal the mechanism of the interrelations between host LC molecules and NP, considering the role of variables such as core composition, size and surface chemistry of NPs (e.g. siloxane shell, aliphatic ligand vs. liquid crystalline ligand) in achieving stable LC composites with desired optical and electro-optical properties.

Download or read book Liquid Crystals with Nano Micro Particles and Their Applications written by Jayeeta Chattopadhyay and published by CRC Press. This book was released on 2023-03-31 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: LCs are self-organized anisotropic fluids that are thermodynamically located between the isotropic liquid and the crystalline phase, exhibiting the fluidity of liquids as well as the long-range lattice order that can only be found in crystalline solids. The addition of nanomaterials to a LC material produces a composite or colloidal dispersion and results into a revolutionary change in their applications. This book will discuss the remarkable performances of nano-particle aided liquid crystals in metamaterials, photonics, functionalized polymer fibres, sensing, and medical diagnostics.

Download or read book Nuclear Magnetic Resonance of Liquid Crystals written by Ronald Y. Dong and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intended for researchers and students in physics, chemistry and materials science, this book provides the necessary background information and sufficient mathematical and physical detail to study the current research literature. The book begins with a survey of liquid crystal phases and field effects, together with an introduction to the basic physics of nuclear magnetic resonance. It then discusses orientational ordering and molecular field theories for various liquid crystal molecules and nmr studies of uniaxial and biaxial phases. Subsequent chapters consider spin relaxation processes and rotational, translational, and internal molecular dynamics of liquid crystals. The final chapter discusses two-dimensional and multiple- quantum nmr spectroscopies and their application in elucidating liquid crystal properties. This second edition, updated throughout, incorporates many new references and includes new mathematical appendices.

Download or read book Lyotropic Liquid Crystals as Templates for the Synthesis of Silver Nanoparticles written by Dmitry Kushnikovskiy and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is focused on the synthesis of silver nanoparticles in various lyotropic liquid crystalline phases formed by biologically friendly surfactants with or without dodecyltrimethylammonium-DNA complex in aqueous solution with different additives. In all cases, silver ions were reduced by components contained in the system, no additional reductants were employed. In total, four different systems have been investigated as potential templates for the nanoparticle preparation. Two different synthetic strategies have been used. Firstly, nanoparticles were synthesized by the chemical reduction of silver ions by the nonionic or zwitterionic surfactant molecules which were used to form the liquid crystalline phase. Secondly, nanoparticles have been synthesized by UV irradiation of DNA-containing liquid crystals where DNA acts as templating and photosensitizing agent. At the first stage, an Ag-DNA complex is formed by embedding silver ions into the double helix. Illumination of this complex with UV light that is absorbed by the nucleobases induced the formation of nanoparticles within the DNA double helix.The effect of the formation of silver nanoparticles on the lyotropic liquid crystalline phase was investigated by 2H and 31P NMR spectroscopy, small angle X-ray scattering, and polarizing optical microscopy. The influence of the template mesophase on the formation rate and nanoparticle size and morphology was studied using UV-spectroscopy, transmission electron and atomic force microscopy techniques. ; eng

Download or read book Surfaces and Interfaces of Liquid Crystals written by Theo Rasing and published by . This book was released on 2014-01-15 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nanoparticle Doping in Nematic Liquid Crystals written by Martin Urbanski and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the influence of spherical nanoparticles on the physical properties of nematic liquid crystals is investigated. The latter are ordered fluids with special anisotropic physical properties, due to which they find diverse technological applications, in particular in the field of display technologies. The question if doping these substances with nanoparticles can improve the electro-optical properties in terms of performance and energy efficiency is topic of actual scientific research. Therefore the influence of nanoparticle doping on the nematic order and the physical properties of nematic liquid crystalline host is investigated. In this work, different organically functionalized gold and CdSe nanoparticles are dispersed in two different host phases and the influence of nanoparticles on the surface alignment as well as on the electro-optical switching characteristics of the dispersions are examined by light microscopy and dielectric measurements. Several key factors could be identified that positively influence on the nematic order and the electro-optical switching behavior of the dispersion. A high stability, chemical compatibility and a strong interaction between the organic ligand shell and the liquid crystal molecules are found to be crucial for the formation of stable dispersions with improved physical properties. Synthesis strategies for new particle systems are suggested, that could pave the way for the future use of nanoparticles in display technology. ; eng

