The Processing of LC Thermosets in Orienting External Fields

1996 ◽  
Vol 425 ◽  
Author(s):  
Hilmar Körner ◽  
Atsushi Shiota ◽  
Christopher K. Ober
Keyword(s):  
Liquid Crystals ◽  
Data Storage ◽  
Liquid Crystalline ◽  
Polymeric Materials ◽  
Optical Filters ◽  
Mechanical Anisotropy ◽  
Molecular Organization ◽  
External Fields ◽  
Wide Range ◽  
Structural Applications

Liquid crystals may possess macroscopically aligned structural, electrical and optical properties when oriented in external fields which leads to a wide range of applications including optical filters, displays, and data storage devices. Combining the properties of thermosets [1, 2] with the properties of liquid crystals (LC) is a logical step towards creating new materials. The development of liquid crystalline thermosets (LCT) has been motivated by their potential use in structural applications and the need for more adaptable polymeric materials with tunable strength and stiffness as well as tailored mechanical anisotropy. It is known that mechanical properties of conventional thermosets are determined by many factors including curing agent, filler, degree of cure, crosslink density, glass transition temperature, and accelerator. In LCT's all of these factors will ultimately be controlled by the both the molecular organization and orientation of the LC phase.

scholarly journals Cubic and Hexagonal Liquid Crystals as Drug Delivery Systems

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Yulin Chen ◽  
Ping Ma ◽  
Shuangying Gui
Keyword(s):  
Drug Delivery ◽  
Liquid Crystals ◽  
Drug Delivery Systems ◽  
Liquid Crystalline ◽  
Hexagonal Phase ◽  
Delivery Systems ◽  
Lyotropic Liquid Crystals ◽  
Cubic Phase ◽  
Sustained Drug Release ◽  
Wide Range

Lipids have been widely used as main constituents in various drug delivery systems, such as liposomes, solid lipid nanoparticles, nanostructured lipid carriers, and lipid-based lyotropic liquid crystals. Among them, lipid-based lyotropic liquid crystals have highly ordered, thermodynamically stable internal nanostructure, thereby offering the potential as a sustained drug release matrix. The intricate nanostructures of the cubic phase and hexagonal phase have been shown to provide diffusion controlled release of active pharmaceutical ingredients with a wide range of molecular weights and polarities. In addition, the biodegradable and biocompatible nature of lipids demonstrates the minimum toxicity and thus they are used for various routes of administration. Therefore, the research on lipid-based lyotropic liquid crystalline phases has attracted a lot of attention in recent years. This review will provide an overview of the lipids used to prepare cubic phase and hexagonal phase at physiological temperature, as well as the influencing factors on the phase transition of liquid crystals. In particular, the most current research progresses on cubic and hexagonal phases as drug delivery systems will be discussed.

Colloidally stable, magnetoresponsive liquid crystals based on clay nanosheets

2021 ◽  
Author(s):  
Olena Khoruzhenko ◽  
Daniel R Wagner ◽  
Sebastian Mangelsen ◽  
Martin Dulle ◽  
Stephan Förster ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
External Fields ◽  
Crystalline Materials ◽  
Liquid Crystalline Materials ◽  
Modern Technologies

Liquid crystalline materials found numerous applications in modern technologies due to their ability to respond to external fields. In this context, ferronematic liquid crystals are fascinating because they offer a...

scholarly journals Failure of structural elements made of polymer supported composite materials during the multiyear natural aging

2018 ◽  
Vol 33 ◽  
pp. 02009
Author(s):  
Pavel Blinkov ◽  
Leonid Ogorodov ◽  
Peter Grabovyy
Keyword(s):  
Composite Materials ◽  
Building Materials ◽  
Polymeric Materials ◽  
Metal Corrosion ◽  
Structural Elements ◽  
Form Complex ◽  
Wood Polymer ◽  
Plastic Materials ◽  
Wide Range ◽  
Structural Applications

Modern high-rise construction introduces a number of limitations and tasks. In addition to durability, comfort and profitability, projects should take into account energy efficiency and environmental problems. Polymer building materials are used as substitutes for materials such as brick, concrete, metal, wood and glass, and in addition to traditional materials. Plastic materials are light, can be formed into complex shapes, durable and low, and also possess a wide range of properties. Plastic materials are available in various forms, colors and textures and require minimal or no color. They are resistant to heat transfer and diffusion of moisture and do not suffer from metal corrosion or microbial attack. Polymeric materials, including thermoplastics, thermoset materials and wood-polymer composites, have many structural and non-structural applications in the construction industry. They provide unique and innovative solutions at a low cost, and their use is likely to grow in the future. A number of polymer composite materials form complex material compositions, which are applied in the construction in order to analyze the processes of damage accumulation under the conditions of complex nonstationary loading modes, and to determine the life of structural elements considering the material aging. This paper present the results of tests on short-term compression loading with a deformation rate of v = 2 mm/min using composite samples of various shapes and sizes.

