Science.gov

Sample records for liquid crystalline block

  1. Exploiting Host-Guest Interactions for the Synthesis of a Rod-Rod Block Copolymer with Crystalline and Liquid-Crystalline Blocks.

    PubMed

    Zhou, Feng; Gu, Ke-Hua; Zhang, Zhen-Yu; Zhang, Meng-Yao; Zhou, Sheng; Shen, Zhihao; Fan, Xing-He

    2016-11-21

    By making use of the host-guest interactions between the host molecule tris-o-phenylenedioxycyclotriphosphazene (TPP) and the rod-coil block copolymer (BCP) poly(ethylene oxide)-block-poly(octyl 4'-octyloxy-2-vinylbiphenyl-4-carboxylate) (PEO-b-PVBP), the supramolecular rod-rod block copolymer P(EO@TPP)-b-PVBP was constructed. It consists of a crystalline segment P(EO@TPP) with a hexagonal crystalline structure and a columnar nematic liquid-crystalline segment (PVBP). As the PVBP segments arrange themselves as columnar nematic phases, the crystalline structure of the inclusion complex P(EO@TPP), which has a smaller diameter, is destroyed. The self-assembled nanostructure is thus clearly affected by the interplay between the two blocks. On the basis of wide- and small-angle X-ray scattering analysis, we conclude that the supramolecular rod-rod BCP can self-assemble into a cylinder-in-cylinder double hexagonal structure. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Liquid Crystalline Block Copolymers with Brush Type Architecture: Toward Functional Membranes by Magnetic Field Alignment

    NASA Astrophysics Data System (ADS)

    Choo, Youngwoo; Gopinadhan, Manesh; Mahajan, Lalit; Kasi, Rajeswari; Osuji, Chinedum

    2015-03-01

    We introduce a novel liquid crystalline block copolymer with brush type architecture for membrane applications by magnetic field directed self-assembly. Ring-opening metathesis of n-alkyloxy cyanobiphenyl and polylactide (PLA) functionalized norbornene monomers provides efficient polymerization yielding low polydispersity block copolymers. The molecular weight of the PLA side chains, spacer length of the cyanobiphenyl mesogens are systematically varied to form well-ordered BCP morphologies at varying volume fractions. Interestingly, the system features morphology dependent anchoring condition where mesogens adopt planar anchoring on cylindrical interface while homeotropic anchoring was preferred on a planar block interface. The minority PLA domains from highly aligned materials can be readily degraded by hydrolysis to produce vertically aligned nanoporous polymer films which exhibit reversible thermal switching behavior. The polymers introduced here provide a versatile platform for scalable fabrication of aligned membranes and further functional materials based on such templates. This work was supported by NSF(CCMI-1246804).

  3. Hydrogen-bonded side chain liquid crystalline block copolymer: Molecular design, synthesis, characterization and applications

    NASA Astrophysics Data System (ADS)

    Chao, Chi-Yang

    Block copolymers can self-assemble into highly regular, microphase-separated morphologies with dimensions at nanometer length scales. Potential applications such as optical wavelength photonic crystals, templates for nanolithographic patterning, or nanochannels for biomacromolecular separation take advantage of the well-ordered, controlled size microdomains of block copolymers. Side-chain liquid crystalline block copolymers (SCLCBCPs) are drawing increasing attention since the incorporation of liquid crystallinity turns their well-organized microstructures into dynamic functional materials. As a special type of block copolymer, hydrogen-bonded SCLCBCPs are unique, compositionally tunable materials with multiple dynamic functionalities that can readily respond to thermal, electrical and mechanical fields. Hydrogen-bonded SCLCBCPs were synthesized and assembled from host poly(styrene- b-acrylic acid) diblock copolymers with narrow molecular weight distributions as proton donors and guest imidazole functionalized mesogenic moieties as proton acceptors. In these studies non-covalent hydrogen bonding is employed to connect mesogenic side groups to a block copolymer backbone, both for its dynamic character as well as for facile materials preparation. The homogeneity and configuration of the hydrogen-bonded complexes were determined by both the molecular architecture of imidazolyl side groups and the process conditions. A one-dimensional photonic crystal composed of high molecular weight hydrogen-bonded SCLCBCP, with temperature dependent optical wavelength stop bands was successfully produced. The microstructures of hydrogen-bonded complexes could be rapidly aligned in an AC electric field at temperatures below the order-disorder transition but above their glass transitions. Remarkable dipolar properties of the mesogenic groups and thermal dissociation of hydrogen bonds are key elements to fast orientation switching. Studies of a wide range of mesogen and polymer

  4. Perforated Layer Structures in Liquid Crystalline Rod-coil Block Copolymers

    SciTech Connect

    Tenneti,K.; Chen, X.; Li, C.; Tu, Y.; Wan, X.; Zhou, Q.; Sics, I.; Hsiao, B.

    2005-01-01

    We report a novel observation of the tetragonal perforated layer structures in a series of rod-coil liquid crystalline block copolymers (BCPs), poly(styrene-block-(2, 5-bis[4-methoxyphenyl]oxycarbonyl)styrene) (PS-b-PMPCS). PMPCS forms rigid rods while PS forms the coil block. Differential scanning calorimetry (DSC), polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and transmission electron microscopy (TEM) techniques were used to investigate these rod-coil molecules, and a perforated layer structure was observed at {sup fPMPCS} {approx} 0.37 in relatively low molecular weight (M{sub w}) samples and {approx}0.5 in high M{sub w} PS-b-PMPCS. This substantial phase boundary shift was attributed to the rod-coil nature of the BCP. The perforation obeys a tetragonal instead of hexagonal symmetry. The 'onset' of perforation was also observed in real space in sample PS{sub 272}-b-PMPCS{sub 93} ({sup fPMPCS} {approx} 0.52), in which few PS chains punctuate PMPCS layers. A slight increase in f{sub PS}, by blending with PS homopolymer, led to a dramatic change in the BCP morphology, and uniform tetragonal perforations were observed at {sup fPMPCS} {approx} 0.48.

  5. Liquid Crystalline Polymers

    DTIC Science & Technology

    1990-02-28

    Liquid crystalline polymers (LCPs); fibers ; thermotropic; lyotropic; processing; rheology; nonlinear optical (4L-" properties* blends* Q2 P- USTRACT...CowMnue on reverse if , cevwy and identify by block number) The remarkable mechanical properties and thermal stability of fibers fabricated from liquid...control of orientation falls short of allowing manipula- tion of macroscopic orientation (except for the case of uniaxial fibers ). This report

  6. Hexakis(4-iodophenyl)-peri-hexabenzocoronene- a versatile building block for highly ordered discotic liquid crystalline materials.

    PubMed

    Wu, Jishan; Watson, Mark D; Zhang, Li; Wang, Zhaohui; Müllen, Klaus

    2004-01-14

    Hexakis (4-iodophenyl)-peri-hexabenzocoronene (5), a novel functionalizable mesogenic building block, was prepared by rational multistep synthesis. Although sparingly soluble in common solvents, it can be obtained in pure form and then functionalized via Hagihara-Sonogashira coupling to give a series of highly ordered columnar liquid crystalline molecules 14a-c. The total synthesis involves five 6-fold transformations, all in excellent to near quantitative isolated yields. Their thermotropic liquid crystalline behavior was studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide-angle X-ray diffraction (WAXD). Compared to the normal alkyl-subsituted hexabenzocoronenes (HBCs), 14a-c exhibit more highly ordered columnar mesophases, including three-dimensionally ordered superstructures (helical columnar mesophase). These could arise from additional intracolumnar pi-pi interactions between, and space-filling requirements introduced by, the rigid-rod side groups. Atomic force microscopy (AFM) revealed self-assembled bundles of columnar aggregates in spin-coated films and isolated several-micron-long nanoribbons composed of a defined number of columns in drop cast films.

  7. Liquid-crystalline semiconducting copolymers with intramolecular donor-acceptor building blocks for high-stability polymer transistors.

    PubMed

    Kim, Do Hwan; Lee, Bang-Lin; Moon, Hyunsik; Kang, Hee Min; Jeong, Eun Jeong; Park, Jeong-Il; Han, Kuk-Min; Lee, Sangyoon; Yoo, Byung Wook; Koo, Bon Won; Kim, Joo Young; Lee, Wi Hyoung; Cho, Kilwon; Becerril, Hector Alejandro; Bao, Zhenan

    2009-05-06

    The ability to control the molecular organization of electronically active liquid-crystalline polymer semiconductors on surfaces provides opportunities to develop easy-to-process yet highly ordered supramolecular systems and, in particular, to optimize their electrical and environmental reliability in applications in the field of large-area printed electronics and photovoltaics. Understanding the relationship between liquid-crystalline nanostructure and electrical stability on appropriate molecular surfaces is the key to enhancing the performance of organic field-effect transistors (OFETs) to a degree comparable to that of amorphous silicon (a-Si). Here, we report a novel donor-acceptor type liquid-crystalline semiconducting copolymer, poly(didodecylquaterthiophene-alt-didodecylbithiazole), which contains both electron-donating quaterthiophene and electron-accepting 5,5'-bithiazole units. This copolymer exhibits excellent electrical characteristics such as field-effect mobilities as high as 0.33 cm(2)/V.s and good bias-stress stability comparable to that of amorphous silicon (a-Si). Liquid-crystalline thin films with structural anisotropy form spontaneously through self-organization of individual polymer chains as a result of intermolecular interactions in the liquid-crystalline mesophase. These thin films adopt preferential well-ordered intermolecular pi-pi stacking parallel to the substrate surface. This bottom-up assembly of the liquid-crystalline semiconducting copolymer enables facile fabrication of highly ordered channel layers with remarkable electrical stability.

  8. Liquid crystalline composites containing phyllosilicates

    DOEpatents

    Chaiko, David J.

    2004-07-13

    The present invention provides phyllosilicate-polymer compositions which are useful as liquid crystalline composites. Phyllosilicate-polymer liquid crystalline compositions of the present invention can contain a high percentage of phyllosilicate while at the same time be transparent. Because of the ordering of the particles liquid crystalline composite, liquid crystalline composites are particularly useful as barriers to gas transport.

  9. Liquid crystalline composites containing phyllosilicates

    DOEpatents

    Chaiko; David J.

    2007-05-08

    The present invention provides barrier films having reduced gas permeability for use in packaging and coating applications. The barrier films comprise an anisotropic liquid crystalline composite layer formed from phyllosilicate-polymer compositions. Phyllosilicate-polymer liquid crystalline compositions of the present invention can contain a high percentage of phyllosilicate while remaining transparent. Because of the ordering of the particles in the liquid crystalline composite, barrier films comprising liquid crystalline composites are particularly useful as barriers to gas transport.

  10. Liquid crystalline order in mucus

    NASA Technical Reports Server (NTRS)

    Viney, C.; Huber, A. E.; Verdugo, P.

    1993-01-01

    Mucus plays an exceptionally wide range of important biological roles. It operates as a protective, exchange, and transport medium in the digestive, respiratory, and reproductive systems of humans and other vertebrates. Mucus is a polymer hydrogel. It is secreted as discrete packages (secretory granules) by specialized secretory cells. Mucus hydrogel is stored in a condensed state inside the secretory granules. Depending upon the architecture of their constituent macromolecules and on the composition of the solvent, polymer gels can form liquid crystalline microstructures, with orientational order being exhibited over optically resolvable distances. Individual mucin molecules consist of alternating rigid segments (heavily glycosylated; hydrophilic) and flexible segments (nonglycosylated; hydrophobic). Polymer molecules consisting of rigid units linked by flexible spacers are frequently associated with liquid crystalline behavior, which again raises the possibility that mucus could form anisotropic fluid phases. Suggestions that mucins may be self-associating in dilute solution have previously been challenged on the basis of sedimentation-equilibrium studies performed on mucus in which potential sites of association were competitively blocked with inhibitors. However, the formation of stable liquid crystalline phases does not depend on the existence of inter- or intramolecular associations; these phases can form on the basis of steric considerations alone.

  11. Liquid crystalline order in mucus

    NASA Technical Reports Server (NTRS)

    Viney, C.; Huber, A. E.; Verdugo, P.

    1993-01-01

    Mucus plays an exceptionally wide range of important biological roles. It operates as a protective, exchange, and transport medium in the digestive, respiratory, and reproductive systems of humans and other vertebrates. Mucus is a polymer hydrogel. It is secreted as discrete packages (secretory granules) by specialized secretory cells. Mucus hydrogel is stored in a condensed state inside the secretory granules. Depending upon the architecture of their constituent macromolecules and on the composition of the solvent, polymer gels can form liquid crystalline microstructures, with orientational order being exhibited over optically resolvable distances. Individual mucin molecules consist of alternating rigid segments (heavily glycosylated; hydrophilic) and flexible segments (nonglycosylated; hydrophobic). Polymer molecules consisting of rigid units linked by flexible spacers are frequently associated with liquid crystalline behavior, which again raises the possibility that mucus could form anisotropic fluid phases. Suggestions that mucins may be self-associating in dilute solution have previously been challenged on the basis of sedimentation-equilibrium studies performed on mucus in which potential sites of association were competitively blocked with inhibitors. However, the formation of stable liquid crystalline phases does not depend on the existence of inter- or intramolecular associations; these phases can form on the basis of steric considerations alone.

  12. Liquid crystalline polymers

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The remarkable mechanical properties and thermal stability of fibers fabricated from liquid crystalline polymers (LCPs) have led to the use of these materials in structural applications where weight savings are critical. Advances in processing of LCPs could permit the incorporation of these polymers into other than uniaxial designs and extend their utility into new areas such as nonlinear optical devices. However, the unique feature of LCPs (intrinsic orientation order) is itself problematic, and current understanding of processing with control of orientation falls short of allowing manipulation of macroscopic orientation (except for the case of uniaxial fibers). The current and desirable characteristics of LCPs are reviewed and specific problems are identified along with issues that must be addressed so that advances in the use of these unique polymers can be expedited.

  13. Molecular composites from liquid crystalline polymers and liquid crystalline thermosets

    SciTech Connect

    Benicewicz, B.C.; Douglas, E.P.; Hjelm, R.P. Jr.

    1993-07-01

    We propose a new approach to molecular composites. This approach uses a mixture of a liquid crystalline polymer and a liquid crystalline thermoset to enhance the miscibility. Preliminary neutron scattering data is presented on a system of short and long rod aromatic amides. The data is interpreted using the interpenetrating phase model of Debye and Bueche. The analysis indicates that the scattering is consistent with this model and shows a characteristic length scale in the range of 70 to 80 A. The intensity of the scattering is lower than calculated for the strong segregation limit, suggesting that there is some intermixing of the components.

  14. Rotationally Molded Liquid Crystalline Polymers

    NASA Technical Reports Server (NTRS)

    Rogers, Martin; Scribben, Eric; Baird, Donald; Hulcher, Bruce

    2002-01-01

    Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semirigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers. This paper will also highlight the interactions between academia and small businesses in developing new products and processes.

  15. Rotationally Molded Liquid Crystalline Polymers

    NASA Technical Reports Server (NTRS)

    Rogers, Martin; Scribben, Eric; Baird, Donald; Hulcher, Bruce

    2002-01-01

    Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semirigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers. This paper will also highlight the interactions between academia and small businesses in developing new products and processes.

  16. Rotationally Molded Liquid Crystalline Polymers

    NASA Technical Reports Server (NTRS)

    Rogers, Martin; Stevenson, Paige; Scribben, Eric; Baird, Donald; Hulcher, Bruce

    2002-01-01

    Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers advantages of low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semi-rigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers.

  17. Theory of liquid crystalline micelles.

    PubMed

    Matsuyama, Akihiko

    2013-01-21

    A theory is introduced to describe self-assembly of liquid crystalline AB diblock copolymers, consisting of a homopolymer (A) and a side-chain liquid crystalline polymer (B). We derive the free energy of the liquid crystalline micellar solutions and examine the equilibrium solution properties: critical micelle concentration (CMC), nematic-isotropic phase transition (NIT) of the rigid side-chains inside the micelle core, and phase separations. It is shown that there is a critical micelle size below which the NIT becomes continuous due to a packing effect. We also find re-entrant micellizations near the NIT temperature. The phase diagrams, including binodal, spinodal, CMC, and NIT curves are also examined on the temperature-concentration plane.

  18. Synthesis and Characterization of Unique Liquid Crystalline Block Copolyesters. A Proposal for a Polymer Research Center at the Atlanta University.

    DTIC Science & Technology

    1984-10-01

    active 2-phenylsulfonylbicyclo- [2.2.21octane can be effected. B. Use of 1,2-Bia( phenylthio )ethylene Catalyzed (AICi3) and uncatalyzed reactions of...spun from rod-like thermotropic polymers generally have high - melting points. Although a high melting temperature is important for many end- use ...block copolymer. morphology. The objectives of the Polk and Bota research team were to use cyclohexane derivatives as the sof t blocks and benzene

  19. Molecular Engineering of Liquid Crystalline Polymers by Living Polymerization. 23. Synthesis and Characterization of AB Block Copolymers

    DTIC Science & Technology

    1992-03-27

    synthesis and characterization of AB block copolymers based on (o-[(4-cyano-4’-biphenyl)oxy]alkyl vinyl ether &M with alkyl being ethyl (. L -2, propyl...distilled under argon before each use. Trifluoromethane sulfonic acid (triflic acid, 98%, Aldrich) was distilled under vacuum. IH,IH,2H,2H- Perfluorodecan- l ...biphenyloxy)ethyl vinyl ether (BEVE) 5f and IH,1H,2H,2H-perfluorodecyl vinyl ether (CF8) 6f were synthesized as described previously. Additional details

  20. Liquid-crystalline physical gels.

    PubMed

    Kato, Takashi; Hirai, Yuki; Nakaso, Suguru; Moriyama, Masaya

    2007-12-01

    Liquid-crystalline (LC) physical gels are a new class of dynamically functional materials consisting of liquid crystals and fibrous aggregates of molecules that are called "gelators". Liquid-crystalline physical gels, which are macroscopically soft solids, exhibit induced or enhanced electro-optical, photochemical, electronic properties due to the combination of two components that form phase-separated structures. In this tutorial review, we describe the materials design and structure-property relationships of the LC physical gels. The introduction of self-assembled fibers into nematic liquid crystals leads to faster responses in twisted nematic (TN) mode and high contrast switching in light scattering mode. Furthermore, the LC physical gels can be exploited as a new type of materials for electro-optical memory. This function is achieved by the control of reversible aggregation processes of gelators under electric fields in nematic liquid crystals. Electronic properties such as hole mobilities are improved by the introduction of fibrous aggregates into triphenylene-based columnar liquid crystals. The incorporation of photochromic azobenzenes or electroactive tetrathiafulvalenes into the chemical structures of gelators leads to the preparation of ordered functional materials.

  1. Liquid blocking check valve

    DOEpatents

    Merrill, John T.

    1984-01-01

    A liquid blocking check valve useful particularly in a pneumatic system utilizing a pressurized liquid fill chamber. The valve includes a floatable ball disposed within a housing defining a chamber. The housing is provided with an inlet aperture disposed in the top of said chamber, and an outlet aperture disposed in the bottom of said chamber in an offset relation to said inlet aperture and in communication with a cutaway side wall section of said housing.

  2. Ferromagnetic viscoelastic liquid crystalline materials

    NASA Astrophysics Data System (ADS)

    Schlesier, Cristina; Shibaev, Petr; McDonald, Scott

    2012-02-01

    Novel ferromagnetic liquid crystalline materials were designed by mixing ferromagnetic nanoparticles with glass forming oligomers and low molar mass liquid crystals. The matrix in which nanoparticles are embedded is highly viscous that reduces aggregation of nanoparticles and stabilizes the whole composition. Mechanical and optical properties of the composite material are studied in the broad range of nanoparticle concentrations. The mechanical properties of the viscoelastic composite material resemble those of chemically crosslinked elastomers (elasticity and reversibility of deformations). The optical properties of ferromagnetic cholesteric materials are discussed in detail. It is shown that application of magnetic field leads to the shift of the selective reflection band of the cholesteric material and dramatically change its color. Theoretical model is suggested to account for the observed effects; physical properties of the novel materials and liquid crystalline elastomers are compared and discussed. [1] P.V. Shibaev, C. Schlesier, R. Uhrlass, S. Woodward, E. Hanelt, Liquid Crystals, 37, 1601 (2010) [2] P.V. Shibaev, R. Uhrlass, S. Woodward, C. Schlesier, Md R. Ali, E. Hanelt, Liquid Crystals, 37, 587 (2010)

  3. Structure Property Relationships in Liquid Crystalline Thermosets

    DTIC Science & Technology

    2003-04-25

    Adhesion Science and Technology , 2002, 16, 15-32 Jianxun Feng and Elliot P. Douglas, “Permeability of a liquid crystalline epoxy”, Materials Research...Arthur J. Gavrin and Elliot P. Douglas, “Cure behavior of liquid crystalline thermosets”, poster presentation at POLY Millenial 2000, Waikoloa, HI...December, 2000 Elliot P. Douglas, "Liquid crystalline thermosets", Massachusetts Institute of Technology , Cambridge, MA, April, 2000 Arthur J. Gavrin

  4. Molecular Engineering of Liquid Crystalline Polymers

    DTIC Science & Technology

    1992-03-27

    INTRODUCTION TO LIQUID CRYSTALS 14.2.1 Introduction to Low Molar Mass Liquid Crystals and Definitions 14.2.2 Liquid Crystalline Polymers 14.3 ISOMORPHISM...Crystals and Definitions A liquid crystalline or mesomorphic phase or mesophase refers to a state of matter in which the degree of order is between...monotropic, the definition of Gkc being apparent from Figure 7. It is easily seen how crystal perfectioning on annealing can lead to a "conversion" of an

  5. Liquid crystalline elastomers as actuators and sensors.

    PubMed

    Ohm, Christian; Brehmer, Martin; Zentel, Rudolf

    2010-08-17

    This review collects recent developments in the field of liquid crystalline elastomers (LCEs) with an emphasis on their use for actuator and sensor applications. Several synthetic pathways leading to crosslinked liquid crystalline polymers are discussed and how these materials can be oriented into liquid crystalline monodomains are described. By comparing the actuating properties of different systems, general structure-property relationships for LCEs are obtained. In the final section, how these materials can be turned into usable devices using different interdisciplinary techniques are described.

  6. Liquid crystalline epoxy nanocomposite material for dental application.

    PubMed

    Tai, Yun-Yuan; Hsu, Sheng-Hao; Chen, Rung-Shu; Su, Wei-Fang; Chen, Min-Huey

    2015-01-01

    Novel liquid crystalline epoxy nanocomposites, which exhibit reduced polymerization shrinkage and effectively bond to tooth structures, can be applied in esthetic dentistry, including core and post systems, direct and indirect restorations, and dental brackets. The purposes of this study were to investigate the properties of liquid crystalline epoxy nanocomposites including biocompatibility, microhardness, and frictional forces of bracket-like blocks with different filler contents for further clinical applications. In this study, we evaluated liquid crystalline epoxy nanocomposite materials that exhibited various filler contents, by assessing their cell activity performance using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and their microhardness with or without thermocycling. We also evaluated the frictional force between bracket-like duplicates and commercially available esthetic bracket systems using Instron 5566. The liquid crystalline epoxy nanocomposite materials showed good biocompatibility. The materials having high filler content demonstrated greater microhardness compared with commercially available bracket materials, before and after the thermocycling treatment. Thus, manufacturing processes are important to reduce frictional force experienced by orthodontic brackets. The microhardness of the bracket-like blocks made by our new material is superior to the commercially available brackets, even after thermocycling. Our results indicate that the evaluated liquid crystalline epoxy nanocomposite materials are of an appropriate quality for application in dental core and post systems and in various restorations. By applying technology to refine manufacturing processes, these new materials could also be used to fabricate esthetic brackets for orthodontic treatment. Copyright © 2014. Published by Elsevier B.V.

  7. Liquid Crystalline Materials for Biological Applications.

    PubMed

    Lowe, Aaron M; Abbott, Nicholas L

    2012-03-13

    Liquid crystals have a long history of use as materials that respond to external stimuli (e.g., electrical and optical fields). More recently, a series of investigations have reported the design of liquid crystalline materials that undergo ordering transitions in response to a range of biological interactions, including interactions involving proteins, nucleic acids, viruses, bacteria and mammalian cells. A central challenge underlying the design of liquid crystalline materials for such applications is the tailoring of the interface of the materials so as to couple targeted biological interactions to ordering transitions. This review describes recent progress toward design of interfaces of liquid crystalline materials that are suitable for biological applications. Approaches addressed in this review include the use of lipid assemblies, polymeric membranes containing oligopeptides, cationic surfactant-DNA complexes, peptide-amphiphiles, interfacial protein assemblies and multi-layer polymeric films.

  8. Nanosecond liquid crystalline optical modulator

    DOEpatents

    Borshch, Volodymyr; Shiyanovskii, Sergij V.; Lavrentovich, Oleg D.

    2016-07-26

    An optical modulator includes a liquid crystal cell containing liquid crystal material having liquid crystal molecules oriented along a quiescent director direction in the unbiased state, and a voltage source configured to apply an electric field to the liquid crystal material wherein the direction of the applied electric field does not cause the quiescent director direction to change. An optical source is arranged to transmit light through or reflect light off the liquid crystal cell with the light passing through the liquid crystal material at an angle effective to undergo phase retardation in response to the voltage source applying the electric field. The liquid crystal material may have negative dielectric anisotropy, and the voltage source configured to apply an electric field to the liquid crystal material whose electric field vector is transverse to the quiescent director direction. Alternatively, the liquid crystal material may have positive dielectric anisotropy and the voltage source configured to apply an electric field to the liquid crystal material whose electric field vector is parallel with the quiescent director direction.

  9. Liquid crystalline thermosetting polyimides. Final report

    SciTech Connect

    Hoyt, A.E.; Huang, S.J.

    1993-07-01

    Phase separation of rodlike reinforcing polymers and flexible coil matrix polymers is a common problem in formulating molecular composites. One way to reduce phase separation might be to employ liquid crystalline thermosets as the matrix material. In this work, functionally terminated polyimide oligomers which exhibit lyotropic liquid crystalline behavior were successfully prepared. Materials based on 2,2{prime}-bis(trifluoromethyl)-4,4{prime}-diaminobiphenyl and 3,3{prime},4,4{prime}-biphenylenetetra-carboxylic dianhydride have been synthesized and characterized.

  10. Orthoconic antiferroelectric liquid crystalline materials

    NASA Astrophysics Data System (ADS)

    Czuprynski, K.; Gasowska, J.; Tykarska, M.; Kula, P.; Sokól, E.; Piecek, W.; Oton, J. M.; Castillo, M. P. L.

    2005-09-01

    New LC materials based on chain fluorinated homologous ester series and exhibiting high tilt angles of the synclinic and anticlinic smectic C phases to the layer surface are synthesized. Their mixtures in surface-stabilized geometry show an unusually huge change of optical properties after application of an electric field during the transition from the antiferroelectric to the ferroelectric state. In the antiferroelectric state they are optically negative uniaxial liquid crystals with the optic axis perpendicular to the cell plates, while in the ferroelectric state they become optically positive biaxial liquid crystals with optic axis parallel to the glass plates. The results of electrooptical characterization of the mixtures are presented.

  11. Liquid-blocking check valve

    DOEpatents

    Merrill, J.T.

    1982-09-27

    A liquid blocking check valve useful particularly in a pneumatic system utilizing a pressurized liquid fill chamber. The valve includes a floatable ball disposed within a housing defining a chamber. The housing is provided with an inlet aperture disposed in the top of said chamber, and an outlet aperture disposed in the bottom of said chamber in an offset relation to said inlet aperture and in communication with a cutaway side wall section of said housing.

  12. Molecular Dynamics Simulations of Liquid-Crystalline Dendritic Architectures

    NASA Astrophysics Data System (ADS)

    Bourgogne, C.; Bury, I.; Gehringer, L.; Zelcer, A.; Cukiernik, F.; Terazzi, E.; Donnio, B.; Guillon, D.

    We report here a few examples of the self-organization behaviour of some novel materials based on liquid-crystalline dendritic architectures. The original design of the molecules imposes the use of all-atomic methods to model correctly every intra- and intermolecular effects. The selected materials are octopus dendrimers with block anisotropic side-arms, segmented amphiphilic block codendrimers, multicore and star-shaped oligomers, and multi-functionalized manganese clusters. The molecular organization in lamellar or columnar phases occurs due to soft/rigid parts self-recognition, hydrogen-bonding networks or from the molecular shape intrinsically.

  13. Combination of ionic self-assembly and hydrogen bonding as a tool for the synthesis of liquid-crystalline materials and organogelators from a simple building block.

    PubMed

    Camerel, Franck; Faul, Charl F J

    2003-08-07

    In this communication we report on the facile combination of hydrogen bonding and the ionic self-assembly (ISA) process to produce organized materials and fiber-containing organogel superstructures from functionalised oligoelectrolytic building blocks.

  14. Nanoparticle Solubility in Liquid Crystalline Defects

    NASA Astrophysics Data System (ADS)

    Whitmer, Jonathan K.; Armas-Perez, Julio C.; Joshi, Abhijeet A.; Roberts, Tyler F.; de Pablo, Juan J.

    2013-03-01

    Liquid crystalline materials often incorporate regions (defects) where the orientational ordering present in the bulk phase is disrupted. These include point hedgehogs, line disclinations, and domain boundaries. Recently, it has been shown that defects will accumulate impurities such as small molecules, monomer subunits or nanoparticles. Such an effect is thought to be due to the alleviation of elastic stresses within the bulk phase, or to a solubility gap between a nematic phase and the isotropic defect core. This presents opportunities for encapsulation and sequestration of molecular species, in addition to the formation of novel structures within a nematic phase through polymerization and nanoparticle self-assembly. Here, we examine the solubility of nanoparticles within a coarse-grained liquid crystalline phase and demonstrate the effects of nanoparticle size and surface interactions in determining sequestration into defect regions.

  15. Liquid crystalline gel beads of curdlan.

    PubMed

    Dobashi, Toshiaki; Yoshihara, Hiromi; Nobe, Masahiro; Koike, Michiru; Yamamoto, Takao; Konno, Akira

    2005-01-04

    Curdlan beads consisting of liquid crystalline gel (LCG) and amorphous gel (AG) in alternating layers in a wide range of diameters were newly prepared by interfacial insolubilization reactions using calcium chloride as the setting reagent. The thickness of the liquid crystalline layer was proportional to the diameter of the gel bead, and the proportional constant agreed with that determined for the cylindrical gel prepared by a dialysis method. The proportional constant initially increased with increasing calcium concentration of the dispersing medium and saturated at a high concentration limit. These results suggest that the mechanisms for forming the alternating LCG/AG structures prepared with different boundary conditions are the same. The LCG/AG structure could be controlled by calcium concentration.

  16. Liquid Crystalline Phases of Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Amini, Kiana; Abukhdeir, Nasser; Matsen, Mark

    The phase behavior of liquid-crystal polymeric brushes in solvent are investigated using self-consistent field theory. The polymers are modeled as freely-jointed chain consisting of N rigid segments. The isotropic interactions between the polymer and the solvent are treated using the standard Flory-Huggins theory, while the anisotropic liquid-crystalline (LC) interactions between rigid segments are taken into account using the Mayer-Saupe theory. For weak LC interactions, the brush exhibits the conventional parabolic-like profile, while for strong LC interactions, the polymers crystallize into a dense brush with a step-like profile. At intermediate interaction strengths, we find the microphase-segregated phase observed previously for lattice-model calculations. In this phase, the brush exhibits a crystalline layer next to the grafting surface with an external layer similar to the conventional brush. This work was supported by NSERC of Canada.

  17. Reactions and Interactions in Liquid Crystalline Media

    DTIC Science & Technology

    1991-10-30

    and C02 gases through a liquid crystalline polysiloxane sandwiched between two porous polypropylene films was investigated. 2 16 The permeation...thermal transitions up to 260 ’C. Optical polarized microscopy of a thin film of the polymer revealed a "disordered mesophase". In a survey, Cser et al...properties of the films thus produced were stable for a year under ambient conditions. The planar cholesteric phase dissipated irreversibly upon heating

  18. Photorefractivity in liquid crystalline composite materials

    SciTech Connect

    Wiederrecht, G.P.; Wasielewski, M.R.

    1997-09-01

    We report recent improvements in the photorefractive of liquid crystalline thin film composites containing electron donor and acceptor molecules. The improvements primarily result from optimization of the exothermicity of the intermolecular charge transfer reaction and improvement of the diffusion characteristics of the photogenerated ions. Intramolecular charge transfer dopants produce greater photorefractivity and a 10-fold decrease in the concentration of absorbing chromophores. The mechanism for the generation of mobile ions is discussed.

  19. Epoxy + liquid crystalline epoxy coreacted network

    NASA Astrophysics Data System (ADS)

    Punchaipetch, Prakaipetch

    2000-10-01

    Molecular reinforcement through in-situ polymerization of liquid crystalline epoxies (LCEs) and a non-liquid crystalline epoxy has been investigated. Three LCEs: diglycidyl ether of 4,4'-dihydroxybiphenol (DGE-DHBP) and digylcidyl ether of 4-hydroxyphenyl-4″-hydroxybiphenyl-4 '-carboxylate (DGE-HHC), were synthesized and blended with diglycidyl ether of bisphenol F (DGEBP-F) and subsequently cured with anhydride and amine curing agents. Curing kinetics were determined using differential scanning calorimetry (DSC). Parameters for autocatalytic curing kinetics of both pure monomers and blended systems were determined. The extent of cure for both monomers was monitored by using Fourier transform infrared spectroscopy (FT-IR). The glass transitions were evaluated as a function of composition using DSC and dynamic mechanical analysis (DMA). The results show that the LC constituent affects the curing kinetics of the epoxy resin and that the systems are highly miscible. The effects of molecular reinforcement of DGEBP-F by DGE-DHBP and DGE-HHC were investigated. The concentration of the liquid crystalline moiety affects mechanical properties. Tensile, impact and fracture toughness tests results are evaluated. Scanning electron microscopy of the fracture surfaces shows changes in failure mechanisms compared to the pure components. Results indicate that mechanical properties of the blended samples are improved already at low concentration by weight of the LCE added into epoxy resin. The improvement in mechanical properties was found to occur irrespective of the absence of liquid crystallinity in the blended networks. The mechanism of crack study indicates that crack deflection and crack bridging are the mechanisms in case of LC epoxy. In case of LC modified epoxy, the crack deflection is the main mechanism. Moreover, the effect of coreacting an epoxy with a reactive monomer liquid crystalline epoxy as a matrix for glass fiber composites was investigated. Mechanical

  20. Polymer crystalline texture controlled through film blowing and block copolymerization

    NASA Astrophysics Data System (ADS)

    Lee, Li-Bong Wei

    Polymer properties can be manipulated through processing or chemical modification. Both methods are explored here, by (a) elucidating the origin of directional tear behavior in polyethylene (PE) films processed under different conditions, and (b) synthesizing new block copolymers, whose architectures permit precise control over crystal thickness and melting temperature. Directional tear in films of PE and its copolymers was traced to the orientation imparted during film blowing, quantified through x-ray scattering. The blow-up ratio (BUR) was the most significant process parameter controlling crystal orientation. The Keller-Machin I structure was observed in low-density polyethylene (LDPE) films, which tore preferentially in the transverse direction (TD). Conversely, the Keller-Machin II structure was observed in ethylene-methacrylic acid copolymer films at low BUR, which also tore TD, but the orientation rotated 90° at high BUR, leading to preferred tear in the machine direction (MD). High-density and linear low-density PE films also exhibited the Keller-Machin I structure (as in LDPE) but tore either along MD (HDPE) or isotropically (LLDPE). These differences in tear behavior between chemically similar but architecturally distinct polymers, differing greatly in the type and level of branching, stem from intercrystallite tie molecules. In the second area, crystalline-amorphous diblock copolymers were synthesized through ring-opening metathesis polymerization and subsequent hydrogenation, where the amorphous block was hydrogenated poly(ethylidene norbornene), hPEN, and the crystalline block was either hydrogenated polycyclopentene, hPCP (identical to HDPE) or hydrogenated polynorbornene, hPN. Acyclic metathesis discovered during the PCP synthesis focused the study on block copolymers containing hPN, which is atactic yet highly crystalline. The hPN crystal structure was solved as monoclinic-beta (space group C2/c), with a = 6.936 A, b = 9.596 A, c = 12.420 A, and

  1. Strong liquid-crystalline polymeric compositions

    DOEpatents

    Dowell, F.

    1993-12-07

    Strong liquid-crystalline polymeric (LCP) compositions of matter are described. LCP backbones are combined with liquid crystalline (LC) side chains in a manner which maximizes molecular ordering through interdigitation of the side chains, thereby yielding materials which are predicted to have superior mechanical properties over existing LCPs. The theoretical design of LCPs having such characteristics includes consideration of the spacing distance between side chains along the backbone, the need for rigid sections in the backbone and in the side chains, the degree of polymerization, the length of the side chains, the regularity of the spacing of the side chains along the backbone, the interdigitation of side chains in sub-molecular strips, the packing of the side chains on one or two sides of the backbone to which they are attached, the symmetry of the side chains, the points of attachment of the side chains to the backbone, the flexibility and size of the chemical group connecting each side chain to the backbone, the effect of semiflexible sections in the backbone and the side chains, and the choice of types of dipolar and/or hydrogen bonding forces in the backbones and the side chains for easy alignment. 27 figures.

  2. Strong liquid-crystalline polymeric compositions

    DOEpatents

    Dowell, Flonnie

    1993-01-01

    Strong liquid-crystalline polymeric (LCP) compositions of matter. LCP backbones are combined with liquid crystalline (LC) side chains in a manner which maximizes molecular ordering through interdigitation of the side chains, thereby yielding materials which are predicted to have superior mechanical properties over existing LCPs. The theoretical design of LCPs having such characteristics includes consideration of the spacing distance between side chains along the backbone, the need for rigid sections in the backbone and in the side chains, the degree of polymerization, the length of the side chains, the regularity of the spacing of the side chains along the backbone, the interdigitation of side chains in sub-molecular strips, the packing of the side chains on one or two sides of the backbone to which they are attached, the symmetry of the side chains, the points of attachment of the side chains to the backbone, the flexibility and size of the chemical group connecting each side chain to the backbone, the effect of semiflexible sections in the backbone and the side chains, and the choice of types of dipolar and/or hydrogen bonding forces in the backbones and the side chains for easy alignment.

  3. Multiscale Control of Hierarchical Structure in Crystalline Block Copolymer Nanoparticles Using Microfluidics.

    PubMed

    Bains, Aman; Cao, Yimeng; Moffitt, Matthew G

    2015-11-01

    Hierarchical semicrystalline block copolymer nanoparticles are produced in a segmented gas-liquid microfluidic reactor with top-down control of multiscale structural features, including nanoparticle morphologies, sizes, and internal crystallinities. Control of multiscale structure on disparate length scales by a single control variable (flow rate) enables tailoring of drug delivery nanoparticle function including release rates. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Actuators Based on Liquid Crystalline Elastomer Materials

    PubMed Central

    Jiang, Hongrui; Li, Chensha; Huang, Xuezhen

    2013-01-01

    Liquid crystalline elastomers (LCEs) exhibit a number of remarkable physical effects, including the unique, high-stroke reversible mechanical actuation when triggered by external stimuli. This article reviews some recent exciting developments in the field of LCEs materials with an emphasis on their utilization in actuator applications. Such applications include artificial muscles, industrial manufacturing, health and microelectromechanical systems (MEMS). With suitable synthetic and preparation pathways and well-controlled actuation stimuli, such as heat, light, electric and magnetic field, excellent physical properties of LCE materials can be realized. By comparing the actuating properties of different systems, general relationships between the structure and the property of LCEs are discussed. How these materials can be turned into usable devices using interdisciplinary techniques is also described. PMID:23648966

  5. Liquid Crystalline Behavior of DNA Fragments

    NASA Astrophysics Data System (ADS)

    English, Sean; Garg, Shila

    2000-03-01

    An investigation of the liquid crystalline phases of DNA fragments in different buffer solutions is reported. Previous studies have shown that a strong correlation exists between the critical concentration and the average length of DNA fragments for the observed mesophases of DNA [1]. The focus of our study is to understand the phase ordering of DNA due to changes in concentration under various boundary conditions. Previous studies have utilized evaporation as a means for increasing the concentration of the DNA samples [2]. The effects of evaporation on the development of precholesteric and cholesteric phases will be examined. [1] K. Merchant and R. Rill, Biophys. J. 73, 3154 (1997). [2] F. Livolant, J. Physique 48, 1051 (1987). This research was partially supported by the Copeland Fund, administered by The College of Wooster.

  6. Dielectric relaxation in liquid crystalline dimers

    NASA Astrophysics Data System (ADS)

    Dunmur, D. A.; Luckhurst, G. R.; de la Fuente, M. R.; Diez, S.; Peréz Jubindo, M. A.

    2001-11-01

    Dielectric measurements are reported for liquid crystalline dimers consisting of two mesogenic groups joined through ether links by a flexible alkyl chain. Results are presented for the odd-symmetric dimer, α,ω-bis[(4-cyanobiphenyl)-4'-yloxy]undecane (BCB.O11), and the odd-asymmetric dimer, α-[(4-cyanobiphenyl)-4'-yloxy]-ω-(4-decylanilinebenzylidene-4'-oxy) nonane (CB.O9O.10). The real and imaginary parts of the electric permittivities of aligned samples were measured as functions of frequency over the range 102-109 Hz at temperatures throughout the nematic phase. Measurements were fitted as a function of frequency to the Havriliak-Negami function, and yielded relaxation times and dielectric strengths for the relaxations at each of the temperatures studied. The static dielectric anisotropy for both materials was positive. For BCB.O11, the parallel and perpendicular components of the permittivity exhibited one low frequency and one high frequency relaxation, while the parallel component of the permittivity for CB.O9O.10 showed three relaxations, which were well-separated in frequency. A generic model of liquid crystalline dimers based on mixtures of linear and bent conformers with the tetrahedral angle has been proposed [A. Ferrarini et al., Chem. Phys. Lett. 214, 409 (1993)]. This model is used to provide a qualitative interpretation of the dielectric measurements reported. To obtain a satisfactory explanation of the results, it is necessary to include additional conformers having either a hairpin shape or a bent shape with an angle of 180° minus the tetrahedral angle. The temperature dependence measured for the strengths of the dielectric relaxations is explained in terms of changes of the order parameter and changes in the relative probabilities of different shaped conformers.

  7. Highly viscous liquid crystalline mixtures: the alternative to liquid crystalline elastomers

    NASA Astrophysics Data System (ADS)

    Shibaev, Petr; Schlesier, Cristina; Newman, Leah; McDonald, Scott

    2012-02-01

    Novel highly viscous liquid crystalline materials based on mixtures of glass forming oligomers and low molar mass liquid crystals were recently designed [1, 2] and studied. In this communication the novel data are presented, the analysis and discussion are extended. It is shown that viscoelastic properties of the materials are due to the physical entanglements between cyclic oligomers and low molar mass mesogens, not due to the chemical crosslinks between molecular moities. However, the mechanical properties of these viscoelastic materials resemble those of chemically crosslinked elastomers (elasticity and reversibility of deformations). The properties of chiral and non-chiral materials loaded with ferromagnetic nanoparticles are discussed in detail. Cholesteric materials undergo gigantic color changes in the wide spectral range under the deformation that allows distant detection of deformation and determination the anisotropy of deformation and its type. The materials doped with laser dyes become mechanically tunable lasers themselves and emit coherent light while pumped by external laser. A simple model is suggested to account for the observed effects; physical properties of the novel materials and liquid crystalline elastomers are compared and discussed. [4pt] [1] P.V. Shibaev, C. Schlesier, R. Uhrlass, S. Woodward, E. Hanelt, Liquid Crystals, 37:12, 1601-1604 [0pt] [2] P.V. Shibaev, P. Riverra, D. Teter, S. Marsico, M. Sanzari, V. Ramakrishnan, E. Hanelt, Optics Express, 16, 2965 (2008)

  8. Wholly aromatic liquid crystalline polyetherimide (LC-PEI) resins

    NASA Technical Reports Server (NTRS)

    Weiser, Erik S. (Inventor); Dingemans, Theodorus J. (Inventor); St. Clair, Terry L. (Inventor); Hinkley, Jeffrey A. (Inventor)

    2011-01-01

    The benefits of liquid crystal polymers and polyetherimides are combined in an all-aromatic thermoplastic liquid crystalline polyetherimide. Because of the unique molecular structure, all-aromatic thermotropic liquid crystal polymers exhibit outstanding processing properties, excellent barrier properties, low solubilities and low coefficients of thermal expansion in the processing direction. These characteristics are combined with the strength, thermal, and radiation stability of polyetherimides.

  9. Free-surface molecular command systems for photoalignment of liquid crystalline materials.

    PubMed

    Fukuhara, Kei; Nagano, Shusaku; Hara, Mitsuo; Seki, Takahiro

    2014-01-01

    The orientation of liquid crystal molecules is very sensitive towards contacting surfaces, and this phenomenon is critical during the fabrication of liquid crystal display panels, as well as optical and memory devices. To date, research has focused on designing and modifying solid surfaces. Here we report an approach to control the orientation of liquid crystals from the free (air) surface side: a skin layer at the free surface was prepared using a non-photoresponsive liquid crystalline polymer film by surface segregation or inkjet printing an azobenzene-containing liquid crystalline block copolymer. Both planar-planar and homoeotropic-planar mode patterns were readily generated. This strategy is applicable to various substrate systems, including inorganic substrates and flexible polymer films. These versatile processes require no modification of the substrate surface and are therefore expected to provide new opportunities for the fabrication of optical and mechanical devices based on liquid crystal alignment.

  10. Free-surface molecular command systems for photoalignment of liquid crystalline materials

    PubMed Central

    Fukuhara, Kei; Nagano, Shusaku; Hara, Mitsuo; Seki, Takahiro

    2014-01-01

    The orientation of liquid crystal molecules is very sensitive towards contacting surfaces, and this phenomenon is critical during the fabrication of liquid crystal display panels, as well as optical and memory devices. To date, research has focused on designing and modifying solid surfaces. Here we report an approach to control the orientation of liquid crystals from the free (air) surface side: a skin layer at the free surface was prepared using a non-photoresponsive liquid crystalline polymer film by surface segregation or inkjet printing an azobenzene-containing liquid crystalline block copolymer. Both planar-planar and homoeotropic-planar mode patterns were readily generated. This strategy is applicable to various substrate systems, including inorganic substrates and flexible polymer films. These versatile processes require no modification of the substrate surface and are therefore expected to provide new opportunities for the fabrication of optical and mechanical devices based on liquid crystal alignment. PMID:24534881

  11. The effect of liquid crystalline structure on chlorhexidine diacetate release.

    PubMed

    Farkas, E; Zelkó, R; Németh, Z; Pálinkás, J; Marton, S; Rácz, I

    2000-01-05

    The aim of this study was to examine different liquid crystalline preparations containing chlorhexidine diacetate and to find connection between their structure and the kinetic of drug release. Nonionic surfactant, Synperonic A7 (PEG(7)-C(13-15)) was selected for the preparation of the examined liquid crystalline systems. Mixtures of different ratios of Synperonic A7 and water were produced. By increasing the water content of the systems, lamellar and hexagonal liquid crystal structures were observed. For the analysis of the prepared liquid crystalline systems polarising microscopy, rheology study, differential scanning calorimetry and dynamic swelling tests were carried out. The chlorhexidine diacetate release was examined by Franz-type vertical diffusion cell apparatus. The chlorhexidine diacetate release from hexagonal liquid crystalline preparations was characterised by zero-order release kinetics, while the drug release from lamellar liquid crystalline systems was described by anomalous (non-Fickian) transport. The results indicate that the drug release kinetic is strongly dependent on the liquid crystalline structure.

  12. Liquid-crystalline nanoparticles: Hybrid design and mesophase structures

    PubMed Central

    Greget, Romain; Dominguez, Cristina; Nagy, Zsuzsanna T; Guillon, Daniel; Gallani, Jean-Louis

    2012-01-01

    Summary Liquid-crystalline nanoparticles represent an exciting class of new materials for a variety of potential applications. By combining supramolecular ordering with the fluid properties of the liquid-crystalline state, these materials offer the possibility to organise nanoparticles into addressable 2-D and 3-D arrangements exhibiting high processability and self-healing properties. Herein, we review the developments in the field of discrete thermotropic liquid-crystalline nanoparticle hybrids, with special emphasis on the relationship between the nanoparticle morphology and the nature of the organic ligand coating and their resulting phase behaviour. Mechanisms proposed to explain the supramolecular organisation of the mesogens within the liquid-crystalline phases are discussed. PMID:22509204

  13. Silylene-diethynyl-arylene polymers having liquid crystalline properties

    DOEpatents

    Barton, T.J.; Yiwei Ding.

    1993-09-07

    The present invention provides linear organosilicon polymers including diethynyl-(substituted)arylene units, and a process for their preparation. These novel polymers possess useful properties including electrical conductivity, liquid crystallinity, and/or photoluminescence. These polymers possess good solubility in organic solvents. A preferred example is produced according to the following reaction scheme. ##STR1## These polymers can be solvent-cast to yield excellent films and can also be pulled into fibers from concentrated solutions. All possess substantial crystallinity as revealed by DSC analysis and observation through a polarizing microscope, and possess liquid crystalline properties.

  14. Characterization of Cholesteric Cyclic Siloxane Liquid Crystalline Materials

    DTIC Science & Technology

    1991-11-01

    34AD-A256 128 CHARACIEUAThIONOFPCl LEST CCYCJC SILOXANE LIQUID CRYSTALLINE MATERIALS TI I Herbert E. Kii C r-• CTr Dept. of Chemical Engineering v... crystalline Materials . 18: 2422 S a.•mo) ... : 01 TJ suning. RR 1*1., Er SamlskI, •L CVa1e. W AMd 7. PWMoaG ORGAIRZAIIO "W3(SC) Sil AQM~SISfS) L. KNOW"ma...ordering of the NLO chromcphore can give rise to large response amplitudes, one system currently being investigated are liquid crystalline materials which

  15. Molecular design of main-chain liquid crystalline polyolefin

    NASA Astrophysics Data System (ADS)

    Naga, Naofumi; Sone, Masato; Noguchi, Keiichi; Murase, Shigemitsu

    2009-08-01

    Liquid crystalline features of polyolefin have been clearly observed in a polyolefin of poly(methlene-1,3-cyclopentane) (PMCP) obtained from cyclization polymerization of 1,5-hexadiene (HD) using metallocene catalysts. PMCP clearly shows fluidity and birefringence above the glass transition temperature under the ambient conditions, at around room temperature and normal pressure. First order structures of PMCP, such as cyclization selectivity of polymerized HD units, stereo-regularity of 1,3-cyclopentane units, and molecular weight, affect the liquid crystalline features of PMCP. High cyclization selectivity and trans-rich structure of 1,3-cyclopentane units are necessary to induce the liquid crystalline phase. Polarized optical micrographs of PMCP show Schlieren-like texture, which indicates nematic liquid crystalline phase. Clear diffraction patterns are observed in wide-angle X-ray diffraction analysis below the isotropization temperatures. The isotropization temperature decreases with decreasing of molecular weight of PMCP. PMCP with the higher molecular weight takes the longer time for liquid crystallization from isotropic phase in the cooling process. We have also synthesized an optically active PMCP with an optically active metallocene catalyst in the presence of a chain transfer reagent to control the molecular weights of the resulting polymers. Optically active PMCP with relatively high molecular weight shows finger print texture which indicates cholesteric liquid crystal. On the other hand, decreasing molecular weight the optically active PMCP induces nematic liquid crystalline phase.

  16. A metastable liquid melted from a crystalline solid under decompression

    DOE PAGES

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; ...

    2017-01-23

    A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid–solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. Themore » decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure–temperature region similar to where the supercooled liquid Bi is observed. Finally, akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought.« less

  17. A metastable liquid melted from a crystalline solid under decompression

    PubMed Central

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; Kono, Yoshio; Park, Changyong; Kenney-Benson, Curtis; Shen, Guoyin

    2017-01-01

    A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid–solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. The decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure–temperature region similar to where the supercooled liquid Bi is observed. Akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought. PMID:28112152

  18. A metastable liquid melted from a crystalline solid under decompression

    NASA Astrophysics Data System (ADS)

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; Kono, Yoshio; Park, Changyong; Kenney-Benson, Curtis; Shen, Guoyin

    2017-01-01

    A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid-solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. The decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure-temperature region similar to where the supercooled liquid Bi is observed. Akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought.

  19. Metal nanoparticles with liquid-crystalline ligands: controlling nanoparticle superlattice structure and properties.

    PubMed

    Lewandowski, Wiktor; Wójcik, Michał; Górecka, Ewa

    2014-05-19

    Nanoparticle ordered aggregates are promising candidates for future application in a variety of sensing, optical and electronic technologies, mainly based on collective interactions between individual nano-building blocks. Physicochemical properties of such assemblies depend on nanoparticle spacing, therefore a lot of effort throughout the last years was put on development of assembly methods allowing control over aggregates structure. In this minireview we describe efficient self-assembly process based on the utilization of liquid-crystalline ligands grafted onto nanoparticle surface. We show strategies used to synthesize liquid-crystalline nanoparticles as well as discuss parameters influencing structural and thermal characteristic of aggregates. It is also demonstrated that the liquid-crystalline approach offers access to dynamic self-assembly and metamaterials with anisotropic plasmonic properties, which makes this strategy unique among others.

  20. Liquid crystallinity driven highly aligned large graphene oxide composites

    SciTech Connect

    Lee, Kyung Eun; Oh, Jung Jae; Yun, Taeyeong; Kim, Sang Ouk

    2015-04-15

    Graphene is an emerging graphitic carbon materials, consisting of sp{sup 2} hybridized two dimensinal honeycomb structure. It has been widely studied to incorporate graphene with polymer to utilize unique property of graphene and reinforce electrical, mechanical and thermal property of polymer. In composite materials, orientation control of graphene significantly influences the property of composite. Until now, a few method has been developed for orientation control of graphene within polymer matrix. Here, we demonstrate facile fabrication of high aligned large graphene oxide (LGO) composites in polydimethylsiloxane (PDMS) matrix exploiting liquid crystallinity. Liquid crystalline aqueous dispersion of LGO is parallel oriented within flat confinement geometry. Freeze-drying of the aligned LGO dispersion and subsequent infiltration with PDMS produce highly aligned LGO/PDMS composites. Owing to the large shape anisotropy of LGO, liquid crystalline alignment occurred at low concentration of 2 mg/ml in aqueous dispersion, which leads to the 0.2 wt% LGO loaded composites. - Graphical abstract: Liquid crystalline LGO aqueous dispersions are spontaneous parallel aligned between geometric confinement for highly aligned LGO/polymer composite fabrication. - Highlights: • A simple fabrication method for highly aligned LGO/PDMS composites is proposed. • LGO aqueous dispersion shows nematic liquid crystalline phase at 0.8 mg/ml. • In nematic phase, LGO flakes are highly aligned by geometric confinement. • Infiltration of PDMS into freeze-dried LGO allows highly aligned LGO/PDMS composites.

  1. Rotational reorganization of doped cholesteric liquid crystalline films.

    PubMed

    Eelkema, Rienk; Pollard, Michael M; Katsonis, Nathalie; Vicario, Javier; Broer, Dirk J; Feringa, Ben L

    2006-11-08

    In this paper an unprecedented rotational reorganization of cholesteric liquid crystalline films is described. This rotational reorganization results from the conversion of a chiral molecular motor dopant to an isomer with a different helical twisting power, leading to a change in the cholesteric pitch. The direction of this reorganization is correlated to the sign of the change in helical twisting power of the dopant. The rotational reorganization of the liquid crystalline film was used to rotate microscopic objects 4 orders of magnitude larger than the bistable dopants in the film, which shows that molecular motors and switches can perform work. The surface of the doped cholesteric liquid crystalline films was found to possess a regular surface relief, whose periodicity coincides with typical cholesteric polygonal line textures. These surface features originate from the cholesteric superstructure in the liquid crystalline film, which in turn is the result of the presence of the chiral dopant. As such, the presence of the dopant is expressed in these distinct surface structures. A possible mechanism at the origin of the rotational reorganization of liquid crystalline films and the cholesteric surface relief is discussed.

  2. Development and evaluation of liquid embolic agents based on liquid crystalline material of glyceryl monooleate.

    PubMed

    Du, Ling-Ran; Lu, Xiao-Jing; Guan, Hai-Tao; Yang, Yong-Jie; Gu, Meng-Jie; Zheng, Zhuo-Zhao; Lv, Tian-Shi; Yan, Zi-Guang; Song, Li; Zou, Ying-Hua; Fu, Nai-Qi; Qi, Xian-Rong; Fan, Tian-Yuan

    2014-08-25

    New type of liquid embolic agents based on a liquid crystalline material of glyceryl monooleate (GMO) was developed and evaluated in this study. Ternary phase diagram of GMO, water and ethanol was constructed and three isotropic liquids (ILs, GMO:ethanol:water=49:21:30, 60:20:20 and 72:18:10 (w/w/w)) were selected as potential liquid embolic agents, which could spontaneously form viscous gel cast when contacting with water or physiological fluid. The ILs exhibited excellent microcatheter deliverability due to low viscosity, and were proved to successfully block the saline flow when performed in a device to simulate embolization in vitro. The ILs also showed good cytocompatibility on L929 mouse fibroblast cell line. The embolization of ILs to rabbit kidneys was performed successfully under monitoring of digital subtraction angiography (DSA), and embolic degree was affected by the initial formulation composition and used volume. At 5th week after embolization, DSA and computed tomography (CT) confirmed the renal arteries embolized with IL did not recanalize in follow-up period, and an obvious atrophy of the embolized kidney was observed. Therefore, the GMO-based liquid embolic agents showed feasible and effective to embolize, and potential use in clinical interventional embolization therapy.

  3. High magnetic field processing of liquid crystalline polymers

    DOEpatents

    Smith, Mark E.; Benicewicz, Brian C.; Douglas, Elliot P.

    1998-01-01

    A process of forming bulk articles of oriented liquid crystalline thermoset material, the material characterized as having an enhanced tensile modulus parallel to orientation of an applied magnetic field of at least 25 percent greater than said material processed in the absence of a magnetic field, by curing a liquid crystalline thermoset precursor within a high strength magnetic field of greater than about 2 Tesla, is provided, together with a resultant bulk article of a liquid crystalline thermoset material, said material processed in a high strength magnetic field whereby said material is characterized as having a tensile modulus parallel to orientation of said field of at least 25 percent greater than said material processed in the absence of a magnetic field.

  4. High magnetic field processing of liquid crystalline polymers

    DOEpatents

    Smith, M.E.; Benicewicz, B.C.; Douglas, E.P.

    1998-11-24

    A process of forming bulk articles of oriented liquid crystalline thermoset material, the material characterized as having an enhanced tensile modulus parallel to orientation of an applied magnetic field of at least 25 percent greater than said material processed in the absence of a magnetic field, by curing a liquid crystalline thermoset precursor within a high strength magnetic field of greater than about 2 Tesla, is provided, together with a resultant bulk article of a liquid crystalline thermoset material, said material processed in a high strength magnetic field whereby said material is characterized as having a tensile modulus parallel to orientation of said field of at least 25 percent greater than said material processed in the absence of a magnetic field.

  5. Liquid crystallinity driven highly aligned large graphene oxide composites

    NASA Astrophysics Data System (ADS)

    Lee, Kyung Eun; Oh, Jung Jae; Yun, Taeyeong; Kim, Sang Ouk

    2015-04-01

    Graphene is an emerging graphitic carbon materials, consisting of sp2 hybridized two dimensinal honeycomb structure. It has been widely studied to incorporate graphene with polymer to utilize unique property of graphene and reinforce electrical, mechanical and thermal property of polymer. In composite materials, orientation control of graphene significantly influences the property of composite. Until now, a few method has been developed for orientation control of graphene within polymer matrix. Here, we demonstrate facile fabrication of high aligned large graphene oxide (LGO) composites in polydimethylsiloxane (PDMS) matrix exploiting liquid crystallinity. Liquid crystalline aqueous dispersion of LGO is parallel oriented within flat confinement geometry. Freeze-drying of the aligned LGO dispersion and subsequent infiltration with PDMS produce highly aligned LGO/PDMS composites. Owing to the large shape anisotropy of LGO, liquid crystalline alignment occurred at low concentration of 2 mg/ml in aqueous dispersion, which leads to the 0.2 wt% LGO loaded composites.

  6. Photoresponsive liquid crystalline epoxy networks with shape memory behavior and dynamic ester bonds

    DOE PAGES

    Rios, Orlando; Chen, Jihua; Li, Yuzhan; ...

    2016-06-01

    Functional polymers are intelligent materials that can respond to a variety of external stimuli. However, these materials have not yet found widespread real world applications because of the difficulties in fabrication and the limited number of functional building blocks that can be incorporated into a material. Here, we demonstrate a simple route to incorporate three functional building blocks (azobenzene chromophores, liquid crystals, and dynamic covalent bonds) into an epoxy-based liquid crystalline network (LCN), in which an azobenzene-based epoxy monomer is polymerized with an aliphatic dicarboxylic acid to create exchangeable ester bonds that can be thermally activated. Lastly, all three functionalmore » building blocks exhibited good compatibility, and the resulting materials exhibits various photomechanical, shape memory, and self-healing properties because of the azobenzene molecules, liquid crystals, and dynamic ester bonds, respectively.« less

  7. Crystalline, liquid crystalline, and isotropic phases of sodium deoxycholate in water

    SciTech Connect

    Su, Ziyang; Luthra, Suman; Krzyzaniak, Joseph F.; Agra-Kooijman, Dena M.; Kumar, Satyendra; Byrn, Stephen R.; Shalaev, Evgenyi Y.

    2012-09-06

    Sodium deoxycholate (NaDC) is an important example of bile salts, representing systems with complex phase behavior involving both crystalline and mesophase structures. In this study, properties of NaDC-water mixtures were evaluated as a function of composition and temperature via X-ray diffraction with synchrotron (sXRD) and laboratory radiation sources, water sorption, polarized light, hot-stage microscopy, and freezing-point osmometry. Several phases were detected depending on the composition and temperature, including isotropic solution phase, liquid crystalline (LC) phase, crystalline hydrate, and ice. The LC phase was identified as hexagonal structure by sXRD, with up to 14 high-order reflections detected. The crystalline phase was found to be nonstoichiometric hydrate, based on XRD and water sorption data. The phase diagram of NaDC-water system has been refined based on both results of this study and other reports in literature.