Download or read book Amorphous Solid Dispersions written by Navnit Shah and published by Springer. This book was released on 2014-11-21 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume offers a comprehensive guide on the theory and practice of amorphous solid dispersions (ASD) for handling challenges associated with poorly soluble drugs. In twenty-three inclusive chapters, the book examines thermodynamics and kinetics of the amorphous state and amorphous solid dispersions, ASD technologies, excipients for stabilizing amorphous solid dispersions such as polymers, and ASD manufacturing technologies, including spray drying, hot melt extrusion, fluid bed layering and solvent-controlled micro-precipitation technology (MBP). Each technology is illustrated by specific case studies. In addition, dedicated sections cover analytical tools and technologies for characterization of amorphous solid dispersions, the prediction of long-term stability, and the development of suitable dissolution methods and regulatory aspects. The book also highlights future technologies on the horizon, such as supercritical fluid processing, mesoporous silica, KinetiSol®, and the use of non-salt-forming organic acids and amino acids for the stabilization of amorphous systems. Amorphous Solid Dispersions: Theory and Practice is a valuable reference to pharmaceutical scientists interested in developing bioavailable and therapeutically effective formulations of poorly soluble molecules in order to advance these technologies and develop better medicines for the future.

Download or read book Nanoscale Patterning and Imaging of Liquid Crystals and Colloids at Surfaces written by Joel S. Pendery and published by . This book was released on 2014 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on liquid crystals and the inherent orientational order that arises from these anisotropic materials. Quasi two-dimensional chiral patterns were scribed via Atomic Force Microscopy (AFM) with robust control onto polyimide substrate, composed of achiral materials, yielding 3D chirality that was localized to within a few nanometers of the surface. The chirality was quantified through the surface electroclinic effect. In addition, a sample with a well controlled easy axis was fabricated and a method to measure the local director orientation with 100 nm resolution using Near-Field Scanning Optical Microscopy yielded the true angular distribution function of the local order with high precision. Finally, gold nanoparticle self-assembly was studied within a cholesteric liquid crystal (CLC) film. The open sample creates a striped texture and gold nanoparticles coated with thiol are deposited within the liquid crystal matrix. Polarized Localized Surface Plasmon Resonance (LSPR) measurements show an anisotropy between light polarized with respect to the stripe orientation. Evaporating the liquid crystal revealed disordered anisometric needles measured by AFM. Generalized Mie theory calculations, in conjunction with LSPR, found a smaller nanoparticle spacing in the CLC compared to a 2D monolayer of the same nanoparticles on a rubbed substrate or 1D chains in smectic A dislocations. The closer spacing suggests trapping sites within the CLC, where nanoparticles are first localized and then aggregate under van der Waals attraction aided and enhanced by the CLC and mediated by steric forces.

Download or read book Synthesis and Conformational Study of Liquid Crystal Materials written by Naser Juman a and published by LAP Lambert Academic Publishing. This book was released on 2015-01-30 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new two series of liquid crystal compounds containing 1,3,4-oxadiazole were synthesized and characterized by melting points, elemental analysis FTIR and 1HNMR spectroscopy. The liquid crystal properties of the synthesized compounds were verified by using hot-stage polarizing optical microscopy and differential scanning calorimeter. All of the compounds in both two series show mesomorphic properties. All members of those two series exhibit smectic A, smectic C and/ or nematic phases. Continually, to improve the physical study, Silver nanoparticles were prepared by reduction method and identified by mostly analysis XRD, SEM and AFM. From all of these techniques the particle size of nano seemed less than (50) nm. A theoretical investigating of core geometry by doing the conformational search over its affective torsion angles with PM3 and RM1 methods in order to include the effect of quantum mechanical factors that effect on the core geometry. Dielectric properties and other physical properties such as electrical conductivity (AC) and relaxation time or activation energy have been studied for two systems pure liquid crystals and their doped with silver nano particles.