Photoresponsive Liquid Crystalline Polymeric Materials

2012 ◽  
Vol 77 ◽  
pp. 325-332 ◽  
Author(s):  
Dan Qing Liu ◽  
Casper Van Oosten ◽  
Cees W.M. Bastiaansen ◽  
Dirk J. Broer
Keyword(s):  
Molecular Orientation ◽  
Order Parameter ◽  
Liquid Crystalline ◽  
Polymer Networks ◽  
Polymeric Materials ◽  
Molecular Organization ◽  
Surface Topology ◽  
Network Configuration ◽  
Lithographic Patterning

In-situ photopolymerization of liquid crystalline (LC) monomers has proven to be a valuable technique for the formation of well-ordered polymer networks. Their anisotropic properties led to a variety of applications in optics, electronics and mechanics. The use of light to initiate polymerization enables lithographic patterning. In addition the LC behavior enables formation of complex morphologies on molecular level. Controlling the director profile of an LC network film in transversal direction gives geometrical morphing upon minor changes in order parameter. Examples of suited profiles of molecular orientation are twisted or splayed director configurations tied up in the network configuration. Reversible order parameter changes can be induced by light using the photo-activated trans-cis isomerization of a copolymerized azobenzene monomer. This is demonstrated in photoresponsive cilia inkjet printed on a substrate. The cilia possess a splayed molecular organization and show well-controlled bending when addressed by light. We demonstrate a patterned film with alternating helicoidal and perpendicular-uniaxial molecular orientation. When applied as coating on glass, photo-activation in this case leads to a dynamically switching surface topology

PRODUCT FORMULATION WITH SURFACTANT NANOSTRUCTURES: LIQUID CRYSTALS, SOFT SOAP AND A PIECE OF CAKE

COSMOS ◽  
2011 ◽  
Vol 07 (01) ◽  
pp. 65-74
Author(s):  
HELEN DUTTON ◽  
FLOR SIPERSTEIN ◽  
GORDON TIDDY
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Consumer Products ◽  
Head Group ◽  
Product Formulation ◽  
Liquid Crystalline Phases ◽  
Wide Range ◽  
Hydrophobic Tail ◽  
Self Association ◽  
And Function

Surfactants self-associate in aqueous solutions to form micelles. Less well-known is that they form a wide range of liquid crystals — through self-association. These liquid crystals often occur in consumer products where they play an essential role in product stability and function. Some products are marketed in a liquid crystalline state although they are not recognized by the consumer (or, on occasion, by the manufacturer). This review describes the formation of micelles and the various liquid crystalline phases. These include lamellar, hexagonal, cubic and gel phases which have different long range structures but are based on micelles. The key factors linking surfactant molecular structure to liquid crystal architecture have been elucidated. These are the sizes of the surfactant hydrophobic tail(s) and head groups, together with the head group charge and the presence of any additives. Examples of liquid crystals in emulsion stabilization, household cleaners, conditioners, detergent liquid and some food are described.

Structure-property relations of liquid crystalline polymers

1987 ◽  
Vol 45 ◽  
pp. 460-463
Author(s):  
Linda C. Sawyer
Keyword(s):  
Solid State ◽  
Liquid Crystalline ◽  
Structural Model ◽  
Crystalline Polymer ◽  
Liquid Crystalline Polymers ◽  
Mechanical Anisotropy ◽  
Structure Property ◽  
Preparation Methods ◽  
Crystalline Polymers ◽  
Extended Chain

Recent liquid crystalline polymer (LCP) research has sought to define structure-property relationships of these complex new materials. The two major types of LCPs, thermotropic and lyotropic LCPs, both exhibit effects of process history on the microstructure frozen into the solid state. The high mechanical anisotropy of the molecules favors formation of complex structures. Microscopy has been used to develop an understanding of these microstructures and to describe them in a fundamental structural model. Preparation methods used include microtomy, etching, fracture and sonication for study by optical and electron microscopy techniques, which have been described for polymers. The model accounts for the macrostructures and microstructures observed in highly oriented fibers and films.Rod-like liquid crystalline polymers produce oriented materials because they have extended chain structures in the solid state. These polymers have found application as high modulus fibers and films with unique properties due to the formation of ordered solutions (lyotropic) or melts (thermotropic) which transform easily into highly oriented, extended chain structures in the solid state.