  8. A liquid crystalline chirality balance for vapours

    NASA Astrophysics Data System (ADS)

    Ohzono, Takuya; Yamamoto, Takahiro; Fukuda, Jun-Ichi

    2014-04-01

    Chiral discrimination of vapours plays an important role in olfactory perception of biological systems and its realization by artificial sensors has been an intriguing challenge. Here, we report a simple method that tangibly visualizes the chirality of a diverse variety of molecules dissolved from vapours with high sensitivity, by making use of a structural change in a periodic microstructure of a nematic liquid crystal confined in open microchannels. This microstructure is accompanied by a topological line defect of a zigzag form with equal lengths of ‘zig’ and ‘zag.’ We find that a tiny amount of vapour of chiral molecules injected onto the liquid crystal induces the imbalance of ‘zig’ and ‘zag’ depending on its enantiomeric excess within a few seconds. Our liquid-crystal-based ‘chirality balance’ offers a simple, quick and versatile chirality-sensing/-screening method for gas-phase analysis (for example, for odours, environmental chemicals or drugs).

  9. A liquid crystalline chirality balance for vapours.

    PubMed

    Ohzono, Takuya; Yamamoto, Takahiro; Fukuda, Jun-ichi

    2014-04-30

    Chiral discrimination of vapours plays an important role in olfactory perception of biological systems and its realization by artificial sensors has been an intriguing challenge. Here, we report a simple method that tangibly visualizes the chirality of a diverse variety of molecules dissolved from vapours with high sensitivity, by making use of a structural change in a periodic microstructure of a nematic liquid crystal confined in open microchannels. This microstructure is accompanied by a topological line defect of a zigzag form with equal lengths of 'zig' and 'zag.' We find that a tiny amount of vapour of chiral molecules injected onto the liquid crystal induces the imbalance of 'zig' and 'zag' depending on its enantiomeric excess within a few seconds. Our liquid-crystal-based 'chirality balance' offers a simple, quick and versatile chirality-sensing/-screening method for gas-phase analysis (for example, for odours, environmental chemicals or drugs).

  10. Thermoplastic High Strain Multishape Memory Polymer: Side-Chain Polynorbornene with Columnar Liquid Crystalline Phase.

    PubMed

    Zhao, Ruiying; Zhao, Tipeng; Jiang, Xuqiang; Liu, Xin; Shi, Dong; Liu, Chenyang; Yang, Shuang; Chen, Er-Qiang

    2017-03-01

    A thermoplastic high strain multishape memory polymer can be fabricated using a hemiphasmid side-chain polynorbornene (P1) with hexagonal columnar liquid crystalline (ΦH ) phase. Without any chemical crosslinks, P1 can memorize multiple temporary shapes with high strain and exhibit excellent shape fixity and shape recovery. As the building blocks of ΦH , the multichain columns in P1 act as robust physical crosslinks. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Plateau borders of smectic liquid crystalline films

    NASA Astrophysics Data System (ADS)

    Trittel, Torsten; Aldred, Ruth; Stannarius, Ralf

    2011-06-01

    We investigate the geometrical properties of Plateau borders in an arrangement of connected smectic A free standing films. The geometry is chosen such that a circular Plateau border surrounds a planar smectic film and connects it with two smectic catenoids. It is demonstrated that, similar to soap films, the smectic film geometry can be described by a negative line tension of the circular contact region. Thus, the equilibrium angle between the films depends upon the liquid content in this region, and with increasing liquid content, deviations from Plateau's rule are observed. The experimental results are qualitatively comparable to soap films. A possible origin of slight quantitative differences is discussed.

  12. Liquid dynamics in partially crystalline glycerol

    NASA Astrophysics Data System (ADS)

    Sanz, Alejandro; Niss, Kristine

    2017-01-01

    We present a dielectric study on the dynamics of supercooled glycerol during crystallization. We explore the transformation into a solid phase in real time by monitoring the temporal evolution of the amplitude of the dielectric signal. Neither the initial nucleation nor the crystal growth influences the liquid dynamics visibly. For one of the samples studied, a tiny fraction of glycerol remained in the disordered state after the end of the transition. We examined the nature of the α relaxation in this frustrated crystal and find that it is virtually identical to the bulk dynamics. In addition, we have found no evidence that supercooled glycerol transforms into a peculiar phase in which either a new solid amorphous state or nano-crystals dispersed in a liquid matrix are formed.

  13. Entropy Calculations for a Supercooled Liquid Crystalline Blue Phase

    ERIC Educational Resources Information Center

    Singh, U.

    2007-01-01

    We observed, using polarized light microscopy, the supercooling of the blue phase (BPI) of cholesteryl proprionate and measured the corresponding liquid crystalline phase transition temperatures. From these temperatures and additional published data we have provided, for the benefit of undergraduate physics students, a nontraditional example…

  14. Entropy Calculations for a Supercooled Liquid Crystalline Blue Phase

    ERIC Educational Resources Information Center

    Singh, U.

    2007-01-01

    We observed, using polarized light microscopy, the supercooling of the blue phase (BPI) of cholesteryl proprionate and measured the corresponding liquid crystalline phase transition temperatures. From these temperatures and additional published data we have provided, for the benefit of undergraduate physics students, a nontraditional example…

  15. Fast Switching of Vertical Alignment Liquid Crystal Cells with Liquid Crystalline Polymer Networks

    NASA Astrophysics Data System (ADS)

    Baek, Jong-In; Kim, Ki-Han; Kim, Jae Chang; Yoon, Tae-Hoon; Woo, Hwa Sung; Shin, Sung Tae; Souk, Jun Hyung

    2009-05-01

    This paper reports on the electro-optic characteristics of vertical alignment (VA) liquid crystal (LC) cells with liquid crystalline polymer networks. Optical bouncing, that occurs during the turn-on of VA cells, can be eliminated by introducing in-cell polymer networks. Furthermore, the turn-off also becomes much faster because of the anchoring effect caused by the anisotropy in the molecular shape of the liquid crystalline polymers. These response times have been found to vary for different LC/prepolymer mixtures. When the concentration of the liquid crystalline prepolymer in the initial LC/prepolymer mixture was 3, 5, or 10 wt %, the response times were measured to be 34, 56, and 87% faster than those of a VA cell with pure LC. These switching behaviors of VA cells with liquid crystalline polymer networks are demonstrated and compared with those using pure LC and with polymer networks made of isotropic prepolymers.

  16. Lyotropic liquid crystalline phase behaviour in amphiphile-protic ionic liquid systems.

    PubMed

    Chen, Zhengfei; Greaves, Tamar L; Fong, Celesta; Caruso, Rachel A; Drummond, Calum J

    2012-03-21

    Approximate partial phase diagrams for nine amphiphile-protic ionic liquid (PIL) systems have been determined by synchrotron source small angle X-ray scattering, differential scanning calorimetry and cross polarised optical microscopy. The binary phase diagrams of some common cationic (hexadecyltrimethyl ammonium chloride, CTAC, and hexadecylpyridinium bromide, HDPB) and nonionic (polyoxyethylene (10) oleyl ether, Brij 97, and Pluronic block copolymer, P123) amphiphiles with the PILs, ethylammonium nitrate (EAN), ethanolammonium nitrate (EOAN) and diethanolammonium formate (DEOAF), have been studied. The phase diagrams were constructed for concentrations from 10 wt% to 80 wt% amphiphile, in the temperature range 25 °C to >100 °C. Lyotropic liquid crystalline phases (hexagonal, cubic and lamellar) were formed at high surfactant concentrations (typically >50 wt%), whereas at <40 wt%, only micelles or polydisperse crystals were present. With the exception of Brij 97, the thermal stability of the phases formed by these surfactants persisted to temperatures above 100 °C. The phase behaviour of amphiphile-PIL systems was interpreted by considering the PIL cohesive energy, liquid nanoscale order, polarity and ionicity. For comparison the phase behaviour of the four amphiphiles was also studied in water.

  17. Liquid crystalline cellulose-based nematogels

    PubMed Central

    Liu, Qingkun; Smalyukh, Ivan I.

    2017-01-01

    Physical properties of composite materials can be pre-engineered by controlling their structure and composition at the mesoscale. However, approaches to achieving this are limited and rarely scalable. We introduce a new breed of self-assembled nematogels formed by an orientationally ordered network of thin cellulose nanofibers infiltrated with a thermotropic nematic fluid. The interplay between orientational ordering within the nematic network and that of the small-molecule liquid crystal around it yields a composite with highly tunable optical properties. By means of combining experimental characterization and modeling, we demonstrate submillisecond electric switching of transparency and facile responses of the composite to temperature changes. Finally, we discuss a host of potential technological uses of these self-assembled nematogel composites, ranging from smart and privacy windows to novel flexible displays. PMID:28835927

  18. Liquid crystalline cellulose-based nematogels.

    PubMed

    Liu, Qingkun; Smalyukh, Ivan I

    2017-08-01

    Physical properties of composite materials can be pre-engineered by controlling their structure and composition at the mesoscale. However, approaches to achieving this are limited and rarely scalable. We introduce a new breed of self-assembled nematogels formed by an orientationally ordered network of thin cellulose nanofibers infiltrated with a thermotropic nematic fluid. The interplay between orientational ordering within the nematic network and that of the small-molecule liquid crystal around it yields a composite with highly tunable optical properties. By means of combining experimental characterization and modeling, we demonstrate submillisecond electric switching of transparency and facile responses of the composite to temperature changes. Finally, we discuss a host of potential technological uses of these self-assembled nematogel composites, ranging from smart and privacy windows to novel flexible displays.

  19. Crystalline liquid and rubber-like behavior in Cu nanowires.

    PubMed

    Yue, Yonghai; Chen, Nianke; Li, Xianbin; Zhang, Shengbai; Zhang, Ze; Chen, Mingwei; Han, Xiaodong

    2013-08-14

    Via in situ TEM tensile tests on single crystalline copper nanowires with an advanced tensile device, we report here a crystalline-liquid-rubber-like (CRYS-LIQUE-R) behavior in fracturing crystalline metallic nanowires. A retractable strain of the fractured crystalline Cu nanowires can approach over 35%. This astonishing CRYS-LIQUE-R behavior of the fracturing highly strained single crystalline Cu nanowires originates from an instant release of the stored ultralarge elastic energy in the crystalline nanowires. The release of the ultralarge elastic energy was estimated to generate a huge reverse stress as high as ~10 GPa. The effective diffusion coefficient (D(eff)) increased sharply due to the consequent pressure gradient. In addition, due to the release of ultrahigh elastic energy, the estimated concomitant temperature increase was estimated as high as 0.6 Tm (Tm is the melting point of nanocrystalline Cu) on the fractured tip of the nanowires. These factors greatly enhanced the atomic diffusion process. Molecular dynamic simulations revealed that the very high reverse stress triggered dislocation nucleation and exhaustion.

  20. Polarized photoluminescence from nematic and chiral- nematic liquid crystalline films

    NASA Astrophysics Data System (ADS)

    Conger, Brooke Morgan

    Polarization control is key to optoelectronics in terms of the processing and display of optical information. In principle, photonic or electronic excitation of anisotropic films should result in polarized light emission. Because of spontaneous molecular self-assembly, liquid crystals are ideal for the exploration of polarized luminescence. Although most studies on polarized luminescence have been based on liquid crystalline fluid films, solid films are preferred in view of morphological stability. Therefore, the theme of my thesis is the study of polarized luminescence from various fluorescent liquid crystal systems. From the fundamental perspective, a theory modeling the process of polarized photoluminescence was validated using fluorophore doped fluid liquid crystal films. To provide the morphological stability crucial to practical application, polarized fluorescence using vitrifiable and polymeric liquid crystals functionalized with fluorescent moieties was investigated. In addition, liquid crystalline π- conjugated polymers were synthesized and characterized as a new class of optical polymers. The effect of the emission source on achievable polarization from pyrene and carbazole systems was also elucidated. The main observations are as follows: (1) The observed degrees of polarization for all fluorescent liquid crystal systems were found to agree with the theories governing polarized fluorescence. (2) Low molar mass vitrifiable and polymeric liquid crystalline cyanoterphenyl and cyanotolane derivatives were found to yield moderate polarized fluorescence. Monomer emission was established as the decay pathway for the precursors and cyclohexane and polymethacrylate derivatives. (3) Ordered solid films from thiophene and p-phenylene π-conjugated polymers were found to induce significant degrees of polarized fluorescence. (4) Emission from glass-forming pyrenyl derivatives exhibited excimer emission in dilute solution and neat film, whereas in solid hosts it was

  1. Liquid crystalline phase transitions in hydrogels

    NASA Astrophysics Data System (ADS)

    Alsayed, A. M.; Dogic, Z.; Islam, M. F.; Yodh, A. G.; Angler, A.; Discher, D. E.

    2003-03-01

    We investigate the isotropic-nematic (IN) phase transition of fd rods dissolved in P(NIPAAm) gel. The P(NIPAAm) gel exhibits a first order phase transition at 32 C from a low temperature expanded state to a high temperature collapsed state. Surprisingly we found it is possible to induce the nematic phase by keeping the volume of the gel constant and changing temperature. The sample exhibits a continuous and reversible transition from isotropic to nematic phase as the temperature is changed between 24-31 C. This unusual behavior is correlated with the presence of heterogeneities in the gel. Dissolving the rods into the gel effectively changes this concentration dependent lyotropic liquid crystal into temperature dependant system. The possibility that fd/gel system exhibits soft elasticity is currently being explored. Additionally we observe a temperature dependent nematic-smectic phase transition in this system and we studied its kinetics. This work is partially supported by NSF grants DMR-0203378, the PENN MRSEC, DMR-0079909, and NASA grant NAG8-2172.

  2. Liquid/Liquid interfacial polymerization to grow single crystalline nanoneedles of various conducting polymers.

    PubMed

    Nuraje, Nurxat; Su, Kai; Yang, Nan-Loh; Matsui, Hiroshi

    2008-03-01

    Single crystalline nanoneedles of polyaniline (PANI) and polypyrrole (PPY) were synthesized using an interfacial polymerization for the first time. The interfacial crystallization of conductive polymers at the liquid/liquid interface allowed PANI and PPY polymers to form single crystalline nanocrystals in a rice-like shape in the dimensions of 63 nm x 12 nm for PANI and 70 nm x 20 nm for PPY. Those crystalline nanoneedles displayed a fast conductance switching in the time scale of milliseconds. An important growth condition necessary to yield highly crystalline conductive polymers was the extended crystallization time at the liquid/liquid interfaces to increase the degree of crystallization. As compared to other interfacial polymerization methods, lower concentrations of monomer and oxidant solutions were employed to further extend the crystallization time. While other interfacial growth of conducting polymers yielded noncrystalline polymer fibers, our interfacial method produced single crystalline nanocrystals of conductive polymers. We recently reported the liquid/liquid interfacial synthesis of conducting PEDOT nanocrystals; however, this liquid/liquid interfacial method needs to be extended to other conductive polymer nanocrystal syntheses in order to demonstrate that our technique could be applied as the general fabrication procedure for the single crystalline conducting polymer growth. In this report, we showed that the liquid/liquid interfacial crystallization could yield PANI nanocrystals and PPY nanocrystals, other important conductive polymers, in addition to PEDOT nanocrystals. The resulting crystalline polymers have a fast conductance switching time between the insulating and conducting states on the order of milliseconds. This technique will be useful to synthesize conducting polymers via oxidative coupling processes in a single crystal state, which is extremely difficult to achieve by other synthetic methods.

  3. Alkyl chains acting as entropy reservoir in liquid crystalline materials.

    PubMed

    Sorai, Michio; Saito, Kazuya

    2003-01-01

    The roles played by the conformational disordering of alkyl chains in determining the aggregation states of matter are reviewed for liquid crystalline materials from a thermodynamic perspective. Entropy, which is one of the most macroscopic concepts but which has a clear microscopic meaning, provides crucial microscopic information for complex systems for which a microscopic description is hard to establish. Starting from structural implication by absolute (third-law) entropy for crystalline solids, the existence of successive phase transitions caused by the successive conformational melting of alkyl chains in discotic mesogens is explained. An experimental basis is given for the "quasi-binary picture" of thermotropic liquid crystals, i.e., the highly disordered alkyl chains behave like a second component (solvent). A novel entropy transfer between the "components" of a molecule and the resulting "alkyl chains as entropy reservoir" mechanism are explained for cubic mesogens.

  4. Synthesis, Characterization and Texture Observations of Calamitic Liquid Crystalline Compounds

    PubMed Central

    Qaddoura, Maher A.; Belfield, Kevin D.

    2009-01-01

    Several divinylic mesogenic monomers were synthesized based on coupling the monomer 4-(4-pentenyloxy)benzoic acid with chlorohydroquinone, 2,5-dihydroxy- acetophenone, methylhydroquinone or 2-methoxyhydroquinone. This resulted in novel mesogens of phenylene esters with different lateral substituent groups. The effect of the lateral substituent group on the thermotropic phase behavior for these liquid crystalline compounds was investigated using DSC and optical polarized microscopy. All the mesogens proved to have a wide nematic liquid crystalline range. Only the phenylene ester, which has a methoxy lateral substituent, exhibited both nematic and smectic phases. Structural confirmation of all new derivatives was accomplished by 1H- and 13C-NMR spectroscopic analysis, along with CH elemental analysis. PMID:20087464

  5. Originating super-strong liquid crystalline polymers (SSLCPs). Final report

    SciTech Connect

    1994-12-31

    The work at the University of North Carolina at Chapel Hill focused on the experimental characterization of ring mobility in labeled polyaramides with deuterium Nuclear Magnetic Resonance (NMR). Los Alamos National Laboratory prepared the deuterium-labeled analogs of Super-Strong (SS), Liquid Crystalline Polymers (LCPs) and oligomers. These materials were studied to ascertain the influence of substituent size (at the diacid moiety) on the mobility of the labeled diamine. The results are currently being finalized for publication.

  6. Liquid crystalline tetrahedra and low-aspect-ratio organic materials

    NASA Astrophysics Data System (ADS)

    Pegenau, A.; Goering, P.; Diele, S.; Tschierske, C.

    1998-01-01

    3,4-Dialkoxybenzoates of pentaerythritol and structural related polyhydroxy compounds have been synthesized and investigated by polarizing microscopy, differential scanning calorimetry and some of them also by x-ray scattering. Despite the fact that these compounds are neither anisometric nor amphilphilic in a classical sense they can display columnar liquid-crystalline phases. It is proposed, that the segregation of the polar regions and the lipophilic alkyl chains into separate regions is mainly responsible for the formation of these mesophases.

  7. Birefringence and DNA Condensation of Liquid Crystalline Chromosomes ▿

    PubMed Central

    Chow, Man H.; Yan, Kosmo T. H.; Bennett, Michael J.; Wong, Joseph T. Y.

    2010-01-01

    DNA can self-assemble in vitro into several liquid crystalline phases at high concentrations. The largest known genomes are encoded by the cholesteric liquid crystalline chromosomes (LCCs) of the dinoflagellates, a diverse group of protists related to the malarial parasites. Very little is known about how the liquid crystalline packaging strategy is employed to organize these genomes, the largest among living eukaryotes—up to 80 times the size of the human genome. Comparative measurements using a semiautomatic polarizing microscope demonstrated that there is a large variation in the birefringence, an optical property of anisotropic materials, of the chromosomes from different dinoflagellate species, despite their apparently similar ultrastructural patterns of bands and arches. There is a large variation in the chromosomal arrangements in the nuclei and individual karyotypes. Our data suggest that both macroscopic and ultrastructural arrangements affect the apparent birefringence of the liquid crystalline chromosomes. Positive correlations are demonstrated for the first time between the level of absolute retardance and both the DNA content and the observed helical pitch measured from transmission electron microscopy (TEM) photomicrographs. Experiments that induced disassembly of the chromosomes revealed multiple orders of organization in the dinoflagellate chromosomes. With the low protein-to-DNA ratio, we propose that a highly regulated use of entropy-driven force must be involved in the assembly of these LCCs. Knowledge of the mechanism of packaging and arranging these largest known DNAs into different shapes and different formats in the nuclei would be of great value in the use of DNA as nanostructural material. PMID:20400466

  8. Carbon Nanotubes as Reinforcement of Cellulose Liquid Crystalline Responsive Networks.

    PubMed

    Echeverria, Coro; Aguirre, Luis E; Merino, Esther G; Almeida, Pedro L; Godinho, Maria H

    2015-09-30

    The incorporation of small amount of highly anisotropic nanoparticles into liquid crystalline hydroxypropylcellulose (LC-HPC) matrix improves its response when is exposed to humidity gradients due to an anisotropic increment of order in the structure. Dispersed nanoparticles give rise to faster order/disorder transitions when exposed to moisture as it is qualitatively observed and quantified by stress-time measurements. The presence of carbon nanotubes derives in a improvement of the mechanical properties of LC-HPC thin films.

  9. Dynamics in dialysis process for liquid crystalline gel formation.

    PubMed

    Nobe, Masahiro; Dobashi, Toshiaki; Yamamoto, Takao

    2005-08-30

    The processes of gelation and liquid crystalline formation in the dialysis of Curdlan solution have been observed under crossed nicols, and the calcium concentration and pH of the inner solution were traced. The results showed that the gelation and the liquid crystalline formation occurred simultaneously to form liquid crystalline gel (LCG), but the birefringence of the LCG increased even after the gelation, suggesting further ordering of the Curdlan molecules. On the basis of the calcium ion diffusion, a simple theory for the time development of the thickness of the LCG layer was developed. The experimental and theoretical results agree very well until an amorphous gel (AG) ring appears. The whole process was expressed by a master curve by reducing time and distance data for different radius dialysis tubes by those at the final state; a scaling behavior with respect to the dialysis tube radius was found. The experimental analysis for the calcium concentrations and the pH indicates that forming Curdlan LCG with high ordering of Curdlan molecules consists of two steps: the diffusion of calcium ions inducing the ordering of Curdlan molecules and yielding cross-links simultaneously, and the local relaxation of the Curdlan molecules increasing the ordering degree further.

  10. Chiroptical switching caused by crystalline/liquid crystalline phase transition of a chiral bowl-shaped molecule.

    PubMed

    Yamamura, Masaki; Sukegawa, Kimiya; Okada, Daichi; Yamamoto, Yohei; Nabeshima, Tatsuya

    2016-03-25

    The liquid crystal of a chiral bowl-shaped molecule having a central-phosphorus atom and long alkyl chains was developed. The DSC and XRD analyses suggested the formation of columnar liquid crystals of both the enantiopure and racemic compounds. The condensed phase of the enantiopure compound in a thin film exhibited a significant signal in CD spectra, which was switched by a reversible phase transition between the crystalline and liquid crystalline states.

  11. Computational analysis of ordering in non-liquid crystalline versus liquid crystalline materials with special reference to nBAC

    SciTech Connect

    Lakshmi Praveen, P.; Veera Bhadra Reddy, K.; Ajeetha, N.; Ojha, D. P.

    2009-12-15

    A computational analysis of ordering in non-liquid crystalline p-n-alkyl benzoic acid, having 1 (1BAC), 2 (2BAC) and 3(3BAC) carbon atoms in the alkyl chain has been carried out with respect to translatory and orientational motions, but detailed results are reported only for 3BAC. The evaluation of net atomic charges and dipole moments at each atomic center has been carried out using complete neglect differential overlap (CNDO/2) method. The modified Rayleigh-Schrodinger perturbation theory along with the multicentered-multipole expansion method has been employed to evaluate long-range interactions, while a '6-exp' potential function has been assumed for short-range interactions. On the basis of stacking, in-plane and terminal interaction energy calculations, all possible arrangements of a molecular pair have been considered. A comparative picture of molecular parameters, such as total energy, binding energy, and total dipole moment of 3BAC with higher homologous series liquid crystalline compounds having 4(4BAC), 5(5BAC), and 6(6BAC) alkyl chain carbon atoms, has been given. It is found that, if a suitable functional group is attached to 3BAC, so that the length to breadth ratio is increased, the molecule will show a change in the long-range order, the phase transition temperature and other liquid crystalline properties.

  12. Dry Powder Precursors of Cubic Liquid Crystalline Nanoparticles (cubosomes)

    NASA Astrophysics Data System (ADS)

    Spicer, Patrick T.; Small, William B.; Small, William B.; Lynch, Matthew L.; Burns, Janet L.

    2002-08-01

    Cubosomes are dispersed nanostructured particles of cubic phase liquid crystal that have stimulated significant research interest because of their potential for application in controlled-release and drug delivery. Despite the interest, cubosomes can be difficult to fabricate and stabilize with current methods. Most of the current work is limited to liquid phase processes involving high shear dispersion of bulk cubic liquid crystalline material into sub-micron particles, limiting application flexibility. In this work, two types of dry powder cubosome precursors are produced by spray-drying: (1) starch-encapsulated monoolein is produced by spray-drying a dispersion of cubic liquid crystalline particles in an aqueous starch solution and (2) dextran-encapsulated monoolein is produced by spray-drying an emulsion formed by the ethanol-dextran-monoolein-water system. The encapsulants are used to decrease powder cohesion during drying and to act as a soluble colloidal stabilizer upon hydration of the powders. Both powders are shown to form (on average) 0.6 μm colloidally-stable cubosomes upon addition to water. However, the starch powders have a broader particle size distribution than the dextran powders because of the relative ease of spraying emulsions versus dispersions. The developed processes enable the production of nanostructured cubosomes by end-users rather than just specialized researchers and allow tailoring of the surface state of the cubosomes for broader application.

  13. Study on the release of chlorhexidine base and salts from different liquid crystalline structures.

    PubMed

    Farkas, Edit; Kiss, Dorottya; Zelkó, Romána

    2007-08-01

    The aim of this study was to investigate the influence of two types of chlorhexidine species, chlorhexidine base and its salts, on the physico-chemical features of liquid crystalline systems and on drug transport through lipophilic membranes. A non-ionic surfactant, Synperonic A7 (PEG7-C13-15) was selected for the preparation of the liquid crystalline systems. Mixtures of different ratios of Synperonic A7 and water were prepared. The liquid crystalline systems were characterized using polarizing microscopy and dynamic oscillatory test. Membrane transport was also examined. The addition of chlorhexidine species to the liquid crystalline system modified the structure of the liquid crystalline system. As a result of the changes of liquid crystalline structures, the drug release of various types of chlorhexidine could be also modified. The combination of the base and salt forms of the drug in one dosage form could eliminate the drug release changes from liquid crystalline systems of dynamically changeable structures.

  14. Morphology-conductivity relationship in crystalline and amorphous sequence-defined peptoid block copolymer electrolytes.

    PubMed

    Sun, Jing; Liao, Xunxun; Minor, Andrew M; Balsara, Nitash P; Zuckermann, Ronald N

    2014-10-22

    Polymers that dissolve and conduct lithium ions are of great interest in the application of rechargeable lithium batteries. It is generally believed that the transport of ions in these systems is facilitated by rapid segmental motion typically found in rubbery, amorphous polymers. In this paper, we demonstrate that chemically identical ethyleneoxy-containing domains of a block copolymer exhibit comparable conductivities when in an amorphous or a crystalline state. An important feature of this study is the use of sequence-defined block copolypeptoids synthesized by submonomer solid-phase synthesis. Two structurally analogous ethyleneoxy-containing diblock copolypeptoids poly-N-(2-ethyl)hexylglycine-block-poly-N-2-(2-(2-methoxyethoxy)ethoxy)ethylglycine (pNeh-b-pNte) and poly-N-decylglycine-block-poly-N-2-(2-(2-methoxyethoxy)ethoxy)ethylglycine (pNdc-b-pNte) with 18 monomer units per block were synthesized. Both diblock copolypeptoids have the same conducting block, pNte, but different nonconducting blocks: pNeh, which is amorphous, and pNdc, which is crystalline. Both diblock copolypeptoids self-assemble into a lamellar morphology; however, pNte chains are amorphous in pNeh-b-pNte and crystalline in pNdc-b-pNte. This provides the platform for comparing lithium ion transport in amorphous and crystalline polymer domains that are otherwise similar.

  15. Non-lamellar lipid liquid crystalline structures at interfaces.

    PubMed

    Chang, Debby P; Barauskas, Justas; Dabkowska, Aleksandra P; Wadsäter, Maria; Tiberg, Fredrik; Nylander, Tommy

    2015-08-01

    The self-assembly of lipids leads to the formation of a rich variety of nano-structures, not only restricted to lipid bilayers, but also encompassing non-lamellar liquid crystalline structures, such as cubic, hexagonal, and sponge phases. These non-lamellar phases have been increasingly recognized as important for living systems, both in terms of providing compartmentalization and as regulators of biological activity. Consequently, they are of great interest for their potential as delivery systems in pharmaceutical, food and cosmetic applications. The compartmentalizing nature of these phases features mono- or bicontinuous networks of both hydrophilic and hydrophobic domains. To utilize these non-lamellar liquid crystalline structures in biomedical devices for analyses and drug delivery, it is crucial to understand how they interact with and respond to different types of interfaces. Such non-lamellar interfacial layers can be used to entrap functional biomolecules that respond to lipid curvature as well as the confinement. It is also important to understand the structural changes of deposited lipid in relation to the corresponding bulk dispersions. They can be controlled by changing the lipid composition or by introducing components that can alter the curvature or by deposition on nano-structured surface, e.g. vertical nano-wire arrays. Progress in the area of liquid crystalline lipid based nanoparticles opens up new possibilities for the preparation of well-defined surface films with well-defined nano-structures. This review will focus on recent progress in the formation of non-lamellar dispersions and their interfacial properties at the solid/liquid and biologically relevant interfaces. Copyright © 2014. Published by Elsevier B.V.

  16. Quantitative Analysis of Matrine in Liquid Crystalline Nanoparticles by HPLC

    PubMed Central

    Peng, Xinsheng; Hu, Min; Ling, Yahao; Tian, Yuan; Zhou, Yanxing; Zhou, Yanfang

    2014-01-01

    A reversed-phase high-performance liquid chromatographic method has been developed to quantitatively determine matrine in liquid crystal nanoparticles. The chromatographic method is carried out using an isocratic system. The mobile phase was composed of methanol-PBS(pH6.8)-triethylamine (50 : 50 : 0.1%) with a flow rate of 1 mL/min with SPD-20A UV/vis detector and the detection wavelength was at 220 nm. The linearity of matrine is in the range of 1.6 to 200.0 μg/mL. The regression equation is y = 10706x − 2959 (R2 = 1.0). The average recovery is 101.7%; RSD = 2.22%  (n = 9). This method provides a simple and accurate strategy to determine matrine in liquid crystalline nanoparticle. PMID:24834359

  17. Crystallization in the Binary Blends of Crystalline-Amorphous Diblock Copolymers Bearing Chemically Different Crystalline Block

    NASA Astrophysics Data System (ADS)

    Chu, Che-Yi; Chen, Hsin-Lung; Nandan, Bhanu; Hsiao, Ming-Siao

    2011-03-01

    The crystallization behavior of a series of lamellae-forming blends of a shorter PS- b -PEO (SEO) and a longer PS- b -PLLA (SLLA) has been studied. In SLLA-rich blends, the junction point constraint coupled with the poor chain mobility at low Tc (<= 45& circ; C) hampered the formal crystallization of PLLA. In this case, a local demixing between a fraction of PEO and PLLA chains took place, yielding the PLLA crystalline domains in which the PLLA crystalline stems were intervened by the PEO chains. This crystalline species gave rise to a relatively broad peak at 2 θ = 15.92circ; in the WAXS profile and displayed a much lower melting point of ca. 100& circ; C compared to that of the typical α -form crystal of PLLA. It was suggested that the inserted PEO chains served as the molecular defects which induced an expansion of the a -axis and b -axis of the α -form PLLA unit cell and lowered the crystal melting point due to introduction of defect free energy. We gratefully acknowledge financial support from the National Science Council Taiwan under Contract NSC 95-2221-E-007-083.

  18. Liquid crystal deposition on poled, single crystalline lithium niobate

    NASA Astrophysics Data System (ADS)

    Bharath, S. C.; Pimputkar, K. R.; Pronschinske, A. M.; Pearl, T. P.

    2008-01-01

    For the purpose of elucidating the mechanisms for molecular organization at poled ferroelectric surfaces, single crystalline lithium niobate (LN), 'Z-cut' along the (0 0 0 1) plane, has been prepared and characterized and subsequently exposed to liquid crystal molecules. As a model system we chose to study the anchoring of 4- n-octyl-4'-cyanobiphenyl (8CB) to LN. Liquid crystalline films are of interest because of their useful electronic and optical properties as well as chemical sensing attributes. Low-energy electron diffraction (LEED), atomic force microscopy (AFM), surface contact angle measurements (CA), and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface of lithium niobate as well as the nature of 8CB films grown on the surface. Atomically flat LN surfaces were prepared as a support for monolayer thick, 8CB molecular domains. 8CB liquid crystal molecules were deposited by an ambient vaporization technique and the films were analyzed using XPS and CA. Understanding electrostatic anchoring mechanisms and thin film organization for this molecule on uniformly poled surfaces allows for a fuller appreciation of how molecular deposition of other polarizable molecules on periodically poled and patterned poled lithium niobate surfaces would occur.

  19. Optical pendulum generator based on photomechanical liquid-crystalline actuators.

    PubMed

    Tang, Rong; Liu, Ziyi; Xu, Dandan; Liu, Jian; Yu, Li; Yu, Haifeng

    2015-04-29

    For converting light energy into electricity, an optical pendulum generator was designed by combining photomechanical movement of liquid-crystalline actuator (LCA) with Faraday's law of electromagnetic induction. Bilayer cantilever actuators were first fabricated with LDPE and LCA. Their photomechanical movement drove the attached copper coils to cut magnetic line of force generating electricity. The output electricity was proportional to the changing rate of the magnetic flux, which was greatly influenced by light intensity, film thickness, and sample size. Continuous electrical output was also achieved. This simple strategy may expand applications of photoactive materials in the capture and storage of light energy.

  20. A Molecular View of Liquid Crystalline Elastomers and Gels

    NASA Astrophysics Data System (ADS)

    de Pablo, Juan

    2011-03-01

    A combination of Monte Carlo and molecular dynamics simulations is used to examine the order-disorder transitions that arise in model liquid crystalline elastomers and colloidal gels as a function of concentration and strain, respectively. Two models are considered. In the first, a lattice model is used to represent a colloidal gel of nematogens and nanoparticles. In the second, a cross-linked elastomer of Gay-Berne mesogens is adopted to examine the order-disroder transition that arises as a function of strain. The results of simulations are compared to those of recent experiments for these two classes of systems.

  1. Perhydroazulene-based liquid-crystalline materials with smectic phases.

    PubMed

    Hussain, Zakir; Hopf, Henning; Eichhorn, S Holger

    2012-01-01

    New liquid-crystalline materials with a perhydroazulene core were synthesized and the stereochemistry of these compounds was investigated. The mesomorphic properties of the new LC compounds were investigated by differential scanning colorimetry, polarizing optical microscopy and X-ray diffraction. We report here on the LC properties of nonchiral materials, which predominantly exhibit smectic phases and display nematic phases only within narrow temperature ranges. The dependence of the mesogenic behavior of the new materials on the stereochemistry of the core system was also investigated. All newly synthesized compounds were fully characterized by the usual spectroscopic and analytical methods.

  2. Liquid water in the domain of cubic crystalline ice Ic

    NASA Technical Reports Server (NTRS)

    Jenniskens, P.; Banham, S. F.; Blake, D. F.; McCoustra, M. R.

    1997-01-01

    Vapor-deposited amorphous water ice when warmed above the glass transition temperature (120-140 K), is a viscous liquid which exhibits a viscosity vs temperature relationship different from that of liquid water at room temperature. New studies of thin water ice films now demonstrate that viscous liquid water persists in the temperature range 140-210 K. where it coexists with cubic crystalline ice. The liquid character of amorphous water above the glass transition is demonstrated by (1) changes in the morphology of water ice films on a nonwetting surface observed in transmission electron microscopy (TEM) at around 175 K during slow warming, (2) changes in the binding energy of water molecules measured in temperature programmed desorption (TPD) studies, and (3) changes in the shape of the 3.07 micrometers absorption band observed in grazing angle reflection-absorption infrared spectroscopy (RAIRS) during annealing at high temperature. whereby the decreased roughness of the water surface is thought to cause changes in the selection rules for the excitation of O-H stretch vibrations. Because it is present over such a wide range of temperatures, we propose that this form of liquid water is a common material in nature. where it is expected to exist in the subsurface layers of comets and on the surfaces of some planets and satellites.

  3. Liquid water in the domain of cubic crystalline ice Ic.

    PubMed

    Jenniskens, P; Banham, S F; Blake, D F; McCoustra, M R

    1997-07-22

    Vapor-deposited amorphous water ice when warmed above the glass transition temperature (120-140 K), is a viscous liquid which exhibits a viscosity vs temperature relationship different from that of liquid water at room temperature. New studies of thin water ice films now demonstrate that viscous liquid water persists in the temperature range 140-210 K. where it coexists with cubic crystalline ice. The liquid character of amorphous water above the glass transition is demonstrated by (1) changes in the morphology of water ice films on a nonwetting surface observed in transmission electron microscopy (TEM) at around 175 K during slow warming, (2) changes in the binding energy of water molecules measured in temperature programmed desorption (TPD) studies, and (3) changes in the shape of the 3.07 micrometers absorption band observed in grazing angle reflection-absorption infrared spectroscopy (RAIRS) during annealing at high temperature. whereby the decreased roughness of the water surface is thought to cause changes in the selection rules for the excitation of O-H stretch vibrations. Because it is present over such a wide range of temperatures, we propose that this form of liquid water is a common material in nature. where it is expected to exist in the subsurface layers of comets and on the surfaces of some planets and satellites.

  4. Liquid water in the domain of cubic crystalline ice Ic

    NASA Technical Reports Server (NTRS)

    Jenniskens, P.; Banham, S. F.; Blake, D. F.; McCoustra, M. R.

    1997-01-01

    Vapor-deposited amorphous water ice when warmed above the glass transition temperature (120-140 K), is a viscous liquid which exhibits a viscosity vs temperature relationship different from that of liquid water at room temperature. New studies of thin water ice films now demonstrate that viscous liquid water persists in the temperature range 140-210 K. where it coexists with cubic crystalline ice. The liquid character of amorphous water above the glass transition is demonstrated by (1) changes in the morphology of water ice films on a nonwetting surface observed in transmission electron microscopy (TEM) at around 175 K during slow warming, (2) changes in the binding energy of water molecules measured in temperature programmed desorption (TPD) studies, and (3) changes in the shape of the 3.07 micrometers absorption band observed in grazing angle reflection-absorption infrared spectroscopy (RAIRS) during annealing at high temperature. whereby the decreased roughness of the water surface is thought to cause changes in the selection rules for the excitation of O-H stretch vibrations. Because it is present over such a wide range of temperatures, we propose that this form of liquid water is a common material in nature. where it is expected to exist in the subsurface layers of comets and on the surfaces of some planets and satellites.

  5. Liquid crystalline gel with refractive index gradient of curdlan.

    PubMed

    Dobashi, Toshiaki; Nobe, Masahiro; Yoshihara, Hiromi; Yamamoto, Takao; Konno, Akira

    2004-08-03

    Curdlan dissolved in aqueous sodium hydroxide was dialyzed to aqueous calcium chloride to form a gel. Transparent and turbid concentric layers observed in the gel cross section perpendicular to the long axis of the dialysis tube were identified as liquid crystalline gels with refractive index gradient and amorphous gels, respectively. The thickness of each layer was proportional to the diameter of the dialysis tube, and the gelation proceeded in proportion to the root of time. The unique pattern formation was attributed to the change of curdlan conformation and calcium-induced cross-linking resulting from a diffusion of calcium cations and hydroxide anions through the dialysis tube. It is suggested that the orderedness of the curdlan molecules decreases by the increase of the curvature of the concentric liquid crystal layers as the layer comes toward the center of the dialysis tube.

  6. Structure analysis methods for crystalline solids and supercooled liquids.

    PubMed

    Yu, Da-Qi; Chen, Min; Han, Xiu-Jun

    2005-11-01

    The three most widely used methods for analyzing atomic structures are evaluated by simulating crystalline solids and supercooled liquids. The local order parameter approach due to Volkov [Phys. Rev. E 66, 061401 (2002)] fails in randomly perturbed body-centered-cubic environments, while the pair analysis method behaves as an approximate approach depending on how the neighborhood is defined. As to the Voronoi analysis method, we improve the procedure of Brostow [Phys. Rev. B 57, 13448 (1998)] to eliminate distorted Voronoi faces and edges which originate from thermal vibrations and computational rounding errors. The improved procedure works robustly in face-centered-cubic, body-centered-cubic, and hexagonal close-packed environments. When the pair analysis technique and the Voronoi analysis method are applied to detect the microstructure and its evolution in supercooled liquids, qualitatively consistent results are attained.

  7. Crystalline Graphdiyne Nanosheets Produced at a Gas/Liquid or Liquid/Liquid Interface.

    PubMed

    Matsuoka, Ryota; Sakamoto, Ryota; Hoshiko, Ken; Sasaki, Sono; Masunaga, Hiroyasu; Nagashio, Kosuke; Nishihara, Hiroshi

    2017-02-15

    Synthetic two-dimensional polymers, or bottom-up nanosheets, are ultrathin polymeric frameworks with in-plane periodicity. They can be synthesized in a direct, bottom-up fashion using atomic, ionic, or molecular components. However, few are based on carbon-carbon bond formation, which means that there is a potential new field of investigation into these fundamentally important chemical bonds. Here, we describe the bottom-up synthesis of all-carbon, π-conjugated graphdiyne nanosheets. A liquid/liquid interfacial protocol involves layering a dichloromethane solution of hexaethynylbenzene on an aqueous layer containing a copper catalyst at room temperature. A multilayer graphdiyne (thickness, 24 nm; domain size, >25 μm) emerges through a successive alkyne-alkyne homocoupling reaction at the interface. A gas/liquid interfacial synthesis is more successful. Sprinkling a very small amount of hexaethynylbenzene in a mixture of dichloromethane and toluene onto the surface of the aqueous phase at room temperature generated single-crystalline graphdiyne nanosheets, which feature regular hexagonal domains, a lower degree of oxygenation, and uniform thickness (3.0 nm) and lateral size (1.5 μm).

  8. Liquid crystalline composites toward organic photovoltaic application (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Shimizu, Yo; Sosa-Vargas, Lydia; Shin, Woong; Higuchi, Yumi; Itani, Hiromichi; Kawano, Koki; Dao, Quang Duy; Fujii, Akihiko; Ozaki, Masanori

    2017-02-01

    Liquid crystalline semiconductor is an interesting category of organic electronic materials and also has been extensively studied in terms of "Printed Electronics". For the wider diversity in research toward new applications, one can consider how to use a combination of miscibility and phase separation in liquid crystals. Here we report discotic liquid crystals in making a composite of which structural order is controlled in nano-scale toward photovoltaic applications. Discotic columnar LCs were studied on their resultant molecular order and carrier transport properties. Liquid crystals of phthalocyanine and its analogues which exhibit columnar mesomorphism with high carrier mobility (10-1 cm2/Vs) were examined with making binary phase diagrams and the correlation to carrier transport properties by TOF measurements was discussed. The shape-analogues in chemical structure shows a good miscibility even for the different lattice-type of columnar arrangement and the carrier mobility is mostly decrease except for a case of combination with a metal-free and the metal complex. For the mixtures with non-mesogenic C60 derivatives, one sees a phase-separated structure due to its immiscibility, though the columnar order is remained in a range of component ratio.Especially, in a range of the ratio, it was observed the phase separated C60 derivatives are fused into the matrix of columnar bundles, indicating C60 derivatives could be diffused in columnar arrays in molecular level.

  9. Understanding the interfacial properties of nanostructured liquid crystalline materials for surface-specific delivery applications.

    PubMed

    Dong, Yao-Da; Larson, Ian; Barnes, Timothy J; Prestidge, Clive A; Allen, Stephanie; Chen, Xinyong; Roberts, Clive J; Boyd, Ben J

    2012-09-18

    Nonlamellar liquid crystalline dispersions such as cubosomes and hexosomes have great potential as novel surface-targeted active delivery systems. In this study, the influence of internal nanostructure, chemical composition, and the presence of Pluronic F127 as a stabilizer, on the surface and interfacial properties of different liquid crystalline particles and surfaces, was investigated. The interfacial properties of the bulk liquid crystalline systems with coexisting excess water were dependent on the internal liquid crystalline nanostructure. In particular, the surfaces of the inverse cubic systems were more hydrophilic than that of the inverse hexagonal phase. The interaction between F127 and the bulk liquid crystalline systems depended on the internal liquid crystalline structure and chemical composition. For example, F127 adsorbed to the surface of the bulk phytantriol cubic phase, while for monoolein cubic phase, F127 was integrated into the liquid crystalline structure. Last, the interfacial adsorption behavior of the dispersed liquid crystalline particles also depended on both the internal nanostructure and the chemical composition, despite the dispersions all being stabilized using F127. The findings highlight the need to understand the specific surface characteristics and the nature of the interaction with colloidal stabilizer for understanding and optimizing the behavior of nonlamellar liquid crystalline systems in surface delivery applications.

  10. Synthesis and characterization of liquid-crystalline supramolecular architecture by a combination of molecular recognition and polymerization reaction

    NASA Astrophysics Data System (ADS)

    Ahn, Cheol-Hee

    In nature, self-assembly with well defined shapes obtained from combinations of polymeric building blocks with complex architecture are abundant since they are responsible for the production of structural materials and for the generation of some of the most efficient mechanisms. One of the many roles liquid crystallinity plays in natural systems is in their self-assembly and organization. The assembly of these complex natural systems is largely under thermodynamic control which is manipulated by their liquid crystallinity. The goal of this thesis is to use Nature as a model for the development of new synthetic concepts and strategies in the field of polymer science. The two models selected are rod-like and icosahedral viruses. The strategy involved in this thesis requires the design of libraries of monodendritic building blocks with well defined flat tapered and conical shapes which self-assemble into cylindrical and respectively spherical shapes. By analogy with viruses these supermolecules will generated hexagonal columnar and spherical cubic thermotropic phases. These liquid crystalline phases allow the determination of their shape by X-ray diffraction and Scanning Force Microscopy. Libraries of flat tapered and conical monodendritic building blocks will be functionalized with polymerizable groups and polymerized to generate the first examples of polymers of cylindrical and spherical shapes with diameter and length, and diameter controlled at the nanoscale level. The organization of these dendritic monomers in a liquid crystalline assembly is also used to aggregate their polymerizable groups in a reactor of artificially enhanced concentration and restricted geometry during the polymerization process and therefore, generate a new approach to the control of polymerization. The resulting liquid crystallinity provides access to the thermodynamically controlled assembly and characterization of these newly developed polymers. With few exceptions, there is no precedent

  11. Liquid-Crystalline Ionic Liquids as Ordered Reaction Media for the Diels-Alder Reaction.

    PubMed

    Bruce, Duncan W; Gao, Yanan; Canongia Lopes, José Nuno; Shimizu, Karina; Slattery, John M

    2016-11-02

    Liquid-crystalline ionic liquids (LCILs) are ordered materials that have untapped potential to be used as reaction media for synthetic chemistry. This paper investigates the potential for the ordered structures of LCILs to influence the stereochemical outcome of the Diels-Alder reaction between cyclopentadiene and methyl acrylate. The ratio of endo- to exo-product from this reaction was monitored for a range of ionic liquids (ILs) and LCILs. Comparison of the endo:exo ratios in these reactions as a function of cation, anion and liquid crystallinity of the reaction media, allowed for the effects of liquid crystallinity to be distinguished from anion effects or cation alkyl chain length effects. These data strongly suggest that the proportion of exo-product increases as the reaction media is changed from an isotropic IL to a LCIL. A detailed molecular dynamics (MD) study suggests that this effect is related to different hydrogen bonding interactions between the reaction media and the exo- and endo-transition states in solvents with layered, smectic ordering compared to those that are isotropic.

  12. Active Mesogenic Droplets: Impact of Liquid Crystallinity and Collective Behavior

    NASA Astrophysics Data System (ADS)

    Bahr, Christian

    Droplets of common mesogenic compounds show a self-propelled motion when immersed in aqueous solutions containing ionic surfactants at concentrations well above the critical micelle concentration. After introducing some general properties of this type of artificial microswimmer, we focus on two topics: the influence of liquid crystallinity on the swimming behavior and the collective behavior of ensembles of a larger number of droplets. The mesogenic properties are not essential for the basic mechanism of self-propulsion, nevertheless they considerably influence the swimming behavior of the droplets. For instance, the shape of the trajectories strongly depends on whether the droplets are in the nematic or isotropic state. The droplet swimmers are also ideally suited for the study of collective behavior: Microfluidics enables the generation of large numbers of identical swimmers and we can tune their buoyancy. We report on the collective behavior in three-dimensional environments. Supported by the Deutsche Forschungsgemeinschaft (SPP 1726 ``Microswimmers'').

  13. Liquid-Crystalline Mesophases of Plasmid DNA in Bacteria

    NASA Astrophysics Data System (ADS)

    Reich, Ziv; Wachtel, Ellen J.; Minsky, Abraham

    1994-06-01

    Bacterial plasmids may often reach a copy number larger than 1000 per cell, corresponding to a total amount of DNA that may exceed the amount of DNA within the bacterial chromosome. This observation highlights the problem of cellular accommodation of large amounts of closed-circular nucleic acids, whose interwound conformation offers negligible DNA compaction. As determined by x-ray scattering experiments conducted on intact bacteria, supercoiled plasmids segregate within the cells into dense clusters characterized by a long-range order. In vitro studies performed at physiological DNA concentrations indicated that interwound DNA spontaneously forms liquid crystalline phases whose macroscopic structural properties are determined by the features of the molecular supercoiling. Because these features respond to cellular factors, DNA supercoiling may provide a sensitive regulatory link between cellular parameters and the packaging modes of interwound DNA in vivo.

  14. Photoinduced Plasticity in Cross-Linked Liquid Crystalline Networks.

    PubMed

    McBride, Matthew K; Hendrikx, Matthew; Liu, Danqing; Worrell, Brady T; Broer, Dirk J; Bowman, Christopher N

    2017-02-24

    Photoactivated reversible addition fragmentation chain transfer (RAFT)-based dynamic covalent chemistry is incorporated into liquid crystalline networks (LCNs) to facilitate spatiotemporal control of alignment, domain structure, and birefringence. The RAFT-based bond exchange process, which leads to stress relaxation, is used in a variety of conditions, to enable the LCN to achieve a near-equilibrium structure and orientation upon irradiation. Once formed, and in the absence of subsequent triggering of the RAFT process, the (dis)order in the LCN and its associated birefringence are evidenced at all temperatures. Using this approach, the birefringence, including the formation of spatially patterned birefringent elements and surface-active topographical features, is selectively tuned by adjusting the light dose, temperature, and cross-linking density.

  15. Structure and elastic properties of smectic liquid crystalline elastomer films.

    PubMed

    Stannarius, R; Köhler, R; Dietrich, U; Lösche, M; Tolksdorf, C; Zentel, R

    2002-04-01

    Mechanical measurements, x-ray investigations, and optical microscopy are employed to characterize the interplay of chemical composition, network topology, and elastic response of smectic liquid crystalline elastomers (LCEs) in various mesophases. Macroscopically ordered elastomer films of submicrometer thicknesses were prepared by cross linking freely suspended smectic polymer films. The cross-linked material preserves the mesomorphism and phase transitions of the precursor polymer. The elastic response of the smectic LCE is entropic, and the corresponding elastic moduli are of the order of MPa. In the tilted ferroelectric smectic-C* phase, the network structure plays an important role. Due to the coupling of elastic network deformations to the orientation of the mesogenic groups in interlayer cross-linked materials (mesogenic cross-linker units), the stress-strain characteristics is found to differ qualitatively from that in the other phases.

  16. Liquid crystalline pattern formation in drying droplets of biopolymers

    NASA Astrophysics Data System (ADS)

    Smalyukh, Ivan; Zribi, Olena; Butler, John; Lavrentovich, Oleg; Wong, Gerard

    2006-03-01

    When a droplet of DNA in water dries out, a ring-like deposit is observed along the perimeter, similar to the stains in spilled drops of coffee. However, the dried ring of DNA is a self-similar birefringent pattern composed of extended molecules. We examine dynamics of the pattern formation at the droplet's rim. This gives us an insight into the underlining physics. During the major part of drying process the contact line is pinned so that DNA molecules are brought to the perimeter and extended by the radial capillary flow. Lyotropic nematic phase is formed in which highly concentrated DNA aligns along the triple line to minimize elastic energy. When the contact angle becomes small, the contact line starts to retract and the radial dilative stress causes buckling distortions at the rim which then propagate deep into the elastic liquid- crystalline medium and give rise to the pattern.

  17. Regiospecific synthesis of tetrasubstituted phthalocyanines and their liquid crystalline order.

    PubMed

    Apostol, Petru; Bentaleb, Ahmed; Rajaoarivelo, Mbolotiana; Clérac, Rodolphe; Bock, Harald

    2015-03-28

    Metal-free and metal(II) all-endo-tetraalkoxy-phthalocyanines of C4h symmetry are synthesised regiospecifically from 3-(2-butyloctyloxy)phthalonitrile with lithium octanolate and subsequent metal ion exchange. The voluminous, yet not overly large, and racemically disordered alkoxy substituent not only renders the cyclotetramerisation regiospecific, but also leads to liquid crystalline self-assembly with attainable clearing temperatures and persisting columnar organisation at room temperature. A rare hexagonal mesophase with twelve columns per hexagonal unit cell is found in the metal-free homologue, whereas the metal complexes show rectangular mesophases. The clearing temperature increases with increasing axial component of the metal ion coordination sphere. At low temperature, significant antiferromagnetic exchange between magnetic centres is observed for the Co(II) homologue, whereas the magnetic centres are magnetically independent in the Cu(II) derivative, in line with the observed higher clearing temperature in the Co(II) case that testifies of stronger interdisk interactions.

  18. Volume phase transitions of cholesteric liquid crystalline gels

    SciTech Connect

    Matsuyama, Akihiko

    2015-05-07

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.

  19. Tailoring liquid crystalline lipid nanomaterials for controlled release of macromolecules.

    PubMed

    Bisset, Nicole B; Boyd, Ben J; Dong, Yao-Da

    2015-11-10

    Lipid-based liquid crystalline materials are being developed as drug delivery systems. However, the use of these materials for delivery of large macromolecules is currently hindered by the small size of the water channels in these structures limiting control over diffusion behaviour. The addition of the hydration-modulating agent, sucrose stearate, to phytantriol cubic phase under excess water conditions incrementally increased the size of these water channels. Inclusion of oleic acid enabled further control of swelling and de-swelling of the matrix via a pH triggerable system where at low pH the hexagonal phase is present and at higher pH the cubic phase is present. Fine control over the release of various sized model macromolecules is demonstrated, indicating future application to controlled loading and release of large macromolecules such as antibodies. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Influence of polymorphism on charge transport properties in isomers of fluorenone-based liquid crystalline semiconductors.

    PubMed

    Lincker, Frédéric; Attias, André-Jean; Mathevet, Fabrice; Heinrich, Benoît; Donnio, Bertrand; Fave, Jean-Louis; Rannou, Patrice; Demadrille, Renaud

    2012-03-28

    We measured the charge carrier mobilities for two isomers of fluorenone-based liquid crystalline organic semiconductors from their isotropic down to crystalline states through one or two mesophases. Improved charge transport properties of melt-processed crystalline films were obtained for the isomer exhibiting a highly ordered mesophase below its disordered smectic phase. This journal is © The Royal Society of Chemistry 2012

  1. Influence of chlorhexidine species on the liquid crystalline structure of vehicle.

    PubMed

    Farkas, E; Zelkó, R; Török, G; Rácz, I; Marton, S

    2001-02-01

    The aim of this study was to investigate the influence of three chlorhexidine species, chlorhexidine base and its salts (diacetate and digluconate), on the physico-chemical features of liquid crystalline systems and on drug transport through lipophilic membranes. Nonionic surfactant, Synperonic A7 (PEG(7)-C(13--15)) was selected for the preparation of the liquid crystalline systems. Mixtures of different ratios of Synperonic A7 and water were prepared. The liquid crystalline systems were characterized using polarizing microscopy, small-angle neutron scattering and transmission electron microscopy. Membrane transport was also examined. The addition of chlorhexidine species to the liquid crystalline system modified the structure of the liquid crystalline system. As a result of liquid crystal--drug interaction, the solubility of chlorhexidine base and its diffusion through lipophilic membranes increased in comparison with those of the chlorhexidine salts.

  2. Kinetics of the crystalline-liquid crystalline phase transition of dimyristoyl L-alpha-lecithin bilayers.

    PubMed

    Tsong, T Y

    1974-07-01

    Aqueous dispersions of synthetic dimyristoyl L-alpha-lecithin undergo a sharp decrease in turbidity in the temperature range where the crystalline-liquid crystalline phase transition occurs. Equilibrium transition curves, monitored by the absorbancy change at 300 nm, reproduce all the important features of a calorimetric melting curve [Hinz & Sturtevant (1972) J. Biol. Chem. 247, 6071]. A rapid temperature-jump of the dispersion, measured by the same absorbancy change, has detected several different molecular processes depending on the magnitude of the perturbation. These processes include a phase transition, permeation of ions and water across the membrane, and repture, annealing, or fusion of the bilayer structures. When the temperature-jump is limited to 1 degree, only reactions associated with the phase transition are detectable and no signal is generated after a temperature-jump except for those which end within or extend beyond the transition zones. At least two relaxation times are resolved for the phase transition reactions. The faster one in the millisecond time range is strongly temperature-dependent and has an activation energy close to one million calories per mole. The second one, in the 100-msec time range, appears to have a much smaller activation energy. These observations indicate that strongly cooperative nucleation processes and energy-dependent fast propagation steps occur during the phase transition. Since the kinetics of the transition are complex, intermediate state or transient structures must exist in the transition regions of the bilayer dispersions. These thermal fluctuations of the bilayer structures may have important effects on the lateral diffusion and permeation of molecules and ions in the membrane structure.

  3. Kinetics of the Crystalline-Liquid Crystalline Phase Transition of Dimyristoyl L-α-Lecithin Bilayers

    PubMed Central

    Tsong, Tian Yow

    1974-01-01

    Aqueous dispersions of synthetic dimyristoyl L-α-lecithin undergo a sharp decrease in turbidity in the temperature range where the crystalline-liquid crystalline phase transition occurs. Equilibrium transition curves, monitored by the absorbancy change at 300 nm, reproduce all the important features of a calorimetric melting curve [Hinz & Sturtevant (1972) J. Biol. Chem. 247, 6071]. A rapid temperature-jump of the dispersion, measured by the same absorbancy change, has detected several different molecular processes depending on the magnitude of the perturbation. These processes include a phase transition, permeation of ions and water across the membrane, and repture, annealing, or fusion of the bilayer structures. When the temperature-jump is limited to 1 degree, only reactions associated with the phase transition are detectable and no signal is generated after a temperature-jump except for those which end within or extend beyond the transition zones. At least two relaxation times are resolved for the phase transition reactions. The faster one in the millisecond time range is strongly temperature-dependent and has an activation energy close to one million calories per mole. The second one, in the 100-msec time range, appears to have a much smaller activation energy. These observations indicate that strongly cooperative nucleation processes and energy-dependent fast propagation steps occur during the phase transition. Since the kinetics of the transition are complex, intermediate state or transient structures must exist in the transition regions of the bilayer dispersions. These thermal fluctuations of the bilayer structures may have important effects on the lateral diffusion and permeation of molecules and ions in the membrane structure. Images PMID:4527862

  4. Review of crystalline structures of some selected homologous series of rod-like molecules capable of forming liquid crystalline phases.

    PubMed

    Zugenmaier, Peter

    2011-01-01

    The crystal structures of four homologous series of rod-like molecules are reviewed, two of which form hydrogen bonds and two with a symmetric chemical constitution. Many of the compounds investigated turn into liquid crystalline phases upon temperature increase. It is of valuable interest to know possible conformations and possible packing arrangements as prerequisites to model liquid crystalline structures. The hydrogen bonds of homologous series of pure 4-(ω-hydroxyalkyloxy)-4'-hydroxybiphenyl (HnHBP, n the alkyloxy tail length) are realized through head to tail arrangements of the hydroxyl groups and crystallize except one compound in chiral space groups without the molecules containing any asymmetric carbon. The hydrogen bonds of the homologous series of 4-substituted benzoic acids with various lengths of the tail provide dimers through strong polar bonding of adjacent carboxyl groups and thus provide the stiff part of a mesogenic unit prerequisite for liquid crystalline phases. The homologous series of dialkanoyloxybiphenyls (BP-n, n = 1, 19), of which nine compounds could be crystallized, show liquid crystalline behavior for longer alkane chain lengths, despite the high mobility of the alkane chain ends already detectable in the crystal phase. A single molecule, half a molecule or two half molecules form the asymmetric unit in a centrosymmetric space group. The homologous series of 1,4-terephthalidene-bis-N-(4'-n-alkylaniline) (TBAA-n) exhibit a large variety of packing arrangements in the crystalline state, with or without relying on the symmetry center within the molecules.

  5. Thermal Characterization of Thermotropic Nematic Liquid-Crystalline Elastomers

    NASA Astrophysics Data System (ADS)

    Thomas, David; Cardarelli, Matt; Sanchez-Ferrer, Antoni; Mbanga, Badel L.; Atherton, Timothy J.; Cebe, Peggy

    Nematic Liquid-Crystallline Elastomers (LCEs) are weakly crosslinked polymeric networks that exhibit rubber elasticity and liquid-crystalline orientational order due to the presence of mesogenic groups. Three end-on side-chain nematic LCEs were investigated using real-time synchrotron wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and thermogravimetry (TG) to correlate thermal behavior with structural and chemical differences among them. The elastomers differed in crosslinking density and mesogen composition. Thermally reversible glass transition temperature, Tg, and nematic-to-isotropic transition temperature, Tni, were observed upon heating and cooling for all samples. By varying the heating rate, Tg0 and Tni0 were determined at zero heating rate. The temperature dependence of the orientational order parameter was determined from the anisotropic azimuthal angular distribution of the equatorial reflection seen during real-time WAXS experiments. Our results show that the choice of crosslinking unit, its shape, density, as well as the structure of co-monomers, all influence the temperature range over which the thermal transitions take place.