Download or read book Phase Transition Studies of Liquid Crystal Colloids with Solvents and Nano solids written by Krishna P. Sigdel and published by . This book was released on 2011 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Liquid crystals (LCs) are anisotropic fluids that exhibit numerous thermodynamically stable phases in between an isotropic liquid and a three-dimensionally ordered solid. In their simplest ordered phase, the nematic, LCs show orientational order due to molecular self assembly and at the same time maintaining fluid flow properties. In the smectic phase, they show both orientational and partial translational order characterized by a 1-d density wave. Liquid crystalline substances have been extensively studied due to their applications and as important physical models of self-assembly. The effect of the disorder and impurities on LC systems is an important and challenging problem to the fundamental understanding of phases ordering or self-assembly and continually attracts the attention of researchers. The disordered systems often display complex and rich phenomena, being the generalization of the pure (ideal) systems. Disorder can dramatically alter the physical properties of multi-component, composite systems. In particular, the effect of disorder on phase transitions is important as the disorder typically couples to the order parameter, which can be usefully described as a random local field that is conjugate to the order parameter. This is usually realized in systems with random inclusions in a phase ordering media, e.g., a colloidal dispersion of solids in a complex fluid. Another form of disorder is presented by dilution effects, which imposes instead the random breaking or weakening of intermolecular bonds or interactions responsible for the phase ordering. Exploring a good physical system representing random dilution effects in a controlled manner offers a physical probe to unresolved problems in the understanding of mesophasic order. This Dissertation presents a series of studies of dilution and different form of disorder effect on liquid crystal phase transitions. We have used high-resolution AC-calorimetry, dielectric spectroscopy as well as polarizing microscopy to characterize the effects of solvent such as hexane, acetone, decane, and nanomaterials such as multiwall carbon nanotubes and ferroelectric nanoparticles on the phase transitions of several liquid crystals. The liquid crystals of interest are: pentylcyanobiphenyl (5CB), octylcyanobiphenyl (8CB), and decylcyanobiphenyl (10CB). Studies have been carried out as a function of solvent, nanotube, and nanoparticles concentration and temperature spanning the isotropic to nematic (I-N), nematic to smectic-A (N-SmA), and isotropic to smectic-A (I-SmA) phase transitions.

Download or read book Liquid Crystals with Nano and Microparticles written by Giusy Scalia and published by . This book was released on 2016 with total page 944 pages. Available in PDF, EPUB and Kindle. Book excerpt: "While liquid crystals are today widely known for their successful application in flat panel displays (LCDs), academic liquid crystal research is more and more targeting situations where these anisotropic fluids are put to completely different use, in varying contexts. A particularly strong focus is on colloidal liquid crystals, where particles, bubbles or drops are dispersed in a liquid crystal phase. The liquid crystal can act as a host phase, with the inclusions constituting foreign guests that disturb the local order in interesting ways, often resulting in large-scale positional arrangement and/or uniform alignment of the guests. But it may also be formed by solid particles themselves, if these are of nanoscale dimensions and of disc- or rod-shape, and if they are suspended in an isotropic liquid host at sufficient concentration. This book aims to cover both the modern research tracks, gathering pioneering researchers of the different subfields to give a concise overview of the basis as well as the prospects of their respective specialties. The scope spans from curiosity-driven fundamental scientific research to applied sciences. Over the course of the next decade, the former is likely to generate new tracks of the latter type, considering the exploratory and productive phase of this young research field."--Publisher's website