Triply-periodic nanostructures in surfactant, block copolymer, and biomembrane systems, and simulation of TEMs

1993 ◽  
Vol 51 ◽  
pp. 884-885
Author(s):  
David M. Anderson ◽  
Tomas Landh
Keyword(s):  
Liquid Crystalline ◽  
Diblock Copolymers ◽  
Cubic Phase ◽  
List Type ◽  
Interpenetrating Networks ◽  
Triply Periodic ◽  
Wide Range ◽  
Bicontinuous Cubic ◽  
Phase Liquid ◽  
Dividing Surface

First discovered in surfactant-water liquid crystalline systems, so-called ‘bicontinuous cubic phases’ have the property that hydropnilic and lipophilic microdomains form interpenetrating networks conforming to cubic lattices on the scale of nanometers. Later these same structures were found in star diblock copolymers, where the simultaneous continuity of elastomeric and glassy domains gives rise to unique physical properties. Today it is well-established that the symmetry and topology of such a morphology are accurately described by one of several triply-periodic minimal surfaces, and that the interface between hydrophilic and hydrophobic, or immiscible polymer, domains is described by a triply-periodic surface of constant, nonzero mean curvature. One example of such a dividing surface is shown in figure 5.The study of these structures has become of increasing importance in the past five years for two reasons:1)Bicontinuous cubic phase liquid crystals are now being polymerized to create microporous materials with monodispersed pores and readily functionalizable porewalls; figure 3 shows a TEM from a polymerized surfactant / methylmethacrylate / water cubic phase; and2)Compelling evidence has been found that these same morphologies describe biomembrane systems in a wide range of cells.

Polymer Chemistry

2004 ◽  
Keyword(s):  
Conducting Polymers ◽  
Liquid Crystalline ◽  
Polymer Chemistry ◽  
Chain Growth ◽  
Crystalline Polymers ◽  
Wide Range ◽  
Cyclic Oligomers ◽  
Step Growth

Polymer Chemistry: A Practical Approach in Chemistry has been designed for both chemists working in and new to the area of polymer synthesis. It contains detailed instructions for preparation of a wide-range of polymers by a wide variety of different techniques, and describes how this synthetic methodology can be applied to the development of new materials. It includes details of well-established techniques, e.g. chain-growth or step-growth processes together with more up-to-date examples using methods such as atom-transfer radical polymerization. Less well-known procedures are also included, e.g. electrochemical synthesis of conducting polymers and the preparation of liquid crystalline elastomers with highly ordered structures. Other topics covered include general polymerization methodology, controlled/"living" polymerization methods, the formation of cyclic oligomers during step-growth polymerization, the synthesis of conducting polymers based on heterocyclic compounds, dendrimers, the preparation of imprinted polymers and liquid crystalline polymers. The main bulk of the text is preceded by an introductory chapter detailing some of the techniques available to the scientist for the characterization of polymers, both in terms of their chemical composition and in terms of their properties as materials. The book is intended not only for the specialist in polymer chemistry, but also for the organic chemist with little experience who requires a practical introduction to the field.

scholarly journals A Slot-Die Technique for the Preparation of Continuous, High-Area, Chitosan-Based Thin Films

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1566
Author(s):  
Oliver J. Pemble ◽  
Maria Bardosova ◽  
Ian M. Povey ◽  
Martyn E. Pemble
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
High Volume ◽  
Mechanical Anisotropy ◽  
Diverse Range ◽  
Direction Parallel ◽  
High Area ◽  
Wide Range ◽  
Slot Die ◽  
Potential Applications

Chitosan-based films have a diverse range of potential applications but are currently limited in terms of commercial use due to a lack of methods specifically designed to produce thin films in high volumes. To address this limitation directly, hydrogels prepared from chitosan, chitosan-tetraethoxy silane, also known as tetraethyl orthosilicate (TEOS) and chitosan-glutaraldehyde have been used to prepare continuous thin films using a slot-die technique which is described in detail. By way of preliminary analysis of the resulting films for comparison purposes with films made by other methods, the mechanical strength of the films produced was assessed. It was found that as expected, the hybrid films made with TEOS and glutaraldehyde both show a higher yield strength than the films made with chitosan alone. In all cases, the mechanical properties of the films were found to compare very favorably with similar measurements reported in the literature. In order to assess the possible influence of the direction in which the hydrogel passes through the slot-die on the mechanical properties of the films, testing was performed on plain chitosan samples cut in a direction parallel to the direction of travel and perpendicular to this direction. It was found that there was no evidence of any mechanical anisotropy induced by the slot die process. The examples presented here serve to illustrate how the slot-die approach may be used to create high-volume, high-area chitosan-based films cheaply and rapidly. It is suggested that an approach of the type described here may facilitate the use of chitosan-based films for a wide range of important applications.

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