  6. Enantioselective separations using chiral supported liquid crystalline membranes.

    PubMed

    Han, Sangil; Rabie, Feras; Marand, Eva; Martin, Stephen M

    2012-07-01

    Porous and nonporous supported liquid crystalline membranes were produced by impregnating porous cellulose nitrate supports with cholesteric liquid crystal (LC) materials consisting of 4-cyano-4'-pentylbiphenyl (5CB) mixed with a cholesterol-based dopant (cholesteryl oleyl carbonate [COC], cholesteryl nonanoate [CN], or cholesteryl chloride [CC]). The membranes exhibit selectivity for R-phenylglycine and R-1-phenylethanol because of increased interactions between the S enantiomers and the left-handed cholesteric phase. The selectivity of both phenylglycine and 1-phenylethanol in 5CB/CN membranes decreases with effective pore diameter while the permeabilities increase, as expected. Phenylglycine, which is insoluble in the LC phase, exhibits no transport in the nonporous (completely filled) membranes; however, 1-phenylethanol, which is soluble in the LC phase, exhibits transport but negligible enantioselectivity. The enantioselectivity for 1-phenylethanol was higher (1.20 in 5CB/COC and 5CB/CN membranes) and the permeability was lower in the cholesteric phase than in the isotropic phase. Enantioselectivity was also higher in the 5CB/COC cholesteric phase than in the nematic phase of undoped 5CB (1.03). Enantioselectivity in the cholesteric phase of 5CB doped with CC (1.1), a dopant lacking hydrogen bonding groups, was lower than in the 5CB/COC phases. Finally, enantioselectivity increases with the dopant concentration up to a plateau value at approximately 17 mol%.

  7. Effect of matrix crystallinity on the ionic conductivity in microstructured block copolymer solid electrolytes

    NASA Astrophysics Data System (ADS)

    Young, Nicholas; Balsara, Nitash

    2012-02-01

    Polyethylene oxide (PEO)-based block copolymers have been studied extensively for use as solid electrolytes for rechargeable lithium metal batteries. Previous work has concentrated on block copolymers containing an amorphous second block, such as polystyrene, for which the modulus is sufficiently high to resist growth of dendrites that would lead to short circuiting. In this work, we instead focus on using semicrystalline polyethylene as the mechanically robust component. Polyethylene-polyethylene oxide (EEO) block copolymers doped with lithium bis(trifluoromethanesulfone) imide (LiTFSI) were characterized using AC impedance spectroscopy over a range of temperature, molecular weight, and composition values in order to determine the effect of crystallinity in the structural microphase on the conductivity of this material.

  8. Single crystalline Ge(1-x)Mn(x) nanowires as building blocks for nanoelectronics.

    PubMed

    van der Meulen, Machteld I; Petkov, Nikolay; Morris, Michael A; Kazakova, Olga; Han, Xinhai; Wang, Kang L; Jacob, Ajey P; Holmes, Justin D

    2009-01-01

    Magnetically doped Si and Ge nanowires have potential application in future nanowire spin-based devices. Here, we report a supercritical fluid method for producing single crystalline Mn-doped Ge nanowires with a Mn-doping concentration of between 0.5-1.0 atomic % that display ferromagnetism above 300 K and a superior performance with respect to the hole mobility of around 340 cm(2)/Vs, demonstrating the potential of using these nanowires as building blocks for electronic devices.

  9. Liquid crystalline phases and their dispersions in aqueous mixtures of glycerol monooleate and glyceryl monooleyl ether.

    PubMed

    Popescu, Georgeta; Barauskas, Justas; Nylander, Tommy; Tiberg, Fredrik

    2007-01-16

    The aqueous phase behavior of mixtures of 1-glycerol monooleate (GMO) and its ether analogue, 1-glyceryl monooleyl ether (GME) has been investigated by a combination of polarized microscopy, X-ray diffraction, and NMR techniques. Three phase diagrams of the ternary GMO/GME/water system have been constructed at 25, 40, and 55 degrees C. The results demonstrate that the increasing amount of GME favors the formation of the reversed phases, evidenced by the transformation of the lamellar and bicontinuous cubic liquid crystalline phases of the binary GMO/water system into reversed micellar or reversed hexagonal phases. For a particular liquid crystalline phase, increasing the GME content has no effect on the structural characteristics and hydration properties, thus suggesting ideal mixing with GMO. Investigations of dispersed nanoparticle samples using shear and a polymeric stabilizer, Pluronic F127, show the possibility of forming two different kinds of bicontinuous cubic phase nanoparticles by simply changing the GMO/GME ratio. Also NMR self-diffusion measurements confirm that the block copolymer, Pluronic F127, used to facilitate dispersion formation, is associated with nanoparticles and provides steric stabilization.

  10. Liquid Crystalline Copolymers of Monomer-Pairs Containing Mesogenic Units Which Exhibit Constitutional Isomerism.

    DTIC Science & Technology

    1987-01-01

    thylenic units presents a smectic A or C mesophase. None of these polymers exhibited side-chain crystallization . INTRODUCTION Side-chain liquid ...isomers, leads to liquid crystalline copoly- mers which do not undergo side-chain crystallization . A quantitative under- standing of these copolymers...D-13 449 LIQUID CRYSTALLINE COPOLYMERS OF ONOER-PIRS 1/1 I CONTAINING NESOGENI UNITS..(U) CASE WESTERN RESERVE UNIV CLEVELAND ON DEPT OF

  11. Liquid Crystalline Polymers and Networks -- orientation, molecular shape change, mechanics

    NASA Astrophysics Data System (ADS)

    Warner, Mark

    2008-03-01

    In a prescient paper of 1969, Pierre-Gilles de Gennes envisaged both liquid crystal polymers and elastomers. 10 years later, these systems were realised. After 25 years, monodomain elastomers were prepared and displayed phenomena he had predicted: rods incorporated into polymers induce liquid crystallinity in polymer melts and elastomers; orientational order causes shape changes in the back bones of such polymers; mechanical ramifications follow in networks, e.g. spontaneous elongations and contractions on changing order. The latter are proposed as the basis of micro-actuation and artificial muscles, both heat and light-driven. In 1969, de Gennes already described ideal networks heated through the nematic-isotropic transition losing all their order by mechanical relaxation. It is not obvious, but is true in theory and largely in experiment, even in highly non-ideal networks. He also envisaged that a cholesteric network, where there is a topological memory of chirality imprinted by crosslinking chains in a twisted state. Chirality cannot relax away on entering the isotropic phase, even in systems without molecular chirality (for instance those crosslinked in the presence of chiral solvent that is subsequently exchanged away). His chiral elastomers have found application as mechanically-tuneable, rubber lasers. De Gennes also constructed the first continuum elastic theories of nematic elastomers (1982), though distortions are generally very large. His elasticity has informed non-linear elasticity that works even at large amplitudes. I shall describe de Gennes' many contributions, and the current state of a field that has since yielded still more remarkable phenomena.

  12. Giant lateral electrostriction in ferroelectric liquid-crystalline elastomers.

    PubMed

    Lehmann, W; Skupin, H; Tolksdorf, C; Gebhard, E; Zentel, R; Krüger, P; Lösche, M; Kremer, F

    2001-03-22

    Mechanisms for converting electrical energy into mechanical energy are essential for the design of nanoscale transducers, sensors, actuators, motors, pumps, artificial muscles, and medical microrobots. Nanometre-scale actuation has to date been mainly achieved by using the (linear) piezoelectric effect in certain classes of crystals (for example, quartz), and 'smart' ceramics such as lead zirconate titanate. But the strains achievable in these materials are small--less than 0.1 per cent--so several alternative materials and approaches have been considered. These include grafted polyglutamates (which have a performance comparable to quartz), silicone elastomers (passive material--the constriction results from the Coulomb attraction of the capacitor electrodes between which the material is sandwiched) and carbon nanotubes (which are slow). High and fast strains of up to 4 per cent within an electric field of 150 MV x m(-1) have been achieved by electrostriction (this means that the strain is proportional to the square of the applied electric field) in an electron-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer. Here we report a material that shows a further increase in electrostriction by two orders of magnitude: ultrathin (less than 100 nanometres) ferroelectric liquid-crystalline elastomer films that exhibit 4 per cent strain at only 1.5 MV x m(-1). This giant electrostriction was obtained by combining the properties of ferroelectric liquid crystals with those of a polymer network. We expect that these results, which can be completely understood on a molecular level, will open new perspectives for applications.

  13. Drug Release and Skin Permeation from Lipid Liquid Crystalline Phases

    NASA Astrophysics Data System (ADS)

    Costa-Balogh, F. O.; Sparr, E.; Sousa, J. J. S.; Pais, A. A. C. C.

    We have studied drug release and skin permeation from several different liquid crystalline lipid formulations that may be used to control the respective release rates. We have studied the release and permeation through human skin of a water-soluble and amphiphilic drug, propranolol hydrochloride, from several formulations prepared with monoolein and phytantriol as permeation enhancers and controlled release excipients. Diolein and cineol were added to selected formulations. We observed that viscosity decreases with drug load, wich is compatible with the occurrence of phase changes. Diolein stabilizes the bicontinuous cubic phases leading to an increase in viscosity and sustained release of the drug. The slowest release was found for the cubic phases with higher viscosity. Studies on skin permeation showed that these latter formulations also presented lower permeability than the less viscous monoolein lamellar phases. Formulations containing cineol originated higher permeability with higher enhancement ratios. Thus, the various formulations are adapted to different circumstances and delivery routes. While a slow release is usually desired for drug sustained delivery, the transdermal route may require a faster release. Lamellar phases, which are less viscous, are more adapted to transdermal applications. Thus, systems involving lamellar phases of monoolein and cineol are good candidates to be used as skin permeation enhancers for propranolol hydrochloride.

  14. New cyanopyridone based luminescent liquid crystalline materials: synthesis and characterization.

    PubMed

    N, Ahipa T; Adhikari, Airody Vasudeva

    2014-11-01

    A new series of 4-(3,4-bis(akyloxy)phenyl)-6-(4-((1-(4-cyano- or 4-nitro-benzyl)-1H-1,2,3-triazol-4-yl)methoxy)phenyl)-2-oxo-1,2-dihydropyridine-3-carbonitriles carrying terminal di-alkoxy chain lengths (viz. octyloxy, decyloxy, dodecyloxy, tetradecyloxy and hexadodecyloxy) as well as terminal polar groups -CN or -NO2 have been designed and synthesized successfully as luminescent mesogens. Their thermotropic behaviors have been studied by means of differential scanning calorimetry and polarized optical microscopy. The supramolecular organizations in them were explored by the temperature dependent X-ray diffraction method and their photophysical properties were investigated using UV-visible and fluorescence spectral methods. The mesogenic study reveals that the presence of hydrogen bonds, as well as dimerization between the molecules, is mainly responsible for the formation of the ambient temperature hexagonal columnar phase (Colh) in the new molecules. Their photophysical study indicates that the compounds exhibit a strong absorption band at ∼370 nm and a blue emission band at ∼466 nm with good quantum yields of ∼0.62 when compared to quinine sulphate (Φf = 0.54) in chloroform. Also, the compounds show a slightly red shift in the absorption band with increased solvent polarity. In liquid crystalline films, they display a bathochromic shift in the emission band because of the intimate overlap of molecular cores in the hexagonal columnar phase.

  15. Sustained release of methotrexate through liquid-crystalline folate nanoparticles.

    PubMed

    Misra, Rahul; Mohanty, Sanat

    2014-09-01

    To make chemotherapy more effective, sustained release of the drug is desirable. By controlling the release rates, constant therapeutic levels can be achieved which can avoid re-administration of drug. This helps to combat tumors more effectively with minimal side effects. The present study reports the control release of methotrexate through liquid-crystalline folate nanoparticles. These nanoparticles are composed of highly ordered folate self-assembly which encapsulate methotrexate molecules. These drug molecules can be released in a controlled manner by disrupting this assembly in the environment of monovalent cations. The ordered structure of folate nanoparticles offers low drug losses of about 4-5%, which is significant in itself. This study reports the size-control method of forming methotrexate encapsulated folate nanoparticles as well as the release of methotrexate through these nanoparticles. It has been demonstrated that methotrexate release rates can be controlled by controlling the size of the nanoparticles, cross-linking cation and cross-linking concentration. The effect of different factors like drug loading, release medium, and pH of the medium on methotrexate release rates was also studied.

  16. Molecular structure and liquid-crystalline characteristics of chitosan phenylcarbamate.

    PubMed

    Kuse, Yasunori; Asahina, Daisuke; Nishio, Yoshiyuki

    2009-01-12

    Chitosan phenylcarbamate (CtsPC) samples were synthesized to have different degrees of substitution (DS) ranging from approximately 2.7 to approximately 3.7, and the lyotropic liquid crystallinity was mainly characterized by spectrophotometry. The products of DS>2.8 formed a cholesteric type of mesophase in concentrated solutions of >44 wt % with polar aprotic solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO), and some of the solutions imparted vivid colorations because of selective visible light reflection. The cholesteric helical pitch increased with increasing temperature and with decreasing polymer concentration, but the helical sense remained left-handed under the adopted measurement conditions. It was also found that the helical pitch increased in proportion to the increment of DS, whereas an average degree of phenylcarbamoyl polyaddition in the side chains (DPs) rather affected the pitch distribution measuring an orderliness in the cholesteric structure. With a small increase in DPs (e.g., from 1.01 to 1.04), the cholesteric orderliness decreased and the temperature sensitivity of the pitch turned sluggish. Wide-angle X-ray diffractometry was also used for evaluating the distance and azimuth difference between adjacent nematic thin layers in the cholesteric mesophase.

  17. A least squares closure approximation for liquid crystalline polymers

    NASA Astrophysics Data System (ADS)

    Sievenpiper, Traci Ann

    2011-12-01

    An introduction to existing closure schemes for the Doi-Hess kinetic theory of liquid crystalline polymers is provided. A new closure scheme is devised based on a least squares fit of a linear combination of the Doi, Tsuji-Rey, Hinch-Leal I, and Hinch-Leal II closure schemes. The orientation tensor and rate-of-strain tensor are fit separately using data generated from the kinetic solution of the Smoluchowski equation. The known behavior of the kinetic solution and existing closure schemes at equilibrium is compared with that of the new closure scheme. The performance of the proposed closure scheme in simple shear flow for a variety of shear rates and nematic polymer concentrations is examined, along with that of the four selected existing closure schemes. The flow phase diagram for the proposed closure scheme under the conditions of shear flow is constructed and compared with that of the kinetic solution. The study of the closure scheme is extended to the simulation of nematic polymers in plane Couette cells. The results are compared with existing kinetic simulations for a Landau-deGennes mesoscopic model with the application of a parameterized closure approximation. The proposed closure scheme is shown to produce a reasonable approximation to the kinetic results in the case of simple shear flow and plane Couette flow.

  18. Theoretical models for the dynamics of liquid crystalline polymers

    NASA Astrophysics Data System (ADS)

    Chaubal, Charu Vaman

    The research encompassed by this work aims to improve the understanding of the physical behavior embodied by the Doi theory of Liquid Crystalline Polymers (LCPs), to develop more accurate, efficient, and robust numerical and computational schemes to obtain theoretical predictions, and to extend the model to describe industrially relevant LCP systems more closely. The mechanisms behind the unusual phenomena exhibited by the Doi theory in simple shear flow is examined by performing nonlinear systems analysis of an approximated version of the theory. A more accurate approximation to the theory is developed and is shown to faithfully reproduce results from the unapproximated theory over a wide range of parameters. A novel solution algorithm for general polymer kinetic theory problems, based on particle methods, is presented and analyzed in the context of application to the Doi theory. This technique is used to study the behavior of LCPs in shear flow and to determine how slight perturbations of simple shear can lead to dramatic changes in dynamical and rheological properties. Finally, the nematic broken rod model for flexible LCPs is developed and the behavior of the model in simple shear flow is explored for both highly flexible and nearly rigid rods.

  19. Molecular weight effect on liquid crystalline gel formation of curdlan.

    PubMed

    Nobe, Masahiro; Kuroda, Naomi; Dobashi, Toshiaki; Yamamoto, Takao; Konno, Akira; Nakata, Mitsuo

    2005-01-01

    Curdlan dissolved in alkaline solution forms a unique gel consisting of liquid crystalline gel (LCG) and amorphous gel (AG) in alternating layers by a dialysis into aqueous calcium chloride. The unique structure has been investigated by measuring the birefringence of the gel Deltan, the ratio q of the thickness of LCG layer delta to the gel radius R, and the calcium content in the gel C(Ca) in a wide range of molecular weights of fractionated Curdlan, as well as unfractionated Curdlan as a control. With increasing molecular weight of Curdlan, Deltan increased and q = delta/R decreased, and both became saturated at high molecular weight. Deltan and q for unfractionated Curdlan were smaller and larger, respectively, than those for fractionated Curdlan. C(Ca) was constant irrespective of molecular weight and its distribution, which means that the abundance of calcium ions per glucose unit in the gel does not depend on the degree of orientation of mesogens. These results suggest that the amorphous phase appears when the size of the Curdlan molecules is larger than the average intermolecular distance, resulting from the random coil to triple helix transformation of Curdlan molecules associated with lowering hydroxide anion concentration in the dialysis process.

  20. Water quantitatively induces the mucoadhesion of liquid crystalline phases of glyceryl monooleate.

    PubMed

    Lee, J; Young, S A; Kellaway, I W

    2001-05-01

    The possible role of water in the mucoadhesion phenomenon exhibited by the liquid crystalline phases of glyceryl monooleate was investigated using an in-vitro tensile strength technique. The mucoadhesion of the liquid crystalline phases of glyceryl monooleate was found to occur following uptake of water. The mucoadhesive force of the cubic phase was consistent since it is not capable of taking up additional water. An increase in pre-load period greatly facilitated the mucoadhesion of glyceryl monooleate (0% w/w initial water content), suggesting that the mucoadhesion is dependent upon the extent of the dehydration of the substrate. A good linear relationship between initial water content of the liquid crystalline phases and mucoadhesive force led to the conclusion that the mucoadhesive force increased with decreasing initial water concentration. Rheological properties of the liquid crystalline phases were also studied to allow a correlation between physical changes and mucoadhesion of the liquid crystalline phases, revealing that higher water concentrations in the liquid crystalline phases led to a more ordered structure that showed less mucoadhesion. The results of this study indicated that the mucoadhesive force of the liquid crystalline phases of glyceryl monooleate is determined by the capability to take up water from a water-rich environment. It may, therefore, be advantageous to use the lamellar phase as a buccal drug carrier as opposed to the relatively less mucoadhesive cubic phase.

  1. The effect of a cholesterol liquid crystalline structure on osteoblast cell behavior.

    PubMed

    Xu, Jian-Ping; Ji, Jian; Shen, Jia-Cong

    2009-04-01

    To investigate the effect of a liquid crystalline structure on cell behavior, polymethylsiloxane-graft-(10-cholesteryloxydecanol) was specially designed to get a thermotropic liquid crystalline polymer. Results of Fourier transform infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance (1H-NMR) spectroscopy and gel permeation chromatography (GPC) indicated that cholesterol was successfully covalently grafted onto polymethylhydrosiloxane via decamethylene 'flexible spacer'. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) investigations revealed that the copolymer with 44.9% mesogenic unit showed obvious thermotropic liquid crystalline transition at about 124.9 degrees C. Polymer films were prepared by spin coating on clean glass plates from 5 mg ml(-1) toluene solutions of the copolymers. The POM investigation indicated that while the unannealed films (SC15, SC45) showed no liquid crystalline structure, the films which were annealed in vacuo at 140 degrees C for 9 h and then quenched to room temperature (SC15C, SC45C) formed discrete island-like liquid crystalline and continuous liquid crystalline structures, respectively. Osteoblast cells (MC3T3) were chosen to test the cell behavior of annealed and unannealed films. In comparison to unannealed films, the annealed films with a cholesterol liquid crystalline structure could promote osteoblast cell attachment and growth significantly.

  2. 31 CFR 537.209 - Expenses of maintaining blocked property; liquidation of blocked account.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Expenses of maintaining blocked property; liquidation of blocked account. 537.209 Section 537.209 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE...

  3. 31 CFR 537.209 - Expenses of maintaining blocked property; liquidation of blocked account.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 31 Money and Finance:Treasury 3 2013-07-01 2013-07-01 false Expenses of maintaining blocked property; liquidation of blocked account. 537.209 Section 537.209 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE...

  4. 31 CFR 537.209 - Expenses of maintaining blocked physical property; liquidation of blocked property.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 31 Money and Finance:Treasury 3 2014-07-01 2014-07-01 false Expenses of maintaining blocked physical property; liquidation of blocked property. 537.209 Section 537.209 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF...

  5. 31 CFR 544.204 - Expenses of maintaining blocked physical property; liquidation of blocked property.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Expenses of maintaining blocked physical property; liquidation of blocked property. 544.204 Section 544.204 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF...

  6. 31 CFR 547.204 - Expenses of maintaining blocked physical property; liquidation of blocked property.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Expenses of maintaining blocked physical property; liquidation of blocked property. 547.204 Section 547.204 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF...

  7. 31 CFR 542.204 - Expenses of maintaining blocked property; liquidation of blocked property.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Expenses of maintaining blocked property; liquidation of blocked property. 542.204 Section 542.204 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE...

  8. 31 CFR 548.204 - Expenses of maintaining blocked physical property; liquidation of blocked property.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Expenses of maintaining blocked physical property; liquidation of blocked property. 548.204 Section 548.204 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF...

  9. 31 CFR 541.205 - Expenses of maintaining blocked property; liquidation of blocked account.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Expenses of maintaining blocked property; liquidation of blocked account. 541.205 Section 541.205 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE...

  10. 31 CFR 543.204 - Expenses of maintaining blocked physical property; liquidation of blocked property.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Expenses of maintaining blocked physical property; liquidation of blocked property. 543.204 Section 543.204 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF...

  11. 31 CFR 546.204 - Expenses of maintaining blocked physical property; liquidation of blocked property.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Expenses of maintaining blocked physical property; liquidation of blocked property. 546.204 Section 546.204 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF...

  12. 31 CFR 545.207 - Expenses of maintaining blocked property; liquidation of blocked account.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Expenses of maintaining blocked property; liquidation of blocked account. 545.207 Section 545.207 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE...

  13. 31 CFR 537.209 - Expenses of maintaining blocked property; liquidation of blocked account.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 31 Money and Finance:Treasury 3 2011-07-01 2011-07-01 false Expenses of maintaining blocked property; liquidation of blocked account. 537.209 Section 537.209 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE...

  14. Azobenzene-based organic salts with ionic liquid and liquid crystalline properties

    SciTech Connect

    Stappert, Kathrin; Muthmann, Johanna; Spielberg, Eike T.; Mudring, Anja -Verena

    2015-07-23

    Two sets of new azobenzene-based bromide salts are synthesized, and their thermal photochromic properties are studied. Both sets are based on the imidazolium cation. The first set (1) features a symmetric biscation where two imidazolium head groups (Im) with different alkyl chains (Cn) are connected to a central azobenzene unit (Azo): [Azo(C1-Im-Cn)2]; n = 6, 8, 10, 12, 14. The other one contains an n-alkyl-imidazolium cation (Cn-Im) bearing a terminal azobenzene unit (C1-Azo) substituted with an alkoxy chain (O-Cm) of either two (2) or six (3) carbon atoms: [C1-Azo-O-Cm-Im-Cn]; m = 2, n = 8, 10, 12 and m = 6, n = 8, 10, 12, 14, 16. For both cation classes, the influence of alkyl chains of varying length on the thermal phase behavior was investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). For five compounds (Azo(-C1-Im-C12)2 (1d), Azo(-C1-Im-C12)2 (1e), C1-Azo-O-C2-Im-C10 (2b), C1-Azo-O-C2-Im-C12 (2c), and C1-Azo-O-C6-Im-C16 (3e)), the formation of a liquid crystalline phase was observed. The biscationic salts (1) are all comparatively high melting organic salts (180–240 °C), and only the two representatives with long alkylchains (C12 and C14) exhibit liquid crystallinity. The monocationic salts with an O–C2 bridge (2) melt between 140 and 170 °C depending on the alkyl chain length, but from an alkyl chain of 10 and more carbon atoms on they form a smectic A liquid crystalline phase. The representatives of the third set with a O–C6 bridge qualify as ionic liquids with melting points less than 100 °C. However, only the representative with a hexadecyl chain forms a liquid crystalline phase. Representative single crystals for all sets of cations could be grown that allowed for single crystal structure analysis. Together with small-angle X-ray scattering experiments they allow for a more detailed understanding of the thermal properties. As a result, through irradiation with UV

  15. Azobenzene-based organic salts with ionic liquid and liquid crystalline properties

    DOE PAGES

    Stappert, Kathrin; Muthmann, Johanna; Spielberg, Eike T.; ...

    2015-07-23

    Two sets of new azobenzene-based bromide salts are synthesized, and their thermal photochromic properties are studied. Both sets are based on the imidazolium cation. The first set (1) features a symmetric biscation where two imidazolium head groups (Im) with different alkyl chains (Cn) are connected to a central azobenzene unit (Azo): [Azo(C1-Im-Cn)2]; n = 6, 8, 10, 12, 14. The other one contains an n-alkyl-imidazolium cation (Cn-Im) bearing a terminal azobenzene unit (C1-Azo) substituted with an alkoxy chain (O-Cm) of either two (2) or six (3) carbon atoms: [C1-Azo-O-Cm-Im-Cn]; m = 2, n = 8, 10, 12 and m =more » 6, n = 8, 10, 12, 14, 16. For both cation classes, the influence of alkyl chains of varying length on the thermal phase behavior was investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). For five compounds (Azo(-C1-Im-C12)2 (1d), Azo(-C1-Im-C12)2 (1e), C1-Azo-O-C2-Im-C10 (2b), C1-Azo-O-C2-Im-C12 (2c), and C1-Azo-O-C6-Im-C16 (3e)), the formation of a liquid crystalline phase was observed. The biscationic salts (1) are all comparatively high melting organic salts (180–240 °C), and only the two representatives with long alkylchains (C12 and C14) exhibit liquid crystallinity. The monocationic salts with an O–C2 bridge (2) melt between 140 and 170 °C depending on the alkyl chain length, but from an alkyl chain of 10 and more carbon atoms on they form a smectic A liquid crystalline phase. The representatives of the third set with a O–C6 bridge qualify as ionic liquids with melting points less than 100 °C. However, only the representative with a hexadecyl chain forms a liquid crystalline phase. Representative single crystals for all sets of cations could be grown that allowed for single crystal structure analysis. Together with small-angle X-ray scattering experiments they allow for a more detailed understanding of the thermal properties. As a result, through irradiation with UV-light (320–366 nm) all

  16. Effects of alkaline or liquid-ammonia treatment on crystalline cellulose: changes in crystalline structure and effects on enzymatic digestibility

    PubMed Central

    2011-01-01

    Background In converting biomass to bioethanol, pretreatment is a key step intended to render cellulose more amenable and accessible to cellulase enzymes and thus increase glucose yields. In this study, four cellulose samples with different degrees of polymerization and crystallinity indexes were subjected to aqueous sodium hydroxide and anhydrous liquid ammonia treatments. The effects of the treatments on cellulose crystalline structure were studied, in addition to the effects on the digestibility of the celluloses by a cellulase complex. Results From X-ray diffractograms and nuclear magnetic resonance spectra, it was revealed that treatment with liquid ammonia produced the cellulose IIII allomorph; however, crystallinity depended on treatment conditions. Treatment at a low temperature (25°C) resulted in a less crystalline product, whereas treatment at elevated temperatures (130°C or 140°C) gave a more crystalline product. Treatment of cellulose I with aqueous sodium hydroxide (16.5 percent by weight) resulted in formation of cellulose II, but also produced a much less crystalline cellulose. The relative digestibilities of the different cellulose allomorphs were tested by exposing the treated and untreated cellulose samples to a commercial enzyme mixture (Genencor-Danisco; GC 220). The digestibility results showed that the starting cellulose I samples were the least digestible (except for corn stover cellulose, which had a high amorphous content). Treatment with sodium hydroxide produced the most digestible cellulose, followed by treatment with liquid ammonia at a low temperature. Factor analysis indicated that initial rates of digestion (up to 24 hours) were most strongly correlated with amorphous content. Correlation of allomorph type with digestibility was weak, but was strongest with cellulose conversion at later times. The cellulose IIII samples produced at higher temperatures had comparable crystallinities to the initial cellulose I samples, but achieved

  17. Effects of alkaline or liquid-ammonia treatment on crystalline cellulose: changes in crystalline structure and effects on enzymatic digestibility.

    PubMed

    Mittal, Ashutosh; Katahira, Rui; Himmel, Michael E; Johnson, David K

    2011-10-19

    In converting biomass to bioethanol, pretreatment is a key step intended to render cellulose more amenable and accessible to cellulase enzymes and thus increase glucose yields. In this study, four cellulose samples with different degrees of polymerization and crystallinity indexes were subjected to aqueous sodium hydroxide and anhydrous liquid ammonia treatments. The effects of the treatments on cellulose crystalline structure were studied, in addition to the effects on the digestibility of the celluloses by a cellulase complex. From X-ray diffractograms and nuclear magnetic resonance spectra, it was revealed that treatment with liquid ammonia produced the cellulose IIII allomorph; however, crystallinity depended on treatment conditions. Treatment at a low temperature (25°C) resulted in a less crystalline product, whereas treatment at elevated temperatures (130°C or 140°C) gave a more crystalline product. Treatment of cellulose I with aqueous sodium hydroxide (16.5 percent by weight) resulted in formation of cellulose II, but also produced a much less crystalline cellulose. The relative digestibilities of the different cellulose allomorphs were tested by exposing the treated and untreated cellulose samples to a commercial enzyme mixture (Genencor-Danisco; GC 220). The digestibility results showed that the starting cellulose I samples were the least digestible (except for corn stover cellulose, which had a high amorphous content). Treatment with sodium hydroxide produced the most digestible cellulose, followed by treatment with liquid ammonia at a low temperature. Factor analysis indicated that initial rates of digestion (up to 24 hours) were most strongly correlated with amorphous content. Correlation of allomorph type with digestibility was weak, but was strongest with cellulose conversion at later times. The cellulose IIII samples produced at higher temperatures had comparable crystallinities to the initial cellulose I samples, but achieved higher levels of

  18. Identification of crystalline elastic anisotropy in PZT ceramics from in-situ blocking stress measurements

    SciTech Connect

    Daniel, L.; Hall, D. A.; Withers, P. J.; Webber, K. G.; King, A.

    2014-05-07

    High energy x-ray diffraction measurements of lattice strains were performed on a rhombohedral Lead Zirconate Titanate ceramic (PZT 55-45) under combinations of applied electric field and compressive stress. These measurements allow the construction of blocking stress curves for different sets of crystallographic orientations which reflect the single crystal elastic anisotropy. A micro-mechanical interpretation of the results is then proposed. Assuming cubic symmetry for the crystalline elastic stiffness tensor and isotropy for the macroscopic elastic properties, the elastic properties of the single crystal are extracted from the measured data. An anisotropy ratio close to 0.3 is found (compared to 1 for isotropic materials). The high level of anisotropy found in this work suggests that crystalline elastic anisotropy should not be neglected in the modelling of ferroelectric materials.

  19. Physics of liquid and crystalline plasmas: Future perspectives

    NASA Astrophysics Data System (ADS)

    Morfill, G. E.

    It has been shown that under certain conditions "complex plasmas" (plasma containing ions, electrons and charged microspheres) may undergo spontaneous phase changes to become liquid and crystalline, without recombination of the charge components. Hence these systems may be regarded as new plasma states "condensed plasmas". The ordering forces are mainly electrostatic, but dipolar effects, anisotropic pressure due shielding, ion flow focussing etc. may all play a role, too. Complex plasmas are of great interest from a fundamental research point of view because the individual particles of one plasma component (the charged microspheres) can be visualised and hence the plasma can be studied at the kinetic level. Also, the relevant time scales (e.g. 1/plasma frequency) are of order 0.1 sec, the plasma processes occur practically in "slow motion". We will discuss some physical processes (e.g. wave propagation, shocks, phase transitions) of these systems and outline the potential of the research for the understanding of strongly coupled systems. Technologically, it is expected that colloidal plasmas will also become very important, because both plasma technology and colloid technology are widely developed already. In this overview first the basic forces between the particles are discussed, then the phase transitions, the lattice structures and results from active experiments will be presented. Finally the future perspectives will be discussed, from the scientific potential point of view and the experimental approaches in the laboratory and in space. Experiments under microgravity conditions are of great importance, because the microspheres are 10's of billions times heavier than the ions.

  20. Multiscale modeling of liquid crystalline/nanotube composites

    NASA Astrophysics Data System (ADS)

    Patrale, Sharil

    The objective of this research is to synthesize structural composites designed with particular areas defined with custom modulus, strength and toughness values in order to improve the overall mechanical behavior of the composite. Such composites are defined and referred to as 3D-designer composites. These composites will be formed from liquid crystalline polymers and carbon nanotubes. The fabrication process is a variation of rapid prototyping process, which is a layered, additive-manufacturing approach. Composites formed using this process can be custom designed by apt modeling methods for superior performance in advanced applications. The focus of this research is on enhancement of Young's modulus in order to make the final composite stiffer. Strength and toughness of the final composite with respect to various applications is also discussed. We have taken into consideration the mechanical properties of final composite at different fiber volume content as well as at different orientations and lengths of the fibers. The orientation of the LC monomers is supposed to be carried out using electric or magnetic fields. A computer program is modeled incorporating the Mori-Tanaka modeling scheme to generate the stiffness matrix of the final composite. The final properties are then deduced from the stiffness matrix using composite micromechanics. Eshelby's tensor, required to calculate the stiffness tensor using Mori-Tanaka method, is calculated using a numerical scheme that determines the components of the Eshelby's tensor (Gavazzi and Lagoudas 1990). The numerical integration is solved using Gaussian Quadrature scheme and is worked out using MATLAB as well. MATLAB provides a good deal of commands and algorithms that can be used efficiently to elaborate the continuum of the formula to its extents. Graphs are plotted using different combinations of results and parameters involved in finding these results.

  1. The liquid crystalline phase behavior of dimerizing hard spherocylinders

    NASA Astrophysics Data System (ADS)

    McGrother, Simon C.; Sear, Richard P.; Jackson, George

    1997-05-01

    The phase behavior of dimerizing (associating) rigid particles is studied by both theory and computer simulation. The model molecule comprises a hard spherocylinder of length L and diameter D with a terminal square well bonding site embedded in one of the hemispherical caps. This model mimics the properties of simple hydrogen bonding mesogens; for example, mesogens with a carboxylic acid end group which are capable of forming dimers. A recently proposed theory of the isotropic (I)-nematic (N) phase transition for long hard spherocylinders with an attractive site at one end [R. P. Sear and G. Jackson, Mol. Phys. 82, 473 (1994)] is extended to shorter molecules. In the original theory the free energy is truncated at the level of the second virial coefficient. We now include the higher virial coefficients in an approximate manner with a Parsons type scaling. The accuracy of the theory is demonstrated by comparison with novel Monte Carlo simulation data for the same model. Excellent agreement is found for densities, pressures and degrees of association especially at the liquid crystalline phase transition. In comparing the results for the L/D=5 associating system with those for its nonassociating analogue, the nematic phase is seen to be stabilized relative to the isotropic phase, while the nematic (N)-smectic-A (SmA) transition occurs at approximately the same density. The I-N transition for the dimerizing system is clearly first order, while the N-SmA is essentially continuous. The smectic-A phase has a monolayer structure which is similar to that formed by the nonassociating system. Furthermore, a system of otherwise nonmesogenic molecules with L/D=3 has a stable liquid crystal phase when dimerization is made possible with the inclusion of the terminal bonding sites. Rather than being a nematic phase, this phase is surprisingly found to have the layered structure of a smectic-A phase. We discuss our results in terms of the increase in the `effective' aspect ratio as

  2. Ion Transport in Nanostructured Block Copolymer/Ionic Liquid Membranes

    NASA Astrophysics Data System (ADS)

    Hoarfrost, Megan Lane

    Incorporating an ionic liquid into one block copolymer microphase provides a platform for combining the outstanding electrochemical properties of ionic liquids with a number of favorable attributes provided by block copolymers. In particular, block copolymers thermodynamically self-assemble into well-ordered nanostructures, which can be engineered to provide a durable mechanical scaffold and template the ionic liquid into continuous ion-conducting nanochannels. Understanding how the addition of an ionic liquid affects the thermodynamic self-assembly of block copolymers, and how the confinement of ionic liquids to block copolymer nanodomains affects their ion-conducting properties is essential for predictable structure-property control. The lyotropic phase behavior of block copolymer/ionic liquid mixtures is shown to be reminiscent of mixtures of block copolymers with selective molecular solvents. A variety of ordered microstructures corresponding to lamellae, hexagonally close-packed cylinders, body-centered cubic, and face-centered cubic oriented micelles are observed in a model system composed of mixtures of imidazolium bis(trifluoromethylsulfonyl)imide ([Im][TFSI]) and poly(styrene- b-2-vinyl pyridine) (PS-b-P2VP). In contrast to block copolymer/molecular solvent mixtures, the interfacial area occupied by each PS-b-P2VP chain decreases upon the addition of [Im][TFSI], indicating a considerable increase in the effective segregation strength of the PS-b-P2VP copolymer with ionic liquid addition. The relationship between membrane structure and ionic conductivity is illuminated through the development of scaling relationships that describe the ionic conductivity of block copolymer/ionic liquid mixtures as a function of membrane composition and temperature. It is shown that the dominant variable influencing conductivity is the overall volume fraction of ionic liquid in the mixture, which means there

  3. Perylenediimide-surfactant complexes: thermotropic liquid-crystalline materials via ionic self-assembly.

    PubMed

    Guan, Ying; Zakrevskyy, Yuriy; Stumpe, Joachim; Antonietti, Markus; Faul, Charl F J

    2003-04-07

    In this communication we present the facile preparation and characterisation of thermotropic liquid-crystalline materials from the ionic self-assembly of a charged perylenediimide derivative and oppositely charged surfactants.

  4. Combinatorial parallel synthesis and automated screening of a novel class of liquid crystalline materials.

    PubMed

    Deeg, Oliver; Kirsch, Peer; Pauluth, Detlef; Bäuerle, Peter

    2002-12-07

    Combinatorial parallel synthesis has led to the rapid generation of a single-compound library of novel fluorinated quaterphenyls. Subsequent automated screening revealed liquid crystalline (LC) behaviour and gave qualitative relationships of molecular structures and solid state properties.

  5. Direct Imaging of Carbon Nanotube Liquid-Crystalline Phase Development in True Solutions.

    PubMed

    Kleinerman, Olga; Liberman, Lucy; Behabtu, Natnael; Pasquali, Matteo; Cohen, Yachin; Talmon, Yeshayahu

    2017-04-13

    Using direct-imaging cryogenic transmission and scanning electron microscopy, we show different stages of liquid-crystalline phase development in progressively more concentrated solutions of carbon nanotubes in chlorosulfonic acid: a dilute phase of individually dissolved carbon nanotubes; semidilute and concentrated isotropic phases; coexisting concentrated isotropic and nematic phases in local equilibrium with each other; and a fully liquid-crystalline phase. Nanometric resolution of cryogenic electron microscopy reveals carbon nanotube self-assembly into liquid-crystalline domains of several nanometers in width at very early stages. We find significant differences in carbon nanotube liquid-crystalline domain morphology as a function of the carbon nanotube aspect ratio, diameter, and degree of purity.

  6. Controlled Shape Memory Behavior of a Smectic Main-Chain Liquid Crystalline Elastomer

    DOE PAGES

    Li, Yuzhan; Pruitt, Cole; Rios, Orlando; ...

    2015-04-10

    Here, we describe how a smectic main-chain liquid crystalline elastomer (LCE), with controlled shape memory behavior, is synthesized by polymerizing a biphenyl-based epoxy monomer with an aliphatic carboxylic acid curing agent. Microstructures of the LCEs, including their liquid crystallinity and cross-linking density, are modified by adjusting the stoichiometric ratio of the reactants to tailor the thermomechanical properties and shape memory behavior of the material. Thermal and liquid crystalline properties of the LCEs, characterized using differential scanning calorimetry and dynamic mechanical analysis, and structural analysis, performed using small-angle and wide-angle X-ray scattering, show that liquid crystallinity, cross-linking density, and network rigiditymore » are strongly affected by the stoichiometry of the curing reaction. With appropriate structural modifications it is possible to tune the thermal, dynamic mechanical, and thermomechanical properties as well as the shape memory and thermal degradation behavior of LCEs.« less

  7. Controlled Shape Memory Behavior of a Smectic Main-Chain Liquid Crystalline Elastomer

    SciTech Connect

    Li, Yuzhan; Pruitt, Cole; Rios, Orlando; Wei, Liqing; Rock, Mitch; Keum, Jong K.; McDonald, Armando G.; Kessler, Michael R.

    2015-04-10

    Here, we describe how a smectic main-chain liquid crystalline elastomer (LCE), with controlled shape memory behavior, is synthesized by polymerizing a biphenyl-based epoxy monomer with an aliphatic carboxylic acid curing agent. Microstructures of the LCEs, including their liquid crystallinity and cross-linking density, are modified by adjusting the stoichiometric ratio of the reactants to tailor the thermomechanical properties and shape memory behavior of the material. Thermal and liquid crystalline properties of the LCEs, characterized using differential scanning calorimetry and dynamic mechanical analysis, and structural analysis, performed using small-angle and wide-angle X-ray scattering, show that liquid crystallinity, cross-linking density, and network rigidity are strongly affected by the stoichiometry of the curing reaction. With appropriate structural modifications it is possible to tune the thermal, dynamic mechanical, and thermomechanical properties as well as the shape memory and thermal degradation behavior of LCEs.

  8. Liquid-crystalline elastomer-nanoparticle hybrids with reversible switch of magnetic memory.

    PubMed

    Haberl, Johannes M; Sánchez-Ferrer, Antoni; Mihut, Adriana M; Dietsch, Hervé; Hirt, Ann M; Mezzenga, Raffaele

    2013-03-25

    A stimuli-responsive material is synthesized that combines the actuation potential of liquid-crystalline elastomers with the anisotropic magnetic properties of ellipsoidal iron oxide nanoparticles. The resulting nanocomposite exhibits unique shape-memory features with magnetic information, which can be reversibly stored and erased via parameters typical of soft materials, such as high deformations, low stresses, and liquid-crystalline smectic-isotropic transition temperatures. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Shape-Selectivity with Liquid Crystal and Side-Chain Liquid Crystalline Polymer SAW Sensor Interfaces

    SciTech Connect

    FRYE-MASON,GREGORY CHARLES; OBORNY,MICHAEL C.; PUGH,COLEEN; RICCO,ANTONIO; THOMAS,ROSS C.; ZELLERS,EDWARD T.; ZHANG,GUO-ZHENG

    1999-09-23

    A liquid crystal (LC) and a side-chain liquid crystalline polymer (SCLCP) were tested as surface acoustic wave (SAW) vapor sensor coatings for discriminating between pairs of isomeric organic vapors. Both exhibit room temperature smectic mesophases. Temperature, electric-field, and pretreatment with self-assembled monolayers comprising either a methyl-terminated or carboxylic acid-terminated alkane thiol anchored to a gold layer in the delay path of the sensor were explored as means of affecting the alignment and selectivity of the LC and SCLCP films. Results for the LC were mixed, while those for the SCLCP showed a consistent preference for the more rod-like isomer of each isomer pair examined.

  10. Formation of a liquid-crystalline interpenetrating poly-(ionic liquid) network hydrogel.

    SciTech Connect

    Becht, G. A.; Sofos, M.; Seifert, S.; Firestone, M. A.

    2011-02-21

    Preparation of a liquid-crystalline ionic-liquid (IL)-based interpenetrating polymer network (IPN) is described. The IPN is prepared sequentially by first photopolymerizing a self-assembled aqueous mixture of an IL monomer (1-(10-(acryloyloxy)decyl)-3-methylimidazolium chloride) that possesses an acryloyl moiety at the terminus of a C{sub 10} alkyl chain of the IL cation. In the second step, an acrylate counteranion is introduced and then photopolymerized to yield a durable self-supporting network polymer. Thermal analysis indicates the formation of a homogeneous (well-blended constituent polymers) IPN. The IPN adopts a lamellar structure possessing some residual in-plane tetragonal perforations, as evidenced by small-angle X-ray scattering (SAXS). The IPN can absorb large quantities of water, swelling to nearly 60 times its original volume, but retains mechanical integrity making it a durable hydrogel.

  11. Selection of thermotropic liquid crystalline polymers for rotational molding

    NASA Astrophysics Data System (ADS)

    Scribben, Eric

    Thermotropic liquid crystalline polymers (TLCPs) possess a number of physical and mechanical properties such as: excellent chemical resistance, low permeability, low coefficient of thermal expansion, high tensile strength and modulus, and good impact resistance, which make them desirable for use in the storage of cryogenic fluids. Rotational molding was selected as the processing method for these containers because it is convenient for manufacturing large storage vessels from thermoplastics. Unfortunately, there are no reports of successful TLCP rotational molding in the technical literature. The only related work reported involved the static coalescence of two TLCP powders, where three key results were reported that were expected to present problems that preclude the rotational molding process. The first result was that conventional grinding methods produced powders that were composed of high aspect ratio particles. Secondly, coalescence was observed to be either slow or incomplete and speculated that the observed difficulties with coalescence may be due to large values of the shear viscosity at low deformation rates. Finally, complete densification was not observed for the high aspect ratio particles. However, the nature of these problems were not evaluated to determine if they did, in fact, create processing difficulties for rotational molding or if it was possible to develop solutions to the problems to achieve successful rotational molding. This work is concerned with developing a resin selection method to identify viable TLCP candidates and establish processing conditions for successful rotational molding. This was accomplished by individually investigating each of the phenomenological steps of rotational molding to determine the requirements for acceptable performance in, or successful completion of, each step. The fundamental steps were: the characteristics and behavior of the powder in solids flow, the coalescence behavior of isolated particles, and the

  12. Helical assembly, liquid crystalline behavior and crystallization of a nonracemic chiral main-chain liquid crystalline polyester and its monomers

    NASA Astrophysics Data System (ADS)

    Weng, Xin

    In this thesis, A non-racemic chiral main-chain liquid crystalline (LC) polyester was synthesized from (R)-(-)-4'-{o-[2-( p-hydroxy-o-nitrophenyloxy)-1-propyloxy]-1-undecyloxy}-4-biphenyl carboxylic acid via an A-B type condensation polymerization. The polymer was abbreviated as PET(R*-11) where eleven is the number of methylene units in the chain backbone. PET(R*-11) exhibited a LC chiral smectic C (SC*), a chiral smectic A (SA*) and a twist grain boundary Smectic A (TGBA*) phase with increasing temperatures as identified by differential scanning calorimetry, polarized optical microscopy, and wide angle X-ray diffraction (WAXD). Flat-elongated lamellae were observed in transmission electron microscopy (TEM) for thin-film melt crystallized samples. Its crystal structure was determined to be a monoclinic basic unit cell with a = 1.03 nm, b = 0.47 nm, c = 6.43 nm and gamma = 83° via selected area electron diffraction (SAED), and these measurements were confirmed by two-dimensional WAXD fiber patterns. Furthermore, SAED results showed that two kinds of crystal twins existed in this polymer: "micro-twinning" within one single lamellar crystal and "rotation-twinning" between two lamellae. This rotation-twinning was possibly a result of a mechanism of a soft epitaxy between two contacting (001) folded surfaces along the (3¯10) planes. Right-handed helical lamellar crystals were also found under the same crystallization conditions, and their pitch lengths were on the micrometer scale as observed by TEM and atomic force microscopy. The helical crystal structure was found to be identical to that of the flat-elongated counterparts. Dendritic crystals with fractal geometry were also obtained as the result of diffusion-controlled crystal growth. The phase structures of two monomers of PET(R*-11) were studied. One of them has carboxylic acid end group (named as K11-acid), while another has ester end group (named as Kl 1-ester). Kl 1-ester does not show any LC behavior, while

  13. Structure and interactions in isotropic and liquid crystalline neurofilament networks

    NASA Astrophysics Data System (ADS)

    Jones, Jayna Bea

    2007-12-01

    Neurofilaments (NFs) are cytoskeletal proteins that are localized within nerve cells, which form long oriented bundles running the length of axons. While abnormal aggregations of these proteins have been implicated in several neurological disorders including Parkinson's disease and ALS, interfilament interactions in both the normal and diseased states are not well understood. In vivo, NFs are supramolecular structures composed of three subunit proteins of low (NF-L), medium (NF-M), and high molecular (NF-H) weight that assemble into a 10 nm diameter rod with radiating sidearms, forming a bottle-brush conformation. In this study we alter the subunit composition and probe the resulting networks with polarized microscopy and synchrotron small angle x-ray scattering (SAXS), in order to isolate the role of each subunit in interfilament interactions. By reassembling NFs in vitro from varying ratios of the subunit proteins, purified from bovine spinal cord, we form filaments with controlled subunit compositions. The resulting filaments, at a high volume fraction, are nematic liquid crystalline gels with a well defined spacing, determined with SAXS. Upon dilution the difference between the subunits is realized with NF-M grafted filaments being dominated by attractive interactions and remaining aligned, while those flanked with NF-H sidearms repel and become isotropic gels. Interplay between these forces is seen in the ternary system composed of all three subunit proteins (NF-LMH). The polyampholytic subunits have a charge distribution that varies along the length of the sidearm, which forms the brush layer, and the distribution is different for each subunit. The interfilament interactions are highly dependent on environmental conditions including salt concentration, pH, and osmotic pressure. Increasing ionic strength induces attractive interactions and a stabilization of the nematic phase in filaments that were repulsive at lower monovalent salt concentration. The

  14. Optimizing the network topology of block copolymer liquid crystal elastomers for enhanced extensibility and toughness

    NASA Astrophysics Data System (ADS)

    Nowak, Christian; Escobedo, Fernando A.

    2017-08-01

    Molecular simulations are used to study the effect of synthesis conditions on the tensile response of liquid-crystalline elastomers formed by block copolymer chains. Remarkably, it is found that despite the significant presence of trapped entanglements, these networks can exhibit the sawtooth tensile response previously predicted for ideal unentangled networks. It is also found that the monomer concentration during crosslinking can be tuned to limit the extent of entanglements and inhomogeneities while also maximizing network extensibility. It is predicted that networks synthesized at a "critical" concentration will have the greatest toughness.

  15. Liquid Crystalline Thermosets from Ester, Ester-imide, and Ester-amide Oligomers

    NASA Technical Reports Server (NTRS)

    Dingemans, Theodorus J. (Inventor); Weiser, Erik S. (Inventor); St. Clair, Terry L. (Inventor)

    2009-01-01

    Main chain thermotropic liquid crystal esters, ester-imides, and ester-amides were prepared from AA, BB, and AB type monomeric materials and end-capped with phenylacetylene, phenylmaleimide, or nadimide reactive end-groups. The end-capped liquid crystal oligomers are thermotropic and have, preferably, molecular weights in the range of approximately 1000-15,000 grams per mole. The end-capped liquid crystaloligomers have broad liquid crystalline melting ranges and exhibit high melt stability and very low melt viscosities at accessible temperatures. The end-capped liquid crystal oli-gomers are stable forup to an hour in the melt phase. They are highly processable by a variety of melt process shape forming and blending techniques. Once processed and shaped, the end-capped liquid crystal oigomers were heated to further polymerize and form liquid crystalline thermosets (LCT). The fully cured products are rubbers above their glass transition temperatures.

  16. Novel Colloidal and Dynamic Interfacial Phenomena in Liquid Crystalline Systems

    DTIC Science & Technology

    2014-09-13

    investigation supported by this grant moved beyond past studies of interfacial and colloidal phenomena involving isotropic liquids to explore and understand a...2010 20-May-2014 Approved for Public Release; Distribution Unlimited Final Report: Novel Colloidal and Dynamic Interfacial Phenomena in Liquid...Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 liquid crystals, interfacial phenomena, colloids , amphiphiles

  17. One-piece micropumps from liquid crystalline core-shell particles

    NASA Astrophysics Data System (ADS)

    Fleischmann, Eva-Kristina; Liang, Hsin-Ling; Kapernaum, Nadia; Giesselmann, Frank; Lagerwall, Jan; Zentel, Rudolf

    2012-11-01

    Responsive polymers are low-cost, light weight and flexible, and thus an attractive class of materials for the integration into micromechanical and lab-on-chip systems. Triggered by external stimuli, liquid crystalline elastomers are able to perform mechanical motion and can be utilized as microactuators. Here we present the fabrication of one-piece micropumps from liquid crystalline core-shell elastomer particles via a microfluidic double-emulsion process, the continuous nature of which enables a low-cost and rapid production. The liquid crystalline elastomer shell contains a liquid core, which is reversibly pumped into and out of the particle by actuation of the liquid crystalline shell in a jellyfish-like motion. The liquid crystalline elastomer shells have the potential to be integrated into a microfluidic system as micropumps that do not require additional components, except passive channel connectors and a trigger for actuation. This renders elaborate and high-cost micromachining techniques, which are otherwise required for obtaining microstructures with pump function, unnecessary.

  18. Towards micrometer sized core-shell actuators from liquid crystalline elastomers by a continuous flow synthesis

    NASA Astrophysics Data System (ADS)

    Fleischmann, Eva-Kristina; Liang, Hsin-Ling; Lagerwall, Jan; Zentel, Rudolf

    2012-03-01

    We present here the successful preparation of liquid crystalline core-shell elastomers via a microfluidic double-emulsion process. The customized set-up allows for a temperature-controlled fabrication of the core-shell particles from a thermoresponsive mesogenic monomer. The nematic liquid crystalline shell is filled with a non-mesogenic core of silicone oil. To verify the core-shell structure with optical microscopy, we prepared particles with a colored core using a red dye. We were also able to micro-manipulate the particles and penetrate them with a small glass capillary to extract the liquid core.

  19. Bio-based ionic liquid crystalline quaternary ammonium salts: properties and applications.

    PubMed

    Sasi, Renjith; Rao, Talasila P; Devaki, Sudha J

    2014-03-26

    In the present work, we describe the preparation, properties, and applications of novel ionic liquid crystalline quaternary ammonium salts (QSs) of 3-pentadecylphenol, a bio-based low-cost material derived from cashew nut shell liquid. Amphotropic liquid crystalline phase formation in QSs was characterized using a combination of techniques, such as DSC, PLM, XRD, SEM, and rheology, which revealed the formation of one, two, and three dimensionally ordered mesophases in different length scales. On the basis of these results, a plausible mechanism for the formation of specific modes of packing in various mesophases was proposed. Observation of anisotropic ionic conductivity and electrochemical stability suggests their application as a solid electrolyte.

  20. Crystalline and liquid structure of zinc chloride trihydrate: a unique ionic liquid.

    PubMed

    Wilcox, Robert J; Losey, Bradley P; Folmer, Jacob C W; Martin, James D; Zeller, Matthias; Sommer, Roger

    2015-02-02

    The water/ZnCl(2) phase diagram in the vicinity of the 75 mol % water composition is reported, demonstrating the existence of a congruently melting phase. Single crystals of this 3-equiv hydrate were grown, and the crystal structure of [Zn(OH(2))(6)][ZnCl(4)] was determined. Synchrotron X-ray and neutron diffraction and IR and Raman spectroscopy along with reverse Monte Carlo modeling demonstrate that a CsCl-type packing of the molecular ions persists into the liquid state. Consistent with the crystalline and liquid structural data, IR spectroscopy demonstrates that the O-H bonds of coordinated water do not exhibit strong intermolecular hydrogen ion bonding but are significantly weakened because of the water's coordination to Lewis acidic zinc ions. The O-H bond weakening makes this system a very strong hydrogen-bond donor, whereas the ionic packing along with the nonpolar geometry of the molecular ions makes this system a novel nonpolar, hydrogen-bonding, ionic liquid solvent.

  1. Clustomesogens: Liquid Crystalline Hybrid Nanomaterials Containing Functional Metal Nanoclusters.

    PubMed

    Molard, Yann

    2016-08-16

    Inorganic phosphorescent octahedral metal nanoclusters fill the gap between metal complexes and nanoparticles. They are finite groups of metal atoms linked by metal-metal bonds, with an exact composition and structure at the nanometer scale. As their phosphorescence internal quantum efficiency can approach 100%, they represent a very attractive class of molecular building blocks to design hybrid nanomaterials dedicated to light energy conversion, optoelectronic, display, lighting, or theragnostic applications. They are obtained as AnM6X(i)8X(a)6 ternary salt powders (A = alkali cation, M = Mo, Re, W, X(i): halogen inner ligand, X(a) = halogen apical ligand) by high temperature solid state synthesis (750-1200 °C). However, their ceramic-like behavior has largely restricted their use as functional components in the past. Since these last two decades, several groups, including ours, started to tackle the challenge of integrating them in easy-to-process materials. Within this context, we have extensively explored the nanocluster ternary salt specificities to develop a new class of self-organized hybrid organic-inorganic nanomaterials known as clustomesogens. These materials, combine the specific properties of nanoclusters (magnetic, electronic, luminescence) with the anisotropy-related properties of liquid crystals (LCs). This Account covers the research and development of clustomesogens starting from the design concepts and synthesis to their introduction in functional devices. We developed three strategies to build such hybrid super- or supramolecules. In the covalent approach, we capitalized on the apical ligand-metal bond iono-covalent character to graft tailor-made organic LC promoters on the {M6X(i)8}(n+) nanocluster cores. The supramolecular approach relies on the host-guest complexation of the ternary cluster salt alkali cations with functional crown ether macrocycles. We showed that the hybrid LC behavior depends on the macrocycles structural features

  2. Self-Assembly of Block Copolymers in an Ionic Liquid

    NASA Astrophysics Data System (ADS)

    He, Yiyong; Li, Zhibo; Lodge, Timothy P.

    2006-03-01

    Amphiphilic diblock copolymers poly((1,2-butadiene)-b-ethylene oxide) (PB-PEO) were shown to aggregate and form well-defined micelles in an ionic liquid, 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIM][PF6]). The universal sequence of micellar structures (spherical micelle, wormlike micelle, and bilayered vesicle) were all resolved by varying the block copolymer composition. For the first time, the nanostructures of PB-PEO micelles formed in an ionic liquid were directly visualized by cryogenic transmission electron microscopy (cryo-TEM). The detailed micelle structure information was extracted from cryo-TEM and dynamic light scattering (DLS) measurements, and compared to their aqueous counterparts. The work demonstrates the feasibility of controlling micellar nanostructures of amphiphilic block copolymers in ionic liquids, and also provides important knowledge for further applications of copolymers for forming microemulsions and ion gels.

  3. Photovoltaic performance of block copolymer devices is independent of the crystalline texture in the active layer

    SciTech Connect

    Guo, Changhe; Lee, Youngmin; Lin, Yen -Hao; Strzalka, Joseph; Wang, Cheng; Hexemer, Alexander; Jaye, Cherno; Fischer, Daniel A.; Verduzco, Rafael; Wang, Qing; Gomez, Enrique D.

    2016-06-15

    The electronic properties of organic semiconductors are strongly influenced by intermolecular packing. When cast as thin films, crystalline π-conjugated molecules are strongly textured, potentially leading to anisotropic charge transport. Consequently, it is hypothesized that the orientation of crystallites in the active layer plays an important role in charge extraction and organic photovoltaic device performance. Here we demonstrate orientation control of molecular packing from mostly face-on to edge-on configurations in the active layer of P3HT-b-PFTBT block copolymer photovoltaics using 1-chloronaphthalene as a solvent additive. The effect of molecular orientations in P3HT crystals on charge transport and solar cell performance is examined. We find that optimized photovoltaic device performance is independent of the crystalline texture of P3HT. Our observations provide further insights into the molecular organization required for efficient charge transport and overall device efficiencies. That is, the dominant crystal orientation, whether face-on or edge-on, is not critical to organic solar cells. Furthermore, a broad distribution of crystallite orientations ensures pathways for charge transport in any direction and enables efficient charge extraction in photovoltaic devices.

  4. Photovoltaic performance of block copolymer devices is independent of the crystalline texture in the active layer

    DOE PAGES

    Guo, Changhe; Lee, Youngmin; Lin, Yen -Hao; ...

    2016-06-15

    The electronic properties of organic semiconductors are strongly influenced by intermolecular packing. When cast as thin films, crystalline π-conjugated molecules are strongly textured, potentially leading to anisotropic charge transport. Consequently, it is hypothesized that the orientation of crystallites in the active layer plays an important role in charge extraction and organic photovoltaic device performance. Here we demonstrate orientation control of molecular packing from mostly face-on to edge-on configurations in the active layer of P3HT-b-PFTBT block copolymer photovoltaics using 1-chloronaphthalene as a solvent additive. The effect of molecular orientations in P3HT crystals on charge transport and solar cell performance is examined.more » We find that optimized photovoltaic device performance is independent of the crystalline texture of P3HT. Our observations provide further insights into the molecular organization required for efficient charge transport and overall device efficiencies. That is, the dominant crystal orientation, whether face-on or edge-on, is not critical to organic solar cells. Furthermore, a broad distribution of crystallite orientations ensures pathways for charge transport in any direction and enables efficient charge extraction in photovoltaic devices.« less

  5. Photovoltaic performance of block copolymer devices is independent of the crystalline texture in the active layer

    SciTech Connect

    Guo, Changhe; Lee, Youngmin; Lin, Yen -Hao; Strzalka, Joseph; Wang, Cheng; Hexemer, Alexander; Jaye, Cherno; Fischer, Daniel A.; Verduzco, Rafael; Wang, Qing; Gomez, Enrique D.

    2016-06-15

    The electronic properties of organic semiconductors are strongly influenced by intermolecular packing. When cast as thin films, crystalline π-conjugated molecules are strongly textured, potentially leading to anisotropic charge transport. Consequently, it is hypothesized that the orientation of crystallites in the active layer plays an important role in charge extraction and organic photovoltaic device performance. Here we demonstrate orientation control of molecular packing from mostly face-on to edge-on configurations in the active layer of P3HT-b-PFTBT block copolymer photovoltaics using 1-chloronaphthalene as a solvent additive. The effect of molecular orientations in P3HT crystals on charge transport and solar cell performance is examined. We find that optimized photovoltaic device performance is independent of the crystalline texture of P3HT. Our observations provide further insights into the molecular organization required for efficient charge transport and overall device efficiencies. That is, the dominant crystal orientation, whether face-on or edge-on, is not critical to organic solar cells. Furthermore, a broad distribution of crystallite orientations ensures pathways for charge transport in any direction and enables efficient charge extraction in photovoltaic devices.

  6. Liquid Crystalline Epoxies with Lateral Substituents Showing a Low Dielectric Constant and High Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Guo, Huilong; Lu, Mangeng; Liang, Liyan; Wu, Kun; Ma, Dong; Xue, Wei

    2017-02-01

    In this work, liquid crystalline epoxies with lateral substituents were synthesized and cured with aromatic amines or anhydride. The liquid crystalline phase structure of liquid crystalline epoxies with lateral substituents was determined by polarized optical microscopy. The relationship between thermal conductivity and dielectric properties and liquid crystalline domain structure was discussed in the paper. The samples show high thermal conductivity up to 0.29 W/(m × K), due to the orientation of mesogenic units in epoxies. The sample's low dielectric constant of 2.29 is associated with the oriented mesogenic units and long nonpolar lateral substituents. This indicates a new way to obtain materials with high thermal conductivity and a low dielectric constant by introducing oriented mesogenic units into cross-linked epoxy systems. The water repellency is reflected in the contact angles of 92-98°, which are apparently higher than that of conventional epoxy systems. It was also found that the better toughness of liquid crystalline epoxies with lateral substituents was attributed to the existence of long flexible alkyl lateral substituents.

  7. Ionic Conductivity of Nanostructured Block Copolymer and Ionic Liquid Membranes

    NASA Astrophysics Data System (ADS)

    Hoarfrost, Megan L.; Virgili, Justin M.; Segalman, Rachel A.

    2010-03-01

    Block copolymer and ionic liquid mixtures are of interest for creating ionically conductive, thermally stable, and nanostructured membranes. For mixtures of poly(styrene-b-2-vinylpyridine) (S2VP) and the ionic liquid bis(trifluoromethanesulfonyl)imide ([Im][TFSI]), nanostructured ion-conducting domains are formed due to [Im][TFSI] selectively residing in the P2VP domains of the block copolymer. The dependence of ionic conductivity on temperature, ionic liquid loading, and volume fraction of PS in the neat block copolymer was investigated for membranes with the matrix phase being P2VP/[Im][TFSI]. It was determined that the temperature dependence of conductivity follows the Vogel-Tamman-Fulcher equation, with the activation energy determined by the ratio of [Im][TFSI] to 2VP monomers. The overall weight fraction of [Im][TFSI] in the mixtures, however, is the dominating factor determining conductivity, regardless of PS volume fraction. The insight gained from this work will be important for further investigation into the effect on the ion transport properties of ionic liquids when confined to minority nanostructured domains.

  8. Luminescent liquid crystalline materials based on palladium(II) imine derivatives containing the 2-phenylpyridine core.

    PubMed

    Micutz, Marin; Iliş, Monica; Staicu, Teodora; Dumitraşcu, Florea; Pasuk, Iuliana; Molard, Yann; Roisnel, Thierry; Cîrcu, Viorel

    2014-01-21

    In this work we report our studies concerning the synthesis and characterisation of a series of imine derivatives that incorporate the 2-phenylpyridine (2-ppy) core. These derivatives were used in the cyclometalating reactions of platinum(II) or palladium(II) in order to prepare several complexes with liquid crystalline properties. Depending on the starting materials used as well as the solvents employed, different metal complexes were obtained, some of them showing both liquid crystalline behaviour and luminescence properties at room temperature. It was found that, even if there are two competing coordination sites, the cyclometalation process takes place always at the 2-ppy core with (for Pt) or without (for Pd) the imine bond cleavage. We successfully showed that it is possible to prepare emissive room temperature liquid crystalline materials based on double cyclopalladated heteroleptic complexes by varying the volume fraction of the long flexible alkyl tails on the ancillary benzoylthiourea (BTU) ligands.

  9. Enhanced light absorption in graphene via a liquid-crystalline optical diode

    NASA Astrophysics Data System (ADS)

    Pantazi, Aikaterini Iria; Yannopapas, Vassilios

    2016-09-01

    We demonstrate theoretically that light absorption in graphene can be boosted via a light-trapping mechanism based on a liquid-crystalline optical diode. The optical diode consists of twisted-nematic and nematic liquid-crystalline slabs. In particular, we show that, using a proper optical-diode setup, the absorption in a single graphene layer can be enhanced by a factor of four. By varying the pitch of the twisted-nematic liquid-crystalline slabs comprising the diode, one can tune the operating spectral region of the diode and thus enhance the absorption of graphene within a desired spectral window. Our calculations are based on Berreman's 4×4 method which treats anisotropic, isotropic and/ or inhomogeneous layered systems on equal footing.

  10. Geometric pumping induced by shear flow in dilute liquid crystalline polymer solutions.

    PubMed

    Yabunaka, Shunsuke; Yabunaka, Shunsuka; Hayakawa, Hisao

    2015-02-07

    We investigate nonlinear rheology of dilute liquid crystalline polymer solutions under time dependent two-directional shear flow. We analyze the Smoluchowski equation, which describes the dynamics of the orientation of a liquid crystalline polymer, by employing technique of the full counting statistics. In the adiabatic limit, we derive the expression for time integrated currents generated by a Berry-like curvature. Using this expression, it is shown that the expectation values of the time-integrated angular velocity of a liquid crystalline polymer and the time-integrated stress tensor are generally not zero even if the time average of the shear rate is zero. The validity of the theoretical calculations is confirmed by direct numerical simulations of the Smoluchowski equation. Nonadiabatic effects are also investigated by means of simulations and it is found that the time-integrated stress tensor depends on the speed of the modulation of the shear rate if we adopt the isotropic distribution as an initial state.

  11. Tuning the crystalline and mesophase structure of olefin block copolymer through self-nucleation and annealing treatments.

    PubMed

    Fan, Jiashu; Zhang, Qinglong; Feng, Jiachun

    2015-06-28

    As a type of novel semi-crystalline block copolymers, the final properties of olefin block copolymers (OBCs) greatly depend on the crystalline and phase-separated structures. In the present work, we systematically investigated the influence of self-nucleation and annealing on the lamellar and mesophase-separated structure of OBCs. According to the crystalline and melting behavior after self-nucleation and annealing treatments, four different regimes can be recognized with the self-seeding temperature Ts varying from 125 to 109 °C. In regime A, only self-nucleation occurs, while it coexists with lamellar thickening in regime B. In regime C, there is only lamellar thickening behavior. The lamellar thickening induced inconsecutive lamellar crystals observed revealed that the rearrangement of the hard blocks, which are next to the soft blocks and trapped in the intermediate regime between crystalline and amorphous phases, into neighboring lamellar crystals should be the mechanism for the lamellar thickening of the OBCs. Surprisingly, no lamellar thickening occurs and a new small melting peak appears at lower temperatures in regime D. Considering the block dispersity of OBCs, the emergence of a small melting peak at lower temperatures can be attributed to the crystallization of the ethylene sequence with relatively weaker crystallization abilities, which are not able to crystallize in a standard crystalline state. Based on these findings, we gained some new understandings on lamellar thickening behavior of OBCs and established the self-nucleation and annealing process as a powerful tool for tuning the crystalline and phase-separated structures of OBCs.

  12. Viewing angle compensation of various LCD modes by using a liquid crystalline polymer film

    NASA Astrophysics Data System (ADS)

    Matsumoto, Takuya; Nishimura, Suzushi

    2013-09-01

    The authors have developed liquid crystalline retardation films to improve certain aspects of LCD image quality such as viewing angle performance and coloration. We have successfully created several types of optical retardation films using a rod-like liquid crystalline polymer. The resulting liquid crystalline polymer films have several advantages over conventional uni- or biaxially stretched retardation films. Precisely controlled structures such as twisted nematic, homogeneous nematic, hybrid nematic and homeotropic structures can provide ideal compensation of various LCD types, such as STN, TN, ECB, VA and IPS-LCDs. Twisted nematic film effectively prevents coloration of STN-LCDs, which is a critical flaw affecting color representation. Short pitch cholesteric film, which utilizes said rod-like liquid crystalline polymer and is the optical equivalent of a negative C-plate, can expand the viewing angle of VA-LCDs. Hybrid nematic film is quite unique in that the film functions not only as a wave plate but also as a viewing angle compensator for TN and ECB-LCDs. Homeotropic film, which acts as a positive-C plate, greatly improves the viewing angle performance of IPS and CPVA-LCDs. Our homeotropically aligned liquid crystalline film, called "NV film", is the world's thinnest retardation film. The thickness of the liquid crystalline layer is a mere 1 micrometer. Homeotropic film can be used to expand the viewing angle not only of LCDs but also OLED displays. And NV film, when used in in combination with a quarter wavelength plate, can expand the viewing angles of the circular polarizers used to prevent reflection in OLED displays.

  13. Homogeneous nucleation of crystalline order in superdense liquid 4He

    NASA Astrophysics Data System (ADS)

    Pederiva, F.; Ferrante, A.; Fantoni, S.; Reatto, L.

    1995-09-01

    We present the results of a numerical crystallization experiment in 4He performed with the shadow wave function and the variational Monte Carlo method. The experiment consists in Monte Carlo simulations starting from liquidlike configurations of the atoms at a density well above the melting point. The system presents spontaneous nucleation of crystalline seeds, proving the spontaneous symmetry-breaking property of the shadow wave function. The final configurations display a face-centered-cubic structure grown preferentially by \\{111\\} planes, accompanied by stacking disorder.

  14. Barium hydroxide hole blocking layer for front- and back-organic/crystalline Si heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Hossain, Jaker; Kasahara, Koji; Harada, Daisuke; Saiful Islam, A. T. M.; Ishikawa, Ryo; Ueno, Keiji; Hanajiri, Tatsuro; Nakajima, Yoshikata; Fujii, Yasuhiko; Tokuda, Masahide; Shirai, Hajime

    2017-08-01

    We demonstrate the potential of barium hydroxide, Ba(OH)2, as a hole blocking layer on the photovoltaic performance of front- and back-organic/n-type crystalline silicon (n-Si) heterojunction solar cells with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS). The power conversion efficiency (PCE) of the front-PEDOT:PSS/n-Si heterojunction solar cell was increased from 12.8% for pristine to 13.6% with a 2-nm-thick Ba(OH)2 interlayer at the rear n-Si and aluminum (Al) cathode interface due to the enhanced hole blocking as well as electron injection capability to the Al cathode in the infrared region. PCE was further increased to 14.3% with a short-circuit density JSC of 30.27 mA/cm2, an open-circuit voltage VOC of 0.632 V, and a fill factor FF of 0.75 using a 20-nm-thick 4,4'-Cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] as an antireflection layer. PCE of the back-PEDOT:PSS/n-Si heterojunction solar cells was also increased from 4.4% for pristine to 8.1% with a JSC of 33.40 mA/cm2, a VOC of 0.573 V, and an FF of 0.423 by inserting a 2-nm-thick Ba(OH)2 layer at the front-Al and isotropically textured n-Si interface. These findings imply that Ba(OH)2 has great potential as an efficient hole-blocking layer for both front- and back-PEDOT:PSS/n-Si heterojunction solar cells.

  15. Some New Side-Chain Liquid Crystalline Polymers For Non Linear Optics

    NASA Astrophysics Data System (ADS)

    Le Barny, P.; Ravaux, G.; Dubois, J. C.; Parneix, J. P.; Njeumo, R.; Legrand, C.; Levelut, A. M.

    1987-01-01

    Two different ways have been investigated to obtain side-chain liquid crystalline polymers suitable for second harmonic generation (SHG). The aim of the first one was to obtain host nematic comb-like homopolymers having a small degree of polar association of their side chains, by using a 3-fluoro-4-cyanophenyl benzoate end group. The second way consisted in synthesizing liquid crystalline polymeric systems where a mesogenic monomer and a monomeric molecule bearing a group exhibiting a large molecular hyperpolarizability p , were copolymerized. In this paper, we report on the synthesis and the phase behaviour of these two families of polymers.

  16. Tuning the phase diagrams: the miscibility studies of multilactate liquid crystalline compounds

    NASA Astrophysics Data System (ADS)

    Bubnov, Alexej; Tykarska, Marzena; Hamplová, Věra; Kurp, Katarzyna

    2016-09-01

    Design of binary and multicomponent liquid crystalline mixtures is a very powerful tool to reach the desired self-assembling properties. Beyond many advantages, this method has a distinct negativity - it is very material-consuming. While working with unique chiral materials in the research laboratory, this problem can be solved by applying miscibility study by the contact preparation method. In this work, the miscibility studies of lactic acid derivatives and non-chiral/chiral liquid crystalline molecules of different structure have been done in order to establish the phase diagrams. Special attention is focused on the ferro(antiferro)electric smectic phases.

  17. Spatial ordering and abnormal optical activity of DNA liquid-crystalline dispersion particles

    NASA Astrophysics Data System (ADS)

    Semenov, S. V.; Yevdokimov, Yu. M.

    2016-12-01

    In our work, we investigate physicochemical and optical properties of double-strand DNA dispersions. The study of these properties is of biological interest, because it allows one to describe the characteristics of certain classes of chromosomes and DNA containing viruses. The package pattern of DNA molecules in the dispersions particles (DP) is examined. The consideration of the DNA liquid-crystalline DP optical activity based on the theory of electromagnetic wave absorption by large molecular aggregates has been performed. The investigation is also focused on various effects induced by the interaction between biological active compounds and DNA in the content of liquid-crystalline DP.

  18. Mechanisms of dielectric polarization in thermotropic liquid-crystalline complexes based on lanthanides

    NASA Astrophysics Data System (ADS)

    Dobrun, L. A.; Kovshik, A. P.; Ryumtsev, E. I.; Knyazev, A. A.; Galyametdinov, Yu. G.

    2016-06-01

    The components of the dielectric constant of a terbium-based liquid-crystalline complex have been measured in the frequency range of 350-5 × 106 Hz. The magnitude and sign of the dielectric anisotropy of the complex have been determined. Dispersion of the dielectric constants in the liquid-crystalline and isotropic phases has been found. The mechanisms responsible for the relaxation phenomena that appear in the studied sample have been determined. The time of dielectric relaxation, the activation energy, and the dipole moment of the complex have been obtained.

  19. Thermomagnetic processing of liquid-crystalline epoxy resins and their mechanical characterization using nanoindentation.

    PubMed

    Li, Yuzhan; Rios, Orlando; Kessler, Michael R

    2014-11-12

    A thermomagnetic processing method was used to produce a biphenyl-based liquid-crystalline epoxy resin (LCER) with oriented liquid-crystalline (LC) domains. The orientation of the LCER was confirmed and quantified using two-dimensional X-ray diffraction. The effect of molecular alignment on the mechanical and thermomechanical properties of the LCER was investigated using nanoindentation and thermomechanical analysis, respectively. The effect of the orientation on the fracture behavior was also examined. The results showed that macroscopic orientation of the LC domains was achieved, resulting in an epoxy network with an anisotropic modulus, hardness, creep behavior, and thermal expansion.

  20. Quasi-Liquid Crystalline Materials with Special Electro-Optic Properties

    DTIC Science & Technology

    1988-12-01

    Side chain liquid crystal polymers, Spectrum broadening,,piropyrans, Thermochromism 4 20. A :5TRACT (Continue am t. .. --.o sid e - d idenii-y , y...WORDS (Continue on reveree slde it nd1eaary and Identify by block number) Aggregation, Liquid crystal -fpolysiloxanes, Liquid crystalpolyacrylates...Merocyanines, Non-linear optics, Optical information storage, Photochromisin, Photochromic liquid crystal polymers,-Rheo-optical effect, Second Harmonic

  1. Planar-fingerprint transition in a thermoreversible liquid crystalline gel

    NASA Astrophysics Data System (ADS)

    de Lózar, Alberto; Schöpf, Wolfgang; Rehberg, Ingo; Lafuente, Oscar; Lattermann, Günter

    2005-05-01

    A thermoreversible (physical) gel consisting of a nematic liquid crystal mixed with a small quantity of a chiral organogelator is investigated in the planar configuration. The response of the system to an external electric field reveals multistability within a small hysteresis. The relaxation of the liquid crystal under this field is characterized by two different time scales: a fast one that is connected to the tilt of the director field, and a slow one that describes the reorientation of the chiral structure. In the first case, the relaxation is nonexponential and can be described by a Kohlrausch-Williams-Watts law with a stretching parameter of 0.5.

  2. Structure and mechanical properties of liquid crystalline filaments

    SciTech Connect

    Eremin, Alexey; Nemes, Alexandru; Stannarius, Ralf; Schulz, Mario; Nadasi, Hajnalka; Weissflog, Wolfgang

    2005-03-01

    The formation of stable freely suspended filaments is an interesting peculiarity of some liquid crystal phases. So far, little is known about their structure and stability. Similarly to free-standing smectic films, an internal molecular structure of the mesophase stabilizes these macroscopically well-ordered objects with length to diameter ratios of 10{sup 3} and above. In this paper, we report observations of smectic liquid crystal fibers formed by bent-shaped molecules in different mesophases. Our study, employing several experimental techniques, focuses on mechanical and structural aspects of fiber formation such as internal structure, stability, and mechanical and optical properties.

  3. Organic solar cells based on liquid crystalline and polycrystalline thin films

    NASA Astrophysics Data System (ADS)

    Yoo, Seunghyup

    This dissertation describes the study of organic thin-film solar cells in pursuit of affordable, renewable, and environmentally-friendly energy sources. Particular emphasis is given to the molecular ordering found in liquid crystalline or polycrystalline films as a way to leverage the efficiencies of these types of cells. Maximum efficiencies estimated based on excitonic character of organic solar cells show power conversion efficiencies larger than 10% are possible in principle. However, their performance is often limited due to small exciton diffusion lengths and poor transport properties which may be attributed to the amorphous nature of most organic semiconductors. Discotic liquid crystal (DLC) copper phthalocyanine was investigated as an easily processible building block for solar cells in which ordered molecular arrangements are enabled by a self-organization in its mesophases. An increase in photocurrent and a reduction in series resistance have been observed in a cell which underwent an annealing process. X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements suggest that structural and morphological changes induced after the annealing process are related to these improvements. In an alternative approach, p-type pentacene thin films prepared by physical vapor deposition were incorporated into heterojunction solar cells with C60 as n-type layers. Power conversion efficiencies of 2.7% under broadband illumination (350--900 nm) with a peak external quantum efficiency of 58% have been achieved with the broad spectral coverage across the visible spectrum. Analysis using an exciton diffusion model shows this efficient carrier generation is mainly due to the large exciton diffusion length of pentacene films. Joint XRD and AFM studies reveal that the highly crystalline nature of pentacene films can account for the observed large exciton diffusion length. In addition, the electrical characteristics are studied as a function of light intensity using

  4. Adsorption of lipid liquid crystalline nanoparticles: effects of particle composition, internal structure, and phase behavior.

    PubMed

    Chang, Debby P; Jankunec, Marija; Barauskas, Justas; Tiberg, Fredrik; Nylander, Tommy

    2012-07-24

    Controlling the interfacial behavior and properties of lipid liquid crystalline nanoparticles (LCNPs) at surfaces is essential for their application for preparing functional surface coatings as well as understanding some aspects of their properties as drug delivery vehicles. Here we have studied a LCNP system formed by mixing soy phosphatidylcholine (SPC), forming liquid crystalline lamellar structures in excess water, and glycerol dioleate (GDO), forming reversed structures, dispersed into nanoparticle with the surfactant polysorbate 80 (P80) as stabilizer. LCNP particle properties were controlled by using different ratios of the lipid building blocks as well as different concentrations of the surfactant P80. The LCNP size, internal structure, morphology, and charge were characterized by dynamic light scattering (DLS), synchrotron small-ange X-ray scattering (SAXS), cryo-transmission electron microscopy (cryo-TEM), and zeta potential measurements, respectively. With increasing SPC to GDO ratio in the interval from 35:65 to 60:40, the bulk lipid phase structure goes from reversed cubic micellar phase with Fd3m space group to reversed hexagonal phase. Adding P80 results in a successive shift toward more disorganized lamellar type of structures. This is also seen from cryo-TEM images for the LCNPs, where higher P80 ratios results in more extended lamellar layers surrounding the inner, more dense, lipid-rich particle core with nonlamellar structure. When put in contact with a solid silica surface, the LCNPs adsorb to form multilayer structures with a surface excess and thickness values that increase strongly with the content of P80 and decreases with increasing SPC:GDO ratio. This is reflected in both the adsorption rate and steady-state values, indicating that the driving force for adsorption is largely governed by attractive interactions between poly(ethylene oxide) (PEO) units of the P80 stabilizer and the silica surface. On cationic surface, i.e., silica modified

  5. Magnetic-field induced orientational transition in a helicoidal liquid-crystalline antiferromagnet

    NASA Astrophysics Data System (ADS)

    Zakhlevnykh, A. N.; Kuznetsova, K. V.

    2016-11-01

    The magnetic-field induced orientational transition in helicoidal liquid-crystalline antiferromagnets representing compensated suspensions of magnetic nanoparticles in cholesteric liquid crystals is theoretically studied. The untwisting of a helicoidal structure and the behavior of mean magnetization as a function of the field strength and material parameters are investigated. It is shown that the magnetic subsystems in the field-untwisted ferronematic phase are not completely compensated, and the ferronematic phase is ferrimagnetic.

  6. Liquid Crystalline Thermosets from Ester, Ester-Imide, and Ester-Amide Oligomers

    NASA Technical Reports Server (NTRS)

    Dingemans, Theodornus J. (Inventor); Weiser, Erik S. (Inventor); SaintClair, Terry L. (Inventor)

    2005-01-01

    Main chain thermotropic liquid crystal esters, ester-imides, and ester-amides were prepared from AA, BB, and AB type monomeric materials and were end-capped with phenylacetylene, phenylmaleimide, or nadimide reactive end-groups. The resulting reactive end-capped liquid crystal oligomers exhibit a variety of improved and preferred physical properties. The end-capped liquid crystal oligomers are thermotropic and have, preferably, molecular weights in the range of approximately 1000-15,OOO grams per mole. The end-capped liquid crystal oligomers have broad liquid crystalline melting ranges and exhibit high melt stability and very low melt viscosities at accessible temperatures. The end-capped liquid crystal oligomers are stable for up to an hour in the melt phase. These properties make the end-capped liquid crystal oligomers highly processable by a variety of melt process shape forming and blending techniques including film extrusion, fiber spinning, reactive injection molding (RIM), resin transfer molding (RTM), resin film injection (RFI), powder molding, pultrusion, injection molding, blow molding, plasma spraying and thermo-forming. Once processed and shaped, the end- capped liquid crystal oligomers were heated to further polymerize and form liquid crystalline thermosets (LCT). The fully cured products are rubbers above their glass transition temperatures. The resulting thermosets display many properties that are superior to their non-end-capped high molecular weight analogs.

  7. Liquid Crystalline Thermosets from Ester, Ester-Imide, and Ester-Amide Oligomers

    NASA Technical Reports Server (NTRS)

    Dingemans, Theodornus J. (Inventor); Weiser, Erik S. (Inventor); SaintClair, Terry L. (Inventor)

    2005-01-01

    Main chain thermotropic liquid crystal esters, ester-imides, and ester-amides were prepared from AA, BB, and AB type monomeric materials and were end-capped with phenylacetylene, phenylmaleimide, or nadimide reactive end-groups. The resulting reactive end-capped liquid crystal oligomers exhibit a variety of improved and preferred physical properties. The end-capped liquid crystal oligomers are thermotropic and have, preferably, molecular weights in the range of approximately 1000-15,OOO grams per mole. The end-capped liquid crystal oligomers have broad liquid crystalline melting ranges and exhibit high melt stability and very low melt viscosities at accessible temperatures. The end-capped liquid crystal oligomers are stable for up to an hour in the melt phase. These properties make the end-capped liquid crystal oligomers highly processable by a variety of melt process shape forming and blending techniques including film extrusion, fiber spinning, reactive injection molding (RIM), resin transfer molding (RTM), resin film injection (RFI), powder molding, pultrusion, injection molding, blow molding, plasma spraying and thermo-forming. Once processed and shaped, the end- capped liquid crystal oligomers were heated to further polymerize and form liquid crystalline thermosets (LCT). The fully cured products are rubbers above their glass transition temperatures. The resulting thermosets display many properties that are superior to their non-end-capped high molecular weight analogs.

  8. Liquid crystalline thermosets from ester, ester-imide, and ester-amide oligomers

    NASA Technical Reports Server (NTRS)

    Dingemans, Theodorous J. (Inventor); Weiser, Erik S. (Inventor); St. Clair, Terry L. (Inventor)

    2005-01-01

    Main chain thermotropic liquid crystal esters, ester-imides, and ester-amides were prepared from AA, BB, and AB type monomeric materials and were end-capped with phenylacetylene, phenylmaleimide, or nadimide reactive end-groups. The resulting reactive end-capped liquid crystal oligomers exhibit a variety of improved and preferred physical properties. The end-capped liquid crystal oligomers are thermotropic and have, preferably, molecular weights in the range of approximately 1000-15,000 grams per mole. The end-capped liquid crystal oligomers have broad liquid crystalline melting ranges and exhibit high melt stability and very low melt viscosities at accessible temperatures. The end-capped liquid crystal oligomers are stable for up to an hour in the melt phase. These properties make the end-capped liquid crystal oligomers highly processable by a variety of melt process shape forming and blending techniques including film extrusion, fiber spinning, reactive injection molding (RIM), resin transfer molding (RTM), resin film injection (RFI), powder molding, pultrusion, injection molding, blow molding, plasma spraying and thermo-forming. Once processed and shaped, the end-capped liquid crystal oligomers were heated to further polymerize and form liquid crystalline thermosets (LCT). The fully cured products are rubbers above their glass transition temperatures. The resulting thermosets display many properties that are superior to their non-end-capped high molecular weight analogs.

  9. Understanding changes in cellulose crystalline structure of lignocellulosic biomass during ionic liquid pretreatment by XRD.

    PubMed

    Zhang, Jiafu; Wang, Yixun; Zhang, Liye; Zhang, Ruihong; Liu, Guangqing; Cheng, Gang

    2014-01-01

    X-ray diffraction (XRD) was used to understand the interactions of cellulose in lignocellulosic biomass with ionic liquids (ILs). The experiment was designed in such a way that the process of swelling and solubilization of crystalline cellulose in plant cell walls was followed by XRD. Three different feedstocks, switchgrass, corn stover and rice husk, were pretreated using 1-butyl-3-methylimidazolium acetate ([C4mim][OAc]) at temperatures of 50-130°C for 6h. At a 5 wt.% biomass loading, increasing pretreatment temperature led to a drop in biomass crystallinity index (CrI), which was due to swelling of crystalline cellulose. After most of the crystalline cellulose was swollen with IL molecules, a low-order structure was found in the pretreated samples. Upon further increasing temperature, cellulose II structure started to form in the pretreated biomass samples as a result of solubilization of cellulose in [C4mim][OAc] and subsequent regeneration.

  10. Stability of Equilibria of Nematic Liquid Crystalline Polymers

    DTIC Science & Technology

    2011-01-01

    Gilles de Gennes was awarded the Nobel Prize ∗Received September 30, 2011. This work is partially supported by the National Science Foundation and by the...crystals have spurted intensive experimental, theoretical and numerical studies [1, 5, 6, 18, 31, 39]. One notable example is that in 1991 Pierre ...finite-aspect-ratio macromolecules in shear and related linear flows. Rheol Acta, 2003, 42: 20–46 [18] De Gennes P G, Prost J. The Physics of Liquid

  11. Carrier Transport and Viscosity of Discotic Liquid Crystalline Photoconductor Hexaoctyloxytriphenylene

    NASA Astrophysics Data System (ADS)

    Monobe, Hirosato; Okamoto, Shuichi; Enomoto, Hiroyuki; Shimizu, Yo

    2010-01-01

    In this study, the carrier transport and viscosity of 2,3,6,7,10,11-hexaoctyloxytriphenylene (C8OTP) have been studied by a time-of-flight method and a rotation viscometer. One-anion and two-cation transport was observed in the isotropic liquid phase, whereas the ambipolar electronic and one-anion transport was observed in the columnar mesophase. The activation energies for the ionic conductions in the isotropic liquid phase and columnar mesophase were 0.3 and 0.3 eV, respectively. The viscosity of C8OTP was investigated in the isotropic liquid phase and the activation energy was 0.4 eV. The Stokes radii of ionic carriers were experimentally estimated using Walden's rule. The Stokes radii for one anion and two cations were approximated to be 1, 2, and 8 Å, respectively. The Stokes radius of 8 Å for the larger cation represented the molecular size of C8OTP itself, assuming that C8OTP is a flat spheroid.

  12. Effect of Liquid Crystalline Systems Containing Antimicrobial Compounds on Infectious Skin Bacteria.

    PubMed

    Souza, Carla; Watanabe, Evandro; Aires, Carolina Patrícia; Lara, Marilisa Guimarães

    2017-08-01

    This study aimed (i) to prepare liquid crystalline systems (LCS) of glyceryl monooleate (GMO) and water containing antibacterial compounds and (ii) to evaluate their potential as drug delivery systems for topical treatment of bacterial infections. Therefore, LCS containing CPC (cetylpyridinium chloride) (LCS/CPC) and PHMB (poly(hexamethylene biguanide) hydrochloride) (LCS/PHMB) were prepared and the liquid crystalline phases were identified by polarizing light microscopy 24 h and 7 days after preparation. The in vitro drug release profile and in vitro antibacterial activity of the systems were assessed using the double layer agar diffusion method against Staphylococcus aureus, methicillin-resistant S. aureus, Staphylococcus epidermidis, Escherichia coli, and Enterococcus faecalis. The interaction between GMO and the drugs was evaluated by a drug absorption study. Stable liquid crystalline systems containing CPC and PHMB were obtained. LCS/PHMB decreased the PHMB release rate and exerted strong antibacterial activity against all the investigated bacteria. In contrast, CPC interacted with GMO so strongly that it became attached to the system; the amount released was not sufficient to exert antibacterial activity. Therefore, the studied liquid crystalline systems were suitable to deliver PHMB, but not CPC. Accordingly, it was demonstrated that GMO interacts with each drug differently, which may interfere in the final efficiency of GMO/water LCS.

  13. Anion-directed self-organization of thermotropic liquid crystalline materials containing a guanidinium moiety.

    PubMed

    Kim, Dongwoo; Jon, Sangyong; Lee, Hyung-Kun; Baek, Kangkyun; Oh, Nam-Keun; Zin, Wang-Cheol; Kim, Kimoon

    2005-11-28

    New wedge-shaped thermotropic liquid crystalline materials containing a guanidinium moiety at the apex organize into various supramolecular structures such as hexagonal columnar, rectangular columnar and Pm3n cubic mesophases depending on anions illustrating guest-directed self-organization in mesophases.

  14. A bundled-stack discotic columnar liquid crystalline phase with inter-stack electronic coupling

    DOE PAGES

    Wang, Bin; Sun, Runkun; Günbaş, Duygu D.; ...

    2015-06-15

    The first compound proving to be capable of forming a bundled-stack discotic columnar liquid crystalline (BSDCLC) phase was designed and synthesized. Finally, the unique perylene anhydride inter-stack interaction was found to be the key to the formation of the BSDCLC structure and inter-stack electronic coupling (ISEC).

  15. Photochemical transformations of 2-arylidene-menthanones: chiral dopants for liquid crystalline systems

    NASA Astrophysics Data System (ADS)

    Chepeleva, L. V.; Doroshenko, A. O.; Kutulya, Lidiya A.; Drushlyak, T. G.; Pivnenko, N. S.; Vashchenko, Valery V.

    2003-12-01

    Photochemical E-Z isomerization reaction in the series of chiral 1R,4R-2-arylidene-p-menthanone derivatives has been studied and the behavior of starting materials and photoproducts in liquid crystalline systems was characterized. The differences in photochemical properties of the studied compounds with several benzene rings in arylidene fragments and those containing ester linking groups were revealed and discussed.

  16. Design of Macroscopically Ordered Liquid Crystalline Hydrogel Columns Knitted with Nanosilver for Topical Applications.

    PubMed

    Lali Raveendran, Reshma; Kumar Sasidharan, Nishanth; Devaki, Sudha J

    2017-04-19

    The design of liquid crystalline hydrogels knitted with silver nanoparticles in macroscopic ordering is becoming a subject of research interest due to their promising multifunctional applications in biomedical and optoelectronic applications. The present work describes the development of liquid crystalline Schiff-based hydrogel decorated with silver nanoparticles and the demonstration of its antifungal applications. Schiff base was prepared from polyglucanaldehyde and chitosan, and the former was prepared by the oxidation of amylose (polyglucopyranose) isolated from abundantly available unutilized jackfruit seed starch. Self-assembled silver columns decorated with macroscopically ordered networks were prepared in a single step of in situ condensation and a reduction/complexation process. The various noncovalent interactions among the -OH, -C═O, and -NH impart rigidity and ordering for the formation of macroscopically ordered liquid crystalline hydrogel and the Ag(I) complexation evidenced from the studies made by FT-IR spectroscopy in combination with rheology and microscopic techniques such as SEM, TEM, AFM, XRD, and PLM. The antifungal studies were screened using species of Candida by disc diffusion method. The MIC and MFC values, in vitro antifungal studies, reactive oxygen species (ROS) production, and propidium iodide (PI) uptake results suggest that the present macroscopically ordered liquid crystalline hydrogel system can be considered an excellent candidate for topical applications. All these results suggest that this design strategy can be exploited for the incorporation of biologically relevant metal nanoparticles for developing unique robust hydrogels for multifunctional applications.

  17. A bundled-stack discotic columnar liquid crystalline phase with inter-stack electronic coupling

    SciTech Connect

    Wang, Bin; Sun, Runkun; Günbaş, Duygu D.; Zhang, Hao; Grozema, Ferdinand C.; Xiao, Kai; Jin, Shi

    2015-06-15

    The first compound proving to be capable of forming a bundled-stack discotic columnar liquid crystalline (BSDCLC) phase was designed and synthesized. Finally, the unique perylene anhydride inter-stack interaction was found to be the key to the formation of the BSDCLC structure and inter-stack electronic coupling (ISEC).

  18. Effect of Liquid-Crystalline Epoxy Backbone Structure on Thermal Conductivity of Epoxy-Alumina Composites

    NASA Astrophysics Data System (ADS)

    Giang, Thanhkieu; Kim, Jinhwan

    2017-01-01

    In a series of papers published recently, we clearly demonstrated that the most important factor governing the thermal conductivity of epoxy-Al2O3 composites is the backbone structure of the epoxy. In this study, three more epoxies based on diglycidyl ester-terminated liquid-crystalline epoxy (LCE) have been synthesized to draw conclusions regarding the effect of the epoxy backbone structure on the thermal conductivity of epoxy-alumina composites. The synthesized structures were characterized by proton nuclear magnetic resonance (1H-NMR) and Fourier-transform infrared (FT-IR) spectroscopy. Differential scanning calorimetry, thermogravimetric analysis, and optical microscopy were also employed to examine the thermal and optical properties of the synthesized LCEs and the cured composites. All three LCE resins exhibited typical liquid-crystalline behaviors: clear solid crystalline state below the melting temperature ( T m), sharp crystalline melting at T m, and transition to nematic phase above T m with consequent isotropic phase above the isotropic temperature ( T i). The LCE resins displayed distinct nematic liquid-crystalline phase over a wide temperature range and retained liquid-crystalline phase after curing, with high thermal conductivity of the resulting composite. The thermal conductivity values ranged from 3.09 W/m-K to 3.89 W/m-K for LCE-Al2O3 composites with 50 vol.% filler loading. The steric effect played a governing role in the difference. The neat epoxy resin thermal conductivity was obtained as 0.35 W/m-K to 0.49 W/m-K based on analysis using the Agari-Uno model. The results clearly support the objective of this study in that the thermal conductivity of the LCE-containing networks strongly depended on the epoxy backbone structure and the degree of ordering in the cured network.

  19. Blocking the 4-1BB Pathway Ameliorates Crystalline Silica-induced Lung Inflammation and Fibrosis in Mice

    PubMed Central

    Li, Chao; Du, Sitong; Lu, Yiping; Lu, Xiaowei; Liu, Fangwei; Chen, Ying; Weng, Dong; Chen, Jie

    2016-01-01

    Long term pulmonary exposure to crystalline silica leads to silicosis that manifests progressive interstitial fibrosis, eventually leading to respiratory failure and death. Despite efforts to eliminate silicosis, clinical cases continue to occur in both developing and developed countries. The exact mechanisms of crystalline silica-induced pulmonary fibrosis remain elusive. Herein, we find that 4-1BB is induced in response to crystalline silica injury in lungs and that it is highly expressed during development of experimental silicosis. Therefore, we explore the role of 4-1BB pathway during crystalline silica-induced lung injury and find that a specific inhibitor blocking the pathway could effectively alleviate crystalline silica-induced lung inflammation and subsequent pulmonary fibrosis in vivo. Compared to controls, the treated mice exhibited reduced Th1 and Th17 responses. The concentrations of pro-inflammatory cytokines in bronchoalveolar lavage fluid (BALF), including tumor necrosis factor (TNF)-α, interferon (IFN)-γ and interleukin (IL)-17A following crystalline silica challenge were also reduced in inhibitor-treated mice. Although there was no significant alteration in Th2 cytokines of IL-4 and IL-13, another type of pro-fibrogenic cell, regulatory T cell (Treg) was significantly affected. In addition, one of the major participants in fibrogenesis, fibrocyte recruited less due to the blockade. Furthermore, we demonstrated the decreased fibrocyte recruitment was associated with chemokine reductions in lung. Our study discovers the 4-1BB pathway signaling enhances inflammatory response and promotes pulmonary fibrosis induced by crystalline silica. The findings here provide novel insights into the molecular events that control crystalline silica-induced lung inflammation and fibrosis through regulating Th responses and the recruitment of fibrocytes in crystalline silica-exposed lung. PMID:27698940

  20. Bacterial transport of colloids in liquid crystalline environments.

    PubMed

    Trivedi, Rishi R; Maeda, Rina; Abbott, Nicholas L; Spagnolie, Saverio E; Weibel, Douglas B

    2015-11-21

    We describe the controlled transport and delivery of non-motile eukaryotic cells and polymer microparticles by swimming bacteria suspended in nematic liquid crystals. The bacteria push reversibly attached cargo in a stable, unidirectional path (or along a complex patterned director field) over exceptionally long distances. Numerical simulations and analytical predictions for swimming speeds provide a mechanistic insight into the hydrodynamics of the system. This study lays the foundation for using cargo-carrying bacteria in engineering applications and for understanding interspecies interactions in polymicrobial communities.

  1. Liquid Crystalline Behavior and Related Properties of Colloidal Systems of Inorganic Oxide Nanosheets

    PubMed Central

    Nakato, Teruyuki; Miyamoto, Nobuyoshi

    2009-01-01

    Inorganic layered crystals exemplified by clay minerals can be exfoliated in solvents to form colloidal dispersions of extremely thin inorganic layers that are called nanosheets. The obtained “nanosheet colloids” form lyotropic liquid crystals because of the highly anisotropic shape of the nanosheets. This system is a rare example of liquid crystals consisting of inorganic crystalline mesogens. Nanosheet colloids of photocatalytically active semiconducting oxides can exhibit unusual photoresponses that are not observed for organic liquid crystals. This review summarizes experimental work on the phase behavior of the nanosheet colloids as well as photochemical reactions observed in the clay and semiconducting nanosheets system.

  2. Lyotropic liquid crystalline L3 phase silicated nanoporous monolithic composites and their production

    DOEpatents

    McGrath, Kathryn M.; Dabbs, Daniel M.; Aksay, Ilhan A.; Gruner, Sol M.

    2003-10-28

    A mesoporous ceramic material is provided having a pore size diameter in the range of about 10-100 nanometers produced by templating with a ceramic precursor a lyotropic liquid crystalline L.sub.3 phase consisting of a three-dimensional, random, nonperiodic network packing of a multiple connected continuous membrane. A preferred process for producing the inesoporous ceramic material includes producing a template of a lyotropic liquid crystalline L.sub.3 phase by mixing a surfactant, a co-surfactant and hydrochloric acid, coating the template with an inorganic ceramic precursor by adding to the L.sub.3 phase tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS) and then converting the coated template to a ceramic by removing any remaining liquids.

  3. Polarization axis-selective realignment of a photoreactive liquid crystalline composite with homogeneous alignment

    NASA Astrophysics Data System (ADS)

    Sasaki, Tomoyuki; Shoho, Takashi; Goto, Kohei; Sakamoto, Moritsugu; Noda, Kohei; Kawatsuki, Nobuhiro; Ono, Hiroshi

    2016-06-01

    We investigated the photoalignment properties of a liquid crystalline composite. The composite consisted of a low molecular weight nematic liquid crystal (LC) and a photoreactive liquid crystalline polymer containing 4-(4-methoxycinnamoyloxy)biphenyl side groups. Homogeneously aligned LC composite cells were fabricated using rubbed substrates and were then exposed to a linearly polarized (LP) ultraviolet (UV) laser beam. The alignment states of the LC composites were characterized using a LP visible laser beam. The LC composite in the cell was realigned by LP UV exposure and subsequent annealing. The direction of the realignment could be controlled by the polarization direction of the LP UV beam. The relationship between the realignment direction and the rubbing strength of the substrates was also investigated. A large realignment was induced in the LC composite cell when the azimuthal anchoring strength of the rubbed substrates was relatively weak.

  4. Shadow wave-function variational calculations of crystalline and liquid phases of 4He

    NASA Astrophysics Data System (ADS)

    Vitiello, S. A.; Runge, K. J.; Chester, G. V.; Kalos, M. H.

    1990-07-01

    A new class of variational wave functions for boson systems, shadow wave functions, is used to investigate the properties of solid and liquid 4He. The wave function is translationally invariant and symmetric under particle interchange. In principle, the calculations for the crystalline phase do not require the use of any auxiliary lattice. Using the Metropolis Monte Carlo algorithm, we show that the additional variational degrees of freedom in the wave function lower the energy significantly. This wave function also allows the crystalization of an equilibrated liquid phase when a crystalline seed is used. The pair correlation function and structure factor S(k) are determined in the liquid phase. The condensate fraction is calculated as well. Results are given for the single-particle distribution function around the lattice positions in the solid phase.

  5. Endotoxin-Induced Structural Transformations in Liquid Crystalline Droplets

    NASA Astrophysics Data System (ADS)

    Lin, I.-Hsin; Miller, Daniel S.; Bertics, Paul J.; Murphy, Christopher J.; de Pablo, Juan J.; Abbott, Nicholas L.

    2011-06-01

    The ordering of liquid crystals (LCs) is known to be influenced by surfaces and contaminants. Here, we report that picogram per milliliter concentrations of endotoxin in water trigger ordering transitions in micrometer-size LC droplets. The ordering transitions, which occur at surface concentrations of endotoxin that are less than 10-5 Langmuir, are not due to adsorbate-induced changes in the interfacial energy of the LC. The sensitivity of the LC to endotoxin was measured to change by six orders of magnitude with the geometry of the LC (droplet versus slab), supporting the hypothesis that interactions of endotoxin with topological defects in the LC mediate the response of the droplets. The LC ordering transitions depend strongly on glycophospholipid structure and provide new designs for responsive soft matter.

  6. Biphenyl liquid crystalline epoxy resin as a low-shrinkage resin-based dental restorative nanocomposite.

    PubMed

    Hsu, Sheng-Hao; Chen, Rung-Shu; Chang, Yuan-Ling; Chen, Min-Huey; Cheng, Kuo-Chung; Su, Wei-Fang

    2012-11-01

    Low-shrinkage resin-based photocurable liquid crystalline epoxy nanocomposite has been investigated with regard to its application as a dental restoration material. The nanocomposite consists of an organic matrix and an inorganic reinforcing filler. The organic matrix is made of liquid crystalline biphenyl epoxy resin (BP), an epoxy resin consisting of cyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (ECH), the photoinitiator 4-octylphenyl phenyliodonium hexafluoroantimonate and the photosensitizer champhorquinone. The inorganic filler is silica nanoparticles (∼70-100 nm). The nanoparticles were modified by an epoxy silane of γ-glycidoxypropyltrimethoxysilane to be compatible with the organic matrix and to chemically bond with the organic matrix after photo curing. By incorporating the BP liquid crystalline (LC) epoxy resin into conventional ECH epoxy resin, the nanocomposite has improved hardness, flexural modulus, water absorption and coefficient of thermal expansion. Although the incorporation of silica filler may dilute the reinforcing effect of crystalline BP, a high silica filler content (∼42 vol.%) was found to increase the physical and chemical properties of the nanocomposite due to the formation of unique microstructures. The microstructure of nanoparticle embedded layers was observed in the nanocomposite using scanning and transmission electron microscopy. This unique microstructure indicates that the crystalline BP and nanoparticles support each other and result in outstanding mechanical properties. The crystalline BP in the LC epoxy resin-based nanocomposite was partially melted during exothermic photopolymerization, and the resin expanded via an order-to-disorder transition. Thus, the post-gelation shrinkage of the LC epoxy resin-based nanocomposite is greatly reduced, ∼50.6% less than in commercialized methacrylate resin-based composites. This LC epoxy nanocomposite demonstrates good physical and chemical properties and good biocompatibility

  7. Nonionic diethanolamide amphiphiles with isoprenoid-type hydrocarbon chains: thermotropic and lyotropic liquid crystalline phase behaviour

    SciTech Connect

    Sagnella, Sharon M.; Conn, Charlotte E.; Krodkiewska, Irena; Drummond, Calum J.

    2014-09-24

    The thermotropic and lyotropic liquid crystalline phase behaviour of a series of diethanolamide amphiphiles with isoprenoid-type hydrocarbon chains (geranoyl, H-farnesoyl, and phytanoyl) has been investigated. When neat, both H-farnesoyl and phytanoyl diethanolamide form a smectic liquid crystalline structure at sub-zero temperatures. In addition, all three diethanolamides exhibit a glass transition temperature at around -73 C. Geranoyl diethanolamide forms a lamellar crystalline phase with a lattice parameter of 17.4 {angstrom} following long term storage accompanied by the loss of the glass transition. In the presence of water, H-farnesoyl and phytanoyl diethanolamide form lyotropic liquid crystalline phases, whilst geranoyl diethanolamide forms an L{sub 2} phase. H-farnesoyl diethanolamide forms a fluid lamellar phase (L{sub {alpha}}) at room temperature and up to {approx} 40 C. Phytanoyl diethanolamide displays a rich mesomorphism forming the inverse diamond (Q{sub II}{sup D}) and gyroid (Q{sub II}{sup G}) bicontinuous cubic phases in addition to an L{sub {alpha}} phase.

  8. Solution-based synthesis of crystalline silicon from liquid silane through laser and chemical annealing.

    PubMed

    Iyer, Ganjigunte R S; Hobbie, Erik K; Guruvenket, Srinivasan; Hoey, Justin M; Anderson, Kenneth J; Lovaasen, John; Gette, Cody; Schulz, Douglas L; Swenson, Orven F; Elangovan, Arumugasamy; Boudjouk, P

    2012-05-01

    We report a solution process for the synthesis of crystalline silicon from the liquid silane precursor cyclohexasilane (Si(6)H(12)). Polysilane films were crystallized through thermal and laser annealing, with plasma hydrogenation at atmospheric pressure generating further structural changes in the films. The evolution from amorphous to microcrystalline is characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and impedance spectroscopy. A four-decade enhancement in the electrical conductivity is attributed to a disorder-order transition in a bonded Si network. Our results demonstrate a potentially attractive approach that employs a solution process coupled with ambient postprocessing to produce crystalline silicon thin films.

  9. Screening in crystalline liquids protects energetic carriers in hybrid perovskites

    NASA Astrophysics Data System (ADS)

    Zhu, Haiming; Miyata, Kiyoshi; Fu, Yongping; Wang, Jue; Joshi, Prakriti P.; Niesner, Daniel; Williams, Kristopher W.; Jin, Song; Zhu, X.-Y.

    2016-09-01

    Hybrid lead halide perovskites exhibit carrier properties that resemble those of pristine nonpolar semiconductors despite static and dynamic disorder, but how carriers are protected from efficient scattering with charged defects and optical phonons is unknown. Here, we reveal the carrier protection mechanism by comparing three single-crystal lead bromide perovskites: CH3NH3PbBr3, CH(NH2)2PbBr3, and CsPbBr3. We observed hot fluorescence emission from energetic carriers with ~102-picosecond lifetimes in CH3NH3PbBr3 or CH(NH2)2PbBr3, but not in CsPbBr3. The hot fluorescence is correlated with liquid-like molecular reorientational motions, suggesting that dynamic screening protects energetic carriers via solvation or large polaron formation on time scales competitive with that of ultrafast cooling. Similar protections likely exist for band-edge carriers. The long-lived energetic carriers may enable hot-carrier solar cells with efficiencies exceeding the Shockley-Queisser limit.

  10. Injectable biomimetic liquid crystalline scaffolds enhance muscle stem cell transplantation.

    PubMed

    Sleep, Eduard; Cosgrove, Benjamin D; McClendon, Mark T; Preslar, Adam T; Chen, Charlotte H; Sangji, M Hussain; Pérez, Charles M Rubert; Haynes, Russell D; Meade, Thomas J; Blau, Helen M; Stupp, Samuel I

    2017-09-19

    Muscle stem cells are a potent cell population dedicated to efficacious skeletal muscle regeneration, but their therapeutic utility is currently limited by mode of delivery. We developed a cell delivery strategy based on a supramolecular liquid crystal formed by peptide amphiphiles (PAs) that encapsulates cells and growth factors within a muscle-like unidirectionally ordered environment of nanofibers. The stiffness of the PA scaffolds, dependent on amino acid sequence, was found to determine the macroscopic degree of cell alignment templated by the nanofibers in vitro. Furthermore, these PA scaffolds support myogenic progenitor cell survival and proliferation and they can be optimized to induce cell differentiation and maturation. We engineered an in vivo delivery system to assemble scaffolds by injection of a PA solution that enabled coalignment of scaffold nanofibers with endogenous myofibers. These scaffolds locally retained growth factors, displayed degradation rates matching the time course of muscle tissue regeneration, and markedly enhanced the engraftment of muscle stem cells in injured and noninjured muscles in mice.

  11. Design of Functional Materials based on Liquid Crystalline Droplets.

    PubMed

    Miller, Daniel S; Wang, Xiaoguang; Abbott, Nicholas L

    2014-01-14

    This brief perspective focuses on recent advances in the design of functional soft materials that are based on confinement of low molecular weight liquid crystals (LCs) within micrometer-sized droplets. While the ordering of LCs within micrometer-sized domains has been explored extensively in polymer-dispersed LC materials, recent studies performed with LC domains with precisely defined size and interfacial chemistry have unmasked observations of confinement-induced ordering of LCs that do not follow previously reported theoretical predictions. These new findings, which are enabled in part by advances in the preparation of LCs encapsulated in polymeric shells, are opening up new opportunities for the design of soft responsive materials based on surface-induced ordering transitions. These materials are also providing new insights into the self-assembly of biomolecular and colloidal species at defects formed by LCs confined to micrometer-sized domains. The studies presented in this perspective serve additionally to highlight gaps in knowledge regarding the ordering of LCs in confined systems.

  12. Three-dimensional colloidal crystals in liquid crystalline blue phases

    PubMed Central

    Ravnik, Miha; Alexander, Gareth P.; Yeomans, Julia M.; Žumer, Slobodan

    2011-01-01

    Applications for photonic crystals and metamaterials put stringent requirements on the characteristics of advanced optical materials, demanding tunability, high Q factors, applicability in visible range, and large-scale self-assembly. Exploiting the interplay between structural and optical properties, colloidal lattices embedded in liquid crystals (LCs) are promising candidates for such materials. Recently, stable two-dimensional colloidal configurations were demonstrated in nematic LCs. However, the question as to whether stable 3D colloidal structures can exist in an LC had remained unanswered. We show, by means of computer modeling, that colloidal particles can self-assemble into stable, 3D, periodic structures in blue phase LCs. The assembly is based on blue phases providing a 3D template of trapping sites for colloidal particles. The particle configuration is determined by the orientational order of the LC molecules: Specifically, face-centered cubic colloidal crystals form in type-I blue phases, whereas body-centered crystals form in type-II blue phases. For typical particle diameters (approximately 100 nm) the effective binding energy can reach up to a few 100 kBT, implying robustness against mechanical stress and temperature fluctuations. Moreover, the colloidal particles substantially increase the thermal stability range of the blue phases, for a factor of two and more. The LC-supported colloidal structure is one or two orders of magnitude stronger bound than, e.g., water-based colloidal crystals. PMID:21368186

  13. Design of Functional Materials based on Liquid Crystalline Droplets

    PubMed Central

    Miller, Daniel S.; Wang, Xiaoguang; Abbott, Nicholas L.

    2014-01-01

    This brief perspective focuses on recent advances in the design of functional soft materials that are based on confinement of low molecular weight liquid crystals (LCs) within micrometer-sized droplets. While the ordering of LCs within micrometer-sized domains has been explored extensively in polymer-dispersed LC materials, recent studies performed with LC domains with precisely defined size and interfacial chemistry have unmasked observations of confinement-induced ordering of LCs that do not follow previously reported theoretical predictions. These new findings, which are enabled in part by advances in the preparation of LCs encapsulated in polymeric shells, are opening up new opportunities for the design of soft responsive materials based on surface-induced ordering transitions. These materials are also providing new insights into the self-assembly of biomolecular and colloidal species at defects formed by LCs confined to micrometer-sized domains. The studies presented in this perspective serve additionally to highlight gaps in knowledge regarding the ordering of LCs in confined systems. PMID:24882944

  14. Injectable biomimetic liquid crystalline scaffolds enhance muscle stem cell transplantation

    PubMed Central

    Sleep, Eduard; McClendon, Mark T.; Preslar, Adam T.; Chen, Charlotte H.; Sangji, M. Hussain; Pérez, Charles M. Rubert; Haynes, Russell D.; Meade, Thomas J.; Blau, Helen M.; Stupp, Samuel I.

    2017-01-01

    Muscle stem cells are a potent cell population dedicated to efficacious skeletal muscle regeneration, but their therapeutic utility is currently limited by mode of delivery. We developed a cell delivery strategy based on a supramolecular liquid crystal formed by peptide amphiphiles (PAs) that encapsulates cells and growth factors within a muscle-like unidirectionally ordered environment of nanofibers. The stiffness of the PA scaffolds, dependent on amino acid sequence, was found to determine the macroscopic degree of cell alignment templated by the nanofibers in vitro. Furthermore, these PA scaffolds support myogenic progenitor cell survival and proliferation and they can be optimized to induce cell differentiation and maturation. We engineered an in vivo delivery system to assemble scaffolds by injection of a PA solution that enabled coalignment of scaffold nanofibers with endogenous myofibers. These scaffolds locally retained growth factors, displayed degradation rates matching the time course of muscle tissue regeneration, and markedly enhanced the engraftment of muscle stem cells in injured and noninjured muscles in mice. PMID:28874575

  15. Nanostructured liquid-crystalline particles for drug delivery.

    PubMed

    Lancelot, Alexandre; Sierra, Teresa; Serrano, José Luis

    2014-04-01

    Nanostructured lyotropic liquid crystal particles (LLC NPs) have proven to be extremely useful tools for applications in drug delivery. These structured nanoparticles are formed by amphiphilic molecules and contain internal water channels, which are not in contact with external water, and where polar drugs can situate; on the other hand, apolar drugs can be loaded in the lipophilic part of the structure and the amphiphilic drugs can locate at the polar/apolar interfaces. A revision of the most relevant results published in the field of LLC NPs has been made. The first section discusses the most common compounds used in these nanoparticles and their preparation and characterization. A summary of recent and relevant results including the composition and type of nanoparticles used, the illness treated, the administration via and some special features in each case have been summarized in a table. LLC NPs are highly versatile drug delivery systems, which can be applied by topical, oral and intravenous treatments. Especially relevant is their use for the release of anticancer drugs, biomolecules and vaccines. Nevertheless a number of critical points need to be solved in order to attain practical applications.

  16. Screening in crystalline liquids protects energetic carriers in hybrid perovskites.

    PubMed

    Zhu, Haiming; Miyata, Kiyoshi; Fu, Yongping; Wang, Jue; Joshi, Prakriti P; Niesner, Daniel; Williams, Kristopher W; Jin, Song; Zhu, X-Y

    2016-09-23

    Hybrid lead halide perovskites exhibit carrier properties that resemble those of pristine nonpolar semiconductors despite static and dynamic disorder, but how carriers are protected from efficient scattering with charged defects and optical phonons is unknown. Here, we reveal the carrier protection mechanism by comparing three single-crystal lead bromide perovskites: CH3NH3PbBr3, CH(NH2)2PbBr3, and CsPbBr3 We observed hot fluorescence emission from energetic carriers with ~10(2)-picosecond lifetimes in CH3NH3PbBr3 or CH(NH2)2PbBr3, but not in CsPbBr3 The hot fluorescence is correlated with liquid-like molecular reorientational motions, suggesting that dynamic screening protects energetic carriers via solvation or large polaron formation on time scales competitive with that of ultrafast cooling. Similar protections likely exist for band-edge carriers. The long-lived energetic carriers may enable hot-carrier solar cells with efficiencies exceeding the Shockley-Queisser limit.

  17. Crystalline oligo(ethylene sulfide) domains define highly stable supramolecular block copolymer assemblies.

    SciTech Connect

    Brubaker, Carrie E.; Velluto, Diana; Demurtas, Davide; Phelps, Edward A.; Hubbell, Jeffrey A.

    2015-07-01

    With proper control over copolymer design and solvation conditions, self-assembled materials display impressive morphological variety that encompasses nanoscale colloids as well as bulk three-dimensional architectures. Here we take advantage of both hydrophobicity and crystallinity to mediate supra-molecular self-assembly of spherical micellar, linear fibrillar, or hydrogel structures by a family of highly asymmetric poly(ethylene glycol)-b-oligo(ethylene sulfide) (PEG-OES) copolymers. Assembly structural polymorphism was achieved with modification of PEG-OES topology (linear versus multiarm) and with precise, monomer-by-monomer control of OES length. Notably, all three morphologies were accessed utilizing OES oligomers with degrees of polymerization as short as three. These exceptionally small assembly forming blocks represent the first application of ethylene sulfide oligomers in supramolecular materials. While the assemblies demonstrated robust aqueous stability over time, oxidation by hydrogen peroxide progressively converted ethylene sulfide residues to increasingly hydrophilic and amorphous sulfoxides and sulfones, causing morphological changes and permanent disassembly. We utilized complementary microscopic and spectroscopic techniques to confirm this chemical stimulus-responsive behavior in self-assembled PEG-OES colloidal dispersions and physical gels. In addition to inherent stimulus-responsive behavior, fibrillar assemblies demonstrated biologically relevant molecular delivery, as confirmed by the dose-dependent activation of murine bone marrow-derived dendritic cells following fibril-mediated delivery of the immunological adjuvant monophosphoryl lipid A. In physical gels composed of either linear or multiarm PEG-OES precursors, rheologic analysis also identified mechanical stimulus-responsive shear thinning behavior. Thanks to the facile preparation, user-defined morphology, aqueous stability, carrier functionality, and stimuli-responsive behaviors of

  18. Crystalline Oligo(ethylene sulfide) Domains Define Highly Stable Supramolecular Block Copolymer Assemblies.

    PubMed

    Brubaker, Carrie E; Velluto, Diana; Demurtas, Davide; Phelps, Edward A; Hubbell, Jeffrey A

    2015-07-28

    With proper control over copolymer design and solvation conditions, self-assembled materials display impressive morphological variety that encompasses nanoscale colloids as well as bulk three-dimensional architectures. Here we take advantage of both hydrophobicity and crystallinity to mediate supramolecular self-assembly of spherical micellar, linear fibrillar, or hydrogel structures by a family of highly asymmetric poly(ethylene glycol)-b-oligo(ethylene sulfide) (PEG-OES) copolymers. Assembly structural polymorphism was achieved with modification of PEG-OES topology (linear versus multiarm) and with precise, monomer-by-monomer control of OES length. Notably, all three morphologies were accessed utilizing OES oligomers with degrees of polymerization as short as three. These exceptionally small assembly forming blocks represent the first application of ethylene sulfide oligomers in supramolecular materials. While the assemblies demonstrated robust aqueous stability over time, oxidation by hydrogen peroxide progressively converted ethylene sulfide residues to increasingly hydrophilic and amorphous sulfoxides and sulfones, causing morphological changes and permanent disassembly. We utilized complementary microscopic and spectroscopic techniques to confirm this chemical stimulus-responsive behavior in self-assembled PEG-OES colloidal dispersions and physical gels. In addition to inherent stimulus-responsive behavior, fibrillar assemblies demonstrated biologically relevant molecular delivery, as confirmed by the dose-dependent activation of murine bone marrow-derived dendritic cells following fibril-mediated delivery of the immunological adjuvant monophosphoryl lipid A. In physical gels composed of either linear or multiarm PEG-OES precursors, rheologic analysis also identified mechanical stimulus-responsive shear thinning behavior. Thanks to the facile preparation, user-defined morphology, aqueous stability, carrier functionality, and stimuli-responsive behaviors of

  19. Cholesteric liquid crystalline materials with a dual circularly polarized light reflection band fixed at room temperature.

    PubMed

    Agez, Gonzague; Mitov, Michel

    2011-05-26

    An unpolarized normal-incidence light beam reflected by a cholesteric liquid crystal is left- or right-circularly polarized, in the cholesteric temperature range. In this article, we present a novel approach for fabricating a cholesteric liquid crystalline material that exhibits reflection bands with both senses of polarization at room temperature. A cholesteric liquid crystal that presents a twist inversion at a critical temperature T(c) is blended with a small quantity of photopolymerizable monomers. Upon ultraviolet irradiation above T(c), the liquid crystal becomes a polymer-stabilized liquid crystal. Below T(c), the material reflects a dual circularly polarized band in the infrared. By quenching the experimental cell at a temperature below the blend's melting point, the optical properties of the material in an undercooled state are conserved for months at room temperature, which is critical to potential applications such as heat-repelling windows and polarization-independent photonic devices.

  20. A bicontinuous tetrahedral structure in a liquid-crystalline lipid

    NASA Astrophysics Data System (ADS)

    Longley, William; McIntosh, Thomas J.

    1983-06-01

    The structure of most lipid-water phases can be visualized as an ordered distribution of two liquid media, water and hydrocarbons, separated by a continuous surface covered by the polar groups of the lipid molecules1. In the cubic phases in particular, rod-like elements are linked into three-dimensional networks1,2. Two of these phases (space groups Ia3d and Pn3m) contain two such three-dimensional networks mutually inter-woven and unconnected. Under the constraints of energy minimization3, the interface between the components in certain of these `porous fluids' may well resemble one of the periodic minimal surface structures of the type described mathematically by Schwarz4,5. A structure of this sort has been proposed for the viscous isotropic (cubic) form of glycerol monooleate (GMO) by Larsson et al.6 who suggested that the X-ray diagrams of Lindblom et al.7 indicated a body-centred crystal structure in which lipid bilayers might be arranged as in Schwarz's octahedral surface4. We have now found that at high water contents, a primitive cubic lattice better fits the X-ray evidence with the material in the crystal arranged in a tetrahedral way. The lipid appears to form a single bilayer, continuous in three dimensions, separating two continuous interlinked networks of water. Each of the water networks has the symmetry of the diamond crystal structure and the bilayer lies in the space between them following a surface resembling Schwarz's tetrahedral surface4.

  1. Formation of liquid crystalline phases in aqueous suspensions of platelet-like tripalmitin nanoparticles

    NASA Astrophysics Data System (ADS)

    Schmiele, Martin; Gehrer, Simone; Westermann, Martin; Steiniger, Frank; Unruh, Tobias

    2014-06-01

    Suspensions of platelet-like shaped tripalmitin nanocrystals stabilized by the pure lecithin DLPC and the lecithin blend S100, respectively, have been studied by small-angle x-ray scattering (SAXS) and optical observation of their birefringence at different tripalmitin (PPP) concentrations φPPP. It could be demonstrated that the platelets of these potential drug delivery systems start to form a liquid crystalline phase already at pharmaceutically relevant concentrations φPPP of less than 10 wt. %. The details of this liquid crystalline phase are described here for the first time. As in a previous study [A. Illing et al., Pharm. Res. 21, 592 (2004)] some platelets are found to self-assemble into lamellar stacks above a critical tripalmitin concentration \\varphi _{PPP}^{st} of 4 wt. %. In this study another critical concentration \\varphi _{PPP}^{lc}≈ 7 wt. % for DLPC and \\varphi _{PPP}^{lc}≈ 9 wt. % for S100 stabilized dispersions, respectively, has been observed. \\varphi _{PPP}^{lc} describes the transition from a phase of randomly oriented stacked lamellae and remaining non-assembled individual platelets to a phase in which the stacks and non-assembled platelets exhibit an overall preferred orientation. A careful analysis of the experimental data indicates that for concentrations above \\varphi _{PPP}^{lc} the stacked lamellae start to coalesce to rather small liquid crystalline domains of nematically ordered stacks. These liquid crystalline domains can be individually very differently oriented but possess an overall preferred orientation over macroscopic length scales which becomes successively more expressed when further increasing φPPP. The lower critical concentration for the formation of liquid crystalline domains of the DLPC-stabilized suspension compared to \\varphi _{PPP}^{lc} of the S100-stabilized suspension can be explained by a larger aspect ratio of the corresponding tripalmitin platelets. A geometrical model based on the excluded volumes of

  2. A general strategy for self-assembly of nanosized building blocks on liquid/liquid interfaces.

    PubMed

    Liu, Jian-Wei; Zhang, Shao-Yi; Qi, Hao; Wen, Wu-Cheng; Yu, Shu-Hong

    2012-08-06

    A family of water/oil interfaces is introduced to provide effective platforms for rapid fabrication of large-area self-assembled nanofilms composed of various nanosized building blocks, including nanoparticles (NPs), nanocubes (NC), nanowires (NWs), and nanosheets, at room temperature. As a general interfacial assembly method, NWs and NPs are co-assembled at the liquid/liquid interface. The as-prepared co-assembled Ag NW and Ag NC films show high surface-enhanced Raman spectroscopy (SERS) intensity, the SERS performance being strongly dependent on the number ratio of the two kinds of nanosized building blocks. The results demonstrate that this interfacial system provides a general method for the assembly of various nanosized building blocks with different shapes and dimensionalities, and thus paves an alternative pathway for further applications of macroscopic assemblies with different functionalities.

  3. Spontaneous dislocation of a crystalline lens to the anterior chamber with pupillary block glaucoma in Noonan Syndrome: a case report

    PubMed Central

    Mukhopadhyaya, Udayaditya; Chakraborti, Chandana; Mondal, Anindita; Pattyanayak, Ujjal; Agarwal, Rajesh Kumar; Tripathi, Partha

    2014-01-01

    We report a 13-year-old child with Noonan Syndrome who developed spontaneous dislocation of the crystalline lens in anterior chamber leading to pupillary block glaucoma in the left eye and subluxation of lens in right eye. Intracapsular extraction of the dislocated lens was done in the left eye. Prompt diagnosis and management is needed in such cases to avoid glaucoma and corneal endothelial cell damage. We could not find any such case after thorough Medline search. PMID:25374640

  4. X-ray diffraction study of thermotropic liquid crystalline polyesters and diester model compounds

    NASA Astrophysics Data System (ADS)

    Chin, H. H.; Azaroff, L. V.; Griffin, A. C.

    1987-10-01

    Two nematic liquid crystalline polyesters were examined by X-ray diffraction following quenching from the nematic temperature in a magnetic field of 15 tesla. It was not possible to quench an aligned nematic glass; instead a polycrystalline phase showing some preferred orientation or an unoriented nematic melt yielded monodomain nematic diffraction patterns with one resembling that of a fiber (crystalline) photograph while the other showed good nematic alignment which could be enhanced slightly by annealing. A series of Siamese-twin diester model compounds also examined at their respective nematic temperatures in a magnetic field of compounds also were examined at their crystalline phase at room temperature. All displayed well-aligned nematic monodomains above the crystallization point.

  5. Ion Transport in Polymerized Ionic Liquid Block and Random Copolymers

    NASA Astrophysics Data System (ADS)

    Elabd, Yossef; Ye, Yuesheng; Choi, Jae-Hong; Winey, Karen

    2012-02-01

    Polymerized ionic liquid (PIL) block copolymers, a new type of solid-state polymer electrolyte, are of interest for energy conversion and storage devices, such as fuel cells, batteries, supercapacitors, and solar cells. In this study, a series of PIL diblock and random copolymers with various PIL compositions were synthesized. These consisted of an IL monomer and a non-ionic monomer, 1-[(2-methacryloyloxy)ethyl]-3-butylimidazolium bis(trifluoromethanesulfonyl)imide (MEBIm-TFSI) and methyl methacrylate (MMA), and 1-[(2-acryloyloxy)ethyl]-3-butylimidazolium bis(trifluoromethanesulfonyl)imide (AEBIm-TFSI) and styrene (S), respectively, were synthesized. The anion conductivity (ion transport) and morphology were measured in all of the polymers with EIS, SAXS/WAXS, and TEM. Ion transport in block copolymers are significantly higher than random copolymers at the same PIL composition and are highly dependent on the block copolymer nanostructure. The relationship between ion transport mechanisms and the phase behavior of these materials will be discussed.

  6. Selective Sequence for the Peptide-Triggered Phase Transition of Lyotropic Liquid-Crystalline Structures.

    PubMed

    Liu, Qingtao; Dong, Yao-Da; Boyd, Ben J

    2016-05-24

    A novel concept of using mixed lipids to construct selective peptide-sequence-sensing lyotropic liquid-crystalline (LLC) dispersion systems was investigated. The LLC systems were constructed using a mixture of phytantriol, a lipid that forms lyotropic liquid-crystalline phases, and a novel synthesized peptide-lipid (peplipid) for sensing a target peptide with the RARAR sequence. The internal structure of the dispersed LLC particles was converted from the lamellar structure (liposomes) to the inverse bicontinuous cubic phase (cubosomes) in the presence of the target peptide. The addition of common human proteins did not induce any structural change, indicating a high selectivity of interaction with the target peptide. The concept has potential for the design of targeted controlled release drug delivery agents.

  7. [Preparation and physiochemical properties of curcumin-loaded lipid cubic liquid crystalline nanoparticles].

    PubMed

    Su, Xun; He, Xiu-li; Liu, Xiu-ju; Guo, Jing-yan; Zhai, Guang-xi

    2012-02-01

    To prepare curcumin-loaded lipid cubic liquid crystalline nanoparticles and evaluate its physiochemical properties. The nanoparticles were prepared using hot and high-pressure homogenization. The prescription and preparation process were optimized by uniform design with drug loading and entrapment efficiency as indexes. The nanoparticles were spherical under transmission electron microscope (TEM) with average particle size of 176.1 nm, zeta potential of -25.19 mV, average drug loading of (1.5 +/- 0.2)% and entrapment efficiency of (95 +/- 1.8)%. The release equation: In (1-Q) = -0.0251t-0.0075. The cumulative release percentage was 60% at 36 h in vitro. The obtained curcumin-loaded lipid cubic liquid crystalline nanoparticles shows high entrapment efficiency and good sustain release property.

  8. Shape-memory effect of nanocomposites based on liquid-crystalline elastomers

    NASA Astrophysics Data System (ADS)

    Marotta, A.; Lama, G. C.; Gentile, G.; Cerruti, P.; Carfagna, C.; Ambrogi, V.

    2016-05-01

    In this work, nanocomposites based on liquid crystalline (LC) elastomers were prepared and characterized in their shape memory properties. For the synthesis of materials, p-bis(2,3-epoxypropoxy)-α-methylstilbene (DOMS) was used as mesogenic epoxy monomer, sebacic acid (SA) as curing agent and multi-walled carbon nanotubes (MWCNT) and graphene oxide (GO) as fillers. First, an effective compatibilization methodology was set up to improve the interfacial adhesion between the matrix and the carbonaceous nanofillers, thus obtaining homogeneous distribution and dispersion of the nanofillers within the polymer phase. Then, the obtained nanocomposite films were characterized in their morphological and thermal properties. In particular, the effect of the addition of the nanofillers on liquid crystalline behavior, as well as on shape-memory properties of the realized materials was investigated. It was found that both fillers were able to enhance the thermomechanical response of the LC elastomers, making them good candidates as shape memory materials.

  9. Tunable structures of mixtures of magnetic particles in liquid-crystalline matrices.

    PubMed

    Peroukidis, Stavros D; Lichtner, Ken; Klapp, Sabine H L

    2015-08-14

    We investigate the self-organization of a binary mixture of similar sized rods and dipolar soft spheres by means of Monte-Carlo simulations. We model interparticle interactions by employing anisotropic Gay-Berne, dipolar and soft-sphere interactions. In the limit of vanishing magnetic moments we obtain a variety of fully miscible liquid crystalline phases including nematic, smectic and lamellar phases. For the magnetic mixture, we find that the liquid crystalline matrix supports the formation of orientationally ordered ferromagnetic chains. Depending on the relative size of the species the chains align parallel or perpendicular to the director of the rods forming uniaxial or biaxial nematic, smectic and lamellar phases. As an exemplary external perturbation we apply a homogeneous magnetic field causing uniaxial or biaxial ordering to an otherwise isotropic state.

  10. Photogeneration and enhanced charge transport in aligned smectic liquid crystalline organic semiconductor

    SciTech Connect

    Paul, Sanjoy; Ellman, Brett; Tripathi, Suvagata; Twieg, Robert J.

    2015-10-07

    Liquid crystalline organic semiconductors are emerging candidates for applications in electronic and photonic devices. One of the most attractive aspects of such materials is the potential, in principle, to easily control and manipulate the molecular alignment of the semiconductor over large length scales. Here, we explore the consequences of alignment in a model smectic liquid crystalline semiconductor, and find that the photogeneration efficiency is a strong function of incident polarization in aligned samples. A straightforward theory shows that such behavior is a general feature of aligned materials, regardless of the details of photophysics. Furthermore, we uncover tentative evidence that the mobility of aligned samples is substantially enhanced. Both of these phenomena are of significant technological importance.

  11. Blue and Green Phosphorescent Liquid-Crystalline Iridium Complexes with High Hole Mobility.

    PubMed

    Wang, Yafei; Cabry, Christopher P; Xiao, ManJun; Male, Louise; Cowling, Stephen J; Bruce, Duncan W; Shi, Junwei; Zhu, Weiguo; Baranoff, Etienne

    2016-01-26

    Blue- and green-emitting cyclometalated liquid-crystalline iridium complexes are realized by using a modular strategy based on strongly mesogenic groups attached to an acetylacetonate ancillary ligand. The cyclometalated ligand dictates the photophysical properties of the materials, which are identical to those of the parent complexes. High hole mobilities, up to 0.004 cm(2) V(-1) s(-1), were achieved after thermal annealing, while amorphous materials show hole mobilities of only approximately 10(-7) -10(-6) cm(2) V(-1) s(-1), similar to simple iridium complexes. The design strategy allows the facile preparation of phosphorescent liquid-crystalline complexes with fine-tuned photophysical properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Self-organized liquid-crystalline nanostructured membranes for water treatment: selective permeation of ions.

    PubMed

    Henmi, Masahiro; Nakatsuji, Koji; Ichikawa, Takahiro; Tomioka, Hiroki; Sakamoto, Takeshi; Yoshio, Masafumi; Kato, Takashi

    2012-05-02

    A membrane with ordered 3D ionic nanochannels constructed by in situ photopolymerization of a thermotropic liquid-crystalline monomer shows high filtration performance and ion selectivity. The nanostructured membrane exhibits water-treatment performance superior to that of an amorphous membrane prepared from the isotropic melt of the monomer. Self-organized nanostructured membranes have great potential for supplying high-quality water. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Early dynamics of guest-host interaction in dye-doped liquid crystalline materials.

    PubMed

    Truong, Thai V; Xu, Lei; Shen, Y R

    2003-05-16

    We have studied in detail the early dynamics of laser-induced molecular reorientation in a dye-doped liquid crystalline (LC) medium that exhibits a significant enhancement of the optical Kerr nonlinearity due to guest-host interaction. Experimental results agree quantitatively with theory based on a model in which the anisotropic dye excitation helps reorient the LC molecules through a mean-field intermolecular interaction.

  14. Investigations on the liquid crystalline phases of cation-induced condensed DNA

    NASA Astrophysics Data System (ADS)

    Pillai, C. K. S.; Sundaresan, Neethu; Radhakrishnan Pillai, M.; Thomas, T.; Thomas, T. J.

    2005-10-01

    Viral and nonviral condensing agents are used in gene therapy to compact oligonucleotides and plasmid DNA into nanostructures for their efficient transport through the cell membranes. Whereas viral vectors are best by the toxic effects on the immune system, most of the nonviral delivery vehicles are not effective for use in clinical system. Recent investigations indicate that the supramolecular organization of DNA in the condensed state is liquid crystalline. The present level of understanding of the liquid crystalline phase of DNA is inadequate and a thorough investigation is required to understand the nature, stability, texture and the influence of various environmental conditions on the structure of the phase. The present study is mainly concerned with the physico-chemical investigations on the liquid crystalline transitions during compaction of DNA by cationic species such as polyamines and metallic cations. As a preliminary to the above investigation, studies were conducted on the evolution of mesophase transitions of DNA with various cationic counterion species using polarized light microscopy. These studies indicated significant variations in the phase behaviour of DNA in the presence of Li and other ions. Apart from the neutralization of the charges on the DNA molecule, these ions are found to influence selectively the hydration sphere of DNA that in turn influences the induction and stabilization of the LC phases. The higher stability observed with the liquid crystalline phases of Li--DNA system could be useful in the production of nanostructured DNA. In the case of the polyamine, a structural specificity effect depending on the nature, charge and structure of the polyamine used has been found to be favoured in the crystallization of DNA.

  15. Cubic liquid crystalline nanoparticles: optimization and evaluation for ocular delivery of tropicamide.

    PubMed

    Verma, Purnima; Ahuja, Munish

    2016-10-01

    The purpose of this study was to investigate the potential of cubic liquid crystalline nanoparticles for ocular delivery of tropicamide. Ultrasound-assisted fragmentation of cubic liquid crystalline bulk phases resulted in cubic liquid crystalline nanoparticles employing Pluronic F127 as dispersant. The effects of process variables such as sonication time, sonication amplitude, sonication depth, and pre-mixing time on particle size and polydispersity index was investigated using central composite design. The morphology of tropicamide-loaded nanoparticles was found to be nearly cubical in shape by transmission electron microscopy observation. Further, small angle X-ray scattering experiment confirmed the presence of D and P phase cubic structures in coexistence. The optimized tropicamide-loaded cubic nanoparticles showed in vitro corneal permeation of tropicamide across isolated porcine cornea comparable to its commercial preparation, Tropicacyl®. Ocular tolerance was evaluated by Hen's egg-chorioallantoic membrane test and histological studies. The results of in vivo mydriatic response study demonstrated a remarkably higher area under mydriatic response curve (AUC0→1440 min) values of cubic nanoparticles over Tropicacyl® indicating better therapeutic value of cubic nanoparticles. Furthermore, tropicamide-loaded cubic nanoparticles exhibited prolonged mydriatic effect on rabbits as compared to commercial conventional aqueous ophthalmic solution.

  16. Crystalline and liquid Si3 N4 characterization by first-principles molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Mauri, Aurelio; Celino, Massimo; Castellani, Niccoló; Erbetta, Davide

    2011-05-01

    Silicon nitride (Si3 N4) has a wide range of engineering applications where its mechanical and electronic properties can be effectively exploited. In particular, in the microelectronics field, the amorphous silicon nitride films are widely used as charge storage layer in metal-alumina-nitrideoxide nonvolatile memory devices. Atomic structure of amorphous silicon nitride is characterized by an high concentration of traps that control the electric behavior of the final device by the trappingde-trapping mechanism of the electrical charge occurring in its traps. In order to have a deep understanding of the material properties and, in particular, the nature of the electrical active traps a detailed numerical characterization of the crystalline and liquid phases is mandatory. For these reasons first-principles molecular dynamics simulations are extensively employed to simulate the crystalline Si3 N4 in its crystalline and liquid phases. Good agreement with experimental results is obtained in terms of density and formation entalpy. Detailed characterization of c-Si3 N4 electronic properties is performed in terms of band structure and band gap. Then constant temperature and constant volume first-principles molecular dynamics is used to disorder a stoichiometric sample of Si3 N4 . Extensive molecular dynamics simulations are performed to obtain a reliable liquid sample whose atomic structure does not depend on the starting atomic configuration. Detailed characterization of the atomic structure is achieved in terms of radial distribution functions and total structure factor.

  17. Side-Chain Liquid Crystalline Poly(meth)acrylates with Bent-Core Mesogens

    SciTech Connect

    Chen,X.; Tenneti, K.; Li, C.; Bai, Y.; Wan, X.; Fan, X.; Zhou, Q.; Rong, L.; Hsiao, B.

    2007-01-01

    We report the design, synthesis, and characterization of side-chain liquid crystalline (LC) poly(meth)acrylates with end-on bent-core liquid crystalline (BCLC) mesogens. Both conventional free radical polymerization and atom transfer radical polymerization have been used to synthesize these liquid crystalline polymers (LCP). The resulting polymers exhibit thermotropic LC behavior. Differential scanning calorimetry, thermopolarized light microscopy, wide-angle X-ray diffraction, and small-angle X-ray scattering were used to characterize the LC structure of both monomers and polymers. The electro-optic (EO) measurement was carried out by applying a triangular wave and measuring the LC EO response. SmCP (Smectic C indicates the LC molecules are tilted with respect to the layer normal; P denotes polar ordering) phases were observed for both monomers and polymers. In LC monomers, typical antiferroelectric switching was observed. In the ground state, SmCP{sub A} (A denotes antiferroelectric) was observed which switched to SmCP{sub F} (F denotes ferroelectric) upon applying an electric field. In the corresponding LCP, a unique bilayer structure was observed, which is different from the reported BCLC bilayer SmCG (G denotes generated) phase. Most of the LCPs did not switch upon applying electric field while weak AF switching was observed in a low molecular weight poly{l_brace}3'-[4-(4-n-dodecyloxybenzoyloxy)benzoyloxy]-4-(12-acryloyloxydodecyloxy)benzoyloxybiphenyl{r_brace} sample.

  18. [Linear clusters of gold nanoparticles in quasinematic layers of DNA liquid-crystalline dispersion particles].

    PubMed

    Evdokimov, Iu M; Shtykova, E V; Salianov, V I; Skuridin, S G

    2013-01-01

    The effects of small size (approximately 2 nm) gold nanoparticles on the properties of particles of cholesteric liquid-crystalline dispersions formed by double-stranded DNA molecules were analyzed. It has been shown that gold nanoparticles induce two different processes. First, they facilitate reorganization of the spatial cholesteric structure of dispersion particles to nematic one. This process is accompanied by the fast decrease in the amplitude of abnormal band in the CD spectrum. Second, they can form ensembles consisting of gold nanoparticles. This process is accompanied by the development and displacement of surface plasmon resonance band in the visible region of the absorption spectrum. The appearance of this band is analyzed by considering two different models of the formation of ensembles consisting of gold nanoparticles. By small-angle X-ray scattering we performed structural analysis of phases formed by DNA cholesteric liquid-crystalline dispersion particles treated with gold nanoparticles. As a result of this study it was possible to prove the formation of linear clusters of gold nanoparticles in the "free space" between the adjacent DNA molecules fixed in the quasinematic layers of liquid-crystalline particles. It has been hypothesized that the formation of linear clusters of gold nanoparticles is most likely related to DNA molecules, ordered in the spatial structure of quasinematic layers, and the toxicity of these nanoparticles in biological systems hypothesized.

  19. From Cellulosic Based Liquid Crystalline Sheared Solutions to 1D and 2D Soft Materials

    PubMed Central

    Godinho, Maria Helena; Almeida, Pedro Lúcio; Figueirinhas, João Luis

    2014-01-01

    Liquid crystalline cellulosic-based solutions described by distinctive properties are at the origin of different kinds of multifunctional materials with unique characteristics. These solutions can form chiral nematic phases at rest, with tuneable photonic behavior, and exhibit a complex behavior associated with the onset of a network of director field defects under shear. Techniques, such as Nuclear Magnetic Resonance (NMR), Rheology coupled with NMR (Rheo-NMR), rheology, optical methods, Magnetic Resonance Imaging (MRI), Wide Angle X-rays Scattering (WAXS), were extensively used to enlighten the liquid crystalline characteristics of these cellulosic solutions. Cellulosic films produced by shear casting and fibers by electrospinning, from these liquid crystalline solutions, have regained wider attention due to recognition of their innovative properties associated to their biocompatibility. Electrospun membranes composed by helical and spiral shape fibers allow the achievement of large surface areas, leading to the improvement of the performance of this kind of systems. The moisture response, light modulated, wettability and the capability of orienting protein and cellulose crystals, opened a wide range of new applications to the shear casted films. Characterization by NMR, X-rays, tensile tests, AFM, and optical methods allowed detailed characterization of those soft cellulosic materials. In this work, special attention will be given to recent developments, including, among others, a moisture driven cellulosic motor and electro-optical devices. PMID:28788696

  20. Self-Assembled Cubic Liquid Crystalline Nanoparticles for Transdermal Delivery of Paeonol.

    PubMed

    Li, Jian-Chun; Zhu, Na; Zhu, Jin-Xiu; Zhang, Wen-Jing; Zhang, Hong-Min; Wang, Qing-Qing; Wu, Xiao-Xiang; Wang, Xiu; Zhang, Jin; Hao, Ji-Fu

    2015-10-30

    The aim of this study was to optimize the preparation method for self-assembled glyceryl monoolein-based cubosomes containing paeonol and to characterize the properties of this transdermal delivery system to improve the drug penetration ability in the skin. In this study, the cubic liquid crystalline nanoparticles loaded with paeonol were prepared by fragmentation of glyceryl monoolein (GMO)/poloxamer 407 bulk cubic gel by high-pressure homogenization. We evaluated the Zeta potential of these promising skin-targeting drug-delivery systems using the Malvern Zeta sizer examination, and various microscopies and differential scanning calorimetry were also used for property investigation. Stimulating studies were evaluated based on the skin irritation reaction score standard and the skin stimulus intensity evaluation standard for paeonol cubosomes when compared with commercial paeonol ointment. In vitro tests were performed on excised rat skins in an improved Franz diffusion apparatus. The amount of paeonol over time in the in vitro penetration and retention experiments both was determined quantitatively by HPLC. Stimulating studies were compared with the commercial ointment which indicated that the paeonol cubic liquid crystalline nanoparticles could reduce the irritation in the skin stimulating test. Thus, based on the attractive characteristics of the cubic crystal system of paeonol, we will further exploit the cosmetic features in the future studies. The transdermal delivery system of paeonol with low-irritation based on the self-assembled cubic liquid crystalline nanoparticles prepared in this study might be a promising system of good tropical preparation for skin application.

  1. Curcumin-Loaded Lipid Cubic Liquid Crystalline Nanoparticles: Preparation, Optimization, Physicochemical Properties and Oral Absorption.

    PubMed

    He, Xiuli; Li, Qinghua; Liu, Xiuju; Wu, Guangsheng; Zhai, Guangxi

    2015-08-01

    In order to improve the oral absorption of curcumin, curcumin-loaded lipid cubic liquid crystalline nanoparticles were prepared and evaluated in vitro and in vivo. The hot and high-pressure homogenization method was used to prepare the nanoparticles. The formulation and process were optimized by uniform design with drug loading and entrapment efficiency as index, and physicochemical properties were also investigated. Spherical nanoparticles were observed under transmission electron microscope (TEM), with average particle size of 176.1 nm, zeta potential of -25.19 mV, average drug loading of (1.5 ± 0.2)% and entrapment efficiency of (95 ± 1.8)%. The in vitro release of curcumin from the nanoparticle formulation showed a sustained property, while the pharmacokinetics results after oral administration of curcumin loaded lipid cubic liquid crystalline nanoparticles in rat showed that the oral absorption of curcumin fitted one-compartment model and relative bioavailability was 395.56% when compared to crude curcumin. It can be concluded from these results that the lipid cubic liquid crystalline nanoparticles, as carriers, can markedly improve the oral absorption of curcumin.

  2. Growth, dynamics, and texture modeling of the lamellar smectic-A liquid crystalline transition

    NASA Astrophysics Data System (ADS)

    Abukhdeir, Nasser Mohieddin

    2009-11-01

    This thesis is focused on the study of material transformations from the disordered state to the lamellar-ordered/smectic-A liquid crystalline state via multi-scale multi-transport modeling and simulation. This approach utilizes a high-order Landau-de Gennes phenomenological model able to bridge the gap between experimentally observed macro-scale phenomena and the nano-scale growth and structure inherent to liquid crystalline ordering. A unique feature of this simulation-based thesis is the direct verification of predictions with past experimental observations. In this context, the main contributions of this thesis work focuses on three experimental systems: free growth of an isolated domain, defect/texture formation, and the evolution of texture/defect interactions as the system approaches equilibrium. Simulation studies of free growth were first performed under conditions of deep undercooling, where non-isothermal effects can be neglected. The growth/shape kinetic evolution of initially textured and homogeneous spherulites growing into an unstable isotropic matrix phase was found, elucidating nano-scale morphology/texture processes and growth instabilities inaccessible experimentally. Undulation instabilities in growing smectic-A spherulites discovered in this work shed light on a possible mechanism for the formation of experimentally observed anisotropic "batonnet" morphologies and two-dimension focal conic defect structures. Recent experimental observations of growth kinetic phenomena of meta-stable nematic pre-ordering was studied, showing that the high-order model both predicts this phenomenon and explains the underlying mechanisms for experimentally determined morphological trends. A non-isothermal extension to the high-order model is derived and applied to study free growth under shallow undercooling conditions, where latent heat and anisotropic thermal diffusion are non-negligible. Growth laws, agreeing with experimental observations, are determined and

  3. Nanofibers with very fine core-shell morphology from anisotropic micelle of amphiphilic crystalline-coil block copolymer.

    PubMed

    Zhai, Fei-Yu; Huang, Wei; Wu, Gang; Jing, Xin-Ke; Wang, Mei-Jia; Chen, Si-Chong; Wang, Yu-Zhong; Chin, In-Joo; Liu, Ya

    2013-06-25

    A novel and facile strategy, combining anisotropic micellization of amphiphilic crystalline-coil copolymer in water and reassembly during single spinneret electrospinning, was developed for preparing nanofibers with very fine core-shell structure. Polyvinyl alcohol (PVA) and polyethylene glycol-block-poly(p-dioxanone) (PEG-b-PPDO) were used as the shell and the crystallizable core layer, respectively. The core-shell structure could be controllably produced by altering concentration of PEG-b-PPDO, and the chain length of the PPDO block. The morphology of the nanofibers was investigated by Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM). X-ray rocking curve measurements were performed to investigate the degree of ordered alignment of the PPDO crystalline lamellae in the nanofiber. The results suggested that the morphology of nanoparticles in spinning solution plays very important role in determining the phase separation of nanofibers. The amphiphilic PEG-b-PPDO copolymer self-assembled into star anise nanoaggregates in water solution induced by the crystallization of PPDO blocks. When incorporated with PVA, the interaction between PVA and PEG-b-PPDO caused a morphological transition of the nanoaggregates from star anise to small flake. For flake-like particles, their flat surface is in favor of compact stacking of PPDO crystalline lamellae and interfusion of amorphous PPDO in the core of nanofibers, leading to a relatively ordered alignment of PPDO crystalline lamellae and well-defined core-shell phase separation. However, for star anise-like nanoaggregates, their multibranched morphology may inevitably prohibit the compact interfusion of PPDO phase, resulting in a random microphase separation.

  4. "Bicontinuous cubic" liquid crystalline materials from discotic molecules: a special effect of paraffinic side chains with ionic liquid pendants.

    PubMed

    Alam, Md Akhtarul; Motoyanagi, Jin; Yamamoto, Yohei; Fukushima, Takanori; Kim, Jungeun; Kato, Kenichi; Takata, Masaki; Saeki, Akinori; Seki, Shu; Tagawa, Seiichi; Aida, Takuzo

    2009-12-16

    Triphenylene (TP) derivatives bearing appropriate paraffinic side chains with imidazolium ion-based ionic liquid (IL) pendants were unveiled to display a phase diagram with liquid crystalline (LC) mesophases of bicontinuous cubic (Cub(bi)) and hexagonal columnar (Col(h)) geometries. While their phase transition behaviors are highly dependent on the length of the side chains and the size of the ionic liquid pendants, TPs with hexadecyl side chains exclusively form a Cub(bi) LC assembly over an extremely wide temperature range of approximately 200 degrees C from room temperature when the anions of the IL pendants are relatively small. Wide-angle X-ray diffraction analysis suggested that the Cub(bi) LC mesophase contains pi-stacked columnar TP arrays with a plane-to-plane separation of approximately 3.5 A. Consistently, upon laser flash photolysis, it showed a transient microwave conductivity comparable to that of a Col(h) LC reference.

  5. [Influence of low-intensity laser radiation on the formation of liquid crystalline structures in a solution of glycoproteins].

    PubMed

    Skopinov, S A; Iakovleva, S V; Denisova, E A; Vazina, A A; Zheleznaia, L A

    1989-01-01

    Liquid-crystalline structure formation in glycoprotein solutions irradiated by helium-neon laser in the presence of hydrogen peroxide was observed by both polarizing microscopy and spectrophotometry. High molecular weight (2.10(6) Da) and heavily glycosylated (about 80%) glycoprotein was isolated from the mucus layer of pig small intestine. Remarkable changes of both optic parameters of the solutions and the morphology of liquid-crystalline structures were detected in irradiated samples compared to the non-irradiated ones.

  6. Study on synthesis processes and crystallinity changes of nanographene materials synthesized by alcohol liquid-plasma

    NASA Astrophysics Data System (ADS)

    Kondo, Hiroki; Hagino, Tatsuya; Takeda, Keigo; Ishikawa, Kenji; Kano, Hiroyuki; Sekine, Makoto; Hori, Masaru

    2012-10-01

    Nanometer-sized graphene is one of promising materials for novel applications such as electrical device, compound materials, and so forth, owing to its excellent and unique electrical, physical and morphological properties. In recent years, we have realized the high-speed synthesis, over 1mg/min., of the nanographene with high-crystallinity using in-liquid plasma. In this study, elementary steps of nanographene synthesis and crystallinity change during synthesis were investigated. A high-voltage (10 kV) 60 Hz ac-voltage was applied to the two electrodes above and below alcohol surface. After the plasma discharge for 15 minutes, nanographene materials were dispersed in the alcohols and collected by a filtration method. According to the Raman spectra, when ethanol was used, types of metal electrodes did not affect synthesis rates and crystallinity. However, when 1-butanol was used, crystallinity of nanographenes drastically changed depending on types of metal electrodes. It is because different synthesis processes depending on types of alcohols have different dependence on metal electrodes.

  7. Silymarin glyceryl monooleate/poloxamer 407 liquid crystalline matrices: physical characterization and enhanced oral bioavailability.

    PubMed

    Lian, Ruyue; Lu, Yi; Qi, Jianping; Tan, Yanan; Niu, Mengmeng; Guan, Peipei; Hu, Fuqiang; Wu, Wei

    2011-12-01

    Silymarin, a mixture of flavonolignans extracted from the seeds of milk thistle, is used clinically as a hepatoprotector to treat liver injuries and chronic hepatitis. However, its therapeutic effect is compromised by its poor oral bioavailability due to the poor solubility and low permeability across intestinal epithelia. The main purpose of this study was to prepare silymarin glyceryl monooleate/poloxamer 407 liquid crystalline matrices (GMO/P407 LCM) to improve the oral bioavailability of silymarin. GMO/P407 LCMs were prepared by a melting/congealing method. The isotropic phenomenon observed under polarized light microscope confirmed the liquid crystalline structure at the junction of LCM and water. Both differential scanning calorimetry and X-ray diffraction analysis confirmed disappearance of silymarin crystallinity after incorporation into the LCMs. In vitro release of silymarin from LCMs was limited, whereas LCMs were readily degraded by lipase and released silymarin quickly and completely. Pharmacokinetic study in beagle dogs showed significantly increased peak concentration for silymarin GMO/P407 LCM, and, most importantly, a 3.46-fold increase in oral bioavailability as compared with Legalon®, a commercial silymarin formulation.

  8. Crystalline monolayer surface of liquid Au-Cu-Si-Ag-Pd: Metallic glass former

    SciTech Connect

    Mechler, S; Yahel, E; Pershan, P S; Meron, M; Lin, B

    2012-02-06

    It is demonstrated by means of x-ray synchrotron reflectivity and diffraction that the surface of the liquid phase of the bulk metallic glass forming alloy Au49Cu26.9Si16.3Ag5.5Pd2.3 consists of a two-dimensional crystalline monolayer phase for temperatures of up to about 50 K above the eutectic temperature. The present alloy as well as glass forming Au82Si18 and Au-Si-Ge alloys containing small amounts of Ge are the only metallic liquids to exhibit surface freezing well above the melting temperature. This suggests that the phenomena of surface freezing in metallic liquids and glass forming ability are related and probably governed by similar physical properties.

  9. Quantitation of liquid-crystalline ordering in F-actin solutions.

    PubMed

    Coppin, C M; Leavis, P C

    1992-09-01

    Actin filaments (F-actin) are important determinants of cellular shape and motility. These functions depend on the collective organization of numerous filaments with respect to both position and orientation in the cytoplasm. Much of the orientational organization arises spontaneously through liquid crystal formation in concentrated F-actin solutions. In studying this phenomenon, we found that solutions of purified F-actin undergo a continuous phase transition, from the isotropic state to a liquid crystalline state, when either the mean filament length or the actin concentration is increased above its respective threshold value. The phase diagram representing the threshold filament lengths and concentrations at which the phase transition occurs is consistent with that predicted by Flory's theory on solutions of noninteracting, rigid cylinders (Flory, 1956b). However, in contrast to other predictions based on this model, we found no evidence for the coexistence of isotropic and anisotropic phases. Furthermore, the phase transition proved to be temperature dependent, which suggests the existence of orientation-dependent interfilament interactions or of a temperature-dependent filament flexibility. We developed a simple method for growing undistorted fluorescent acrylodan-labeled F-actin liquid crystals; and we derived a simple theoretical treatment by which polarization-of-fluorescence measurements could be used to quantitate, for the first time, the degree of spontaneous filament ordering (nematic order parameter) in these F-actin liquid crystals. This order parameter was found to increase monotonically with both filament length and concentration. Actin liquid crystals can readily become distorted by a process known as "texturing." Zigzaging and helicoidal liquid crystalline textures which persisted in the absence of ATP were observed through the polarizing microscope. Possible texturing mechanisms are discussed.

  10. Method for forming single phase, single crystalline 2122 BCSCO superconductor thin films by liquid phase epitaxy

    NASA Technical Reports Server (NTRS)

    Pandey, Raghvendra K. (Inventor); Raina, Kanwal (Inventor); Solayappan, Narayanan (Inventor)

    1994-01-01

    A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83 K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

  11. Ionic-liquid-assisted synthesis of YF{sub 3} with different crystalline phases and morphologies

    SciTech Connect

    Zhong Haoxiang; Hong Jianming; Cao Xiaofeng; Chen Xuetai Xue Ziling

    2009-03-05

    YF{sub 3} with different crystalline phases and morphologies have been prepared via a facile hydrothermal route assisted by imidazolium ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate (C{sub 4}mimBF{sub 4}) or 1-butyl-3-methylimidazolium hexafluorophosphate (C{sub 4}mimPF{sub 6}). The microstructures and morphologies of YF{sub 3} particles were characterized by X-ray powder diffraction, X-ray photoelectron spectra (XPS), transmission electron microscopy (TEM), high resolution electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). Cubic and orthorhombic YF{sub 3} were selectively synthesized by adjusting the molar ratio of the reagents and using C{sub 4}mimBF{sub 4} as the fluoride source, while only orthorhombic YF{sub 3} was obtained using C{sub 4}mimPF{sub 6}, indicating that the crystalline phases and morphologies of the products were significantly influenced by fluoride source and reaction media.

  12. Low temperature Raman study of a liquid crystalline system 4-Decyloxy benzoic acid (4DBA)

    NASA Astrophysics Data System (ADS)

    Vikram, K.; Nandi, Rajib; Singh, Ranjan K.

    2013-08-01

    The Raman spectra of a liquid crystalline system, 4-Decyloxy benzoic acid (4DBA) have been recorded at different temperatures within the interval 300-78 K in order to identify the structural changes in crystalline state of a nematogen and to understand the molecular alignment therein. The earlier predicted dimer structure of 4DBA was optimized with DFT method and the theoretical Raman spectra of dimer as well as monomer have been calculated for comparison with the experimental spectra. The mode specific quartic coupling coefficient; Ai,ω and phonon frequency; ωi have been calculated using temperature dependent anharmonic perturbation theory. The precise band shape analysis of Raman bands at ˜807, ˜881, ˜1255, ˜1282, ˜1436, ˜1576, ˜1604, ˜2881 and ˜3081 cm-1 gives signature of temperature induced slow crystal modification. The structural changes leading to crystal modification have been discussed.

  13. Solution-Based Synthesis of Crystalline Silicon from Liquid Silane through Laser and Chemical Annealing

    SciTech Connect

    Iyer, Ganjigunte R. S.; Hobbie, Erik K.; Guruvenket, Srinivasan; Hoey, Justin M.; Anderson, Kenneth J.; Lovaasen, John; Gette, Cody; Schulz, Douglas L.; Swenson, Orven F.; Elangovan, Arumugasamy; Boudjouk, P.

    2012-05-23

    We report a solution process for the synthesis of crystalline silicon from the liquid silane precursor cyclohexasilane (Si6H12). Polysilane films were crystallized through thermal and laser annealing, with plasma hydrogenation at atmospheric pressure generating further structural changes in the films. The evolution from amorphous to microcrystalline is characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and impedance spectroscopy. A four-decade enhancement in the electrical conductivity is attributed to a disorder-order transition in a bonded Si network. Lastly, our results demonstrate a potentially attractive approach that employs a solution process coupled with ambient post-processing to produce crystalline silicon thin films.

  14. Swollen liquid-crystalline lamellar phase based on extended solid-like sheets.

    PubMed

    Gabriel, J C; Camerel, F; Lemaire, B J; Desvaux, H; Davidson, P; Batail, P

    2001-10-04

    Ordering particles at the nanometre length scale is a challenging and active research area in materials science. Several approaches have so far been developed, ranging from the manipulation of individual particles to the exploitation of self-assembly in colloids. Nanometre-scale ordering is well known to appear spontaneously when anisotropic organic moieties form liquid-crystalline phases; this behaviour is also observed for anisotropic mineral nanoparticles resulting in the formation of nematic, smectic and hexagonal mesophases. Here we describe a lyotropic liquid-crystalline lamellar phase comprising an aqueous dispersion of planar solid-like sheets in which all the atoms involved in a layer are covalently bonded. The spacing of these phosphatoantimonate single layers can be increased 100-fold, resulting in one-dimensional structures whose periodicity can be tuned from 1.5 to 225 nanometres. These highly organized materials can be mechanically or magnetically aligned over large pH and temperature ranges, and this property can be used to measure residual dipolar couplings for the structure determination of biomolecules by liquid-state NMR. We also expect that our approach will result in the discovery of other classes of mineral lyotropic lamellar phases.

  15. Dynamical Study of Guest-Host Orientational Interaction in LiquidCrystalline Materials

    SciTech Connect

    Truong, Thai Viet

    2005-01-01

    Guest-host interaction has long been a subject of interest in many disciplines. Emphasis is often on how a small amount of guest substance could significantly affect the properties of a host material. This thesis describe our work in studying a guest-host effect where dye-doping of liquid crystalline materials greatly enhances the optical Kerr nonlinearity of the material. The dye molecules, upon excitation and via intermolecular interaction, provides an extra torque to reorient the host molecules, leading to the enhanced optical Kerr nonlinearity. We carried out a comprehensive study on the dynamics of the photoexcited dye-doped liquid crystalline medium. Using various experimental techniques, we separately characterized the dynamical responses of the relevant molecular species present in the medium following photo-excitation, and thus were able to follow the transient process in which photo-excitation of the dye molecules exert through guest-host interaction a net torque on the host LC material, leading to the observed enhanced molecular reorientation. We also observed for the first time the enhanced reorientation in a pure liquid crystal system, where the guest population is created through photoexcitation of the host molecules themselves. Experimental results agree quantitatively with the time-dependent theory based on a mean-field model of the guest-host interaction.

  16. Vitrified chiral-nematic liquid crystalline films for selective reflection and circular polarization

    SciTech Connect

    Katsis, D.; Chen, P.H.M.; Mastrangelo, J.C.; Chen, S.H.; Blanton, T.N.

    1999-06-01

    Nematic and left-handed chiral-nematic liquid crystals comprising methoxybiphenylbenzoate and (S)-(-)-1-phenylethylamine pendants to a cyclohexane core were synthesized and characterized. Although pristine samples were found to be polycrystalline, thermal quenching following heating to and annealing at elevated temperatures permitted the molecular orders characteristic of liquid crystalline mesomorphism to be frozen in the glassy state. Left at room temperature for 6 months, the vitrified liquid crystalline films showed no evidence of recrystallization. An orientational order parameter of 0.65 was determined with linear dichroism of a vitrified nematic film doped with Exalite 428 at a mole fraction of 0.0025. Birefringence dispersion of a blank vitrified nematic film was determined using a phase-difference method complemented by Abbe refractometry. A series of vitrified chiral-nematic films were prepared to demonstrate selective reflection and circular polarization with a spectral region tunable from blue to the infrared region by varying the chemical composition. The experimentally measured circular polarization spectra were found to agree with the Good-Karali theory in which all four system parameters were determined a priori: optical birefringence, average refractive index, selective reflection wavelength, and film thickness.

  17. Crystallization induced block copolymer assembly at curved liquid-liquid interface

    NASA Astrophysics Data System (ADS)

    Qi, Hao; Zhou, Tian; Zhou, Hao; Li, Christopher; Soft Materials Lab Team

    In a selected solvent, amphiphilic block copolymers can self-assemble into various micelle structures which find widespread applications in nanomedicine. Herein we report a directed assembly of poly (l-lactide acid)-b-poly (ethylene glycol) (PLLA-b-PEG) at curved oil/water interfaces. Oil droplets were dispersed in water phase upon sonication with amphiphilic PLLA-b-PEG as the surfactant. Subsequent crystallization of PLLA segments resulted in the formation of lamellasomes consisting of crystalline PLLA shell and densely-grafted (approx.1chain/nm2) PEG layer. The structure, morphology, and mechanical properties of these unique polymer ensembles were investigated using transmission electron microscopy and atomic force microscopy. Detailed formation mechanism will be discussed in detail.

  18. Self-Assembled Cubic Liquid Crystalline Nanoparticles for Transdermal Delivery of Paeonol

    PubMed Central

    Li, Jian-Chun; Zhu, Na; Zhu, Jin-Xiu; Zhang, Wen-Jing; Zhang, Hong-Min; Wang, Qing-Qing; Wu, Xiao-Xiang; Wang, Xiu; Zhang, Jin; Hao, Ji-Fu

    2015-01-01

    Background The aim of this study was to optimize the preparation method for self-assembled glyceryl monoolein-based cubosomes containing paeonol and to characterize the properties of this transdermal delivery system to improve the drug penetration ability in the skin. Material/Methods In this study, the cubic liquid crystalline nanoparticles loaded with paeonol were prepared by fragmentation of glyceryl monoolein (GMO)/poloxamer 407 bulk cubic gel by high-pressure homogenization. We evaluated the Zeta potential of these promising skin-targeting drug-delivery systems using the Malvern Zeta sizer examination, and various microscopies and differential scanning calorimetry were also used for property investigation. Stimulating studies were evaluated based on the skin irritation reaction score standard and the skin stimulus intensity evaluation standard for paeonol cubosomes when compared with commercial paeonol ointment. In vitro tests were performed on excised rat skins in an improved Franz diffusion apparatus. The amount of paeonol over time in the in vitro penetration and retention experiments both was determined quantitatively by HPLC. Results Stimulating studies were compared with the commercial ointment which indicated that the paeonol cubic liquid crystalline nanoparticles could reduce the irritation in the skin stimulating test. Thus, based on the attractive characteristics of the cubic crystal system of paeonol, we will further exploit the cosmetic features in the future studies. Conclusions The transdermal delivery system of paeonol with low-irritation based on the self-assembled cubic liquid crystalline nanoparticles prepared in this study might be a promising system of good tropical preparation for skin application. PMID:26517086

  19. Estimation of ground- and excited-state dipole moments of oxazine 1 in liquid and liquid crystalline media.

    PubMed

    Gilani, A Ghanadzadeh; Moghadam, M; Zakerhamidi, M S

    2011-06-01

    The absorption and fluorescence spectra of a laser dye, oxazine-1 (OX1), in liquid and liquid crystalline media were studied at room temperature. The solvatochromic method was used to determine the ground- and excited-state dipole moments by means of Lippert-Mataga, Bakshiev, Kawski-Chamma-Viallet polarity functions. The solvent polarity has no large and regular effect on the spectral behavior of OX1, and thus it might be considered as a poor solvatochromic indicator dye. In addition, applicability of solvatochromic method for this dye in anisotropic media was investigated. On the other hand, nature and degree of the solute-solvent interactions were characterized using correlation of multi-parameter solvent polarity scales. Due to the theoretical restrictions and the dye molecular structure, deviations from the solvatochromic correlation were observed.

  20. Estimation of ground- and excited-state dipole moments of oxazine 1 in liquid and liquid crystalline media

    NASA Astrophysics Data System (ADS)

    Ghanadzadeh Gilani, A.; Moghadam, M.; Zakerhamidi, M. S.

    2011-06-01

    The absorption and fluorescence spectra of a laser dye, oxazine-1 (OX1), in liquid and liquid crystalline media were studied at room temperature. The solvatochromic method was used to determine the ground- and excited-state dipole moments by means of Lippert-Mataga, Bakshiev, Kawski-Chamma-Viallet polarity functions. The solvent polarity has no large and regular effect on the spectral behavior of OX1, and thus it might be considered as a poor solvatochromic indicator dye. In addition, applicability of solvatochromic method for this dye in anisotropic media was investigated. On the other hand, nature and degree of the solute-solvent interactions were characterized using correlation of multi-parameter solvent polarity scales. Due to the theoretical restrictions and the dye molecular structure, deviations from the solvatochromic correlation were observed.

  1. Interferometric Sensor of Wavelength Detuning Using a Liquid Crystalline Polymer Waveplate

    PubMed Central

    Wierzba, Paweł

    2016-01-01

    Operation of a polarization interferometer for measurement of the wavelength changes of a tunable semiconductor laser was investigated. A λ/8 waveplate made from liquid crystalline polymer is placed in one of interferometers’ arms in order to generate two output signals in quadrature. Wavelength was measured with resolution of 2 pm in the wavelength range 628–635 nm. Drift of the interferometer, measured in the period of 500 s, was 8 nm, which corresponded to the change in the wavelength of 1.3 pm. If needed, wavelength-dependent Heydemann correction can be used to expand the range of operation of such interferometer. PMID:27171082

  2. Liquid crystalline polymer networks based on a nematic epoxy resin with azoxy group

    NASA Astrophysics Data System (ADS)

    Włodarska, M.; Mossety-Leszczak, B.; Bąk, G. W.; Galina, H.; Ledzion, R.

    2009-06-01

    The paper presents research results on curing two recently synthesized liquid crystalline epoxy materials with selected amines. The process of cross-linking, the final product of curing, and the pure monomers were examined using polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and dielectric spectroscopy (DS). Chemical structure of the products was confirmed using spectroscopic methods. The authors attempted to demonstrate how selection of curing conditions (such as the amine used as curing agent, the curing temperature or preparation of the surface in contact with the sample) influences optical properties of the cured product.

  3. Liquid crystalline nanowires in porous alumina: geometric confinement versus influence of pore walls.

    PubMed

    Steinhart, Martin; Zimmermann, Sven; Göring, Petra; Schaper, Andreas K; Gösele, Ulrich; Weder, Christoph; Wendorff, Joachim H

    2005-03-01

    Aligned liquid crystalline nanowires within ordered porous alumina templates show a pronounced texture on a macroscopic scale. We have investigated the influence of the geometric confinement and the nature of the pore walls on the mesophase formation by means of X-ray diffraction. The apparent texture is the result of a complex interplay of the pore geometry, interfacial phenomena, and the thermal history. Pores with a diameter of a few hundred nm guide the mesophase formation more efficiently than those with a diameter below 100 nm.

  4. Molecular Engineering of Liquid Crystalline Polymers by Living Polymerization. 22. Synthesis and Characterization of Binary Copolymers

    DTIC Science & Technology

    1992-03-27

    are isomorphic but behave as a non-ideal solution. Poly [( l 5-8)-¢o-( -li: ] X/Y 10 This copolymer is synthesized from a pair of monomers whose parent...Science Case Western Reserve University D T IC Cleveland, OH 44106-2699 E L EC fE 7 Submitted for Publication • APR07 1992 , D in Liquid Crystal March...Crystalline Polymers by Living Polymerization. 22. Synthesis and Characterization of Binary Copolymers Of I l -14 -Cyano-4*-biphenyl)oxy]undecany Vinyl Ether

  5. Large scale molecular dynamics simulations of a liquid crystalline droplet with fast multipole implementations

    SciTech Connect

    Wang, Z.; Lupo, J.; Patnaik, S.S.; McKenney, A.; Pachter, R.

    1999-07-01

    The Fast Multipole Method (FMM) offers an efficient way (order O(N)) to handle long range electrostatic interactions, thus enabling more realistic molecular dynamics simulations of large molecular systems. The performance of the fast molecular dynamics (FMD) code, a parallel MD code being developed in the group, using the three-dimensional fast multipole method, shows a good speedup. The application to the full atomic-scale molecular dynamics simulation of a liquid crystalline droplet of 4-n-pentyl-4{prime}-cyanobiphenyl (5CB) molecules, of size 35,872 atoms, shows strong surface effects on various orientational order parameters.

  6. Preparation of ordered and crosslinked films from liquid crystalline vinyl ether monomers

    SciTech Connect

    Andersson, H.; Sahlen, F.; Gedde, U.W.; Hult, A.

    1993-12-31

    Highly ordered densely crosslinked liquid crystalline poly(vinyl ether) films have been prepared by in-situ photopolymerization of oriented bifunctional mesogenic vinyl ether monomers. Orientation was achieved either by a simple surface treatment, using an unidirectionally rubbed polyimide film or by a magnetic field. Polymerization from various monomer phases resulted in LC polymer network films with different molecular organizations. The films were analyzed with small-angle X-ray scattering, polarized light microscopy and infrared-dichroism measurements. It was shown that films with nematic, smectic A and smectic B structures were obtained, the latter having a very high degree of orientation.

  7. Finite-difference time-domain analysis of light propagation in cholesteric liquid crystalline droplet array

    NASA Astrophysics Data System (ADS)

    Yamamoto, Kaho; Iwai, Yosuke; Uchida, Yoshiaki; Nishiyama, Norikazu

    2016-08-01

    We numerically analyzed the light propagation in cholesteric liquid crystalline (CLC) droplet array by the finite-difference time-domain (FDTD) method. The FDTD method successfully reproduced the experimental light path observed in the complicated photonic structure of the CLC droplet array more accurately than the analysis of CLC droplets by geometric optics with Bragg condition, and this method help us understand the polarization of the propagating light waves. The FDTD method holds great promise for the design of various photonic devices composed of curved photonic materials like CLC droplets and microcapsules.

  8. Synergistic properties of PEN fibers blended with novel thermotropic liquid crystalline copolyesters

    SciTech Connect

    Lo, V.C.; Choi, C.K.; Farris, R.J.

    1996-12-31

    This work discusses the formulation, melt-processing, and properties of PEN and its polyblends with a series of novel semi-flexible thermotropic liquid crystalline polymer (TLCP) copolyesters. Several new structure-property relationships for the pure PEN fiber are established with strong implications for further processing studies. Thermal data and morphology data indicate that model predictions involving ideal, high-modulus in-situ reinforcement are insufficient to account for the observed levels of mechanical property enhancement. Evidence from thermal studies shows clearly that the TLCPs can modify the PEN matrix in which they are blended.

  9. Alignment engineering in liquid crystalline elastomers: Free-form microstructures with multiple functionalities

    SciTech Connect

    Zeng, Hao; Cerretti, Giacomo; Wiersma, Diederik S. E-mail: wiersma@lens.unifi.it; Wasylczyk, Piotr; Martella, Daniele; Parmeggiani, Camilla E-mail: wiersma@lens.unifi.it

    2015-03-16

    We report a method to fabricate polymer microstructures with local control over the molecular orientation. Alignment control is achieved on molecular level in a structure of arbitrary form that can be from 1 to 100 μm in size, by fixing the local boundary conditions with micro-grating patterns. The method makes use of two-photon polymerization (Direct Laser Writing) and is demonstrated specifically in liquid-crystalline elastomers. This concept allows for the realization of free-form polymeric structures with multiple functionalities which are not possible to realize with existing techniques and which can be locally controlled by light in the micrometer scale.

  10. Light-Driven Liquid Crystalline Materials: From Photo-Induced Phase Transitions and Property Modulations to Applications.

    PubMed

    Bisoyi, Hari Krishna; Li, Quan

    2016-12-28

    Light-driven phenomena both in living systems and nonliving materials have enabled truly fascinating and incredible dynamic architectures with terrific forms and functions. Recently, liquid crystalline materials endowed with photoresponsive capability have emerged as enticing systems. In this Review, we focus on the developments of light-driven liquid crystalline materials containing photochromic components over the past decade. Design and synthesis of photochromic liquid crystals (LCs), photoinduced phase transitions in LC, and photoalignment and photoorientation of LCs have been covered. Photomodulation of pitch, polarization, lattice constant and handedness inversion of chiral LCs is discussed. Light-driven phenomena and properties of liquid crystalline polymers, elastomers, and networks have also been analyzed. The applications of photoinduced phase transitions, photoalignment, photomodulation of chiral LCs, and photomobile polymers have been highlighted wherever appropriate. The combination of photochromism, liquid crystallinity, and fabrication techniques has enabled some fascinating functional materials which can be driven by ultraviolet, visible, and infrared light irradiation. Nanoscale particles have been incorporated to widen and diversify the scope of the light-driven liquid crystalline materials. The developed materials possess huge potential for applications in optics, photonics, adaptive materials, nanotechnology, etc. The challenges and opportunities in this area are discussed at the end of the Review.

  11. Nondisruptive Dissolution of Hyperpolarized 129 Xe into Viscous Aqueous and Organic Liquid Crystalline Environments

    SciTech Connect

    Truxal, Ashley E.; Slack, Clancy C.; Gomes, Muller D.; Vassiliou, Christophoros C.; Wemmer, David E.; Pines, Alexander

    2016-03-08

    Studies of hyperpolarized xenon-129 in media such as liquid crystals and cell suspensions are in demand for applications ranging from biomedical imaging to materials engineering but have been hindered by the inability to bubble Xe through the desired media as a result of viscosity or perturbations caused by bubbles. This research reports on a device that can be reliably used to dissolve hp- 129 Xe into viscous aqueous and organic samples without bubbling. This method is robust, requires small sample volumes ( < 60 μL), is compatible with existing NMR hardware, and is made from readily available materials. Experiments show that Xe can be introduced into viscous and aligned media without disrupting molecular order. We detected dissolved xenon in an aqueous liquid crystal that is disrupted by the shear forces of bubbling, and we observed liquid-crystal phase transitions in (MBBA). This tool allows an entirely new class of samples to be investigated by hyperpolarized-gas NMR spectroscopy. Blending into the crowd: A new device that facilitates the direct dissolution of hyperpolarized 129 Xe into viscous liquid-crystalline media is presented. 129 Xe and 2 H NMR spectra show the nondisruptive dissolution of xenon, the presence of ordered phases, and, in the case of the thermotropic liquid crystal N-(4-methoxybenzylidene)-4-butylaniline, a nematic-isotropic phase transition.

  12. A liquid-crystalline hexagonal columnar phase in highly-dilute suspensions of imogolite nanotubes

    NASA Astrophysics Data System (ADS)

    Paineau, Erwan; Krapf, Marie-Eve M.; Amara, Mohamed-Salah; Matskova, Natalia V.; Dozov, Ivan; Rouzière, Stéphan; Thill, Antoine; Launois, Pascale; Davidson, Patrick

    2016-01-01

    Liquid crystals have found wide applications in many fields ranging from detergents to information displays and they are also increasingly being used in the `bottom-up' self-assembly approach of material nano-structuration. Moreover, liquid-crystalline organizations are frequently observed by biologists. Here we show that one of the four major lyotropic liquid-crystal phases, the columnar one, is much more stable on dilution than reported so far in literature. Indeed, aqueous suspensions of imogolite nanotubes, at low ionic strength, display the columnar liquid-crystal phase at volume fractions as low as ~0.2%. Consequently, due to its low visco-elasticity, this columnar phase is easily aligned in an alternating current electric field, in contrast with usual columnar liquid-crystal phases. These findings should have important implications for the statistical physics of the suspensions of charged rods and could also be exploited in materials science to prepare ordered nanocomposites and in biophysics to better understand solutions of rod-like biopolymers.

  13. Ab initio calculations of the optical properties of crystalline and liquid InSb

    SciTech Connect

    Sano, Haruyuki; Mizutani, Goro

    2015-11-15

    Ab initio calculations of the electronic and optical properties of InSb were performed for both the crystalline and liquid states. Two sets of atomic structure models for liquid InSb at 900 K were obtained by ab initio molecular dynamics simulations. To reduce the effect of structural peculiarities in the liquid models, an averaging of the two sets of the calculated electronic and optical properties corresponding to the two liquid models was performed. The calculated results indicate that, owing to the phase transition from crystal to liquid, the density of states around the Fermi level increases. As a result, the energy band gap opening near the Fermi level disappears. Consequently, the optical properties change from semiconductor to metallic behavior. Namely, owing to the melting of InSb, the interband transition peaks disappear and a Drude-like dispersion is observed in the optical dielectric functions. The optical absorption at a photon energy of 3.06 eV, which is used in Blu-ray Disc systems, increases owing to the melting of InSb. This increase in optical absorption is proposed to result from the increased optical transitions below 2 eV.

  14. A liquid-crystalline hexagonal columnar phase in highly-dilute suspensions of imogolite nanotubes

    PubMed Central

    Paineau, Erwan; Krapf, Marie-Eve M.; Amara, Mohamed-Salah; Matskova, Natalia V.; Dozov, Ivan; Rouzière, Stéphan; Thill, Antoine; Launois, Pascale; Davidson, Patrick

    2016-01-01

    Liquid crystals have found wide applications in many fields ranging from detergents to information displays and they are also increasingly being used in the ‘bottom-up' self-assembly approach of material nano-structuration. Moreover, liquid-crystalline organizations are frequently observed by biologists. Here we show that one of the four major lyotropic liquid-crystal phases, the columnar one, is much more stable on dilution than reported so far in literature. Indeed, aqueous suspensions of imogolite nanotubes, at low ionic strength, display the columnar liquid-crystal phase at volume fractions as low as ∼0.2%. Consequently, due to its low visco-elasticity, this columnar phase is easily aligned in an alternating current electric field, in contrast with usual columnar liquid-crystal phases. These findings should have important implications for the statistical physics of the suspensions of charged rods and could also be exploited in materials science to prepare ordered nanocomposites and in biophysics to better understand solutions of rod-like biopolymers. PMID:26728415

  15. Impact of ionic liquid pretreatment conditions on cellulose crystalline structure using 1-ethyl-3-methylimidazolium acetate.

    PubMed

    Cheng, Gang; Varanasi, Patanjali; Arora, Rohit; Stavila, Vitalie; Simmons, Blake A; Kent, Michael S; Singh, Seema

    2012-08-23

    Ionic liquids (ILs) have been shown to affect cellulose crystalline structure in lignocellulosic biomass during pretreatment. A systematic investigation of the swelling and dissolution processes associated with IL pretreatment is needed to better understand cellulose structural transformation. In this work, 3-20 wt % microcrystalline cellulose (Avicel) solutions were treated with 1-ethyl-3-methylimidazolium acetate ([C(2)mim][OAc]) and a mixture of [C(2)mim][OAc] with the nonsolvent dimethyl sulfoxide (DMSO) at different temperatures. The dissolution process was slowed by decreasing the temperature and increasing cellulose loading, and was further retarded by addition of DMSO, enabling in-depth examination of the intermediate stages of dissolution. Results show that the cellulose I lattice expands and distorts prior to full dissolution in [C(2)mim][OAc] and that upon precipitation the former structure leads to a less ordered intermediate structure, whereas fully dissolved cellulose leads to a mixture of cellulose II and amorphous cellulose. Enzymatic hydrolysis was more rapid for the intermediate structure (crystallinity = 0.34) than for cellulose II (crystallinity = 0.54).

  16. Anchoring Strength of Thin Aligned-Polymer Films Formed by Liquid Crystalline Monomer

    NASA Astrophysics Data System (ADS)

    Murashige, Takeshi; Fujikake, Hideo; Ikehata, Seiichiro; Sato, Fumio

    2003-04-01

    We have evaluated the polar anchoring strength of a thin molecule-aligned polymer film formed by a liquid crystalline monomer. The polymer film was obtained by photopolymerization of the monomer oriented by a rubbed polyimide alignment layer in a chamber filled with N2 gas. We fabricated a nematic liquid crystal cell using the thin aligned-polymer films as alignment layers, and then evaluated the anchoring strength of the polymer by measuring the optical retardation curve of the cell driven by voltages. The experimental result showed that the anchoring strength was one order of magnitude lower than that of a conventional rubbed polyimide alignment layer, and decreased with increasing the cure temperature of the monomer film.

  17. Arrangement and SERS Applications of Nanoparticle Clusters Using Liquid Crystalline Template.

    PubMed

    Kim, Dae Seok; Honglawan, Apiradee; Yang, Shu; Yoon, Dong Ki

    2017-02-16

    Manipulation of nanomaterials such as nanoparticles (NPs) and nanorods (NRs) to make clusters is of significant interest in material science and nanotechnology due to the unusual collective opto-electric properties in such structures that cannot be found in the individual NPs. This work demonstrates an effective way to arrange NP clusters (NPCs) to make the desired arrays based on removable and NP-guidable liquid crystalline template using sublimation and reconstruction phenomenon. The position of the NPCs is precisely controlled by the defect structure of the liquid crystal (LC), namely toric focal conic domains (TFCDs), during thermal annealing to construct the LC and corresponding NPC structures. As a proof of concept, the surface-enhanced Raman scattering (SERS) activity of a fabricated array of gold nanorod (GNR) clusters is measured and shown to have highly sensitive detection characteristics essential for potential sensing applications.

  18. Molecular dynamics simulation of the liquid crystalline semiconductor: 8-TTP-8

    NASA Astrophysics Data System (ADS)

    Yoneya, Makoto; Funahashi, Masahiro; Yokoyama, Hiroshi

    2009-02-01

    In this study, the structure and dynamics of a liquid crystalline semiconductor dioctylterthiophene system, 8-TTP-8, were examined by molecular dynamics simulations. We especially focus on the melting transition from the crystal to the liquid crystal smectic G phase. Simulations of the rotational autocorrelation functions show that the transition is characterized by the onset of rotation around the long molecular axis, while maintaining a hexagonal packing within the smectic layers. This implies that the stepwise decrease of the carrier mobility at the melting transition point may be caused by this rotational disordering. We also found the molecular diffusions (at a rate of D~0.9x-10m2/s) in the simulated SmG phase. All these characteristics of the simulated SmG phase, including the molecular diffusions, are similar to those of a rotator (plastic crystal) phase.

  19. Localised actuation in composites containing carbon nanotubes and liquid crystalline elastomers.

    PubMed

    Camargo, Carlos J; Campanella, Humberto; Marshall, Jean E; Torras, Núria; Zinoviev, Kirill; Terentjev, Eugene M; Esteve, Jaume

    2011-12-15

    A liquid crystalline elastomer-carbon nanotube (LCE-CNT) composite displays a reversible shape change property in response to light. The development of some systems such as tactile devices requires localised actuation of this material. A method is reported that combines mechanical stretching and thermal crosslinking of an LCE-CNT for creating sufficiently well-aligned liquid crystal units to produce localised actuation. The method demonstrates that it is feasible to optically drive a LCE-CNT film within a localised area, since only the walls of the stretched parts of the film contain aligned LC domains. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Towards photo-induced swimming: actuation of liquid crystalline elastomer in water

    NASA Astrophysics Data System (ADS)

    Cerretti, Giacomo; Martella, Daniele; Zeng, Hao; Parmeggiani, Camilla; Palagi, Stefano; Mark, Andrew G.; Melde, Kai; Qiu, Tian; Fischer, Peer; Wiersma, Diederik S.

    2016-04-01

    Liquid Crystalline Elastomers (LCEs) are very promising smart materials that can be made sensitive to different external stimuli, such as heat, pH, humidity and light, by changing their chemical composition. In this paper we report the implementation of a nematically aligned LCE actuator able to undergo large light-induced deformations. We prove that this property is still present even when the actuator is submerged in fresh water. Thanks to the presence of azo-dye moieties, capable of going through a reversible trans-cis photo-isomerization, and by applying light with two different wavelengths we managed to control the bending of such actuator in the liquid environment. The reported results represent the first step towards swimming microdevices powered by light.

  1. Liquid Crystalline Granules Align in a Hierarchical Structure To Produce Spider Dragline Microfibrils.

    PubMed

    Lin, Ting-Yu; Masunaga, Hiroyasu; Sato, Ryota; Malay, Ali D; Toyooka, Kiminori; Hikima, Takaaki; Numata, Keiji

    2017-04-10

    The spider silk spinning process converts spidroins from an aqueous form to a tough fiber. This spinning process has been investigated by numerous researchers, and micelles or liquid crystals of spidroins have been reported to form silk fibers, which are bundles of silk microfibrils. However, the formation process of silk microfibrils has not been clarified previously. Here, we report that silk microfibrils are generated through the formation, homogenization, and linkage of liquid crystalline granules without micelle-like structures. Heterogeneous granules on the submicron to micron scale were observed in the storage sac, whereas homogeneous granules with diameters of approximately 100 nm were aligned along the tapering duct. In the spun fibers, the homogeneous granules were connected along the fiber axis. This is the first clear description of the formation of granule-based microfibrils in the spinning process, which is the key conversion process leading to the unique hierarchical structure of spider dragline.

  2. Thermo- and photo-driven soft actuators based on crosslinked liquid crystalline polymers

    NASA Astrophysics Data System (ADS)

    Gu, Wei; Wei, Jia; Yu, Yanlei

    2016-09-01

    Crosslinked liquid crystalline polymers (CLCPs) are a type of promising material that possess both the order of liquid crystals and the properties of polymer networks. The anisotropic deformation of the CLCPs takes place when the mesogens experience order to disorder change in response to external stimuli; therefore, they can be utilized to fabricate smart actuators, which have potential applications in artificial muscles, micro-optomechanical systems, optics, and energy-harvesting fields. In this review the recent development of thermo- and photo-driven soft actuators based on the CLCPs are summarized. Project supported by the National Natural Science Foundation of China (Grant Nos. 21134003, 21273048, 51225304, and 51203023) and Shanghai Outstanding Academic Leader Program, China (Grant No. 15XD1500600).

  3. Polarization-Sensitive Two-Photon Microscopy Study of the Organization of Liquid-Crystalline DNA

    PubMed Central

    Mojzisova, Halina; Olesiak, Joanna; Zielinski, Marcin; Matczyszyn, Katarzyna; Chauvat, Dominique; Zyss, Joseph

    2009-01-01

    Abstract Highly concentrated DNA solutions exhibit self-ordering properties such as the generation of liquid-crystalline phases. Such organized domains may play an important role in the global chromatin topology but can also be used as a simple model for the study of more complex 3D DNA structures. In this work, using polarized two-photon fluorescence microscopy, we report on the orientation of DNA molecules in liquid-crystalline phases. For this purpose, we analyze the signal emitted by fluorophores that are noncovalently bound to DNA strands. In nonlinear processes, excitation occurs exclusively in the focal volume, which offers advantages such as the reduction of photobleaching of out-of-focus molecules and intrinsic 3D sectioning capability. Propidium iodide and Hoechst, two fluorophores with different DNA binding modes, have been considered. Polarimetric measurements show that the dyes follow the alignment with respect to the DNA strands and allow the determination of the angles between the emission dipoles and the longitudinal axis of the DNA double strand. These results provide a useful starting point toward the application of two-photon polarimetry techniques to determine the local orientation of condensed DNA in physiological conditions. PMID:19843467

  4. Controlling the Spatial Organization of Liquid Crystalline Nanoparticles by Composition of the Organic Grafting Layer.

    PubMed

    Wójcik, Michał M; Olesińska, Magdalena; Sawczyk, Michał; Mieczkowski, Józef; Górecka, Ewa

    2015-07-06

    Understanding how the spatial ordering of liquid crystalline nanoparticles can be controlled by different factors is of great importance in the further development of their photonic applications. In this paper, we report a new key parameter to control the mesogenic behavior of gold nanoparticles modified by rodlike thiols. An efficient method to control the spatial arrangement of hybrid nanoparticles in a condensed state is developed by changing the composition of the mesogenic grafting layer on the surface of the nanoparticles. The composition can be tuned by different conditions of the ligand exchange reaction. The thermal and optical behavior of the mesogenic and promesogenic ligands were investigated by using differential scanning calorimetry (DSC) and hot-stage polarized optical microscopy. The chemical structure of the synthesized hybrid nanoparticles was characterized by (1) H NMR spectroscopy, thermogravimetric analysis (TGA), XPS, and elemental analysis, whereas the superstructures were examined by small-angle X-ray diffraction (SAXSRD) analysis. Structural studies showed that the organic sublayer made of mesogenic ligands is denser with an increasing the average ligand number, thereby separating the nanoparticles in the liquid crystalline phases, which changes the parameters of these phases. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Enzyme Kinetics in Liquid Crystalline Mesophases: Size Matters, But Also Topology.

    PubMed

    Sun, Wenjie; Vallooran, Jijo J; Mezzenga, Raffaele

    2015-04-21

    Lyotropic liquid crystalline systems (LLCs) are excellent immobilizing carriers for enzymes, due to their biocompatibility and well-defined pore nanostructure. Here we show that the liquid crystalline mesophase topology can greatly influence the enzymatic activity in a typical peroxidase (Horseradish peroxidase, HRP) enzymatic reaction. Enzyme kinetics was investigated in different LLC mesophases based on monolinolein, with varying symmetries and dimensions such as the 1D cylindrical inverse hexagonal phase (HII), the 2D planar lamellar phase (Lα), and two 3D bicontinuous cubic phases of double diamond (Pn3m) and gyroid (Ia3d) space groups. As expected, the mesophase with largest water channel size shows highest activity, regardless of the topology. Interestingly, however, when mesophases with different topologies have the same water channel size, then the topology plays the dominant role, and the enzyme showed the highest activity in the 3D tetra-fold connected Pn3m, followed by the Ia3d with trifold connectivity, and finally the 1D HII phase. This study demonstrates that the enzymatic activity in LLC mesophases depends on both the water channel size and the topology of the mesophase.

  6. Influence of internal structure and composition of liquid crystalline phases on topical delivery of paclitaxel.

    PubMed

    Hosmer, Jaclyn M; Shin, Soo H; Nornoo, Adwoa; Zheng, Haian; Lopes, Luciana B

    2011-04-01

    This study aimed to evaluate whether and how the internal structure and composition of liquid crystalline systems can be tailored to maximize paclitaxel cutaneous delivery. Liquid crystalline phases of water, Brij-97, and medium-chain mono/diglycerides (MCG) were characterized by polarized light microscopy. Lamellar phases containing 20% (w/w) water and MCG at 10% (LP-10) or 20% (LP-20), and a hexagonal phase (HP) with 45% water and 10% MCG were selected; paclitaxel was incorporated at 0.5% (w/w). Compared with drug solution in myvacet oil, LP-20 provided the highest paclitaxel cutaneous delivery (threefold), and LP-10 the highest transdermal delivery (fourfold). Using a fluorescent drug derivative [at 0.5%, (w/w)], we observed that penetration occurred through intact stratum corneum. To evaluate whether penetration results relate to drug release differences, paclitaxel self-diffusion coefficient (D) and in vitro release were studied. D was the highest in LP-20, but release from LP-20 and LP-10 was similar. The low D in HP was associated with the lowest drug release. As an index of efficacy, we assessed the cytotoxicity of paclitaxel-loaded LP-20 against fibroblasts. Cell viability was 1.3-2 times smaller with LP-20 than with drug solution. Our results demonstrate that LP-20 provides optimization of paclitaxel cutaneous delivery and efficient cytotoxicity. Copyright © 2010 Wiley-Liss, Inc.

  7. Highly ordered monodomain ionic self-assembled liquid-crystalline materials.

    PubMed

    Zakrevskyy, Y; Smarsly, B; Stumpe, J; Faul, C F J

    2005-02-01

    Liquid-crystalline properties of the ionic self assembled complex benzenehexacarboxylic- (didodecyltrimethylammonium)6 [BHC- (C12D)6] were investigated by polarizing microscopy, differential scanning calorimetry (DSC), x-ray analysis, null ellipsometry, UV and IR spectroscopy. The complex exhibits a bilayer smectic Sm- A2 liquid-crystalline phase and aligns spontaneously. Alignment properties do not depend on the hydrophobic or hydrophilic treatment of the surfaces. The aligned complex possesses a negative (delta n=-0.02) homeotropically oriented optical axis, with layers aligned parallel to the surface. X-ray analysis of the aligned sample revealed a lamellar structure with a d spacing of 3.15 nm, consisting of sublayers of thicknesses d1 = 1.41 and d2 = 1.74 nm . This was confirmed by simple geometrical calculations and detailed temperature-dependent investigations, revealing that the first layer contains the BHC molecules and oppositely charged groups of the surfactants, and the second the alkyl tails of the surfactant. Changes in the order parameters (as calculated from the IR investigations) are correlated with the phase transitions as found by DSC. The properties of the complex are strongly influenced by the ionic interactions within the complex. The presence of these groups slows down the dynamics within the material sufficiently to allow for crystallization of the complex from an aligned LC phase into a single crystal domain, as well as restricting the transition to the isotropic phase.

  8. Surface-frustrated periodic textures of smectic- A liquid crystals on crystalline surfaces

    NASA Astrophysics Data System (ADS)

    Zappone, Bruno; Lacaze, Emmanuelle

    2008-12-01

    Using polarizing optical microscopy we studied thin films and droplets of smectic- A 4-cyano- 4' -n-octylbiphenyl (8CB) liquid crystal deposited in air on crystalline surfaces of muscovite mica that induce monostable planar anchoring. The competition with the homeotropic anchoring at the 8CB-air interface leads to the formation of one-dimensional (1D) patterns composed of straight, parallel defect domains that are organized in periodic arrays over areas as large as several mm2 . We have developed a simple model which identifies the arrays with self-assembled “oily streaks,” comprising straight disclination lines and curvature walls. The model reproduces the observed monotonic increase of the period p with the film thickness h in the range p=1-4μm and h=0.8-17μm . For higher values of h we observed a sharp transition to a 2D lattice of fragmented focal conic domains. Despite the apparent generality of our model for hybrid planar-homeotropic anchoring conditions, periodic arrays of straight oily streaks have been observed so far only for 8CB on crystalline surfaces such as mica or MoS2 . Our model indicates that this specificity is due to a particularly strong anchoring of the liquid crystal on such surfaces.

  9. True Vapor-Liquid-Solid Process Suppresses Unintentional Carrier Doping of Single Crystalline Metal Oxide Nanowires.

    PubMed

    Anzai, Hiroshi; Suzuki, Masaru; Nagashima, Kazuki; Kanai, Masaki; Zhu, Zetao; He, Yong; Boudot, Mickaël; Zhang, Guozhu; Takahashi, Tsunaki; Kanemoto, Katsuichi; Seki, Takehito; Shibata, Naoya; Yanagida, Takeshi

    2017-08-09

    Single crystalline nanowires composed of semiconducting metal oxides formed via a vapor-liquid-solid (VLS) process exhibit an electrical conductivity even without an intentional carrier doping, although these stoichiometric metal oxides are ideally insulators. Suppressing this unintentional doping effect has been a challenging issue not only for metal oxide nanowires but also for various nanostructured metal oxides toward their semiconductor applications. Here we demonstrate that a pure VLS crystal growth, which occurs only at liquid-solid (LS) interface, substantially suppresses an unintentional doping of single crystalline SnO2 nanowires. By strictly tailoring the crystal growth interface of VLS process, we found the gigantic difference of electrical conduction (up to 7 orders of magnitude) between nanowires formed only at LS interface and those formed at both LS and vapor-solid (VS) interfaces. On the basis of investigations with spatially resolved single nanowire electrical measurements, plane-view electron energy-loss spectroscopy, and molecular dynamics simulations, we reveal the gigantic suppression of unintentional carrier doping only for the crystal grown at LS interface due to the higher annealing effect at LS interface compared with that grown at VS interface. These implications will be a foundation to design the semiconducting properties of various nanostructured metal oxides.

  10. Influence of liquid crystalline phases on the tunability of a random laser.

    PubMed

    Trull, José; Salud, Josep; Diez-Berart, Sergio; López, David O

    2017-05-01

    In this paper, we report the temperature behavior of an optimized disordered photonic system-based liquid crystal by means of heat capacity and refractive index measurements. The scattering system is formed by a porous borosilicate glass random matrix (about 60%) infiltrated with a smectogenic liquid crystal (about 16%) and a small amount of laser dye (0.1%). The rest of the scattering system is about 24% air, giving rise to a high refractive index contrast scattering system. Such a system has the functionality to change the refractive index contrast with temperature due to the liquid crystal temperature behavior. The system, optically pumped by the second harmonic of a Q-switched Nd:YAG pulsed laser working at 532 nm, exhibits random laser action, the threshold of which depends upon the liquid crystalline mesophase. Temperatures of existence of the smectic-B phase correspond to the most optimized random laser. In such a mesophase, the transport mean free path has been determined as about 16 μm in a coherent backscattering experiment.

  11. The effect of liquid crystalline structures on antiseizure properties of aqueous solutions of ethoxylated alcohols.

    PubMed

    Sulek, Marian Wlodzimierz; Bak, Anna

    2010-01-12

    Aqueous solutions of ethoxylated alcohols which form lyotropic liquid crystals at high concentrations (40-80%) were selected as model lubricating substances. Microscopic studies under polarized light and viscosity measurements were carried out in order to confirm the presence of liquid crystalline structures in the case of alcohol solutions with ethoxylation degrees of 3, 5, 7 and 10. Microscopic images and viscosity coefficient values characteristic of various mesophases were obtained. As expected, the viscosity of LLCs decreases considerably with an increase in shearing rate which is characteristic of liquid crystals being non-Newtonian liquids. Antiseizure properties were determined by means of a four-ball machine (T-02 Tester) and characterized by scuffing load (P(t)), seizure load (P(oz)) and limiting pressure of seizure (p(oz)). Alcohol ethoxylates forming mesophases in aqueous solutions have the strongest effect on the P(t) values which are several times higher than those measured in the presence of water. Ethoxylates with higher degrees of ethoxylation exhibit higher values of scuffing load. Those changes have been interpreted as a result of higher cloud points at which those compounds lose their amphiphilic properties. In general, the presence of mesophases in the bulk phase and particularly in the surface phase may lead to the formation of a lubricant film which separates the frictionally cooperating elements of a friction pair. The antiseizure efficiency of alcohol solutions is highest up to the load value which does not exceed the scuffing load value.

  12. The Effect of Liquid Crystalline Structures on Antiseizure Properties of Aqueous Solutions of Ethoxylated Alcohols

    PubMed Central

    Sulek, Marian Wlodzimierz; Bak, Anna

    2010-01-01

    Aqueous solutions of ethoxylated alcohols which form lyotropic liquid crystals at high concentrations (40–80%) were selected as model lubricating substances. Microscopic studies under polarized light and viscosity measurements were carried out in order to confirm the presence of liquid crystalline structures in the case of alcohol solutions with ethoxylation degrees of 3, 5, 7 and 10. Microscopic images and viscosity coefficient values characteristic of various mesophases were obtained. As expected, the viscosity of LLCs decreases considerably with an increase in shearing rate which is characteristic of liquid crystals being non-Newtonian liquids. Antiseizure properties were determined by means of a four-ball machine (T-02 Tester) and characterized by scuffing load (Pt), seizure load (Poz) and limiting pressure of seizure (poz). Alcohol ethoxylates forming mesophases in aqueous solutions have the strongest effect on the Pt values which are several times higher than those measured in the presence of water. Ethoxylates with higher degrees of ethoxylation exhibit higher values of scuffing load. Those changes have been interpreted as a result of higher cloud points at which those compounds lose their amphiphilic properties. In general, the presence of mesophases in the bulk phase and particularly in the surface phase may lead to the formation of a lubricant film which separates the frictionally cooperating elements of a friction pair. The antiseizure efficiency of alcohol solutions is highest up to the load value which does not exceed the scuffing load value. PMID:20162010

  13. Silica nanoparticle stabilization of liquid crystalline lipid dispersions: impact on enzymatic digestion and drug solubilization.

    PubMed

    Bhatt, Achal B; Barnes, Timothy J; Prestidge, Clive A

    2015-01-01

    The high internal surface area and drug solubilizing capacity of liquid crystal lipids makes them promising oral drug delivery systems. Pluronic F127 is typically used to disperse highly viscous cubic liquid crystal lipids into cubosomes; however, such copolymers alter the internal structure and provide little control over enzymatic digestion. This study aimed to use hydrophilic silica nanoparticles to stabilize glyceryl monooleate (GMO) cubosomes prepared by ultrasonication. We investigate the influence of silica nanoparticles size and concentration on the physical (colloidal) and chemical (enzymatic digestion) stability, as well as in vitro solubilization of cinnarizine as a poorly soluble model drug. Silica stabilized nanostructured liquid crystal dispersions (120 nm to150 nm in diameter and zeta potentials of-30 mV to -60 mV) were successfully prepared with excellent long-term stability (<10% size change after 30 days). Silica stabilized GMO cubosomes demonstrated reduced enzymatic digestion compared to pluronic F127 stabilized cubosomes. This reduced digestion was attributed to a combination of adsorbed silica nanoparticles acting as a physical barrier and excess dispersed silica adsorbing/scavenging the lipase enzyme. Under simulated intestinal digestion conditions, silica stabilized GMO cubosomes showed a greater solubilization capacity for cinnarizine, which precipitated in non-crystalline form, in comparison to pure drug suspensions or pluronic F127 stabilized GMO cubosomes. Silica nanoparticle stabilized GMO liquid crystal dispersions are a promising oral delivery vehicle.

  14. Planar-orientation polycrystalline thin film of liquid-crystalline organic semiconductor by template-directed self-assembly

    NASA Astrophysics Data System (ADS)

    Wang, Yi-Fei; Iino, Hiroaki; Hanna, Jun-ichi

    2017-10-01

    We fabricated planar-orientation crystalline thin films of organic semiconductors, in which molecules sit parallel, i.e., “face-on”, on the substrate and favor vertical charge transport. Thanks to molecular orientation that is sensitive to surface properties and the self-organization of liquid crystals, planar-orientation crystalline thin films can be prepared by simply cooling a smectic liquid-crystalline organic semiconductor from isotropic temperature with the aid of a poly(vinyl alcohol) (PVA) microtemplate. The molecular orientation of crystalline thin films was investigated by polarized optical microscopy (POM) and X-ray diffraction (XRD) analysis, and the current–voltage characteristics of the films were studied in a diode configuration. The results showed high potential for device applications.

  15. Phase Structure and Properties of a Biodegradable Block Copolymer Coalesced from It's Crystalline Inclusion Compound Formed with alpha-Cyclodextrin

    NASA Astrophysics Data System (ADS)

    Shuai, Xintao; Wei, Min; Probeni, Francis; Bullions, Todd A.; Shin, I. Daniel; Tonelli, Alan E.

    2002-03-01

    A well-defined biodegradable block copolymer of poly(epsilon caprolactone) (PCL) and poly(L-lactic acid) (PLLA) was synthesized and characterized and then included as a guest in an inclusion compound (IC) formed with the host alpha-cyclodextrin (CD). The PCL-b-PLLA block copolymer was subsequently coalesced from it's CD-IC crystals by either treatment with hot water (50 C) or an aqueous amylase solution at 25 C. The coalesced PCL-b-PLLA was examined by FTIR, DSC, TGA, and WAXD and was found to be much more homogeneosly organized, with much less segregation and crystallinity of the PCL and PLLA microphases. The morpholgy, crystallization kinetics, thermal behavior, and biodegradability of the coalesced PCL-b-PLLA block copolymer was studied by comparison to similar observations made on as-synthesized PCL-b-PLLA, PCL and PLLA homopolymers, and their solution-cast blend. The PCL and PLLA blocks are found to be more intimately mixed, with less phase segregation, in the coalesced diblock copolymer, and this leads to homogeneous bulk crystallization, which is not observed for the as-synthesized diblock copolymer. The coalesced PCL-b-PLLA was also found to be more quickly biodegraded (lipase from Rhizopus arrhizus)than the as-synthesized PCL-b-PLLA or the physical blend of PCL and PLLA homopolymers. Overall, the coalescence of the inherently phase segregated diblock copolymer PCL-b-PLLA results in a small amount of compact, chain-extended PCL and PLLA crystals embedded in an amorphous phase, largely consisting of well-mixed PCL and PLLA blocks. Thus, we have demonstrated that it is possible to control the morpholgy of a biodegradable diblock copolymer, thereby significantly modifying it's properties, by coalescence from it's CD-IC crystals.

  16. On the molecular anisotropy of liquid crystalline and flexible polymer systems

    NASA Astrophysics Data System (ADS)

    van Horn, Brett L.

    The demand for products of ever increasing quality or for novel applications has required increasing attention to or manipulation of the anisotropy of manufactured parts. Oriented plastics are used everywhere from recording film to automotive body parts to monofilament fishing line. Liquid crystals are also used in a wide array of applications including their dominance in the flat panel display industry, color changing temperature sensors, and woven bullet resistant fabrics. Anisotropy can also be detrimental, for instance sometimes leading to poor fracture resistance or low yield stress along specific directions. Controlling and measuring anisotropy of materials has become increasingly important, but doing so is wrought with challenges. Measuring physical properties of isotropic liquids, such as water or most oils can be done in a straightforward fashion. Their viscosities and densities, for example, have unique values under a given set of conditions. With anisotropic fluids, like liquid crystals, the viscosity, for instance, will not only depend upon temperature, concentration, etc. but also upon the direction of observation, degree of anisotropy, source of anisotropy, and so forth. This added degree of complexity complicates our ability to define the state of the material at which the measurements are made and generally necessitates the use of more sophisticated measurement strategies or techniques. This work presents techniques and tools for investigating anisotropy in liquid crystalline and stretched polymeric systems. Included are the use of conoscopy for the determination of birefringence and orientation of nematic liquid crystals and stretched polymers, the shear response of flow aligning nematic liquid crystal monodomains, and the design of a novel linear rheometer that allows for in situ optical or scattering investigations.

  17. More than one way to spin a crystallite: multiple trajectories through liquid crystallinity to solid silk

    PubMed Central

    Walker, Andrew A.; Holland, Chris; Sutherland, Tara D.

    2015-01-01

    Arthropods face several key challenges in processing concentrated feedstocks of proteins (silk dope) into solid, semi-crystalline silk fibres. Strikingly, independently evolved lineages of silk-producing organisms have converged on the use of liquid crystal intermediates (mesophases) to reduce the viscosity of silk dope and assist the formation of supramolecular structure. However, the exact nature of the liquid-crystal-forming-units (mesogens) in silk dope, and the relationship between liquid crystallinity, protein structure and silk processing is yet to be fully elucidated. In this review, we focus on emerging differences in this area between the canonical silks containing extended-β-sheets made by silkworms and spiders, and ‘non-canonical’ silks made by other insect taxa in which the final crystallites are coiled-coils, collagen helices or cross-β-sheets. We compared the amino acid sequences and processing of natural, regenerated and recombinant silk proteins, finding that canonical and non-canonical silk proteins show marked differences in length, architecture, amino acid content and protein folding. Canonical silk proteins are long, flexible in solution and amphipathic; these features allow them both to form large, micelle-like mesogens in solution, and to transition to a crystallite-containing form due to mechanical deformation near the liquid–solid transition. By contrast, non-canonical silk proteins are short and have rod or lath-like structures that are well suited to act both as mesogens and as crystallites without a major intervening phase transition. Given many non-canonical silk proteins can be produced at high yield in E. coli, and that mesophase formation is a versatile way to direct numerous kinds of supramolecular structure, further elucidation of the natural processing of non-canonical silk proteins may to lead to new developments in the production of advanced protein materials. PMID:26041350

  18. A Comprehensive Study on Lyotropic Liquid-Crystalline Behavior of an Amphiphile in 20 Kinds of Amino Acid Ionic Liquids.

    PubMed

    Fujimura, Kanae; Ichikawa, Takahiro; Yoshio, Masafumi; Kato, Takashi; Ohno, Hiroyuki

    2016-02-18

    We examined the self-organization behavior of a designed amphiphilic molecule in 20 kinds of amino acid ionic liquids composed of 1-butyl-3-methylimidazolium cation and natural amino acid anion ([C4mim][AA]). Addition of [C4mim][AA], regardless of their anion species, to the amphiphile provided homogeneous mixtures showing lyotropic liquid-crystalline (LC) behavior. Upon increasing the component ratio of [C4mim][AA] in the mixtures, a successive change of the mesophase patterns from inverted hexagonal columnar, in some case via bicontinuous cubic, to layered phases was observed. By examining the LC properties at various temperatures and component ratios, we constructed lyotropic LC phase diagrams. Interestingly, the appearance of these phase diagrams is greatly different according to the selection of [AA]. Through comparison, we found that the self-organization behavior of an amphiphile in ionic liquids can be tuned by controlling their ability to form hydrogen-bond, van der Waals, and π-π interactions.

  19. Photo-orientation of azobenzene-containing liquid-crystalline materials by means of domain structure rearrangement.

    PubMed

    Bogdanov, Alexey V; Vorobiev, Andrey Kh

    2013-11-07

    A novel mechanism of photo-orientation of azobenzene-containing liquid-crystalline materials is proposed. This mechanism is based on the notion of photochemically induced domain rearrangement driven by destabilization of liquid-crystalline phase in light absorbing domains due to photochemical formation of non-mesogenic cis-azobenzene moieties. The experimental evidence of photoinduced movement of a domain boundary is presented, and the velocity of this movement is measured. A mathematical model for photo-orientation of a polydomain azobenzene-containing material is formulated. The values of model parameters for a liquid-crystalline azopolymer have been measured in separate experiments. Theoretical predictions demonstrate quantitative agreement with the experimental observations.

  20. Ocular delivery of cyclosporine A based on glyceryl monooleate/poloxamer 407 liquid crystalline nanoparticles: preparation, characterization, in vitro corneal penetration and ocular irritation.

    PubMed

    Chen, Yan; Lu, Yi; Zhong, Yanqiang; Wang, Qingping; Wu, Wei; Gao, Shen

    2012-12-01

    The purpose of this study was to develop an ophthalmic drug delivery system for cyclosporine A (CsA) based on glyceryl monooleate (GMO)/poloxamer 407 liquid crystalline nanoparticles with reduced ocular irritancy and improved corneal penetration. CsA-loaded liquid crystalline nanoparticles were prepared via fragmentation of a bulk GMO/poloxamer 407 cubic phase gel by high-pressure homogenization and characterized. Corneal permeation and retention was evaluated using modified Franz diffusing cells. Intra-corneal transportation was investigated with fluorescein isothiocyanate (FITC)-labeled liquid crystalline nanoparticles. Ocular irritation was then evaluated using the Draize method. The mean particle size of liquid crystalline nanoparticles was 193.5 nm and the entrapment efficiency was 95.11 ± 0.67%. A bicontinuous cubic phase of cubic P-type was determined using cryo-transmission electron microscopy (cryo-TEM) observation and small angle X-ray diffraction (SAXD) analysis. A 1.52-fold increase in J(s) and a 2.2-fold increase in corneal retention was achieved by liquid crystalline nanoparticles compared with oil solution. In vitro corneal permeation investigated with FITC-labeled liquid crystalline nanoparticles revealed that CsA penetrated across the cornea under the transportation of liquid crystalline nanoparticles. Liquid crystalline nanoparticles exhibited excellent ocular tolerance in the ocular irritation test. This low-irritant vehicle based on liquid crystalline nanoparticles might be a promising system for effective ocular CsA delivery.

  1. Peptide KSL-W-Loaded Mucoadhesive Liquid Crystalline Vehicle as an Alternative Treatment for Multispecies Oral Biofilm.

    PubMed

    Bernegossi, Jéssica; Calixto, Giovana Maria Fioramonti; Sanches, Paulo Ricardo da Silva; Fontana, Carla Raquel; Cilli, Eduardo Maffud; Garrido, Saulo Santesso; Chorilli, Marlus

    2015-12-25

    Decapeptide KSL-W shows antibacterial activities and can be used in the oral cavity, however, it is easily degraded in aqueous solution and eliminated. Therefore, we aimed to develop liquid crystalline systems (F1 and F2) for KSL-W buccal administration to treat multispecies oral biofilms. The systems were prepared with oleic acid, polyoxypropylene (5) polyoxyethylene (20) cetyl alcohol (PPG-5-CETETH-20), and a 1% poloxamer 407 dispersion as the oil phase (OP), surfactant (S), and aqueous phase (AP), respectively. We characterized them using polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), rheology, and in vitro bioadhesion, and performed in vitro biological analysis. PLM showed isotropy (F1) or anisotropy with lamellar mesophases (F2), confirmed by peak ratio quantification using SAXS. Rheological tests demonstrated that F1 exhibited Newtonian behavior but not F2, which showed a structured AP concentration-dependent system. Bioadhesion studies revealed an AP concentration-dependent increase in the system's bioadhesiveness (F2 = 15.50 ± 1.00 mN·s) to bovine teeth blocks. Antimicrobial testing revealed 100% inhibition of multispecies oral biofilm growth after KSL-W administration, which was incorporated in the F2 aqueous phase at a concentration of 1 mg/mL. Our results suggest that this system could serve as a potential vehicle for buccal administration of antibiofilm peptides.

  2. The influence of liquid crystalline structure and ceramic nanoparticles inclusion on thermal conductivity of epoxy based thermosets

    NASA Astrophysics Data System (ADS)

    Scamardella, A. M.; Iacono, S. Dello; Carfagna, C.; Ho, C. H.; Kornmann, X.; Amendola, E.

    2012-07-01

    Epoxy nanocomposites with ceramic nanoparticles and liquid crystalline epoxy thermosets have been prepared and characterized with the aim to improve thermal conductivity of polymeric networks, without sacrificing processibility of reactive mixture and electrical insulation of final products. The influence of mesogenic liquid crystalline structure and fillers addition on thermal, mechanical and dielectric properties have been investigated by means of Differential Scanning Calorimetry (DSC), Dynamic-mechanical analysis (DMA) and volume resistivity. Morphological investigations by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) has been also performed.

  3. Segmented polyurethane elastomers with liquid crystalline hard segments. 1. Synthesis, characterization and rheology

    SciTech Connect

    Tang, W.; MacKnight, W.J.; Welder, W.

    1995-12-01

    Segmented liquid crystalline polyurethanes (LCPUE) have been studied with hard segments composed of the mesogen 4,4`-bis(6-hydroxyhexoxy)biphenyl, 2,4-tolylene diisocyanate, and 2,6-tolylene diisocyanate and soft segments composed of poly(tetramethylene oxides). Differential scanning calorimetry and wide-angle X-ray scattering experiments show the existence of an enantiotropic mesophase in the hard domains of the elastomer. Compared with nonsegmented polyurethane containing the same mesogen, the isotropization temperature of the mesophase in the elastomer is depressed. This is a result of the oligomeric structure of the hard domains. The endotherm corresponding to the isotropization transition is also broadened, reflecting a lack of uniformity of the hard domains. Furthermore, the mesophase can be oriented by elastic deformation, and it forms a more ordered chain packing during this process. The tensile properties of these segmented polyurethanes are determined by their morphologies and can be manipulated by controlling the hard- and soft-segment concentration ratio. The rheological study indicates a broad transition from a viscoelastic solid to a viscoelastic liquid at the isotropization temperature of the mesophase. Physical gelation studies identify a liquid/solid transition when cooled to 106{degrees}C or below, and show the characteristic, critical behavior at the gel point with a power law relaxation spectrum at low frequencies.

  4. Effect of the gel to liquid crystalline phase transition on the osmotic behaviour of phosphatidylcholine liposomes.

    PubMed

    Blok, M C; van Deenen, L L; De Gier, J

    1976-04-16

    Aspects of osmotic properties of liposomes, prepared from synthetic lecithin, above, at and below the gel to liquid crystalline phase transition temperature are described. The experiments show that liposomal membranes with their lipids in the gel state are still permeable to water. The rate of water permeation changes drastically on passing the transition temperature. The water permeation has activation energies of 9.5 +/- 1.28 and 26.4 +/- 0.9 kcal/mol above and below the transition temperature, respectively, indicating that the diffusion processes take place by different mechanisms. With respect to the barrier properties of the liposomes in the vicinity of the transition temperature, the following conclusions can be made. (1) Studying the osmotic shrinkage of liposomes at a fixed temperature near the transition point, the experiments indicate that dimyristoyl phosphatidylcholine membranes are highly permeable to glucose under these conditions, where liquid and solid domains co-exist. Under the same conditions the osmotic experiments did not indicate a strong increase in glucose permeability of dipalmitoyl phosphatidylcholine membranes as compared to the situation above and below the transition temperature. (2) On the other hand, perturbations of the phase equilibrium by temperature varations resulted in a marked increase of the glucose permeation through dipalmitoyl phosphatidylcholine bilayers. Once a new phase equilibrium of liquid and solid regions is established the permeation rate of glucose is much less.

  5. High-pressure Raman study of liquid and crystalline CH3F up to 12 GPa

    NASA Astrophysics Data System (ADS)

    Wu, Y. H.; Shimizu, H.

    1995-01-01

    High-pressure Raman spectra of liquid and crystalline CH3F were measured up to 12 GPa at 300 K in a gasketed diamond-anvil cell. Two solid phases have been found; the transition pressures of liquid to solid phase I and phase I to phase II were determined to be 2.75 and 3.63 GPa, respectively. Among these, the solid phase I is an orientationally disordered (plastic) phase, while the solid phases II is an orientationally ordered phase. The frequency of CF stretching ν3(A1) vibration shows a large red shift with a slope dν/dP of about -2.6 cm-1/GPa in the liquid phase, and it splits into the TO and LO modes in the two solid phases. The Fermi resonances between the same symmetry vibrations of ν1(A1) and 2ν5(A1), and of ν4(E) and 2ν5(E) have been observed and their behaviors have been analyzed by the Fermi resonance theory. The pressure dependence of the CH stretching mode is compared with those of the other fluorinated methanes CH2F2, CHF2Cl, and CHF3.

  6. Photolithographically patternable electroluminescent liquid crystalline materials for full-colour organic light emitting displays

    NASA Astrophysics Data System (ADS)

    McGlashon, Andrew J.; Whitehead, Katherine S.; Bradley, Donal D. C.; Heeney, Martin; McCulloch, Iain; Zhang, Weimin; Campbell, Alasdair J.

    2006-02-01

    Displays based on polymer light emitting diodes are attractive due to their emissive nature, their wide viewing angles and the ability of electroluminescent conjugated polymers to be solution processable at room temperature and pressure. It is difficult, however, to deposit separate red, green and blue (RGB) pixels and to maximize performance by making the devices multi-layered. Here we present recent results on a semiconducting conjugated reactive-mesogen OLED material which is solution processable, can be potentially cured and patterned by photolithography and used in multi-layer devices. This material consists of a conjugated pentathiophene core with reactive endgroups. Spectroscopy, calorimetry and microscopy show that it forms crystalline, aggregate, liquid-crystalline and isotropic phases at a range of different temperatures. The material is deposited by spincoating from solution. Low density doping with a cationic photointiator and exposure to a specific UV wavelength to avoid damage to the conjugated core leads to cross-linking into an insoluble network. Current-voltage-luminousity and spectral measurements in standard OLED device structures show the effect of cross-linking on the transport and injection properties of the material. Quenching of fluorescence and electroluminescence is discussed. Insertion of lower-energy gap, fluorescent small molecules can potentially be used to tune the emission to any desired colour but material limitations to this technique due to dopant removal during the washing procedure were observed.

  7. Bio-inspired production of chitosan/chitin films from liquid crystalline suspensions.

    PubMed

    João, Carlos F C; Echeverria, Coro; Velhinho, Alexandre; Silva, Jorge C; Godinho, Maria H; Borges, João P

    2017-01-02

    Inspired by chitin based hierarchical structures observed in arthropods exoskeleton, this work reports the capturing of chitin nanowhiskers' chiral nematic order into a chitosan matrix. For this purpose, highly crystalline chitin nanowhiskers (CTNW) with spindle-like morphology and average aspect ratio of 24.9 were produced by acid hydrolysis of chitin. CTNW were uniformly dispersed at different concentrations in aqueous suspensions. The suspensions liquid crystalline phase domain was determined by rheological measurements and polarized optical microscopy (POM). Chitosan (CS) was added to the CTNW isotropic, biphasic and anisotropic suspensions and the solvent was evaporated to allow films formation. The Films' morphologies as well as the mechanical properties were explored. A correlation between experimental results and a theoretical model, for layered matrix' structures with fibers acting as a reinforcement agent, was established. The results evidence the existence of two different layered structures, one formed by chitosan layers induced by the presence of chitin and another formed by chitin nanowhiskers layers. By playing on the ratio chitin/chitosan one layered structure or the other can be obtained allowing the tunning of materials' mechanical properties.

  8. Birefringence-dependent linearly-polarized emission in a liquid crystalline organic light emitting polymer.

    PubMed

    Lee, Dong-Myoung; Lee, You-Jin; Kim, Jae-Hoon; Yu, Chang-Jae

    2017-02-20

    We investigated the linearly polarized emission of uniformly aligned poly(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thia-diazol-4,8-diyl) (F8BT) with a liquid crystalline phase on a rubbed alignment layer. The polarization ratio, defined by the ratio of luminous intensities polarized parallel and perpendicular to the rubbed direction, gradually decreased with increasing thickness of the F8BT film. In the photoluminescence (PL) process, the polarized light is emitted throughout the whole F8BT film, while in the electroluminescence (EL) process, the polarized light is emitted at a certain region within the F8BT film. The thickness-dependent polarization ratios in both PL and EL processes were successfully described based on a simple model wherein the mean optical birefringence was expressed as a function of the thickness of the F8BT film.

  9. Improved Oral Bioavailability, Therapeutic Efficacy, and Reduced Toxicity of Tamoxifen-Loaded Liquid Crystalline Nanoparticles.

    PubMed

    Jain, Sanyog; Heeralal, B; Swami, Rajan; Swarnakar, Nitin K; Kushwah, Varun

    2017-08-07

    Present investigation deals with formulation and evaluation of tamoxifen (TMX)-loaded liquid crystalline nanoparticles (TMX-LCNPs) for improving oral bioavailability and safety of the existing treatment. Hexagonal Glyceryl monooleate-based TMX-LCNPs (GLCNPs) and Phytantriol-based TMX-LCNPs (PLCNPs) were prepared by dilution-through-hydrotrope method for oral administration. Oleic acid was incorporated in the lipid matrix to enhance the drug loading in the LCNPs. Optimized LCNPs displayed small particle size with a narrow distribution, sustained drug release and high gastrointestinal stability. TMX-LCNPs were found to be considerably higher cytotoxic to MCF-7 cells as compared to free TMX. Substantial fold enhancement in oral bioavailability (~7- and ~5-folds with TMX-GLCNPs and TMX-PLCNPs, respectively) was evident followed by significant reduction in tumor burden with lesser hepatotoxicity. Out of the two LCNP formulations, PLCNPs were found to be better in convalescing the disease.

  10. Solution-Based Synthesis of Crystalline Silicon from Liquid Silane through Laser and Chemical Annealing

    DOE PAGES

    Iyer, Ganjigunte R. S.; Hobbie, Erik K.; Guruvenket, Srinivasan; ...

    2012-05-23

    We report a solution process for the synthesis of crystalline silicon from the liquid silane precursor cyclohexasilane (Si6H12). Polysilane films were crystallized through thermal and laser annealing, with plasma hydrogenation at atmospheric pressure generating further structural changes in the films. The evolution from amorphous to microcrystalline is characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and impedance spectroscopy. A four-decade enhancement in the electrical conductivity is attributed to a disorder-order transition in a bonded Si network. Lastly, our results demonstrate a potentially attractive approach that employs a solution process coupled with ambient post-processing to produce crystallinemore » silicon thin films.« less

  11. Photo-Induced Bending Behavior of Post-Crosslinked Liquid Crystalline Polymer/Polyurethane Blend Films.

    PubMed

    Pang, Xinlei; Xu, Bo; Qing, Xin; Wei, Jia; Yu, Yanlei

    2017-06-30

    Photoresponsive blend films with post-crosslinked liquid crystalline polymer (CLCP) as a photosensitive component and flexible polyurethane (PU) as the matrix are successfully fabricated. After being uniaxially stretched, even at low concentration, the azobenzene-containing CLCP effectively transfers its photoresponsiveness to the photoinert PU matrix, resulting in the fast photo-induced bending behavior of whole blend film thanks to the effective dispersion of CLCP. Specifically, the blend film shows photo-induced deformations upon exposure to unpolarized UV light at ambient temperature. The film unbends after thermal treatment, and the randomly orientated mesogens in the film can be realigned by the mechanical stretching, which endows the film with a reversible deformation behavior. The photosensitive blend film possesses favorable mechanical property and good processability at low cost, and it is a promising candidate for a new generation of actuators. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Photomobile polymer materials with crosslinked liquid-crystalline structures: molecular design, fabrication, and functions.

    PubMed

    Ube, Toru; Ikeda, Tomiki

    2014-09-22

    Crosslinked liquid-crystalline polymer materials that macroscopically deform when irradiated with light have been extensively studied in the past decade because of their potential in various applications, such as microactuators and microfluidic devices. The basic motions of these materials are contraction-expansion and bending-unbending, which are observed mainly in polysiloxanes and polyacrylates that contain photochromic moieties. Other sophisticated motions such as twisting, oscillation, rotation, and translational motion have also been achieved. In recent years, efforts have been made to improve the photoresponsive and mechanical properties of this novel class of materials through the modification of molecular structures, development of new fabrication methods, and construction of composite structures. Herein, we review structures, functions, and working mechanisms of photomobile materials and recent advances in this field.

  13. Macroscopic Ordering of CNTs in a Liquid Crystalline Polymer Nano-Composite by Shearing

    NASA Astrophysics Data System (ADS)

    Kalakonda, P.; Sarkar, S.; Iannacchione, G. S.; Gombos, E.; Hoonjan, G. S.; Georgiev, G.; Cebe, P.

    2012-02-01

    We present a series of complimentary experiments exploring the macroscopic alignment of carbon nanotubes (CNTs) in a liquid crystalline polymer (isotactic polypropylene - iPP) nano-composites as a function of temperature, shear, and CNT concentration. The phase behavior of iPP+CNT, studied by Modulated Differential Scanning Calorimetry, revealed the evolution of the α-monoclinic transition and its dynamics, which are dependent on CNT content and thermal treatment. These results indicate that the CNT nucleates crystal formation from the melt. Spectroscopic ellipsometry reveals a change in the optical constants that are connected to the ordering of CNTs when the iPP+CNT is sheared. This anisotropy is also exhibited in measurements of the electrical and thermal conductivities parallel and perpendicular to the shear direction. The amount of order induced into the dispersed CNTs is relatively low for these low concentration samples (< 5 wt%).

  14. The relationship between photooxidation defects and quantum yield loss in a liquid crystalline oligofluorene

    NASA Astrophysics Data System (ADS)

    Wesely, E. Jane; Rothberg, Lewis; Geng, Yanhou; Chen, Shaw

    2004-03-01

    We have studied the photophysics of a liquid crystalline oligofluorene which emits blue light with a quantum efficiency of forty-nine percent.( Y. Geng, S. Culligan, A. Trajkovska, J. Wallace and S. Chen, Chem. Mater; 2003, 15, 542-549.) The fluorescent yield is reduced when the film has been exposed to ultra-violet light and air. The resulting photooxidation creates luminescent defects that have previously been observed in some polyfluorenes.( E. J. W. List, R. Guentner, P. Scanducci de Freitas, and U. Scherf, Adv Mater., 2002, 14, 374-378.) The defects decrease the overall fluorescent yield because they divert energy away from the blue-emitting chromophores and emit at longer wavelengths with low efficiency. In contrast with previous studies of photooxidized polyfluorenes, we observe two emission peaks associated with defects that have distinct intensity dependence and decay dynamics.

  15. Photoluminescent nematic liquid crystalline elastomer with a thermomechanical emission variation function.

    PubMed

    Wei, Renbo; He, Yaning; Wang, Xiaogong; Keller, Patrick

    2014-09-01

    Nematic liquid crystalline elastomer (LCE) microactuators are developed, showing simultaneous thermomechanical deformation and photoluminescence (PL) emission variation functions. The microactuators are prepared by a method combining soft-lithography and photo-polymerization/crosslinking. 1,4-Bis(α-cyano-4-methoxystyryl)benzene as the PL dye is synthesized, characterized, and introduced into LCEs as a dopant in the preparation process. During the heating process, PL emission of the LCE micropillars under blue light excitation becomes significantly weak when the micropillars contract. When cooling down, the emission completely recovers as the micropillars stretches back to their original shape. The PL intensity variation at the transition is proved to be related to the thermomechanical deformation.

  16. Dynamics of the guest-host orientational interaction in dye-doped liquid-crystalline materials.

    PubMed

    Truong, Thai V; Xu, Lei; Shen, Y R

    2005-11-01

    We present a comprehensive study on the dynamics of laser-induced molecular reorientation in a dye-doped liquid crystalline (LC) medium that exhibits significant enhancement of the optical Kerr nonlinearity due to guest-host interaction. Using various techniques, we separately characterized the dynamical responses of the relevant molecular species present in the medium following photoexcitation and, thus, were able to follow the transient process in which photoexcitation of the dye molecules exert through guest-host interaction a net torque on the host LC material, leading to the observed enhanced optical Kerr nonlinearity. Experimental results agree quantitatively with the time-dependent theory based on a mean-field model of the guest-host interaction.

  17. Supramolecular ordering of DNA in the cholesteric liquid crystalline phase: an ultrastructural study.

    PubMed Central

    Leforestier, A; Livolant, F

    1993-01-01

    Aqueous solutions of 146-base pair DNA fragments form a cholesteric liquid crystalline phase in the range of about 160-290 mg/ml. We present a structural analysis of this phase by comparing the data obtained from polarizing and electron microscopy. This phase shows multiple aspects or "textures" which are presented and interpreted. They mainly depend on the orientation of the structure relative to the observation plane and on the nature, distribution, and amount of defects present in the phase. These defects are then analyzed with the two methods, and the molecular orientations can be defined precisely in their core. The biological interest of such structural analyses is discussed in relation with the understanding of chromatin structure and function. Images FIGURE 2 FIGURE 4 FIGURE 6 FIGURE 8 FIGURE 9 FIGURE 13 PMID:8369461

  18. Glass-sandwich-type organic solar cells utilizing liquid crystalline phthalocyanine

    NASA Astrophysics Data System (ADS)

    Usui, Toshiki; Nakata, Yuya; De Romeo Banoukepa, Gilles; Fujita, Kento; Nishikawa, Yuki; Shimizu, Yo; Fujii, Akihiko; Ozaki, Masanori

    2017-02-01

    Glass-sandwich-type organic solar cells utilizing liquid crystalline phthalocyanine, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2), have been fabricated and their photovoltaic properties have been studied. The short-circuit current density (J sc) and power conversion efficiency (PCE) depend on the C6PcH2 layer thickness, and the maximum performance, such as a J sc of 7.1 mA/cm2 and a PCE of 1.64%, was demonstrated for a device having a 420-nm-thick C6PcH2 layer. We examined the photovoltaic properties from the viewpoint of the C6PcH2-layer electrical conductance, based on the distribution of the column-axis direction.

  19. The influence of intraannular templates on the liquid crystallinity of shape-persistent macrocycles

    PubMed Central

    Vollmeyer, Joscha

    2014-01-01

    Summary A series of shape-persistent phenylene–ethynylene–naphthylene–butadiynylene macrocycles with different extraannular alkyl groups and intraannular bridges is synthesized by oxidative Glaser-coupling of the appropriate precursors. The intraannular bridges serve in this case as templates that reduce the oligomerization even when the reaction is not performed under pseudo high-dilution conditions. The extraannular as well as the intraannular substituents have a strong influence on the thermal behavior of the compounds. With branched alkyl chains at the periphery, the macrocycles exhibit liquid crystalline (lc) phases when the interior is empty or when the length of the alkyl bridge is just right to cross the ring. With a longer alkyl or an oligoethylene oxide bridge no lc phase is observed, most probably because the mesogene is no longer planar. PMID:24991240

  20. Electron tomography of the nucleoid of Gemmata obscuriglobus reveals complex liquid crystalline cholesteric structure

    PubMed Central

    Yee, Benjamin; Sagulenko, Evgeny; Morgan, Garry P.; Webb, Richard I.; Fuerst, John A.

    2012-01-01

    The nucleoid of the planctomycete Gemmata obscuriglobus is unique within the Bacteria in being both highly condensed and enclosed by a double-membrane nuclear envelope, seemingly analogous to the nucleus of eukaryotes. Here we have applied electron tomography to study high-pressure frozen, cryosubstituted cells of G. obscuriglobus and found multiple nested orders of DNA organization within the condensed nucleoid structure. Detailed examination of the nucleoid revealed a series of nested arcs characteristic of liquid crystalline cholesteric DNA structure. The finest fibers were arranged in parallel concentrically in a double-twist organization. At the highest order of nucleoid organization, several of these structures come together to form the core of the G. obscuriglobus nucleoid. The complex structure of DNA within this nucleoid may have implications for understanding the evolutionary significance of compartmentalized planctomycete cells. PMID:22993511

  1. Stereodynamic control of star-epoxy/anhydride crosslinking actuated by liquid-crystalline phase transitions.

    PubMed

    Pin, Jean-Mathieu; Mija, Alice; Sbirrazzuoli, Nicolas

    2017-03-08

    The epoxy/anhydride copolymerization kinetics of an original star-epoxy monomer (TriaEP) was explored in dynamic heating mode using a series of isoconversional methods. Negative values of the apparent activation energy (Eα) related to an anti-Arrhenius behavior were observed. The transition from Arrhenius to anti-Arrhenius behavior and vice versa depending on the Eα of polymerization was correlated with the dynamics of mesophasic fall-in/fall-out events, physically induced transition (PIT) and chemically induced transition (CIT). This self-assembly phenomenon induces the generation of an anisotropic crosslinked architecture exhibiting both nematic discotic (ND) and nematic columnar (NC) organization. Particular emphasis was placed on evaluating the juxtaposition/contribution of the liquid-crystalline transitions to crosslinking, considering both the reaction dynamics and the macromolecular vision.

  2. Layer-by-layer polymer coating on discrete particles of cubic lyotropic liquid crystalline dispersions (cubosomes).

    PubMed

    Driever, Chantelle D; Mulet, Xavier; Waddington, Lynne J; Postma, Almar; Thissen, Helmut; Caruso, Frank; Drummond, Calum J

    2013-10-22

    Cubic phase lyotropic liquid crystalline colloidal dispersions (cubosomes) were surface-modified with seven polyelectrolyte layers using a layer-by-layer (LbL) approach. The first layer consisted of a copolymer synthesized from methacrylic acid and oleoyl methacrylate for enhanced incorporation within the bilayer of the cubic nanostructure. Six additional layers of poly(L-lysine) and poly(methacrylic acid) were then sequentially added, followed by a washing procedure to remove polymer aggregates from the soft matter particles. Polymer buildup was monitored via microelectrophoresis, dynamic light scattering, and small-angle X-ray scattering. Polymer-coated cubosomes were observed with cryo-transmission electron microscopy. A potential application of the modified nanostructured particles presented in this study is to reduce the burst-release effect associated with drug-loaded cubosomes. The effectiveness of this approach was demonstrated through loading and release results from a model hydrophilic small molecule (fluorescein).

  3. Controlled release of folic acid through liquid-crystalline folate nanoparticles.

    PubMed

    Misra, Rahul; Katyal, Henna; Mohanty, Sanat

    2014-11-01

    The present study explores folate nanoparticles as nano-carriers for controlled drug delivery. Cross-linked nanoparticles of liquid crystalline folates are composed of ordered stacks. This paper shows that the folate nanoparticles can be made with less than 5% loss in folate ions. In addition, this study shows that folate nanoparticles can disintegrate in a controlled fashion resulting in controlled release of the folate ions. Release can be controlled by the size of nanoparticles, the extent of cross-linking and the choice of cross-linking cation. The effect of different factors like agitation, pH, and temperature on folate release was also studied. Studies were also carried out to show the effect of release medium and role of ions in the release medium on disruption of folate assembly.

  4. Structure and optical properties of glasses in binary liquid crystalline systems based on cobalt octanoate

    NASA Astrophysics Data System (ADS)

    Mirnaya, T. A.; Tokmenko, I. I.; Yaremchuk, G. G.; Tolochko, A. S.

    2015-04-01

    The effect of composition and aggregative state (melt, mesophase, glass) on the coordination state of Co (II) ions in an octanoate ligand field has been studied for binary liquid crystalline systems based on cobalt (II) octanoate by the analysis of electronic absorption spectra. It has been shown that several coordination forms of Co (II) ions: octahedral, tetrahedral and dodecahedral ones can coexist in cobalt octanoate based systems. It has been found by positron annihilation lifetime spectroscopy and small-angle X-ray scattering that glasses of cobalt octanoate based systems have a bilayer and nanoporous structure. The thickness of cation-anion bilayers in mesophases and glasses of binary systems depends on the polarizing power of cations: it is the smaller, the higher the polarizing power of cations.

  5. Immune cell activation from multivalent interactions with liquid-crystalline polycation-DNA complexes

    NASA Astrophysics Data System (ADS)

    Schmidt, Nathan; Jin, Fan; Lande, Roberto; Curk, Tine; Xian, Wujing; Frasca, Loredana; Dobnikar, Jure; Frenkel, Daan; Gilliet, Michel; Wong, Gerard

    2014-03-01

    Microbial DNA can trigger type I interferon (IFN) production in plasmacytoid cells (pDCs) by binding to endosomal toll-like receptor 9 (TLR9). TLR9 in pDCs do not normally respond to self-DNA, but in certain autoimmune diseases self-DNA can complex with the polycationic antimicrobial peptide LL37 into condensed structures which allow DNA to access endosomal compartments and stimulate TLR9 in pDCs. We use x-ray studies and cell measurements of IFN secretion by pDCs to show that a broad range of polycation-DNA complexes stimulate pDCs and elucidate the criterion for high IFN production. Furthermore, we show via experiments and computer simulations that the distinguishing factor for why certain complexes activate pDCs while others do not is the self-assembled structure of the liquid-crystalline polycation-DNA complex.

  6. Orientational order in three nO.m liquid crystalline compounds

    NASA Astrophysics Data System (ADS)

    Usha, M. K.; Pardhasaradhi, P.; Vinutha, N.; Revannasiddaiah, D.

    2015-04-01

    Refractive index and density measurements have been carried out on three nO.m liquid crystalline compounds, namely, 4O.2, 4O.3 and 1O.10 belonging to the N-(p-n-alkoxybenzylidene)-p-n-alkylaniline series. From the data, the orientational order parameter has been estimated using Vuks and Neugebauer local field models. Furthermore, the orientational order parameter has been calculated directly from refractive index data employing the Vuks scaling factor method, Neugebauer f(B) parameter, effective geometry parameter and a method proposed by Kuczyński et al. It is observed that order parameter values estimated from different methods agree well near the nematic-isotropic transition and diverge as the nematic phase attains equilibrium. The temperature gradient of refractive indices and the nematic crossover temperatures have also been estimated for these compounds. The results obtained are compared and discussed.

  7. Thermodynamics and phase behavior of acid-tethered block copolymers with ionic liquids.

    PubMed

    Jung, Ha Young; Park, Moon Jeong

    2016-12-21

    We investigate the phase behavior of acid-tethered block copolymers with and without ionic liquids. Two phosphonated block copolymers and their sulfonated analogs were synthesized by fine-tuning the degree of polymerization and the acid content. The block copolymers carrying acid groups with ionic liquids exhibited rich phase sequences, i.e., disorder-lamellae (LAM), gyroid-LAM, gyroid-hexagonal cylinder (HEX), and gyroid-A15 lattice, and the cation/anion ratio in the ionic liquid exerted profound effects on the segregation strength and topology of the self-assembled structures. Additionally, using ionic liquids with excessive cation content was found to enhance the effective Flory-Huggins interaction parameter, χeff, of the samples. However, as the anion content of the ionic liquids increased the segregation strength decreased. This is attributed to the packing frustration accompanied by the prevailing repulsive electrostatic interactions of the anions in the ionic liquid and the polymer matrix. As the hydrophobicity of the ionic liquids increased, well-defined ordered phases emerged in the phosphonated block copolymers with increased anion content, contrary to the disordered phases of the sulfonated samples. Thus, the balance between solvation energy of the anions and the electrostatic interactions is a key determinant of the thermodynamics of acid-tethered block copolymers containing ionic liquids.

  8. Thin film polarizer based on photo-curable chromonic liquid crystalline solutions

    NASA Astrophysics Data System (ADS)

    Yang, Hye-Jin; Yoon, Sora; Bae, Yun-Ju; Shin, Seung-Han; Jeong, Kwang-Un; Lee, Myong-Hoon

    2012-03-01

    Lyotropic chromonic liquid crystals (LCLCs) form a columnar discotic liquid crystalline (LC) phase in aqueous solution due to the disc-like or plank-like molecular shape of chromonic dyes and their ionic peripheries. Such columnar structures in the chromonic columnar N phase can be coated on a glass substrate, and aligned in one direction by applying external forces. The resulting thin crystalline film (TCF) can absorb a polarized light parallel to the molecular axis while transmitting a polarized light parallel to the columnar axis, which constructs an E-polarizer. Although the concept of the coatable polarizer known, it has not been commercially successful due to numerous problems mainly originated from the use of aqueous solution. It is extremely difficult to coat the aqueous solution on most of substrates, especially on plastic substrates. Large volume shrinkage occurs during the crystallization process generating unfavorable defects. Also, weak adhesion becomes an important issue when a TCF is applied to a flexible substrate. In this presentation, we demonstrate a novel preparation method of coatable polarizer from a photo-curable organicbased LCLC solution. Lyotropic LC solutions were prepared by dissolving amino-functional chromonic dye in acrylic acid containing photoinitiator and crosslinking agents. The solution was shear-coated with subsequent UV irradiation to provide a thin film polarizer. The coating processibility of this organic-based solution was outstanding, particularly on a plastic substrate. The maximum polarization efficiency was measured to be > 98 %. The resulting thin film polarizer showed excellent film characteristics, such as good adhesion strength to various substrates, superior surface hardness, good solvent resistance and decent thermal stability.

  9. Molecular characterization of gel and liquid-crystalline structures of fully hydrated POPC and POPE bilayers.

    PubMed

    Leekumjorn, Sukit; Sum, Amadeu K

    2007-05-31

    Molecular dynamics simulations were used for a comprehensive study of the structural properties of monounsaturated POPC and POPE bilayers in the gel and liquid-crystalline state at a number of temperatures, ranging from 250 to 330 K. Though the chemical structures of POPC and POPE are largely similar (choline versus ethanolamine headgroup), their transformation processes from a gel to a liquid-crystalline state are contrasting. In the similarities, the lipid tails for both systems are tilted below the phase transition and become more random above the phase transition temperature. The average area per lipid and bilayer thickness were found less sensitive to phase transition changes as the unsaturated tails are able to buffer reordering of the bilayer structure, as observed from hysteresis loops in annealing simulations. For POPC, changes in the structural properties such as the lipid tail order parameter, hydrocarbon trans-gauche isomerization, lipid tail tilt-angle, and level of interdigitation identified a phase transition at about 270 K. For POPE, three temperature ranges were identified, in which the lower one (270-280 K) was associated with a pre-transition state and the higher (290-300 K) with the post-transition state. In the pre-transition state, there was a significant increase in the number of gauche arrangements formed along the lipid tails. Near the main transition (280-290 K), there was a lowering of the lipid order parameters and a disappearance of the tilted lipid arrangement. In the post-transition state, the carbon atoms along the lipid tails became less hindered as their density profiles showed uniform distributions. This study also demonstrates that atomistic simulations of current lipid force fields are capable of capturing the phase transition behavior of lipid bilayers, providing a rich set of molecular and structural information at and near the main transition state.

  10. Phase behavior of lipid mixtures based on human ceramides: coexistence of crystalline and liquid phases.

    PubMed

    Bouwstra, J A; Gooris, G S; Dubbelaar, F E; Ponec, M

    2001-11-01

    The lipid regions in the outermost layer of the skin (stratum corneum) form the main barrier for diffusion of substances through the skin. In this layer the main lipid classes are ceramides, cholesterol (CHOL), and FFA. Previous studies revealed a coexistence of two crystalline lamellar phases with periodicities of approximately 13 nm (referred to as long periodicity phase) and 6 nm (short periodicity phase). Additional studies showed that lipid mixtures prepared with isolated pig ceramides (pigCER) mimic lipid phase behavior in stratum corneum closely. Because the molecular structure of pigCER differs in some important aspects from that of human ceramides (HCER), in the present study the phase behavior of mixtures prepared with HCER has been examined. Phase behavior studies of mixtures based on HCER revealed that in CHOL:HCER mixtures the long periodicity phase dominates. In the absence of HCER1 the short periodicity phase is dominant. Addition of FFA promotes the formation of the short periodicity phase and induces a transition from a hexagonal sublattice to an orthorhombic sublattice. Furthermore, the presence of FFA promotes the formation of a liquid phase. Finally, cholesterol sulfate, a minor but important lipid in the stratum corneum, reduces the amount of cholesterol that phase separates in crystalline domains. From these observations it can be concluded that the phase behavior of mixtures prepared from HCER differs in some important aspects from that prepared from pigCER. The most prevalent differences are the following: i) the addition of FFA promotes the formation of the short periodicity phase; and ii) liquid lateral packing is obviously present in CHOL:HCER:FFA mixtures. These changes in phase behavior might be due to a larger amount of linoleic acid moiety in HCER mixtures compared with that in pigCER mixtures.

  11. Self-assembled liquid-crystalline folate nanoparticles for in vitro controlled release of doxorubicin.

    PubMed

    Misra, Rahul; Mohanty, Sanat

    2015-02-01

    Liquid-crystalline folate nanoparticles are ordered in structure which offers several advantages like high encapsulation of drugs, controlled release rates, biocompatible in nature. Moreover, it facilitates the cellular uptake of nanodrugs without any extra step of folate ligand based targeting. The size of these nanocarriers as well as the release profiles of drugs from these nano-carriers can be controlled precisely. Folate molecules self-assemble in ordered stacks and columns even at low concentration of 0.1wt%. Doxorubicin molecules get intercalated within the folate stacks and are developed into nanoparticles. These nanoparticles are composed of highly ordered folate self-assembly which encapsulate doxorubicin molecules. These drug molecules can be released in a controlled manner by disrupting this assembly in the environment of monovalent cations. The ordered structure of folate nanoparticles offers low drug losses of about 4-5%, which is significant in itself. This study reports the size-control method of forming doxorubicin encapsulated folate nanoparticles as well as the parameters to control the release rates of doxorubicin through liquid-crystalline folate nanoparticles. It has been demonstrated that doxorubicin release rates can be controlled by controlling the size of the nanoparticles, cross-linking cation and cross-linking concentration. The effect of different factors like drug loading, release medium, and pH of the medium on doxorubicin release rates was also studied. Moreover, this study also addresses the comparative in vitro cytotoxic performance of Doxorubicin loaded folate nanoparticles and cellular uptake of nano-carriers on cancer and normal cell line. Copyright © 2014. Published by Elsevier Masson SAS.

  12. New liquid crystalline materials based on two generations of dendronised cyclophosphazenes.

    PubMed

    Jiménez, Josefina; Laguna, Antonio; Gascón, Elena; Sanz, José Antonio; Serrano, José Luis; Barberá, Joaquín; Oriol, Luis

    2012-12-21

    A divergent approach was used for the synthesis of dendritic structures based on a cyclotriphosphazene core with 12 or 24 hydroxyl groups, by starting from [N(3)P(3)(OC(6)H(4)OH-4)(6)] and using an acetal-protected 2,2-di(hydroxymethyl)propionic anhydride as the acylating agent. Hydroxyl groups in these first- and second-generation dendrimers, G1-(OH)(12) or G2-(OH)(24), were then condensed in turn with mono- or polycatenar pro-mesogenic acids to study their ability to promote self-assembly into liquid crystalline structures. Reactions were monitored by using (31)P{(1)H} and (1)H NMR spectroscopy and the chemical structure of the resulting materials was confirmed by using different spectroscopic techniques and mass spectrometry (MALDI-TOF MS). The results were in accordance with monodisperse, fully functionalised cyclotriphosphazene dendrimers. Thermal and liquid crystalline properties were studied by using optical microscopy, differential scanning calorimetry and X-ray diffraction. The dendrimer with 12 4-pentylbiphenyl mesogenic units gives rise to columnar rectangular organisation, whereas the one with 24 pentylbiphenyl units does not exhibit mesomorphic behaviour. In the case of materials that contain polycatenar pro-mesogenic units with two aromatic rings (A4 vs. A5), the incorporation of a short flexible spacer connected to the periphery of the dendron (acid A5) was needed to achieve mesomorphic organisation. In this case, both dendrimer generations G1 A5 and G2 A5 exhibit a hexagonal columnar mesophase. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Electrodeposition of crystalline GaAs on liquid gallium electrodes in aqueous electrolytes.

    PubMed

    Fahrenkrug, Eli; Gu, Junsi; Maldonado, Stephen

    2013-01-09

    Crystalline GaAs (c-GaAs) has been prepared directly through electroreduction of As(2)O(3) dissolved in an alkaline aqueous solution at a liquid gallium (Ga(l)) electrode at modest temperatures (T ≥ 80 °C). Ga(l) pool electrodes yielded consistent electrochemical behavior, affording repetitive measurements that illustrated the interdependences of applied potential, concentration of dissolved As(2)O(3), and electrodeposition temperature on the quality of the resultant c-GaAs(s). Raman spectra indicated the composition of the resultant film was strongly dependent on both the electrodeposition temperature and dissolved concentration of As(2)O(3) but not to the applied bias. For electrodepositions performed either at room temperature or with high (≥0.01 M) concentrations of dissolved As(2)O(3), Raman spectra of the electrodeposited films were consistent with amorphous As(s). X-ray diffractograms of As(s) films collected after thermal annealing indicated metallurgical alloying occurred only at temperatures in excess of 200 °C. Optical images and Raman spectra separately showed the composition of the as-electrodeposited film in dilute (≤0.001 M) solutions of dissolved As(2)O(3)(aq) was pure c-GaAs(s) at much lower temperatures than 200 °C. Diffractograms and transmission electron microscopy performed on as-prepared films confirmed the identity of c-GaAs(s). The collective results thus provide the first clear demonstration of an electrochemical liquid-liquid-solid (ec-LLS) process involving a liquid metal that serves simultaneously as an electrode, a solvent/medium for crystal growth, and a coreactant for the synthesis of a polycrystalline semiconductor. The presented data serve as impetus for the further development of the ec-LLS process as a controllable, simple, and direct route for technologically important optoelectronic materials such as c-GaAs(s).

  14. Electropolymerization of a bifunctional ionic liquid monomer yields as electroactive liquid-crystalline polymer.

    SciTech Connect

    Lee, S.; Becht, G. A.; Lee, B.; Burns, C. T.; Firestone, M. A.

    2010-07-09

    The preparation and polymerization of a bifunctional imidazolium-based ionic liquid (IL) monomer that incorporates both a vinyl group and a thiophene moiety is reported. Potentiodynamic electropolymerization of the monomer produces an optically birefringent polymer film that strongly adheres to the electrode surface. Fourier transform IR spectroscopy shows that polymerization occurs through both the vinyl and thienyl groups. Cylic voltammetry (CV) is used to determine the polymer oxidation potential (1.66 V) and electrochemical bandgap, Eg, of 2.45 eV. The polymer exhibits electrochromism, converting from yellow in the neutral form ({lambda}{sub max} = 380 nm) to blue in the polaronic state at 0.6 V ({lambda}{sub max} = 672 nm) and to blue-grey in the bipolaronic state at 1.2 V ({lambda}{sub max} > 800 nm). Topographic atomic force microscopy (AFM) images reveal isolated (separated) fibrils. Grazing-incidence small-angle X-ray scattering (GISAXS) studies indicate a lamellar structure with a lattice spacing of 3.2 nm. Wide-angle X-ray diffraction (WAXD) studies further suggest that the polymerized thiophene sheets are oriented perpendicular to the polymerized vinylimidazolium. The electrical conductivity, as determined by four-probe dc conductivity measurements was found to be 0.53 S cm{sup -1} in the neutral form and 2.36 S cm{sup -1} in the iodine-doped state, values higher than typically observed for polyalkylthiophenes. The structural ordering is believed to contribute to the observed enhancement of the electrical conductivity.

  15. PEGylation of phytantriol-based lyotropic liquid crystalline particles--the effect of lipid composition, PEG chain length, and temperature on the internal nanostructure.

    PubMed

    Nilsson, Christa; Østergaard, Jesper; Larsen, Susan Weng; Larsen, Claus; Urtti, Arto; Yaghmur, Anan

    2014-06-10

    Poly(ethylene glycol)-grafted 1,2-distearoyl-sn-glycero-3-phosphoethanolamines (DSPE-mPEGs) are a family of amphiphilic lipopolymers attractive in formulating injectable long-circulating nanoparticulate drug formulations. In addition to long circulating liposomes, there is an interest in developing injectable long-circulating drug nanocarriers based on cubosomes and hexosomes by shielding and coating the dispersed particles enveloping well-defined internal nonlamellar liquid crystalline nanostructures with hydrophilic PEG segments. The present study attempts to shed light on the possible PEGylation of these lipidic nonlamellar liquid crystalline particles by using DSPE-mPEGs with three different block lengths of the hydrophilic PEG segment. The effects of lipid composition, PEG chain length, and temperature on the morphology and internal nanostructure of these self-assembled lipidic aqueous dispersions based on phytantriol (PHYT) were investigated by means of synchrotron small-angle X-ray scattering and Transmission Electron Cryo-Microscopy. The results suggest that the used lipopolymers are incorporated into the water-PHYT interfacial area and induce a significant effect on the internal nanostructures of the dispersed submicrometer-sized particles. The hydrophilic domains of the internal liquid crystalline nanostructures of these aqueous dispersions are functionalized, i.e., the hydrophilic nanochannels of the internal cubic Pn3m and Im3m phases are significantly enlarged in the presence of relatively small amounts of the used DSPE-mPEGs. It is evident that the partial replacement of PHYT by these PEGylated lipids could be an attractive approach for the surface modification of cubosomal and hexosomal particles. These PEGylated nanocarriers are particularly attractive in designing injectable cubosomal and hexosomal nanocarriers for loading drugs and/or imaging probes.

  16. Novel lecithin-integrated liquid crystalline nanogels for enhanced cutaneous targeting of terconazole: development, in vitro and in vivo studies.

    PubMed

    Elnaggar, Yosra Sr; Talaat, Sara M; Bahey-El-Din, Mohammed; Abdallah, Ossama Y

    Terconazole (Tr) is the first marketed, most active triazole for vaginal candidiasis. Owing to poor skin permeation and challenging physicochemical properties, Tr was not employed for the treatment of cutaneous candidiasis. This is the first study to investigate the relevance of novel lecithin-integrated liquid crystalline nano-organogels (LCGs) to improve physicochemical characteristics of Tr in order to enable its dermal application in skin candidiasis. Ternary phase diagram was constructed using lecithin/capryol 90/water to identify the region of liquid crystalline organogel. The selected organogel possessed promising physicochemical characteristics based on particle size, rheological behavior, pH, loading efficiency, and in vitro antifungal activity. Microstructure of the selected organogel was confirmed by polarized light microscopy and transmission electron microscopy. Ex vivo and in vivo skin permeation studies revealed a significant 4.7- and 2.7-fold increase in the permeability of Tr-loaded LCG when compared to conventional hydrogel. Moreover, acute irritation study indicated safety and compatibility of liquid crystalline organogel to the skin. The in vivo antifungal activity confirmed the superiority of LCG over the conventional hydrogel for the eradication of Candida infection. Overall, lecithin-based liquid crystalline organogel confirmed its potential as an interesting dermal nanocarrier for skin targeting purpose.

  17. Novel lecithin-integrated liquid crystalline nanogels for enhanced cutaneous targeting of terconazole: development, in vitro and in vivo studies

    PubMed Central

    Elnaggar, Yosra SR; Talaat, Sara M; Bahey-El-Din, Mohammed; Abdallah, Ossama Y

    2016-01-01

    Terconazole (Tr) is the first marketed, most active triazole for vaginal candidiasis. Owing to poor skin permeation and challenging physicochemical properties, Tr was not employed for the treatment of cutaneous candidiasis. This is the first study to investigate the relevance of novel lecithin-integrated liquid crystalline nano-organogels (LCGs) to improve physicochemical characteristics of Tr in order to enable its dermal application in skin candidiasis. Ternary phase diagram was constructed using lecithin/capryol 90/water to identify the region of liquid crystalline organogel. The selected organogel possessed promising physicochemical characteristics based on particle size, rheological behavior, pH, loading efficiency, and in vitro antifungal activity. Microstructure of the selected organogel was confirmed by polarized light microscopy and transmission electron microscopy. Ex vivo and in vivo skin permeation studies revealed a significant 4.7- and 2.7-fold increase in the permeability of Tr-loaded LCG when compared to conventional hydrogel. Moreover, acute irritation study indicated safety and compatibility of liquid crystalline organogel to the skin. The in vivo antifungal activity confirmed the superiority of LCG over the conventional hydrogel for the eradication of Candida infection. Overall, lecithin-based liquid crystalline organogel confirmed its potential as an interesting dermal nanocarrier for skin targeting purpose. PMID:27822033

  18. Evaluation of Microemulsion and Lamellar Liquid Crystalline Systems for Transdermal Zidovudine Delivery.

    PubMed

    Carvalho, André Luis Menezes; Silva, José Alexsandro da; Lira, Ana Amélia Moreira; Conceição, Tamara Matos Freire; Nunes, Rogéria de Souza; de Albuquerque Junior, Ricardo Luiz Cavalcanti; Sarmento, Victor Hugo Vitorino; Leal, Leila Bastos; de Santana, Davi Pereira

    2016-07-01

    This study proposed to investigate and to compare colloidal carrier systems containing Zidovudine (3'-azido-3'-deoxythymidine) (AZT) for transdermal administration and optimization of antiretroviral therapy. Microemulsion (ME) and lamellar phase (LP) liquid crystal were obtained and selected from pseudoternary diagrams previously developed. Small-angle X-ray scattering and rheology analysis confirmed the presence of typical ME and liquid crystalline structures with lamellar arrangement, respectively. Both colloidal carrier systems, ME, and LP remained stable, homogeneous, and isotropic after AZT addition. In vitro permeation study (using pig ear skin) showed that the amount of permeated drug was higher for ME compared to the control and LP, obtaining a permeation enhancing effect on the order of approximately 2-fold (p < 0.05). Microscopic examination after in vivo skin irritation studies using mice suggested few histological changes in the skin of animals treated with the ME compared to the control group (hydrogel). Thus, ME proved to be adequate and have promising effects, being able to promote the drug permeation without causing apparent skin irritation. On the order hand, LP functioned as a drug reservoir reducing AZT partitioning into the skin.

  19. Controlling molecular transport and sustained drug release in lipid-based liquid crystalline mesophases.

    PubMed

    Zabara, Alexandru; Mezzenga, Raffaele

    2014-08-28

    Lipid-based lyotropic liquid crystals, also referred to as reversed liquid crystalline mesophases, such as bicontinuous cubic, hexagonal or micellar cubic phases, have attracted deep interest in the last few decades due to the possibility of observing these systems at thermodynamic equilibrium in excess water conditions. This becomes of immediate significance for applications in the colloidal environment, such as in the food, cosmetic and pharmaceutical arenas. One possible application regarded as very promising is that of controlled delivery of functional ingredients. Different crystallographic structures of the lipid mesophase give access to different diffusion coefficients and distinct diffusion modes. It becomes thus crucial to engineer the space group of the mesophase in a controlled way, and ideally, in a stimuli-responsive manner. In this article we review the state of the art on diffusion and molecular transport in lipid-based mesophases and we discuss recent contributions to the controlled delivery of molecules and colloids through these systems. In particular we focus on the different available strategies relying on either endogenous or exogenous stimuli to induce changes in the symmetry and transport properties of lipid-based mesophases and we discuss the impact and implications this may have on controlled drug delivery.

  20. Ionic liquid crystalline phases in 3-hexadecylimidazolium bromide and binary mixtures with 1-decanol.

    PubMed

    Li, Cuihua; He, Jinhua; Chen, Jiahui; Liu, Jianhong; Zhang, Qianling; Yu, Zhenqiang

    2011-07-15

    3-Hexadecylimidazolium bromide was synthesized and characterized showing formation of thermotropic smectic liquid crystals at temperatures above its melting point from 48.5 to 150.9°C. With decreasing temperature, the peak intensities in XRD patterns increase and full widths at half-maximum decrease, suggesting structural order increases with decreasing temperature. Compared with 1,2-dimethyl-3-hexadecyl-imidazolium bromide and hexafluorophosphate, the IL shows a lower melting point and less degree of chain interdigitation. The main reason is due to a more symmetrical structure and denser assembly of the IL molecules, which results in more steric resistance for the alkyl chain to interdigitate. The self-assembly behavior of the hydrophobic IL in an organic solvent was investigated showing SmA(2) lyotropic liquid crystalline phases. The first-order scattering peak shifts to lower q values with increasing IL content, which is opposite to the shift directions of the binary mixtures of the soluble imidazolium IL and water, indicating a different packing behavior of the hydrophobic IL in 1-decanol.

  1. Carrier transport and viscosity of discotic liquid-crystalline photoconductor hexaoctylthio-triphenylene

    NASA Astrophysics Data System (ADS)

    Monobe, Hirosato; Shimizu, Yo

    2014-01-01

    In this study, the electronic and ionic carrier transports and viscosity of 2,3,6,7,10,11-hexaoctylthio-triphenylene (C8STP) were studied by a time-of-flight method and using a rotational viscometer. Ambipolar charge carrier transport was investigated in the isotropic liquid (Iso) phase of C8STP, similarly to the columnar hexagonal mesophase, and the activation energies were estimated to be 0.1 eV for one positive and one negative, and 0.4 eV for the other negative charge carrier mobility in Iso. The viscosity of C8STP was investigated using a rotation viscometer, and relative viscosity was measured by a capillary method in the isotropic phase, and the activation energy of viscosity was 0.4 eV. The Stokes radii of ionic carriers were experimentally estimated using Walden’s rule. The existence of ionic and electronic (hopping) carrier transports in Iso was implied for the discotic liquid crystalline photoconductor.

  2. Flow-Induced Assembly of Colloidal Liquid Crystalline Nanosheets Toward Unidirectional Macroscopic Structures.

    PubMed

    Nono, Yoshihiro; Mouri, Emiko; Nakata, Munetaka; Nakato, Teruyuki

    2016-03-01

    Multiscale structures of anisotropic nanoparticles up to macroscopic scales are important in order to produce practical materials through nanotechnology. As an example of such structures, hierarchical organization of colloidal liquid crystals of niobium oxide nanosheets yields stripe textures observable by naked eyes. The stripes are generated by the growth of liquid crystalline domains (tactoids) and the alignment of the tactoids under an electric field and gravity applied in the directions orthogonal to each other. The nanosheets forming the tactoids are unidirectionally aligned along the flow induced by gravity, and the aligned tactoids are stretched to be connected each other to form the stripes. Time evolution of the stripes indicates that they are generated during the settlement of the nanosheets. The nanosheets are debundled with the settlement, and thus the stripes are gradually degenerated during the settlement. Larger tactoids cause faster nanosheet settlement and stripe degeneration. The electric field applied orthogonally to gravity has roles of pinning the nanosheets to slow down their settlement and retains the stripes for several hours.

  3. Ultrafast vibrational dynamics of BH{sub 4}{sup −} ions in liquid and crystalline environments

    SciTech Connect

    Tyborski, Tobias Costard, Rene; Woerner, Michael; Elsaesser, Thomas

    2014-07-21

    Ultrafast vibrational dynamics of BH{sub 4}{sup −} ions, the key units in boron hydride materials for hydrogen storage, are studied in diluted polar liquid solution and in NaBH{sub 4} crystallites by femtosecond infrared spectroscopy. Two-color pump-probe experiments reveal v = 1 lifetimes of 3 ps for the asymmetric BH{sub 4}{sup −} stretching mode ν{sub 3} and of 3.6 ps for the asymmetric bending mode ν{sub 4} in the solvent isopropylamine. We provide direct evidence for the BH{sub 4}{sup −} stretching relaxation pathway via the asymmetric bending mode ν{sub 4} by probing the latter after femtosecond excitation of ν{sub 3}. Pump-probe traces measured in the crystalline phase show signatures of radiative coupling between the densely packed BH{sub 4}{sup −} oscillators, most clearly manifested in an accelerated subpicosecond depopulation of the v = 1 state of the ν{sub 4} mode. The radiative decay is followed by incoherent vibrational relaxation similar to the liquid phase. The excess energy released in the relaxation processes of the BH{sub 4}{sup −} intramolecular modes is transferred into the environment with thermal pump-probe signals being much more pronounced in the dense solid than in the diluted solution.

  4. Facile dispersion and control of internal structure in lyotropic liquid crystalline particles by auxiliary solvent evaporation.

    PubMed

    Martiel, Isabelle; Sagalowicz, Laurent; Handschin, Stephan; Mezzenga, Raffaele

    2014-12-09

    Submicron sized, structured lyotropic liquid crystalline (LLC) particles, so-called hexosomes and cubosomes, are generally obtained by high energy input dispersion methods, notably ultrasonication and high-pressure emulsification. We present a method to obtain dispersions of such LLC particles with a significantly reduced energy input, by evaporation of an auxiliary volatile solvent immiscible with water, e.g. cyclohexane or limonene. The inner structure of the particles can be precisely controlled by the addition of a nonvolatile oil, such as α-tocopherol or tetradecane consistently with bulk phase diagrams,. Two different lyotropic surfactants were employed, industrial grade monolinoleine (MLO) and soy bean phosphatidylcholine (PC). The lyotropic surfactant and oil phase modifier were first dissolved in the volatile solvent to give a liquid reverse micellar (L2) phase, which requires significantly less energy input to be dispersed in an aqueous solution of secondary emulsifier compared to the corresponding gel-like bulk mesophase. The auxiliary volatile solvent was then removed from the emulsion by evaporation at room temperature, yielding LLC particles of the desired inner structure, Pn3̅m, H2, or Fd3̅m. The obtained particles were characterized by small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and cryogenic transmission electron microscopy (cryo-TEM). Our method enables fine-tuning of the final particle size through the volatile-to-nonvolatile volume ratio and processing conditions.

  5. The synaptonemal complex has liquid crystalline properties and spatially regulates meiotic recombination factors

    PubMed Central

    Rog, Ofer; Köhler, Simone; Dernburg, Abby F

    2017-01-01

    The synaptonemal complex (SC) is a polymer that spans ~100 nm between paired homologous chromosomes during meiosis. Its striated, periodic appearance in electron micrographs led to the idea that transverse filaments within this structure ‘crosslink’ the axes of homologous chromosomes, stabilizing their pairing. SC proteins can also form polycomplexes, three-dimensional lattices that recapitulate the periodic structure of SCs but do not associate with chromosomes. Here we provide evidence that SCs and polycomplexes contain mobile subunits and that their assembly is promoted by weak hydrophobic interactions, indicative of a liquid crystalline phase. We further show that in the absence of recombination intermediates, polycomplexes recapitulate the dynamic localization of pro-crossover factors during meiotic progression, revealing how the SC might act as a conduit to regulate chromosome-wide crossover distribution. Properties unique to liquid crystals likely enable long-range signal transduction along meiotic chromosomes and underlie the rapid evolution of SC proteins. DOI: http://dx.doi.org/10.7554/eLife.21455.001 PMID:28045371

  6. Lateral solidification of a liquid crystalline semiconductor film induced by temperature gradient

    NASA Astrophysics Data System (ADS)

    Hoshino, Tomoya; Ito, Hayato; Fujieda, Ichiro; Hanasaki, Tomonori

    2013-09-01

    Derivatives of [1]benzothieno[3,2-b]benzothiophene (BTBT) are attracting much attention as a highly soluble, highmobility semiconductor material for thin-film transistor applications. These small molecules are known to organize themselves into a single crystalline structure after spin coating or drop casting. Charge transport in a single crystal material is anisotropic in nature. Hence, it is desired to control its orientation during growth or recrystallization so that the source and drain electrodes of a transistor are to be placed along a faster transport direction. We propose to generate temperature gradient in a heated liquid crystalline thin film to induce lateral recrystallization. In experiment, we tried two methods. First, an aluminum plate with two narrow ridges was inserted between a temperature-controlled stage and a square silicon substrate with a 200nm-thick SiO2 and a spin-coated C8-BTBT film. We raised the temperature of the stage to 120oC and let it cool gradually. During cooling at around 105oC , the color of the sample started to change, indicating a phase change. This change proceeded from the corners of the film and in about 30 seconds, darker regions merged at the center of the substrate. Second, the sample was placed at the edge of the stage. In this case, the color change started from the protruding corner of the sample and proceeded toward the other end. Micrograph observation revealed that cracks were formed in these films and they were perpendicular to the direction of the phase change.

  7. PH-Induced Nanosegregation of Ritonavir to Lyotropic Liquid Crystal of Higher Solubility Than Crystalline Polymorphs

    SciTech Connect

    Rodriguez-Spong, B.; Acciacca, A.; Fleisher, D.; Rodriguez-Hornedo, N.

    2009-05-27

    Birefringent spherical vesicles of ritonavir (RTV) are formed by increasing the pH of aqueous solutions from 1 to 3 or to 7 and by addition of water to ethanol solutions at room temperature. Increasing the pH creates supersaturation levels of 30--400. Upon this change in pH, the solutions become translucent, implying that some kind of RTV assembly was formed. Small spherical vesicles of narrow size distribution are detectable only after a few hours by optical microscopy. The vesicles show similar X-ray diffraction patterns and differential scanning calorimetry (DSC) behavior to amorphous RTV prepared by melt-quenching crystalline RTV. Examination by polarized optical microscopy suggests that these are lyotropic liquid crystalline (LLC) assemblies. Small-angle X-ray scattering and synchrotron X-ray diffraction further support the presence of orientational order that is associated with a nematic structure. RTV self-organizes into various phases as a result of the supersaturation created in aqueous solutions. The LLC vesicles do not fuse but slowly transform to the polymorphs of RTV (in days), Form I and finally Form II. Amorphous RTV in aqueous suspension also undergoes a transformation to a mesophase of similar morphology. Transformation pathways are consistent with measured dissolution rates and solubilities: amorphous > LLC >> Form I > Form II. The dissolution and solubility of LLC is slightly lower than that of the amorphous phase and about 20 times higher than that of Form II. RTV also self-assembles at the air/water interface as indicated by the decrease in surface tension of aqueous solutions. This behavior is similar to that of amphiphilic molecules that induce LLC formation.

  8. A Simple Evaporation Method for Large-Scale Production of Liquid Crystalline Lipid Nanoparticles with Various Internal Structures.

    PubMed

    Kim, Do-Hoon; Lim, Sora; Shim, Jongwon; Song, Ji Eun; Chang, Jong Soo; Jin, Kyeong Sik; Cho, Eun Chul

    2015-09-16

    We present a simple and industrially accessible method of producing liquid crystalline lipid nanoparticles with various internal structures based on phytantriol, Pluronic F127, and vitamin E acetate. Bilayer vesicles were produced when an ethanolic solution dissolving the lipid components was mixed with deionized water. After the evaporation of ethanol from the aqueous mixture, vesicles were transformed into lipid-filled liquid crystalline nanoparticles with well-defined internal structures such as hexagonal lattices (mostly inverted cubic Pn3m), lined or coiled pattern (inverted hexagonal H2), and disordered structure (inverse microemulsion, L2), depending on the compositions. Further studies suggested that their internal structures were also affected by temperature. The internal structures were characterized from cryo-TEM and small-angle X-ray scattering results. Microcalorimetry studies were performed to investigate the degree of molecular ordering/crystallinity of lipid components within the nanostructures. From the comparative studies, we demonstrated the present method could produce the lipid nanoparticles with similar characteristics to those made from a conventional method. More importantly, the production only requires simple tools for mixing and ethanol evaporation and it is possible to produce 10 kg or so per batch of aqueous lipid nanoparticles dispersions, enabling the large-scale production of the liquid crystalline nanoparticles for various biomedical applications.

  9. Charge transport in liquid crystalline smectic and discotic organic semiconductors: New results and experimental methodologies

    NASA Astrophysics Data System (ADS)

    Paul, Sanjoy

    Organic electronics offer the possibility of producing low cost, flexible, and large area electronics. Organic semiconductors (OSCs) (organic polymers and crystals), used in organic electronics, are promising materials for novel optical and electronic devices such as organic light emitting diodes, organic field effect transistors, organic sensors, and organic photovoltaics (OPVs). OSCs are composed of molecules weakly held together via van der Walls forces rather than covalent bonds as in the case of inorganic semiconductors such as Si. The combined effect of small wave function overlap, spatial and energetic disorder in organic semiconducting materials lead to localization of charge carriers and, in many cases, hopping conduction. OSCs also differ from conventional semiconductors in that charges photogeneration (e.g., in OPVs) proceeds via the production, diffusion, and dissociation of excitons. Liquid crystalline OSCs (LCOSCs) are semiconductors with phases intermediate between the highly ordered crystalline and completely disordered liquid phases. These materials offer many advantages including facile alignment and the opportunity to study the effects of differing intermolecular geometries on transfer integrals, disorder-induced trapping, charge mobilities, and photogeneration efficiency. In this dissertation work, we explored the photogeneration and charge transport mechanisms in a few model smectic and discotic LCs to better understand the governing principles of photogeneration and charge transport using conventional and novel methods based on the pulsed laser time-of-flight charge carrier transport technique. Four major interrelated topics were considered in this research. First, a sample of smectic LC was aligned in order to compare the resulting hole mobility to that of an unaligned sample, with the aim of understanding how the intermolecular alignment over large length scales affects the hopping probability. The role of the polarization of the

  10. Self-assembled multicompartment liquid crystalline lipid carriers for protein, peptide, and nucleic acid drug delivery.

    PubMed

    Angelova, Angelina; Angelov, Borislav; Mutafchieva, Rada; Lesieur, Sylviane; Couvreur, Patrick

    2011-02-15

    Lipids and lipopolymers self-assembled into biocompatible nano- and mesostructured functional materials offer many potential applications in medicine and diagnostics. In this Account, we demonstrate how high-resolution structural investigations of bicontinuous cubic templates made from lyotropic thermosensitive liquid-crystalline (LC) materials have initiated the development of innovative lipidopolymeric self-assembled nanocarriers. Such structures have tunable nanochannel sizes, morphologies, and hierarchical inner organizations and provide potential vehicles for the predictable loading and release of therapeutic proteins, peptides, or nucleic acids. This Account shows that structural studies of swelling of bicontinuous cubic lipid/water phases are essential for overcoming the nanoscale constraints for encapsulation of large therapeutic molecules in multicompartment lipid carriers. For the systems described here, we have employed time-resolved small-angle X-ray scattering (SAXS) and high-resolution freeze-fracture electronic microscopy (FF-EM) to study the morphology and the dynamic topological transitions of these nanostructured multicomponent amphiphilic assemblies. Quasi-elastic light scattering and circular dichroism spectroscopy can provide additional information at the nanoscale about the behavior of lipid/protein self-assemblies under conditions that approximate physiological hydration. We wanted to generalize these findings to control the stability and the hydration of the water nanochannels in liquid-crystalline lipid nanovehicles and confine therapeutic biomolecules within these structures. Therefore we analyzed the influence of amphiphilic and soluble additives (e.g. poly(ethylene glycol)monooleate (MO-PEG), octyl glucoside (OG), proteins) on the nanochannels' size in a diamond (D)-type bicontinuous cubic phase of the lipid glycerol monooleate (MO). At body temperature, we can stabilize long-living swollen states, corresponding to a diamond cubic phase

  11. Non-covalent modification of reduced graphene oxide by a chiral liquid crystalline surfactant

    NASA Astrophysics Data System (ADS)

    Lin, Pengcheng; Cong, Yuehua; Sun, Cong; Zhang, Baoyan

    2016-01-01

    In order to effectively disperse reduced graphene oxide (RGO) in functional materials and take full advantage of its exceptional physical and chemical properties, a novel and effective approach for non-covalent modification of RGO by a chiral liquid crystalline surfactant (CLCS) consisting of chiral mesogenic units, nematic mesogenic units with carboxyl groups and non-mesogenic units with a polycyclic conjugated structure is firstly established. The polycyclic conjugated structure can anchor onto the RGO surface via π-π interactions, the chiral mesogenic units possess affinity for chiral materials by joining the helical matrix of chiral material and the carboxyl groups in nematic mesogenic units are supposed to form coordination bonds with nano zinc oxide (ZnO) to fabricate functional nano hybrids. The transmittances of CLCS-RGO hybrids exhibit S-shaped nonlinear increase with the increase of wavelength, but the total transmittances from 220 nm to 800 nm show a linear decreasing trend with the increase of RGO content in the CLCS-RGO hybrid. Due to the superior thermal properties of RGO and the interactions between RGO and CLCS, the dispersed RGO can improve the glass transition and increase the thermal stability and decomposition activation energy of CLCS. The intercalation of RGO can decrease the thermochromism temperature and improve the pitch uniformity of CLCS. Furthermore, CLCS can promote the dispersion of RGO in chiral nematic liquid crystals (CNLCs), and the CNLC-RGO-CLCS hybrids present decreased driving voltage and accelerated electro-optical response. The CLCS non-covalently modified RGO can strengthen the photocatalytic degradation of ZnO by suppressing the aggregation of ZnO and RGO.In order to effectively disperse reduced graphene oxide (RGO) in functional materials and take full advantage of its exceptional physical and chemical properties, a novel and effective approach for non-covalent modification of RGO by a chiral liquid crystalline surfactant

  12. Examining the gastrointestinal transit of lipid-based liquid crystalline systems using whole-animal imaging.

    PubMed

    Pham, Anna C; Nguyen, Tri-Hung; Nowell, Cameron J; Graham, Bim; Boyd, Ben J

    2015-12-01

    Lipid-based liquid crystalline (LC) systems have the potential to sustain the oral absorption of poorly water-soluble drugs in vivo, facilitating slow drug release from their complex internal structure. To further evaluate the dynamic relationship between gastric retention and sustained drug absorption for these systems, this study aimed to explore non-invasive X-ray micro-CT imaging as an approach to assess gastric retention. Pharmacokinetic studies were also conducted with cinnarizine-loaded LC formulations to correlate gastric retention of the formulation to drug absorption. The in vivo studies demonstrated the interplay between gastric retention and drug absorption based on the digestibility of the LC structures. An increase in non-digestible phytantriol (PHY) composition in the formulation relative to digestible glyceryl monooleate (GMO) increased the gastric retention, with 68 ± 4 % of formulation intensity remaining at 8 h for 85 % w/w PHY, and 26 ± 9 % for 60 % w/w PHY. Interestingly, it was found that PHY 30 % w/w in GMO provided the highest bioavailability for cinnarizine (CZ) amongst the other combinations, including GMO alone. The studies demonstrated that combining digestible and non-digestible lipids into LC systems allowed for an optimal balance between sustaining drug absorption whilst increasing plasma concentration (C max) over time, leading to enhanced oral bioavailability. The results demonstrate the potential for utilising non-invasive X-ray micro-CT imaging to dynamically assess the GI transit of orally administered liquid crystal-forming formulations.

  13. Monodisperse nonionic isoprenoid-type hexahydrofarnesyl ethylene oxide surfactants: high throughput lyotropic liquid crystalline phase determination.

    PubMed

    Fong, Celesta; Weerawardena, Asoka; Sagnella, Sharon M; Mulet, Xavier; Krodkiewska, Irena; Chong, Josephine; Drummond, Calum J

    2011-03-15

    The neat and lyotropic phase behavior of eight new ethylene oxide amphiphiles (EO = 1-8) with a hexahydrofarnesyl chain (3,7,11-trimethyldodecyl) and narrow polydispersity (>98.5% purity) is reported. Below five EO units the behavior of the neat surfactants show only a glass transition, Tg ∼ -90 °C. Above four EO units, crystallization (Tcrys) and crystal-isotropic liquid (Tm) transitions are also observed that increase with degree of ethoxylation of the surfactant headgroup. The lyotropic liquid crystalline phase behavior spans a complex spectrum of surfactant-water interfacial curvatures. Specifically, inverse phases are present below ambient temperatures for EO < 4, with HFarn(EO)2 exhibiting an inverse hexagonal (H(II)) phase stable to dilution. The phase diagram of HFarn(EO)3 displays both the gyroid (Ia3d) and double diamond (Pn3m) inverse bicontinuous cubic phases, with the latter being thermodynamically stable in excess water within the physiological regime. There is a strong preference for planar bilayer structures at intermediate headgroup ethoxylation, with the crossover to normal phases occurring at HFarn(EO)(7-8) which exhibits normal hexagonal (H(I)) and cubic (Q(I)) phases at ambient temperatures. The toxicity of colloidal dispersions of these EO amphiphiles was assayed against normal breast epithelial (HMEpiC) and breast cancer (MCF7) cell lines. The IC50 of the EO amphiphiles was similar in both cell lines with moderate toxicity ranging from ca. <5 to 140 μM in an in vitro cell viability assay. Observations are qualitatively rationalized in terms of the molecular geometry of the surfactant. The physicochemical behavior of the HFarnesyl ethylene oxide amphiphiles is compared to other ethylene oxide surfactants.

  14. Magneto-responsive liquid crystalline elastomer nanocomposites as potential candidates for dynamic cell culture substrates.

    PubMed

    Herrera-Posada, Stephany; Mora-Navarro, Camilo; Ortiz-Bermudez, Patricia; Torres-Lugo, Madeline; McElhinny, Kyle M; Evans, Paul G; Calcagno, Barbara O; Acevedo, Aldo

    2016-08-01

    Recently, liquid crystalline elastomers (LCEs) have been proposed as active substrates for cell culture due to their potential to attach and orient cells, and impose dynamic mechanical signals through the application of external stimuli. In this report, the preparation of anisotropic and oriented nematic magnetic-sensitized LCEs with iron oxide nanoparticles, and the evaluation of the effect of particle addition at low concentrations on the resultant structural, thermal, thermo-mechanical, and mechanical properties is presented. Phase transformations produced by heating in alternating magnetic fields were investigated in LCEs in contact with air, water, and a common liquid cell culture medium was also evaluated. The inclusion of nanoparticles into the elastomers displaced the nematic-to-isotropic phase transition, without affecting the nematic structure as evidenced by similar values of the order parameter, while reducing the maximum thermomechanical deformations. Remote and reversible deformations of the magnetic LCEs were achieved through the application of alternating magnetic fields, which induces the nematic-isotropic phase transition through nanoparticle heat generation. Formulation parameters can be modified to allow for remote actuation at values closer to the human physiological temperature range and within the range of deformations that can affect the cellular behavior of fibroblasts. Finally, a collagen surface treatment was performed to improve compatibility with NIH-3T3 fibroblast cultures, which enabled the attachment and proliferation of fibroblasts on substrates with and without magnetic particles under quiescent conditions. The LCEs developed in this work, which are able to deform and experience stress changes by remote contact-less magnetic stimulation, may allow for further studies on the effect of substrate morphology changes and dynamic mechanical properties during in vitro cell culture. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Homogeneous alignment of liquid crystalline dendrimers confined in a slit-pore. A simulation study

    NASA Astrophysics Data System (ADS)

    Workineh, Zerihun G.; Vanakaras, Alexandros G.

    2016-03-01

    In this work we present results from isobaric-isothermal (NPT) Monte Carlo simulation studies of model liquid crystalline dendrimer (LCDr) systems confined in a slit-pore made of two parallel flat walls. The dendrimers are modelled as a collection of spherical and ellipsoidal particles corresponding to the junction points of the dendritic core and to the mesogenic units respectively. Assuming planar uniform (unidirectional) soft anchoring of the mesogenic units on the substrates we investigate the conformational and alignment properties of the LCDr system at different thermodynamic state points. Tractable coarse grained force fields have been used from our previous work. At low pressures the interior of the pore is almost empty, since almost all LCDrs are anchored to the substrates forming two-dimensional smectic-like structures with the mesogens aligned along the aligning direction of the substrates. As the pressure grows the LCDrs occupy the whole pore. However, even at low temperatures, the smectic organization does not transmit in the interior of the pore and is preserved for distances of 2-3 mesogenic diameters from the walls. For this reason, the global orientational order decreases with increasing pressure (density). In the vicinity (2-3 mesogenic diameters) of the pore walls, mesogenic units preserve the smectic structure whose layers are separated by layers of spherical beads. In this region individual LCDrs possess a rod like shape.

  16. Bulk and Surface Molecular Orientation Distribution in Injection-molded Liquid Crystalline Polymers: Experiment and Simulation

    SciTech Connect

    Fang, J.; Burghardt, W; Bubeck, R; Burgard, S; Fischer, D

    2010-01-01

    Bulk and surface distributions of molecular orientation in injection-molded plaques of thermotropic liquid crystalline polymers (TLCPs) have been studied using a combination of techniques, coordinated with process simulations using the Larson-Doi 'polydomain' model. Wide-angle X-ray scattering was used to map out the bulk orientation distribution. Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) were utilized to probe the molecular orientation states to within about {approx}5 {micro}m and {approx}2 nm, respectively, of the sample surface. These noninvasive, surface-sensitive techniques yield reasonable self-consistency, providing complementary validation of the robustness of these methods. An analogy between Larson-Doi and fiber orientation models has allowed the first simulations of TLCP injection molding. The simulations capture many fine details in the bulk orientation distribution across the sample plaque. Direct simulation of surface orientation at the level probed by FTIR-ATR and NEXAFS was not possible due to the limited spatial resolution of the simulations. However, simulation results extracted from the shear-dominant skin region are found to provide a qualitatively accurate indicator of surface orientation. Finally, simulations capture the relation between bulk and surface orientation states across the different regions of the sample plaque.

  17. Synthesis and molecular characterization of acrylate liquid crystalline resin monomers (ALCRM).

    PubMed

    He, X P; Cai, W; Guo, L; Zhou, L Z; Nie, M H

    2015-10-16

    A novel biocompatible resin monomer 4—3—(acryloyloxy)—2—hydroxypropoxy) phenyl 4—(3—(acryloyloxy)—2—hydroxypropoxy) benzoate, as an oral restorative — acrylate liquid crystalline resin monomer (ALCRM) was synthesized. The intermediate product and the final product were characterized by differential scanning calorimetry (DSC), polarized optical microscope (POM), and nuclear magnetic resonance (NMR). A resin matrix which has a potential application in dental composites was prepared by photopolymerizing ALCRM and triethylene glycol dimethacrylate (TEGDMA) as a primary and diluted monomer with a photosensitizer of camphorquinone (CQ) and 2—(Dimethylamino)ethyl methacrylate (DMAEMA) mixture. The molar ratio of ALCRM and TEGDMA was 7:3. The properties such as the curing depth, curing time, and the volumetric shrinkage of the resin matrix were investigated and compared with a traditional composite resin matrix Bis—GMA. After photocuring polymerization, the conversion degree of the resin matrix is 68.06%, higher than Bis—GMA/TEGDMA; the curing time is 4.08±0.20min, the curing depth is 2.10±0.17mm, and the volumetric shrinkage is 3.62%±0.26%. All the properties exhibit a better performance of the prepared resin matrix than Bis—GMA.

  18. Effect of Mesophase Order on the Dynamics of Side Group Liquid Crystalline Polymers

    SciTech Connect

    Auad, M.L.; Kempe, M.D.; Kornfield, J.A.; Rendon, S.; Burghardt, W.R.; Yoon, K.

    2010-07-13

    Rheology and X-ray scattering were employed to probe the viscoelastic properties and structural transitions of model cyano-biphenyl-based side-group liquid-crystalline polymers (SGLCPs) with molecular weights ranging from 91 to 1900 kg/mol. Temperature-dependent rheological data show a rapid change in dynamics over a small temperature range. Small-angle X-ray scattering reveals these changes to be associated with an isotropic to smectic transition with an appreciable biphasic region. The presence of a biphasic region is attributed to inhomogeneity in chain structure resulting from incomplete attachment of mesogens to every monomeric unit in the SGLCP polymer. While isotropic and smectic phase data may be separately time-temperature shifted to create master curves for the individual phases, we argue against attempts to achieve superposition between the two phases in the high-frequency regime, since smectic ordering may not simply slow the dynamics but also increase the modulus of the sample. Molecular weight has a strong influence on rheology in the isotropic phase, where an entanglement plateau emerges; however, the smectic-phase rheology is dominated by the layer structure and is fairly insensitive to molecular weight.

  19. Mesophase and size manipulation of itraconazole liquid crystalline nanoparticles produced via quasi nanoemulsion precipitation.

    PubMed

    Mugheirbi, Naila A; Tajber, Lidia

    2015-10-01

    The fabrication of drug nanoparticles (NPs) with process-mediated tunable properties and performances continues to grow rapidly during the last decades. This study investigates the synthesis and phase tuning of nanoparticulate itraconazole (ITR) mesophases using quasi nanoemulsion precipitation from acetone/water systems to seek out an alternative pathway to the nucleation-based NP formation. ITR liquid crystalline (LC) phases were formed and nematic-smectic mesomorphism was achieved via controlling solvent:antisolvent temperature difference (ΔTS:AS). The use of ΔTS:AS=49.5°C was associated with a nematic assembly, while intercalated smectic A layering was observed at ΔTS:AS=0°C, with both phases confined in the nanospheres at room temperature. The quasi emulsion system has not been investigated at the nanoscale to date and in contrary to the microscale, quasi nanoemulsion was observed over the solvent:antisolvent viscosity ratios of 1:7-1:1.4. Poly(acrylic acid) in the solvent phase exhibited a concentration dependent interaction when ITR formed NPs. This nanodroplet-based approach enabled the preparation of a stable ITR nanodispersion using Poloxamer 407 at 80°C, which was unachievable before using precipitation via nucleation. Findings of this work lay groundwork in terms of rationalised molecular assembly as a tool in designing pharmaceutical LC NPs with tailored properties. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. The enhancing effect of mesogen-jacketed liquid crystalline polymer PBPCS on epoxy resin

    NASA Astrophysics Data System (ADS)

    Chai, C. P.; Li, X. J.; Zhu, Y.; Gao, Y. X.; Li, G. P.; Luo, Y. J.

    2015-12-01

    The mixtures of mesogen-jacketed liquid crystalline polymers (MJLCP) and epoxy resin (E-51) have been prepared in a certain proportion. The category of the MJLCP is poly{2, 5-bis[(4-butoxyphenyl) oxycarbonyl] styrenes} (PBPCS). Methyl tetrahydro phthalic anhydride (MeTHPA) is served as a curing agent, and N, N-dimethylbenzylamine plays the role of catalyst. Then, based on the curing process, the modified materials have been acquired by casting molding. The effect of PBPCS's improvement has been researched through the mechanical properties test, dynamic thermal mechanical test and scanning electron microscope (SEM). The results indicated that PBPCS could apparently improve the mechanical properties of resin E-51. Compared with unmodified materials, the elongation at break and the tensile strength of PBPCS have been improved remarkably through modification. Both mechanical properties of the 4wt% PBPCS/E-51/MeTHPA were enhanced by 48% and 153% separately, and the characteristics of the 3wt% one were raised by 47% and 19% respectively. Also, the ductile fracture morphology of the resins was exhibited in SEM photograph clearly.

  1. The Phase Transition Behavior of Side Chain Liquid Crystalline Polymers Containing Sulfone Group

    NASA Astrophysics Data System (ADS)

    Lee, Daewon

    2005-03-01

    The phase transition behavior in side chain liquid crystalline polymers (SCLCPs) based on a hydrophilic poly(ethylene oxide) (PEO) main chain and a hydrophobic alkyl side chain containing sulfone groups was investigated by using DSC, POM, synchrotron X- ray scattering, FT-IR and rheological measurements. In the case of poly[oxy(octylsulfonylhexylthiomethyl) ethylene] (8S6EO) containing sulfone groups located at the intermediate position in the side chain, the presence of sulfone groups made it possible to obtain a highly ordered layer structure mainly due to the strong dipole-dipole interactions among sulfone groups. It is also noted that the scattering patterns completely disappeared in the isotropic state. On the other hand, a series of three SCLCPs containing sulfone groups near the hydrophilic backbone, poly[oxy(n-decylsulfonylmethyl) ethylene] (nSEO, n = 14, 16, 18), showed the evident mesophase stability due to its amphiphilic character. Interestingly, it was clearly observed for SEO-series that a broad scattering, related to the correlation hole peak due to the presence of dynamic density inhomogeneity in the disordered state, persisted even above the Ti. We also investigated the effect of length of alkyl side chains on the phase transition behavior of SEO-series, showing the layered structures with a periodic undulation of backbone chains for both 16SEO and 18SEO.

  2. Lattice Statistical Models for the Nematic Transitions in Liquid-Crystalline Systems

    NASA Astrophysics Data System (ADS)

    Nascimento, E. S.; Vieira, A. P.; Salinas, S. R.

    2016-12-01

    We investigate the connections between some simple Maier-Saupe lattice models, with a discrete choice of orientations of the microscopic directors, and a recent proposal of a two-tensor formalism to describe the phase diagrams of nematic liquid-crystalline systems. This two-tensor proposal is used to formulate the statistical problem in terms of fully connected lattice Hamiltonians, with the local nematic directors restricted to the Cartesian axes. Depending on the choice of interaction parameters, we regain all of the main features of the original mean-field two-tensor calculations. With a standard choice of parameters, we obtain the well-known sequence of isotropic, uniaxial, and biaxial nematic structures, with a Landau multicritical point. With another suitably chosen set of parameters, we obtain two tricritical points, according to some recent predictions of the two-tensor calculations. The simple statistical lattice models are quite easy to work with, for all values of parameters, and the present calculations can be carried out beyond the mean-field level.

  3. Tough and Thermosensitive Poly(N-isopropylacrylamide)/Graphene Oxide Hydrogels with Macroscopically Oriented Liquid Crystalline Structures.

    PubMed

    Zhu, Zhongcheng; Li, Yang; Xu, Hui; Peng, Xin; Chen, Ya-Nan; Shang, Cong; Zhang, Qin; Liu, Jiaqi; Wang, Huiliang

    2016-06-22

    Bulk graphene oxide (GO) nanocomposite materials with macroscopically oriented GO liquid crystalline (LC) structures exhibit interesting anisotropic properties, but their facile preparations remain challenging. This work reports for the first time the facile preparation of poly(N-isopropylacrylamide) (PNIPAM)/GO nanocomposite hydrogels with macroscopically oriented LC structures with the assistance of a flow field induced by vacuum degassing and the in situ polymerization accelerated by GO. The hydrogel prepared with a GO concentration of 5.0 mg mL(-1) exhibits macroscopically aligned LC structures, which endow the gels with anisotropic optical, mechanical properties, and dimensional changes during the phase transition. The hydrogels show dramatically enhanced tensile mechanical properties and phase transition rates. The oriented LC structures are not damaged during the phase transition of the PNIPAM/GO hydrogels, and hence their LC behavior undergoes reversible change. Moreover, highly oriented LC structures can also be formed when the gels are elongated, even for the gels which do not have macroscopically oriented LC structures. Very impressively, the oriented LC structures in the hydrogels can be permanently maintained by drying the gel samples elongated to and then kept at a constant tensile strain. The thermosensitive nature of PNIPAM and the angle-dependent nature of the macroscopically aligned GO LC structures allow the practical applications of the PNIPAM/GO hydrogels as optical switches, soft sensors, and actuators and so on.

  4. The Role of Liquid-crystalline Structures in the Morphogenesis of Animal Fibers.

    PubMed

    McKinnon, A John; Harland, Duane P

    2010-07-01

    The role of liquid-crystalline (mesophase) structures in extra-cellular morphogenesis is widely recognized. This paper summarizes a model for the more unusual case of intra-cellular mesophases. In the nascent mammalian hair cortex, cell differentiation is correlated with different mesophase textures within tactoids that are composed of intermediate filaments (IFs), and which form by a concerted process of unit-length-filament (ULF) polymerization and phase separation. Nematic and double-twist textures arise from differences in mesogen orientation and length in apposed tactoids. The model explains features of mature structures such as the fibril-matrix ratios in different cell types. The rapidity of IF formation suggests that a sudden-transition equilibrium polymerization, involving a high-energy initiating species, obeying the same statistical model as several other biological transitions, may be involved. This leads to an appealing symmetry, with the key factor in both polymerization and mesophase stability being the retention of protein head-group entropy.

  5. Revealing the potential of Didodecyldimethylammonium bromide as efficient scaffold for fabrication of nano liquid crystalline structures.

    PubMed

    Kanwar, Rohini; Kaur, Gurpreet; Mehta, S K

    2016-03-01

    To exploit the potential of Didodecyldimethylammonium bromide (D12DAB) as a core lipidic constituent, an attempt was made to fabricate and optimize cationic nanostructured lipid carriers (cNLCs) using a cost-effective microemulsification methodology. Designed composition was optimized by studying the effect of different microemulsion components on D12DAB cNLCs characteristics. ​Spherical shaped D12DAB cNLCs were obtained with an average size of ∼160 nm and zeta potential of +30.2 mV. Differential Scanning Calorimetry (DSC) depicted the presence of thermotropic character, whereas polarized optical microscopy confirmed the mesophase like behavior of D12DAB based cNLCs. In addition, hemolysis analysis revealed that the toxicity was concentration dependent as LC50 was reached at a concentration of 50 μg/mL of cNLCs. This class of cNLCs is expected to become a potent candidate for a broad spectrum of medicaments as carriers, targeting for pharmaceutical and medicinal purposes, due to the combination of a hard lipid with a soft lipid, where the liquid crystalline structure of the lipid co-exists.

  6. Gradient measurement technique to identify phase transitions in nano-dispersed liquid crystalline compounds

    NASA Astrophysics Data System (ADS)

    Pardhasaradhi, P.; Madhav, B. T. P.; Venugopala Rao, M.; Manepalli, R. K. N. R.; Pisipati, V. G. K. M.

    2016-09-01

    Characterization and phase transitions in pure and 0.5% BaTiO3 nano-dispersed liquid crystalline (LC) N-(p-n-heptyloxybenzylidene)-p-n-nonyloxy aniline, 7O.O9, com-pounds are carried out using a polarizing microscope attached with hot stage and camera. We observed that when any of these images are distorted, different local structures suffer from various degradations in a gradient magnitude. So, we examined the pixel-wise gradient magnitude similarity between the reference and distorted images combined with a novel pooling strategy - the standard deviation of the GMS map - to determine the overall phase transition variations. In this regard, MATLAB software is used for gradient measurement technique to identify the phase transitions and transition temperature of the pure and nano-dispersed LC compounds. The image analysis of this method proposed is in good agreement with the standard methods like polarizing microscope (POM) and differential scanning calorimeter (DSC). 0.5% BaTiO3 nano-dispersed 7O.O9 compound induces cholesteric phase quenching the nematic phase, which the pure compound exhibits.

  7. Distance-dependent metal enhanced fluorescence by flowerlike silver nanostructures fabricated in liquid crystalline phase

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Yang, Chengliang; Zhang, Guiyang; Peng, Zenghui; Yao, Lishuang; Wang, Qidong; Cao, Zhaoliang; Mu, Quanquan; Xuan, Li

    2017-10-01

    Flowerlike silver nanostructure substrates were fabricated in liquid crystalline phase and the distance dependent property of metal enhanced fluorescence for such substrate was studied for the first time. The distance between silver nanostructures and fluorophore was controlled by the well-established layer-by-layer (LbL) technique constructing alternate layers of poly (allylamine hydrochloride) (PAH) and poly (sodium 4-styrenesulfonate) (PSS). The Rhodamine 6G (R6G) molecules were electrostatically attached to the outmost negative charged PSS layer. The fluorescence enhancement factor of flowerlike nanostructure substrate increased firstly and then decreased with the distance increasing. The best enhanced fluorescence intensity of 71 fold was obtained at a distance of 5.2 nm from the surface of flowerlike silver nanostructure. The distance for best enhancement effect is an instructive parameter for the applications of such substrates and could be used in the practical MEF applications with the flowerlike nanostructure substrates fabricated in such way which is simple, controllable and cost-effective.

  8. Study of Friction between Liquid Crystals and Crystalline Surfaces by Molecular Dynamic Simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Yong-Wen; Chen, Xiao-Song; Chen, Wei

    2016-10-01

    The lubrication characteristics of liquid crystal (LC) molecules sheared between two crystalline surfaces obtained from molecular dynamics (MD) simulations are reported in this article. We consider a coarse-grained rigid bead-necklace model of the LC molecules confined between two atomic surfaces subject to different shearing velocities. A systematic study shows that the slip length of LC lubrication changes significantly as a function of the LC-surface interaction energy, which can be well described though a theoretical curve. The slip length increases as shear rate increases at high LC-surface interaction energy. However, this trend can not be observed for low interaction energy. The orientation of the LC molecules near the surface is found to be guided by the atomics surfaces. The influence of temperature on the lubrication characteristics is also discussed in this article. Supported by the National Natural Science Foundation of China under Grant Nos. 11504384 and 11121403 and computational resources provided by Supercomputing Center of Chinese Academy of Sciences (SCCAS)

  9. Homogeneous alignment of liquid crystalline dendrimers confined in a slit-pore. A simulation study.

    PubMed

    Workineh, Zerihun G; Vanakaras, Alexandros G

    2016-03-23

    In this work we present results from isobaric-isothermal (NPT) Monte Carlo simulation studies of model liquid crystalline dendrimer (LCDr) systems confined in a slit-pore made of two parallel flat walls. The dendrimers are modelled as a collection of spherical and ellipsoidal particles corresponding to the junction points of the dendritic core and to the mesogenic units respectively. Assuming planar uniform (unidirectional) soft anchoring of the mesogenic units on the substrates we investigate the conformational and alignment properties of the LCDr system at different thermodynamic state points. Tractable coarse grained force fields have been used from our previous work. At low pressures the interior of the pore is almost empty, since almost all LCDrs are anchored to the substrates forming two-dimensional smectic-like structures with the mesogens aligned along the aligning direction of the substrates. As the pressure grows the LCDrs occupy the whole pore. However, even at low temperatures, the smectic organization does not transmit in the interior of the pore and is preserved for distances of 2-3 mesogenic diameters from the walls. For this reason, the global orientational order decreases with increasing pressure (density). In the vicinity (2-3 mesogenic diameters) of the pore walls, mesogenic units preserve the smectic structure whose layers are separated by layers of spherical beads. In this region individual LCDrs possess a rod like shape.

  10. Copper-Coated Liquid-Crystalline Elastomer via Bioinspired Polydopamine Adhesion and Electroless Deposition.

    PubMed

    Frick, Carl P; Merkel, Daniel R; Laursen, Christopher M; Brinckmann, Stephan A; Yakacki, Christopher M

    2016-12-01

    This study explores the functionalization of main-chain nematic elastomers with a conductive metallic surface layer using a polydopamine binder. Using a two-stage thiol-acrylate reaction, a programmed monodomain is achieved for thermoreversible actuation. A copper layer (≈155 nm) is deposited onto polymer samples using electroless deposition while the samples are in their elongated nematic state. Samples undergo 42% contraction when heated above the isotropic transition temperature. During the thermal cycle, buckling of the copper layer is seen in the direction perpendicular to contraction; however, transverse cracking occurs due to the large Poisson effect experienced during actuation. As a result, the electrical conductivity of the layer reduced quickly as a function of thermal cycling. However, samples do not show signs of delamination after 25 thermal cycles. These results demonstrate the ability to explore multifunctional liquid-crystalline composites using relatively facile synthesis, adhesion, and deposition techniques. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Surface Orientation in Injection-Molded Thermotropic Liquid Crystalline Copolyester (TLCP) Plaques

    NASA Astrophysics Data System (ADS)

    Bubeck, Robert; Fang, Jun; Burghardt, Wesley; Burgard, Susan; Robertson, Katherine; Fischer, Daniel

    2008-03-01

    Attenuated total reflection Fourier transform infra-red (ATR-FTIR), C K edge near edge X-ray adsorption fine structure (NEXAFS) spectroscopies, and 2-D WAXS in transmission were used to characterize surface orientation in thermotropic liquid crystalline copolyester (TLCP) injection-molded plaques to varying depths into the samples. Injection-molded TLCPs have bimodal orientation states due to contributions from ``skin'' and ``core'' regions resulting from extensional and shear flow, respectively, in the mold. The NEXAFS is sensitive to the orientation of the molecular pi orbital of backbone phenyl groups of the top 2 nm of a surface. ATR-FTIR obtained using a Herrick Seagull variable angle reflectance accessory is sensitive for dichroic ratios to a depth of 5 microns. Orientation parameters derived from the 1502/cm absorption band for equivalent positions are often typically about 5 to 10 percent less by ATR-FTIR than by NEXAFS. The orientational states are being correlated with physical properties of injection-molded TLCP samples.

  12. Phase biaxiality in nematic liquid crystalline side-chain polymers of various chemical constitutions.

    PubMed

    Severing, Kirsten; Stibal-Fischer, Elke; Hasenhindl, Alfred; Finkelmann, Heino; Saalwächter, Kay

    2006-08-17

    In a previous deuterium NMR study conducted on a liquid crystalline (LC) polymer with laterally attached book-shaped molecules as the mesogenic moiety, we have revealed a biaxial nematic phase below the conventional uniaxial nematic phase (Phys. Rev. Lett. 2004, 92, 125501). To elucidate details of its formation, we here report on deuterium NMR experiments that have been conducted on different types of LC side-chain polymers as well as on mixtures with low-molar-mass mesogens. Different parameters that affect the formation of a biaxial nematic phase, such as the geometry of the attachment, the spacer length between the polymer backbone and the mesogenic unit, as well as the polymer dynamics, were investigated. Surprisingly, also polymers with terminally attached mesogens (end-on polymers) are capable of forming biaxial nematic phases if the flexible spacer is short and thus retains a coupling between the polymer backbone and the LC phase. Furthermore, the most important parameter for the formation of a biaxial nematic phase is the dynamics of the polymer backbone, as the addition of a small percentage of low molar mass LC to the biaxial nematic polymer from the original study served to shift both the glass transition and the appearance of detectable biaxiality in a very similar fashion. Plotting different parameters for the investigated systems as a function of T/Tg also reveals the crucial role of the dynamics of the polymer backbone and hence the glass transition.

  13. Two-Dimensional Bipyramid Plasmonic Nanoparticle Liquid Crystalline Superstructure with Four Distinct Orientational Packing Orders.

    PubMed

    Shi, Qianqian; Si, Kae Jye; Sikdar, Debabrata; Yap, Lim Wei; Premaratne, Malin; Cheng, Wenlong

    2016-01-26

    Anisotropic plasmonic nanoparticles have been successfully used as constituent elements for growing ordered nanoparticle arrays. However, orientational control over their spatial ordering remains challenging. Here, we report on a self-assembled two-dimensional (2D) nanoparticle liquid crystalline superstructure (NLCS) from bipyramid gold nanoparticles (BNPs), which showed four distinct orientational packing orders, corresponding to horizontal alignment (H-NLCS), circular arrangement (C-NLCS), slanted alignment (S-NLCS), and vertical alignment (V-NLCS) of constituent particle building elements. These packing orders are characteristic of the unique shape of BNPs because all four packing modes were observed for particles with various sizes. Nevertheless, only H-NLCS and V-NLCS packing orders were observed for the free-standing ordered array nanosheets formed from a drying-mediated self-assembly at the air/water interface of a sessile droplet. This is due to strong surface tension and the absence of particle-substrate interaction. In addition, we found the collective plasmonic coupling properties mainly depend on the packing type, and characteristic coupling peak locations depend on particle sizes. Interestingly, surface-enhanced Raman scattering (SERS) enhancements were heavily dependent on the orientational packing ordering. In particular, V-NLCS showed the highest Raman enhancement factor, which was about 77-fold greater than the H-NLCS and about 19-fold greater than C-NLCS. The results presented here reveal the nature and significance of orientational ordering in controlling plasmonic coupling and SERS enhancements of ordered plasmonic nanoparticle arrays.

  14. Electro-rheological effects of liquid crystalline polymer on one-sided pattern electrodes

    NASA Astrophysics Data System (ADS)

    Takesue, Naoyuki; Furusho, Junji; Inoue, Akio

    2002-02-01

    In most industrial robots, serious problems of vibratory behavior are caused because of elasticity in the drive systems. An electro-rheological (ER) fluid is a substance that can change its apparent viscosity by the application of an electric field, and homogeneous ER fluids are effective in reducing vibration in robots. Conventional research into ER fluids is based on parallel electrodes with ER fluids between them. Since a high voltage is required for use of ER fluids with parallel electrodes, problems of cost, safety and wiring for practical applications are of concern. In this article, we propose one-sided pattern electrodes that solve some of the above problems. A one-sided pattern electrode is an electrode in a pattern arranged on only one of the two surfaces of a pair of electrodes, with an insulator arranged on the other surface. We developed two kinds of one-sided pattern electrodes: a concentric circle form and a radial form, experimentally verifying the manifestation of ER effects in a liquid crystalline polymer (a homogeneous ER fluid). In addition, the effect of disk gap upon viscosity change was investigated.

  15. Tunable emissive lanthanidomesogen derived from a room-temperature liquid-crystalline Schiff-base ligand.

    PubMed

    Pramanik, Harun A R; Das, Gobinda; Bhattacharjee, Chira R; Paul, Pradip C; Mondal, Paritosh; Prasad, S Krishna; Rao, D S Shankar

    2013-09-23

    A novel photoluminescent room-temperature liquid-crystalline salicylaldimine Schiff base with a short alkoxy substituent and a series of lanthanide(III) complexes of the type [Ln(LH)3(NO3)3] (Ln = La, Pr, Sm, Gd, Tb, Dy; LH = (E)-5-(hexyloxy)-2-[{2-(2-hydroxyethylamino)ethylimino]methyl}phenol) have been synthesized and characterized by FTIR, (1)H and (13)C NMR, UV/Vis, and FAB-MS analyses. The ligand coordinates to the metal ions in its zwitterionic form. The thermal behavior of the compounds was investigated by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The ligand exhibits an enantiotropic hexagonal columnar (Col(h)) mesophase at room temperature and the complexes show an enantiotropic lamellar columnar (Col(L)) phase at around 120 °C with high thermal stability. Based on XRD results, different space-filling models have been proposed for the ligand and complexes to account for the columnar mesomorphism. The ligand exhibits intense blue emission both in solution and in the condensed state. The most intense emissions were observed for the samarium and terbium complexes, with the samarium complex glowing with a bright-orange light (ca. 560-644 nm) and the terbium complex emitting green light (ca. 490-622 nm) upon UV irradiation. DFT calculations performed by using the DMol3 program at the BLYP/DNP level of theory revealed a nine-coordinate structure for the lanthanide complexes.

  16. Liquid crystalline phase as a probe for crystal engineering of lactose: carrier for pulmonary drug delivery.

    PubMed

    Patil, Sharvil S; Mahadik, Kakasaheb R; Paradkar, Anant R

    2015-02-20

    The current work was undertaken to assess suitability of liquid crystalline phase for engineering of lactose crystals and their utility as a carrier in dry powder inhalation formulations. Saturated lactose solution was poured in molten glyceryl monooleate which subsequently transformed into gel. The gel microstructure was analyzed by PPL microscopy and SAXS. Lactose particles recovered from gels after 48 h were analyzed for polymorphism using techniques such as FTIR, XRD, DSC and TGA. Particle size, morphology and aerosolisation properties of prepared lactose were analyzed using Anderson cascade impactor. In situ seeding followed by growth of lactose crystals took place in gels with cubic microstructure as revealed by PPL microscopy and SAXS. Elongated (size ∼ 71 μm) lactose particles with smooth surface containing mixture of α and β-lactose was recovered from gel, however percentage of α-lactose was more as compared to β-lactose. The aerosolisation parameters such as RD, ED, %FPF and % recovery of lactose recovered from gel (LPL) were found to be comparable to Respitose® ML001. Thus LC phase (cubic) can be used for engineering of lactose crystals so as to obtain particles with smooth surface, high elongation ratio and further they can be used as carrier in DPI formulations. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Interfacial properties of POPC/GDO liquid crystalline nanoparticles deposited on anionic and cationic silica surfaces.

    PubMed

    Chang, Debby P; Dabkowska, Aleksandra P; Campbell, Richard A; Wadsäter, Maria; Barauskas, Justas; Tiberg, Fredrik; Nylander, Tommy

    2016-09-29

    Reversed lipid liquid crystalline nanoparticles (LCNPs) of the cubic micellar (I2) phase have high potential in drug delivery applications due to their ability to encapsulate both hydrophobic and hydrophilic drug molecules. Their interactions with various interfaces, and the consequences for the particle structure and integrity, are essential considerations in their effectiveness as drug delivery vehicles. Here, we have studied LCNPs formed of equal fractions of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and glycerol dioleate in the presence of different fractions of the stabilizer Polysorbate 80. We have used a combination of ellipsometry, quartz crystal microbalance with dissipation monitoring and neutron reflectometry to reveal the structure and composition of the adsorbed layer on both anionic silica and cationic (aminopropyltriethoxysilane) silanized surfaces. For both types of surfaces, there is a spread near-surface layer comprising lipid and polymer as well as a sparse coverage of intact particles. The composition of the near-surface layer is very close to that of the particles, in contrast to the lipid bilayer observed with related systems. The interaction is stronger for cationic than anionic surfaces, which is rationalized in terms of the negative zeta potential of the LCNPs. The work shows that the attachment of and spreading from LCNPs is influenced by the properties of the surface, the internal structure, composition and stability of the particles as well as the nature of the stabilizer.

  18. A molecular nematic liquid crystalline material for high-performance organic photovoltaics

    PubMed Central

    Sun, Kuan; Xiao, Zeyun; Lu, Shirong; Zajaczkowski, Wojciech; Pisula, Wojciech; Hanssen, Eric; White, Jonathan M.; Williamson, Rachel M.; Subbiah, Jegadesan; Ouyang, Jianyong; Holmes, Andrew B.; Wong, Wallace W.H.; Jones, David J.

    2015-01-01

    Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs. PMID:25586307

  19. Liquid-crystalline ordering of antimicrobial peptide-DNA complexes controls TLR9 activation

    NASA Astrophysics Data System (ADS)

    Schmidt, Nathan W.; Jin, Fan; Lande, Roberto; Curk, Tine; Xian, Wujing; Lee, Calvin; Frasca, Loredana; Frenkel, Daan; Dobnikar, Jure; Gilliet, Michel; Wong, Gerard C. L.

    2015-07-01

    Double-stranded DNA (dsDNA) can trigger the production of type I interferon (IFN) in plasmacytoid dendritic cells (pDCs) by binding to endosomal Toll-like receptor-9 (TLR9; refs , , , , ). It is also known that the formation of DNA-antimicrobial peptide complexes can lead to autoimmune diseases via amplification of pDC activation. Here, by combining X-ray scattering, computer simulations, microscopy and measurements of pDC IFN production, we demonstrate that a broad range of antimicrobial peptides and other cationic molecules cause similar effects, and elucidate the criteria for amplification. TLR9 activation depends on both the inter-DNA spacing and the multiplicity of parallel DNA ligands in the self-assembled liquid-crystalline complex. Complexes with a grill-like arrangement of DNA at the optimum spacing can interlock with multiple TLR9 like a zipper, leading to multivalent electrostatic interactions that drastically amplify binding and thereby the immune response. Our results suggest that TLR9 activation and thus TLR9-mediated immune responses can be modulated deterministically.

  20. Highly Oriented Neurofilament Liquid Crystalline Gels for Imaging and Scattering Studies

    NASA Astrophysics Data System (ADS)

    Holger, H. C.; Beck, R.; Ding, C.; Jones, J. B.; Deek, J.; MacDonald, N. C.; Li, Y.; Safinya, C. R.

    2009-03-01

    The neuronal cytoskeleton is composed of a variety of filamentous proteins including, neurofilaments (NFs), microtubules (MTs) and actin. These components form networks that maintain the cell's structure and shape. At high filament concentration, the proteins self-assemble in-vitro and form liquid crystalline phases maintained by their spatial anisotropy and interfilament interactions. Under physical confinement in microchannel with widths less than few persistence lengths, both MT and actin bundles align parallel to the surface^1. AFM imaging shows that despite being shorter and more flexible filamentous protein, NF networks maintain larger oriented domains over much longer length scales and unexpectedly align perpendicular to the microchannel walls^2. We discuss the extended orientation order in NFs in terms of the inter-filaments interactions originating from their polyampholyte side-chains. Supported by DOE DE-FG-02-06ER46314, NSF DMR-0803103, and the Human Frontier Science Program organization. [1] N.F.Bouxsein et al., APL 85 (2004) 5775; L.S.Hirst et al. Langmuir 21 (2005) 3910 [2] H.C.Hesse, R.Beck, J.Deek et al. Langmuir 24 (2008) 8397

  1. Liquid crystalline phase transitions in virus and virus/polymer suspensions

    NASA Astrophysics Data System (ADS)

    Dogic, Zvonimir

    Using experimental, theoretical, and simulation methods, we investigate the relationship between the intermolecular interactions of rod-like colloids and the resulting liquid crystalline phase diagrams. As a model system of rod-like particles we use bacteriophage fd, which is a charge stabilized colloid. We are able to engineer complex attractive and repulsive intermolecular interactions by changing the ionic strengths of the suspensions, attaching covalently bound polymers and adding nonadsorbing polymers. Using standard molecular cloning techniques it is also shown that the aspect ratio of the rod-like particle can be manipulated. In the limit of high ionic strength the fd virus quantitatively agrees with the Onsager theory for the isotropic-nematic (I-N) phase transition in hard rods. The role of attractive interaction on the nature of the I-N phase transition is investigated. As the strength of the attraction is increased we observe isotropic-smectic (I-S) phase transitions. Using an optical microscope we follow the kinetics of the I-S phase transition and observe a wide range of novel structures of unexpected complexity. We also investigate the influence of adding hard spheres, or polymers on the nematic-smectic phase transition. We conclude that adding small spheres stabilizes the smectic phase and destabilizes the nematic phase.

  2. Tunable Photocontrolled Motions Using Stored Strain Energy in Malleable Azobenzene Liquid Crystalline Polymer Actuators.

    PubMed

    Lu, Xili; Guo, Shengwei; Tong, Xia; Xia, Hesheng; Zhao, Yue

    2017-07-01

    A new strategy for enhancing the photoinduced mechanical force is demonstrated using a reprocessable azobenzene-containing liquid crystalline network (LCN). The basic idea is to store mechanical strain energy in the polymer beforehand so that UV light can then be used to generate a mechanical force not only from the direct light to mechanical energy conversion upon the trans-cis photoisomerization of azobenzene mesogens but also from the light-triggered release of the prestored strain energy. It is shown that the two mechanisms can add up to result in unprecedented photoindued mechanical force. Together with the malleability of the polymer stemming from the use of dynamic covalent bonds for chain crosslinking, large-size polymer photoactuators in the form of wheels or spring-like "motors" can be constructed, and, by adjusting the amount of prestored strain energy in the polymer, a variety of robust, light-driven motions with tunable rolling or moving direction and speed can be achieved. The approach of prestoring a controllable amount of strain energy to obtain a strong and tunable photoinduced mechanical force in azobenzene LCN can be further explored for applications of light-driven polymer actuators. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Impact of regeneration process on the crystalline structure and enzymatic hydrolysis of cellulose obtained from ionic liquid.

    PubMed

    Cao, Xuefei; Peng, Xinwen; Sun, Shaoni; Zhong, Linxin; Wang, Sha; Lu, Fachuang; Sun, Runcang

    2014-10-13

    The present study investigated the impact of regeneration process on the crystalline structure and enzymatic hydrolysis behaviors of microcrystalline cellulose (MCC) regenerated from ionic liquid 1-butyl-3-methylimidazolium chloride. The crystalline structures of these regenerated samples were analyzed by X-ray diffraction. Results suggested that almost amorphous cellulose was obtained by regenerating MCC in acetone (DRC-a), while partial cellulose II structure could be found in these regenerated samples from water and ethanol. Additionally, the enzymatic hydrolysis behaviors of MCC and its regenerated samples were comparatively studied. Results showed that above 90% of cellulose could be converted into glucose within 4h for DRC-a and regenerated cellulose without drying (WRC-w) as compared to that of MCC (9.7%). Therefore, the regeneration process could significantly influence the crystallinity and digestibility of cellulose.

  4. Effect of fatty acyl chain length and structure on the lamellar gel to liquid-crystalline and lamellar to reversed hexagonal phase transitions of aqueous phosphatidylethanolamine dispersions

    SciTech Connect

    Lewis, R.N.A.H.; Mannock, D.A.; McElhaney, R.N.; Turner, D.C.; Gruner, S.M. )

    1989-01-24

    The lamellar gel/liquid-crystalline and the lamellar liquid-crystalline/reversed hexagonal phase transitions of aqueous dispersions of a number of synthetic phosphatidylethanolamines containing linear saturated, branched chain, and alicyclic fatty acyl chains of varying length were studied by differential scanning calorimetry, {sup 31}P nuclear magnetic resonance spectroscopy, and X-ray diffraction. For any given homologous series of phosphatidylethanolamines containing a single chemical class of fatty acids, the lamellar gel/liquid-crystalline phase transition temperature increases and the lamellar liquid-crystalline/reversed hexagonal phase transition temperature decreases with increases in hydrocarbon chain length. For a series of phosphatidylethanolamines of the same hydrocarbon chain length but with different chemical structures, both the lamellar gel/liquid-crystalline and the lamellar liquid-crystalline/reversed hexagonal phase transition temperatures vary markedly and in the same direction. These results suggest that for any given hydrocarbon chain length, there may be a critical thickness at which the liquid-crystalline phosphatidylethanolamine bilayer becomes unstable with respect to inverted nonbilayer phases such as the H{sub II} phase and that the temperature at which this critical thickness is reached is dependent upon that bilayers proximity to the hydrocarbon chain-melting phase transition temperature.

  5. Synthesis of Side Chain Liquid Crystal Polymers by Living Ring Opening Metathesis Polymerization. 4. Synthesis of Amorphous and Side Chain Liquid Crystal AB Block Copolymers

    DTIC Science & Technology

    1992-05-01

    Metathesis Polymerization. 4. Synthesis of C N00014-89-JI542 Amorphous and Side Chain Liquid Crystal AB Block Copolym rs 6. AUTHOR(S) Zen Komiya, Coleen ...Liquid Crystal AB Block Copolymers by Zen Komiya, Coleen Pugh: and Richard R. Schrock* Submitted to Macromolecules F r fCarnegie Mellon University...Amorphous and Side Chain Liquid Crystal AB Block Copolymers by Zen Komiya, Coleen Pught, and Richard R. Schrock* Contribution from Department of Chemistry 6

  6. Quantitation of crystalline material within a liquid vehicle using 1H/19F CP/MAS NMR.

    PubMed

    Farrer, Brian T; Peresypkin, Andrey; Wenslow, Robert M

    2007-02-01

    A method to detect and quantify a small amount crystalline material within a liquid solution of solubilized material is described. 19F CP-MAS ssNMR was investigated as a technique to detect low levels (0.2 mg/g) of crystalline sodium (2R)-7-{3-[2-chloro-4-(2,2,2-trifluoroethoxy)phenoxy]propoxy}-2-methyl-3,4-dihydro-2H-chromane-2-carboxylate (I) within a solid mixture (with microcrystalline cellulose) and a slurry with a liquid vehicle (capric and caprylic acid triglycerides). The results demonstrate that the area of the 19F CP/MAS signal obtained in 25 min at 25 degrees C is linearly dependent (R2=0.997) on the mass of I within the ssNMR rotor. Slopes of CP-MAS peak area versus mass of I in the rotor were nearly identical for the solid mixture and slurry suspension. Signal-to-noise ratio for the low potency slurry suggest detection and quantitation of 0.1 mg of crystalline I in the rotor, corresponding to 2 mg/g of crystalline material within the slurry suspension.

  7. Large-scale controlled fabrication of highly roughened flower-like silver nanostructures in liquid crystalline phase

    PubMed Central

    Yang, Chengliang; Xiang, Xiangjun; Zhang, Ying; Peng, Zenghui; Cao, Zhaoliang; Wang, Junlin; Xuan, Li

    2015-01-01

    Large-scale controllable fabrication of highly roughened flower-like silver nanostructures is demonstrated experimentally via electrodeposition in the liquid crystalline phase. Different sizes of silver flowers are fabricated by adjusting the deposition time and the concentration of the silver nitrate solution. The density of the silver flowers in the sample is also controllable in this work. The flower-like silver nanostructures can serve as effective surface-enhanced Raman scattering and surface-enhanced fluorescence substrates because of their local surface plasmon resonance, and they may have applications in photoluminescence and catalysis. This liquid crystalline phase is used as a soft template for fabricating flower-like silver nanostructures for the first time, and this approach is suitable for large-scale uniform fabrication up to several centimetres. PMID:26216669

  8. Photoinduced bending behavior of cross-linked azobenzene liquid-crystalline polymer films with a poly(oxyethylene) backbone.

    PubMed

    Lv, Jiu-an; Wang, Weiru; Xu, Jixiang; Ikeda, Tomiki; Yu, Yanlei

    2014-07-01

    Cross-linked azobenzene liquid-crystalline polymer films with a poly(oxyethylene) backbone are synthesized by photoinitiated cationic copolymerization. Azobenzene moieties in the film surface toward the light source are simultaneously photoaligned during photopolymerization with unpolarized 436 nm light and thus form a splayed alignment in the whole film. The prepared films show reversible photoinduced bending behavior with opposite bending directions when different surfaces of one film face to ultraviolet light irradiation.

  9. Fastest non-ionic azo dyes and transfer of their thermal isomerisation kinetics into liquid-crystalline materials.

    PubMed

    Garcia-Amorós, Jaume; Castro, M Cidália R; Coelho, Paulo; Raposo, M Manuela M; Velasco, Dolores

    2016-04-14

    Push-pull bithienylpyrrole-based azo dyes exhibit thermal isomerisation rates as fast as 1.4 μs in acetonitrile at 298 K becoming, thus, the fastest neutral azo dyes reported so far. These remarkably low relaxation times can be transferred into liquid-crystalline matrices enabling light-triggered oscillations in the optical density of the final material up to 11 kHz under ambient conditions.

  10. Functional Polymers and Sequential Copolymers by Phase Transfer Catalysis. 30. Synthesis of Liquid Crystalline Poly(epichlorohydrin) and Copolymers.

    DTIC Science & Technology

    1986-10-01

    Copolymers K0 By Coleen Pugh and V. Percec Department of Macromolecular Science Case Western Reserve University Cleveland, OH 44106 Submitted for... Coleen Pugh and V. Percec Department of Macromolecular Science Case Western Reserve University Cleveland, OH 44106 f ABSTRACT/ -Poly(epichlotohydrin...Catalysis. 30. Synthesis of Liquid Crystalline Poly(epichlorohydrin) and Copolymers 12 PERSONAL AUTIIOR(S C Coleen Pugh and V. Percec 13a TYPE OF

  11. "Pressure Blocking" Effect in the Growing Vapor Bubble in a Highly Superheated Liquid

    NASA Astrophysics Data System (ADS)

    Zudin, Yu. B.; Zenin, V. V.

    2016-09-01

    The problem on the growth of a vapor bubble in a liquid whose superheating enthalpy exceeds the phase transition heat has been considered. A physical model of the "pressure blocking" in the bubble is presented. The problem for the conditions of the experiment on the effervescence of a butane drop has been solved numerically. An algorithm for constructing an analytical solution of the problem on the bubble growth in a highly superheated liquid is proposed.

  12. Investigation of flow and microstructure in rheometric and processing flow conditions for liquid crystalline pitch

    NASA Astrophysics Data System (ADS)

    Kundu, Santanu

    The microstructure development within mesophase pitch-based carbon materials depends on the flow history that the pitch is subjected to. Therefore, a fundamental understanding of flow and its influence on the microstructure is required to obtain carbon materials with desired properties. The objective of this research was to investigate the flow and microstructural behavior of a synthetic mesophase pitch (AR-HP) in rheometric and processing flow conditions. In addition, simulation studies were performed to establish a frame work for modeling the flow behavior of this complex material in different flow situations. The steady-shear viscosities obtained from a cone-plate rheometer during increasing rate-sweep experiments exhibited shear-thinning (Region I) and plateau (Region II) responses. However, the slope of the shear-thinning region was only about -0.2, much lower than -0.5 observed in some pitches and liquid-crystalline polymers. This difference could arise from the different molecular constituents of pitches. At higher shear rates, as measured from capillary rheometers, the viscosity values remained almost constant. The transient shear stress responses, as measured from cone-plate rheometer, exhibited nonmonotonic behavior as a function of applied strain at all shear rates and temperatures tested. After rheological experiments, the samples were collected by developing a new experimental protocol for preservation of the sample for microstructural analysis. Microstructural observations obtained from three orthogonal sections, reported for the first time in the literature, indicate that the local maximum in shear stress was due to yielding of initial microstructure. The microstructure became flow oriented with further shearing, and the structure size decreased with increasing shear rates. In addition to high-strain experiments, dynamic experiments were also performed in the linear viscoelastic region where no significant deformation of fluid takes place. The

  13. Interplay Between Liquid Crystalline And Isotropic Gels in Self-Assembled Neurofilament Networks

    SciTech Connect

    Jones, J.B.; Safinya, C.R.

    2009-05-18

    Neurofilaments (NFs) are a major constituent of nerve cell axons that assemble from three subunit proteins of low (NF-L), medium (NF-M), and high (NF-H) molecular weight into a 10nm diameter rod with radiating sidearms to form a bottle-brush-like structure. Here, we reassemble NFs in vitro from varying weight ratios of the subunit proteins, purified from bovine spinal cord, to form homopolymers of NF-L or filaments composed of NF-L and NF-M (NF-LM), NF-L and NF-H (NF-LH), or all three subunits (NF-LMH). At high protein concentrations, NFs align to form a nematic liquid crystalline gel with a well-defined spacing determined with synchrotron small angle x-ray scattering. Near physiological conditions (86mM monovalent salt and pH 6.8), NF-LM networks with a high NF-M grafting density favor nematic ordering whereas filaments composed of NF-LH transition to an isotropic gel at low protein concentrations as a function of increasing mole fraction of NF-H subunits. The interfilament distance decreases with NF-M grafting density, opposite the trend seen with NF-LH networks. This suggests a competition between the more attractive NF-M sidearms, forming a compact aligned nematic gel, and the repulsive NF-H sidearms, favoring a more expansive isotropic gel, at 86mM monovalent salt. These interactions are highly salt dependent and the nematic gel phase is stabilized with increasing monovalent salt.

  14. Prediction and design of first super-strong liquid-crystalline polymers

    SciTech Connect

    Dowell, F.

    1989-07-15

    This paper presents the details of the theoretical prediction and design (atom by atom, bond by bond) of the molecule chemical structures of the first candidate super-strong liquid-crystalline polymers (SS LCPs). These LCPs are the /ital first/ LCPs designed to have good compressive strengths, as well as to have tensile strengths and tensile moduli significantly larger than those of existing strong LCPs (such as Kevlar). The key feature of this new class of LCPs is that the exceptional strength is three dimensional on a microscopic, /ital molecular/ level (thus, on a macroscopic level), in contrast to present LCPs (such as Kevlar) with their one-dimensional exceptional strength. These SS LCPs also have some solubility and processing advantages over existing strong LCPs. These SS LCPs are specially-designed combined LCPs such that the side chains of a molecule interdigitate with the side chains of other molecules. This paper also presents other essential general and specific features required for SS LCPs. Considerations in the design of SS LCPs include the spacing distance between side chains along the backbone, the need for rigid sections in the backbone and side chains, the degree of polymerization, the length of the side chains, the regularity of spacing of the side chains along the backbone, the interdigitation of side chains in submolecular strips, the packing of the side chains on one or two sides of the backbone, the symmetry of the side chains, the points of attachment of the side chains to the backbone, the flexibility and size of the chemical group connecting each side chain to the backbone, the effect of semiflexible sections in the backbone and side chains, and the choice of types of dipolar and/or hydrogen bonding forces in the backbones and side chains for easy alignment.

  15. Re-entrant cholesteric phase in DNA liquid-crystalline dispersion particles.

    PubMed

    Yevdokimov, Yuri M; Skuridin, Sergey G; Semenov, Sergey V; Dadinova, Ljubov A; Salyanov, Viktor I; Kats, Efim I

    2017-03-01

    In this research, we observe and rationalize theoretically the transition from hexagonal to cholesteric packing of double-stranded (ds) DNA in dispersion particles. The samples were obtained by phase exclusion of linear ds DNA molecules from water-salt solutions of poly(ethylene glycol)-PEG-with concentrations ranging from 120 mg ml(-1) to 300 mg ml(-1). In the range of PEG concentrations from 120 mg ml(-1) to 220 mg ml(-1) at room temperature, we find ds DNA molecule packing, typical of classical cholesterics. The corresponding parameters for dispersion particles obtained at concentrations greater than 220 mg ml(-1) indicate hexagonal packing of the ds DNA molecules. However, slightly counter-intuitively, the cholesteric-like packing reappears upon the heating of dispersions with hexagonal packing of ds DNA molecules. This transition occurs when the PEG concentration is larger than 220 mg ml(-1). The obtained new cholesteric structure differs from the classical cholesterics observed in the PEG concentration range 120-220 mg ml(-1) (hence, the term 're-entrant'). Our conclusions are based on the measurements of circular dichroism spectra, X-ray scattering curves and textures of liquid-crystalline phases. We propose a qualitative (similar to the Lindemann criterion for melting of conventional crystals) explanation of this phenomenon in terms of partial melting of so-called quasinematic layers formed by the DNA molecules. The quasinematic layers change their spatial orientation as a result of the competition between the osmotic pressure of the solvent (favoring dense, unidirectional alignment of ds DNA molecules) and twist Frank orientation energy of adjacent layers (favoring cholesteric-like molecular packing).

  16. Tuning the thermotropic and lyotropic properties of liquid-crystalline terpyridine ligands.

    PubMed

    Camerel, Franck; Donnio, Bertrand; Bourgogne, Cyril; Schmutz, Marc; Guillon, Daniel; Davidson, Patrick; Ziessel, Raymond

    2006-05-24

    A rational synthetic strategy is developed to provide compact and simple terpyridine (terpy) mesogens that show liquid-crystallinity both as pure compounds and in organic solution (amphotropic compound). The use of a central 4-methyl-3,5-diacylaminophenyl platform equipped with two lateral aromatic rings, each bearing three appended aliphatic chains, allows connection of a 2,2':6',2''-terpyridine fragment through a polar group such as an ester, amide, or flat conjugated alkyne linker. For the T(12)ester and T(12)amide scaffolds, the mesophase is best described as a lamellar phase, in which the molecules self-assemble into columnar stacks held together in layers. In the T(12)amide case, the additional amide link results in significant stabilization of the lamellar phase. The driving forces for the appearance of columnar ordering are the hydrogen-bonding interactions of the amide groups, which induce head-to-tail pi-stacking of the terpy subunits. Replacing the polar linker by a nonpolarized but linear alkyne spacer, as in the T(12)ethynyl compound, provides a columnar mesophase organized in a rectangular lattice of p2gg symmetry. In this arrangement, two nondiscotic molecules arranged into dimers by hydrogen bonding and pi-pi stacking pile up in a head-to-tail manner to form columns. In addition, the T(12)amide compound proves to be an excellent gelator of cyclohexane, linear alkanes, and DMSO. The resulting robust and transparent gels are birefringent and formed by large aggregates that are readily aligned by shear-flow. TEM and freeze-fracture microscopy reveal that the gels have an original layered morphology made of fibers.

  17. Molecular dynamics simulations of a fully hydrated dimyristoylphosphatidylcholine membrane in liquid-crystalline phase

    NASA Astrophysics Data System (ADS)

    Zubrzycki, Igor Z.; Xu, Yan; Madrid, Marcela; Tang, Pei

    2000-02-01

    Molecular dynamics (MD) simulations were performed to investigate the structure of a fully hydrated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayer in liquid-crystalline (fluid) phase at 30 °C. The bilayer consists of 200 DMPC lipid molecules with nw=27.4 water molecules per lipid. The membrane was built with reference to the coordinates of a previously published 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membrane patch. A four-step dynamic procedure (110 ps) with Berendsen pressure rescaling (P=0 and 1 bar), applied in all three directions, was used to rapidly prepare the bilayer. This system was then subjected to two separate constant pressure and temperature simulations at 1 bar and 30 °C for ˜380 ps, using the Nosé-Hoover NPT method with periodical boundaries and Berendsen temperature and pressure rescaling method, respectively. The resultant bilayer has an area per lipid of 59.2 Å2 and a head-to-head thickness (DHH) of 36.3 Å. These values are in good agreement with the x-ray diffraction data of 59.7 Å2 and 34.4 Å, respectively, for DMPC at 30 °C with nw of 25.7 [H. I. Petrache, S. Tristram-Nagle, and J. F. Nagle, Chem. Phys. Lipids 95, 83 (1998)]. The fractions of trans and gauche bonds in the hydrocarbon chains, averaged for the last 94 ps of simulation, are 81.7% and 18.3%, respectively, suggesting a fluid phase of the membrane. The electron density profile resembles closely that measured by x-ray diffraction. Water density profile suggests a significant penetration of water molecules into the bilayer head region to as deep as the carbonyl groups, with phosphate groups being strongly hydrated.

  18. Revisiting β-casein as a stabilizer for lipid liquid crystalline nanostructured particles.

    PubMed

    Zhai, Jiali; Waddington, Lynne; Wooster, Tim J; Aguilar, Marie-Isabel; Boyd, Ben J

    2011-12-20

    Lipid liquid crystalline nanoparticles such as cubosomes and hexosomes have unique internal nanostructures that have shown great potential in drug and nutrient delivery applications. The triblock copolymer, Pluronic F127, is usually employed as a steric stabilizer in dispersions of lipid nanostructured particles. In this study, we investigated the formation, colloidal stability and internal nanostructure and morphology of glyceryl monooleate (GMO) and phytantriol (PHYT) cubosome dispersions on substituting β-casein with F127 in increasing proportion as the stabilizer. Internal structure and particle morphology were evaluated using small-angle X-ray scattering (SAXS) and cryo-transmission electron microscopy (cryo-TEM), while protein secondary structure was studied using synchrotron radiation circular dichroism (SRCD). The GMO cubosome dispersion stabilized by β-casein alone displayed a V(2) (Pn3m) phase structure and a V(2) to H(2) phase transition at 60 °C. In comparison, F127-stabilized GMO dispersion had a V(2) (Im3m) phase structure and the H(2) phase only appeared at higher temperature, that is, 70 °C. In the case of PHYT dispersions, only the V(2) (Pn3m) phase structure was observed irrespective of the type and concentration of stabilizers. However, β-casein-stabilized PHYT dispersion displayed a V(2) to H(2) to L(2) transition behavior upon heating, whereas F127-stabilized PHYT dispersion displayed only a direct V(2) to L(2) transition. The protein secondary structure was not disturbed by interaction with GMO or PHYT cubosomes. The results demonstrate that β-casein provides steric stabilization to dispersions of lipid nanostructured particles and avoids the transition to Im3m structure in GMO cubosomes, but also favors the formation of the H(2) phase, which has implications in drug formulation and delivery applications.

  19. Modelling charge transport of discotic liquid-crystalline triindoles: the role of peripheral substitution.

    PubMed

    Volpi, Riccardo; Camilo, Ana Claudia Santos; Filho, Demetrio A da Silva; Navarrete, Juan T López; Gómez-Lor, Berta; Delgado, M Carmen Ruiz; Linares, Mathieu

    2017-08-25

    We have performed a multiscale approach to study the influence of peripheral substitution in the semiconducting properties of discotic liquid-crystalline triindoles. Charge carrier mobility as high as 1.4 cm(2) V(-1) s(-1) was experimentally reported for triindoles substituted with alkynyl chains on the periphery (Gómez-Lor et al. Angew. Chem., Int. Ed., 2011, 50, 7399-7402). In this work, our goal is to get a deeper understanding of both the molecular electronic structure and microscopic factors affecting the charge transport properties in triindoles as a function of the spacer group connecting the central cores with the external alkyl chains (i.e., alkyne or phenyl spacers groups). To this end, we first perform Quantum Mechanical (QM) calculations to assess how the peripheral substitution affects the electronic structure and the internal reorganization energy. Secondly, boxes of stacked molecules were built and relaxed through molecular dynamics to obtain realistic structures. Conformational analysis and calculations of transfer integrals for closed neighbours were performed. Our results show that the insertion of ethynyl spacers between the central aromatic core and the flexible peripheral chains results in lower reorganization energies and enhanced intermolecular order within the stacks with a preferred cofacial 60° staggered conformation, which would result in high charge-carrier mobilities in good agreement with the experimental data. This work allows a deeper understanding of charge carrier mobility in columnar phases, linking the structural order at the molecular level to the property of interest, i.e. the charge carrier mobility. We hope that this understanding will improve the design of systems at the supramolecular level aiming at obtaining a more defined conducting channel, higher mobility and smaller fluctuations within the column.

  20. Enhancement of skin penetration of vitamin K using monoolein-based liquid crystalline systems.

    PubMed

    Lopes, Luciana B; Speretta, Fernanda F F; Bentley, M Vitória L B

    2007-11-01

    Application of vitamin K (vitK) to the skin has been used for suppression of pigmentation and resolution of bruising. However, there is no report concerning the extent of its penetration in the skin. In this study, we investigated the in vitro skin penetration and transdermal delivery of vitK, and whether these parameters may be enhanced by lipid-based drug delivery systems. The lipid formulation used in this study contains monoolein (MO), which is structured as a liquid crystalline phase, named hexagonal phase. The skin penetration of vitK was assessed in vitro using porcine ear skin mounted in a Franz diffusion cell. VitK (2.5%, w/w) was incorporated in either of three formulations: liquid vaseline, MO-based hexagonal phase gel (MO-vitK-water at 77.5/2.5/20, w/w/w) and MO-based nanodispersion of hexagonal phase (MO-vitK-poloxamer-water at 15/2.5/0.9/81.6, w/w/w/w). When vaseline was used, vitK was delivered mainly to the stratum corneum (SC): 9.50+/-0.97 microg/cm(2) of vitK was delivered to the SC at 12 h post-application, whereas 4.90 +/- 1.28 microg/cm(2) of vitK was delivered to the epidermis (E)+dermis (D) at the same time point. The hexagonal phase gel and the nanodispersion delivered approximately 2 times more vitK to the SC and 2.0-3.7 times more vitK to the [E+D] than the vaseline solution. The nanodispersion (but not the gel) also increased the transdermal delivery of vitK at 9 h ( approximately 3-fold increase). These results demonstrate that the topical delivery of vitK incorporated in a lipophilic vehicle is small, but it may be enhanced by MO-based systems, which might be useful to increase the effectiveness of topical vitK therapy.

  1. 21 CFR 524.2620 - Liquid crystalline trypsin, Peru balsam, castor oil.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...) Conditions of use. The drug is used as an aid in the treatment of external wounds and assists healing by... delivered to the wound site contains 0.12 milligram of crystalline trypsin, 87.0 milligrams of Peru balsam... gram delivered to the wound site contains 0.1 milligram of crystalline trypsin, 72.5 milligrams of...

  2. 21 CFR 524.2620 - Liquid crystalline trypsin, Peru balsam, castor oil.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...) Conditions of use. The drug is used as an aid in the treatment of external wounds and assists healing by... delivered to the wound site contains 0.12 milligram of crystalline trypsin, 87.0 milligrams of Peru balsam... gram delivered to the wound site contains 0.1 milligram of crystalline trypsin, 72.5 milligrams of...

  3. 21 CFR 524.2620 - Liquid crystalline trypsin, Peru balsam, castor oil.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) Conditions of use. The drug is used as an aid in the treatment of external wounds and assists healing by... delivered to the wound site contains 0.12 milligram of crystalline trypsin, 87.0 milligrams of Peru balsam... gram delivered to the wound site contains 0.1 milligram of crystalline trypsin, 72.5 milligrams of...

  4. 21 CFR 524.2620 - Liquid crystalline trypsin, Peru balsam, castor oil.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...) Conditions of use. The drug is used as an aid in the treatment of external wounds and assists healing by... delivered to the wound site contains 0.12 milligram of crystalline trypsin, 87.0 milligrams of Peru balsam... gram delivered to the wound site contains 0.1 milligram of crystalline trypsin, 72.5 milligrams of...

  5. Ionic liquid expedites partition of curcumin into solid gel phase but discourages partition into liquid crystalline phase of 1,2-dimyristoyl-sn-glycero-3-phosphocholine liposomes.

    PubMed

    El Khoury, Elsy D; Patra, Digambara

    2013-08-22

    The hydrolysis of curcumin in alkaline and neutral buffer conditions is of interest because of the therapeutic applicability of curcumin. We show that hydrolysis of curcumin can be remarkably suppressed in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes. The fluorescence of curcumin sensitively detects the phase transition temperature of liposomes. However, at greater concentrations, curcumin affects the phase transition temperature, encouraging fusion of two membrane phases. The interaction of curcumin with DMPC is found to be strong, with a partition coefficient value of Kp = 2.78 × 10(5) in the solid gel phase, which dramatically increases in the liquid crystalline phase to Kp = 1.15 × 10(6). The importance of ionic liquids as green solvents has drawn interest because of their toxicological effect on human health; however, the impact of ionic liquids (ILs) on liposomes is not yet understood. The present study establishes that ILs such as 1-methyl-3-octylimidazolium chloride (moic) affect the permeability and fluidity of liposomes and thus influence parition of curcumin into DMPC liposomes, helping in the solid gel phase but diminishing in the liquid crystalline phase. The Kp value of curcumin does not change appreciably with moic concentration in the solid gel state but decreases with moic concentration in the liquid crystalline phase. Curcumin, a rotor sensitive to detect phase transition temperature, is applied to investigate the influence of ionic liquids such as 1-methyl-3-octylimidazolium chloride, 1-buytl-3-methyl imadazolium tetrafluoroborate, and 1-benzyl-3-methyl imidazolium tetrafluoroborate on DMPC liposome properties. 1-Methyl-3-octylimidazolium chloride lowers the phase transition temperature, but 1-buytl-3-methyl imidazolium tetrafluoroborate and 1-benzyl-3-methyl imidazolium tetrafluoroborate do not perceptibly modify the phase transition temperature; rather, they broaden the phase transition.

  6. Bilayer membrane permeability of ionic liquid-filled block copolymer vesicles in aqueous solution.

    PubMed

    Bai, Zhifeng; Zhao, Bin; Lodge, Timothy P

    2012-07-19

    The bilayer membrane permeability of block copolymer vesicles ("polymersomes") with ionic liquid interiors dispersed in water is quantified using fluorescence quenching. Poly((1,2-butadiene)-b-ethylene oxide) (PB-PEO) block copolymer vesicles in water with their interiors filled with a common hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, were prepared containing a hydrophobic dye, Nile Red, by intact migration of dye-encapsulated vesicles from the ionic liquid to water at room temperature. A small quencher molecule, dichloroacetamide, was added to the aqueous solution of the dye-loaded vesicles, and the permeation of the quencher passing through the membrane into the interior was determined from the fluorescence quenching kinetics. Rapid permeation of the quencher across the nanoscale membrane was observed, consistent with the high fluidity of the liquid polybutadiene membrane. Two different PB-PEO copolymers were employed, in order to vary the thickness of the solvophobic membrane. A significant increase in membrane permeability was also observed with decreasing membrane thickness, which is tentatively attributable to differences in quencher solubility in the membranes. Quantitative migration of the vesicles from the aqueous phase back to an ionic liquid phase was achieved upon heating. These microscopically heterogeneous and thermoresponsive vesicles with permeable and robust membranes have potential as recyclable nanoreactors, in which the high viscosity and capital expense of an ionic liquid reaction medium can be mitigated, while retaining the desirable features of ionic liquids as reaction media, and facile catalyst recovery.

  7. Self-Assembled Liquid-Crystalline Membranes Form Supramolecular Hydrogels via Hydrogen Bonding.

    PubMed

    Yue, Youfeng

    2017-04-01

    Developing simple methods to organize nanoscale building blocks into ordered superstructures is a crucial step toward the practical development of nanotechnology. Bottom-up nanotechnology using self-assembly bridges the molecular and macroscopic, and can provide unique material properties, different from the isotropic characteristics of common substances. In this study, a new class of supramolecular hydrogels comprising 40 nm thick linear polymer layers sandwiched between nanolayers of self-assembled amphiphilic molecules are prepared and studied by nuclear magnetic resonance spectroscopy, scanning electronic microscopy, small angle X-ray diffraction, and rheometry. The amphiphilic molecules spontaneously self-assemble into bilayer membranes when they are in liquid-crystal state. The hydrogen bonds at the interface of the nanolayers and linear polymers serve as junctions to stabilize the network. These hydrogels with layered structure are facile to prepare, mechanically stable, and with unique temperature-dependent optical transparency, which makes it interesting in applications, such as soft biological membranes, drug release, and optical filters. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Assembly of Biological Nanostructures: Isotropic and Liquid Crystalline Phases of Neurofilament Hydrogels

    NASA Astrophysics Data System (ADS)

    Safinya, Cyrus R.; Deek, Joanna; Beck, Roy; Jones, Jayna B.; Li, Youli

    2015-03-01

    Neurofilaments are the building blocks of the major cytoskeletal network found in the axons of vertebrate neurons. The filaments consist of three distinct molecular-weight subunits - neurofilament-low, neurofilament-medium, and neurofilament-high - which coassemble into 10-nm flexible rods with protruding intrinsically disordered C-terminal sidearms that mediate interfilament interactions and hydrogel formation. Molecular neuroscience research includes areas focused on elucidating the functions of each subunit in network formation, during which disruptions are a hallmark of motor-neuron diseases. Here, modern concepts and methods from soft condensed matter physics are combined to address the role of subunits as it relates to interfilament forces and phase behavior in neurofilament networks. Significantly, the phase behavior studies reveal that although neurofilament-medium subunits promote nematic liquid crystal hydrogel phase stability with parallel filament orientation, neurofilament-high subunits stabilize the hydrogel in the nematic phase close to the isotropic gel phase with random, crossed-filament orientation. This indicates a regulatory role for neurofilament-high subunits in filament orientational plasticity required for organelle (e.g., membrane-bound vesicle or mitochondrion) transport along microtubules embedded in neurofilament hydrogels. Future studies - for example, on neurofilament subunits mixed with tubulin and microtubule-associated proteins - should lead to a deeper understanding of forces and heterogeneous structures in neuronal cytoskeletons.

  9. High-Performance Active Liquid Crystalline Shutters for Stereo Computer Graphics and Other 3-D Technologies

    NASA Astrophysics Data System (ADS)

    Sergan, Tatiana; Sergan, Vassili; MacNaughton, Boyd

    2007-03-01

    Stereoscopic computer displays create a 3-D image by alternating two separate images for each of the viewer's eyes. Field-sequential viewing systems supply each eye with the appropriate image by blocking the wrong image for the wrong eye. In our work, we have developed a new mode of operation of a liquid crystal shutter that provides for highly effective blockage of undesired images when the screen is viewed in all viewing directions and eliminates color shifts associated with long turn-off times. The goal was achieved by using a π-cell filled with low-rotational-viscosity and high-birefringence fluid and additional negative birefringence films with splay optic axis distribution. The shutter demonstrates a contrast ratio higher than 800:1 for head-on viewing and 10:1 in the viewing cone of about 45°. The relaxation time of the shutter does not exceed 2 ms and is the same for all three primary colors.

  10. Molecular transport into and out of ionic-liquid filled block copolymer vesicles in water

    NASA Astrophysics Data System (ADS)

    Lodge, Timothy; Yao, Letitia; So, Soonyong

    We have developed a method to prepare stable, size-controlled block copolymer vesicles that contain ionic liquid in the interior, but that are dispersed in water. Such nanoemulsions are of interest as nanoreactors, because the mass transfer and cost limitations of ionic liquids are circumvented. However, a crucial question is whether target molecules (e . g ., reagents and products) can enter and leave the vesicles, respectively, on a useful time scale (i . e ., seconds or shorter). In this talk we will briefly describe methods to prepare such vesicles with narrow size distributions, using poly(styrene)-block-poly(ethylene oxide) and poly(butadiene)-block-poly(ethylene oxide) copolymers of various compositions. We will then present results of pulsed-field gradient NMR measurements of probe diffusion that yield independent measurements of the entry and escape rates for selected small molecules, as a function of membrane thickness and temperature.

  11. Controlling the nanostructure of gold nanorod-lyotropic liquid-crystalline hybrid materials using near-infrared laser irradiation.

    PubMed

    Fong, Wye-Khay; Hanley, Tracey L; Thierry, Benjamin; Kirby, Nigel; Waddington, Lynne J; Boyd, Ben J

    2012-10-09

    Lipid-based liquid-crystalline matrixes provide a unique prospect for stimuli-responsive nanomaterials, attributed to the ability to effect self-assembly of the lipids at the molecular level. Differences in liquid crystal nanostructure have previously been shown to change drug diffusion and hence release, with research progressing toward the use of in situ changes to nanostructure to control drug release. Toward this goal, we have previously communicated the ability to switch between nonlamellar structures using gold nanorod (GNR)-phytantriol-based liquid-crystalline hybrid nanomaterials as near-infrared light responsive systems (Fong et al. Langmuir 2010, 26, 6136-6139). In this study, the effect of laser activation on matrix nanostructure with changes in a number of system variables including lipid composition, GNR aspect ratio, GNR concentration, and laser pulse time were investigated. The nanostructure of the matrix was followed using small-angle X-ray scattering, while both cryoFESEM and cryoTEM were used to visualize the effect of GNR incorporation into the liquid crystal nanostructure. The system response was found to be dependent on all variables, thus demonstrating the potential of these nanocomposite materials as reversible "on-demand" drug delivery applications.

  12. Morphology and Proton Conductivity of Ionic Liquid Containing Sulfonated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Kim, Sung Yeon; Park, Moon Jeong

    2011-03-01

    Proton exchange membrane fuel cells (PEMFC) offer the prospect of supplying clean electrical power for a wide variety of systems such as portable electronic devices and vehicles. Although, significant effort has been devoted to improvement of the transport properties of PEMs which is operated relatively lower temperature below 80circ; C, it suffers from a CO poisoning at Pt catalysis, complexity of water and heat management in the system. Herein, we report unique block copolymer electrolyte membrane systems containing ionic liquid. Due to the nonvolatile property of ionic liquid the systems exhibit effective proton transport above 100circ; C without humidification. In present study, sulfonated block copolymers, i.e., poly(styrenesulfonate-b-methylbuthylene) (SnMBm), are utilized for matrix materials by varying the ion contents and molecular weight. Imidazolium based ionic liquids are selectively incorporated into polystyrenesulfonate phases, which results in various morphological transitions as a function of the amount of the ionic liquid. The effect of counter ions on the observed morphologies is significant yielding concurrently different values of conductivity. Small angle x-ray scattering and transmission electron microscopy have been employed to determine various morphologies of the ionic liquid containing sulfonated block copolymer membranes and impedance spectroscopy is used for the conductivity measurements.

  13. Effect of water uptake on morphology of polymerized ionic liquid block copolymers and random copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Tsen-Shan; Ye, Yuesheng; Elabd, Yossef; Winey, Karen

    2012-02-01

    Dynamic studies of polymer morphology probe how the physical properties of polymerized ionic liquids are affected by the environment, such as temperature or moisture. For a series of poly(methyl methacrylate-b-1-[2-(methacryloyloxy)ethyl]-3-Butylimidazolium X^-) block and random copolymers with hydrophilic counterions (X^- = Br^-, HCO3^-, OH^-), the introduction of water vapor to the system can swell the ionic liquid block, causing enlarged hydrophilic domains and swollen channels for ion conduction. This expected expansion of ionic liquid domains in humid environments can be used to intelligently design these copolymers for use in technological applications. The effect of water vapor exposure in these imidazolium-based acrylate polymers is studied by small-angle X-ray scattering. These morphology results will be discussed alongside complementary studies of water uptake and ion conductivity.

  14. Part-crystalline part-liquid state and rattling-like thermal damping in materials with chemical-bond hierarchy

    PubMed Central

    Xi, Lili; Wei, Ping; Ke, Xuezhi; Yang, Jihui; Zhang, Wenqing

    2014-01-01

    Understanding thermal and phonon transport in solids has been of great importance in many disciplines such as thermoelectric materials, which usually requires an extremely low lattice thermal conductivity (LTC). By analyzing the finite-temperature structural and vibrational characteristics of typical thermoelectric compounds such as filled skutterudites and Cu3SbSe3, we demonstrate a concept of part-crystalline part-liquid state in the compounds with chemical-bond hierarchy, in which certain constituent species weakly bond to other part of the crystal. Such a material could intrinsically manifest the coexistence of rigid crystalline sublattices and other fluctuating noncrystalline sublattices with thermally induced large-amplitude vibrations and even flow of the group of species atoms, leading to atomic-level heterogeneity, mixed part-crystalline part-liquid structure, and thus rattling-like thermal damping due to the collective soft-mode vibrations similar to the Boson peak in amorphous materials. The observed abnormal LTC close to the amorphous limit in these materials can only be described by an effective approach that approximately treats the rattling-like damping as a “resonant” phonon scattering. PMID:25288751

  15. Part-crystalline part-liquid state and rattling-like thermal damping in materials with chemical-bond hierarchy

    DOE PAGES

    Qiu, Wujie; Xi, Lili; Wei, Ping; ...

    2014-10-06

    Understanding thermal and phonon transport in solids has been of great importance in many disciplines such as thermoelectric materials, which usually requires an extremely low lattice thermal conductivity (LTC). Here, by analyzing the finite-temperature structural and vibrational characteristics of typical thermoelectric compounds such as filled skutterudites and Cu3SbSe3, we demonstrate a concept of part-crystalline part-liquid state in the compounds with chemical-bond hierarchy, in which certain constituent species weakly bond to other part of the crystal. Such a material could intrinsically manifest the coexistence of rigid crystalline sublattices and other fluctuating noncrystalline sublattices with thermally induced large-amplitude vibrations and even flowmore » of the group of species atoms, leading to atomic-level heterogeneity, mixed part-crystalline part-liquid structure, and thus rattling-like thermal damping due to the collective soft-mode vibrations similar to the Boson peak in amorphous materials. Lastly, the observed abnormal LTC close to the amorphous limit in these materials can only be described by an effective approach that approximately treats the rattling-like damping as a “resonant” phonon scattering.« less

  16. Part-crystalline part-liquid state and rattling-like thermal damping in materials with chemical-bond hierarchy

    SciTech Connect

    Qiu, Wujie; Xi, Lili; Wei, Ping; Ke, Xuezhi; Yang, Jihui; Zhang, Wenqing

    2014-10-06

    Understanding thermal and phonon transport in solids has been of great importance in many disciplines such as thermoelectric materials, which usually requires an extremely low lattice thermal conductivity (LTC). Here, by analyzing the finite-temperature structural and vibrational characteristics of typical thermoelectric compounds such as filled skutterudites and Cu3SbSe3, we demonstrate a concept of part-crystalline part-liquid state in the compounds with chemical-bond hierarchy, in which certain constituent species weakly bond to other part of the crystal. Such a material could intrinsically manifest the coexistence of rigid crystalline sublattices and other fluctuating noncrystalline sublattices with thermally induced large-amplitude vibrations and even flow of the group of species atoms, leading to atomic-level heterogeneity, mixed part-crystalline part-liquid structure, and thus rattling-like thermal damping due to the collective soft-mode vibrations similar to the Boson peak in amorphous materials. Lastly, the observed abnormal LTC close to the amorphous limit in these materials can only be described by an effective approach that approximately treats the rattling-like damping as a “resonant” phonon scattering.

  17. Part-crystalline part-liquid state and rattling-like thermal damping in materials with chemical-bond hierarchy.

    PubMed

    Qiu, Wujie; Xi, Lili; Wei, Ping; Ke, Xuezhi; Yang, Jihui; Zhang, Wenqing

    2014-10-21

    Understanding thermal and phonon transport in solids has been of great importance in many disciplines such as thermoelectric materials, which usually requires an extremely low lattice thermal conductivity (LTC). By analyzing the finite-temperature structural and vibrational characteristics of typical thermoelectric compounds such as filled skutterudites and Cu3SbSe3, we demonstrate a concept of part-crystalline part-liquid state in the compounds with chemical-bond hierarchy, in which certain constituent species weakly bond to other part of the crystal. Such a material could intrinsically manifest the coexistence of rigid crystalline sublattices and other fluctuating noncrystalline sublattices with thermally induced large-amplitude vibrations and even flow of the group of species atoms, leading to atomic-level heterogeneity, mixed part-crystalline part-liquid structure, and thus rattling-like thermal damping due to the collective soft-mode vibrations similar to the Boson peak in amorphous materials. The observed abnormal LTC close to the amorphous limit in these materials can only be described by an effective approach that approximately treats the rattling-like damping as a "resonant" phonon scattering.

  18. Combinatorial approach for the rapid determination of thermochromic behavior of binary and ternary cholesteric liquid crystalline mixtures.

    PubMed

    van der Werff, Louise C; Robinson, Andrea J; Kyratzis, Ilias L

    2012-11-12

    A combinatorial approach was developed for the rapid determination of thermochromic behavior of a large number of binary and ternary sterol based thermochromic liquid crystalline formulations. A binary mixture containing cholesteryl oleyl carbonate and cholesteryl nonanoate, and ternary mixtures also containing a third component, either cholesteryl oleate, cholesteryl benzoate, cholesteryl 2,4-dichlorobenzoate or cholesteryl propionate, were formulated via solvent deposition into a black Teflon coated aluminum 96 well plate. The temperature of the well plate was then varied, and the color appearance of the deposited mixture in each well was recorded. This approach allowed expedient examination of the thermochromic behavior for a large range of liquid crystal formulations. The accuracy of the rapid combinatorial technique was validated on selected thermochromic liquid crystal mixture compositions by comparing well thermochromic output with that observed using UV-vis spectroscopy on material produced in gram quantities.

  19. Electrical induction and optical erasure of birefringence in the isotropic liquid phase of a dichiral azobenzene liquid-crystalline compound (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takahiro; Nishiyama, Isa

    2015-10-01

    Liquid crystal is a representative soft matter, which has physical properties between those of conventional liquid and those of crystal in a temperature range above a melting point. A liquid-crystal display (LCD) employs the response of the liquid-crystal alignment to the electric field and is a key device of an information display. For common LCDs, the precise control of the initial alignment of LC molecules is needed so that a good dark state, thus a high contrast ratio, can be obtained. If the birefringence can be induced in the liquid phase by the application of electric field, it is of great use as a material for the LCD application. In this study, we will report a unique property of dichiral azobenzene liquid crystals: an electric induction of birefringence in a liquid phase of an antiferroelectric dichiral azobenzene liquid crystal. The optically isotropic texture changes into the homogenous birefringent texture by the application of the in-plane electric field above the clearing temperature of the liquid crystal. We find that one of the possible reasons of the induction of the birefringence in the isotropic phase is the electrically-induced increase of the phase transition temperature between the antiferroelectric liquid-crystalline and "liquid" phases, i.e., increase in the clearing temperature. The resulting birefringence can be disappeared by the irradiation of UV light, due to the photoinduced isomerization of the azobenzene compound, thus dual control of the birefringent structure, by the irradiation of light and/or by the application of the electric field, is achieved.

  20. Complex dendrimer-lyotropic liquid crystalline systems: structural behavior and interactions.

    PubMed

    Bitan-Cherbakovsky, Liron; Libster, Dima; Aserin, Abraham; Garti, Nissim

    2011-10-27

    The incorporation of dendrimer into three lyotropic liquid crystalline (LLCs) mesophases is demonstrated for the first time. A second generation (G2) of poly(propylene imine) dendrimer (PPI) was solubilized into lamellar, diamond reverse cubic, and reverse hexagonal LLCs composed of glycerol monooleate (GMO), and water (and D-α-tocopherol in the H(II) system). The combination of PPI with LLCs may provide an advantageous drug delivery system. Cross-polarized light microscope, small-angle X-ray scattering (SAXS), and attenuated total reflectance Fourier transform infrared (ATR-FTIR) were utilized to study the structural behavior of the mesophases, the localization of PPI within the system, and the interactions between the guest molecule and the system's components. It was revealed that PPI-G2 functioned as a "water pump", competing with the lipid headgroups for water binding. As a result, L(α)→H(II) and Q(224)→H(II) structural shifts were detected (at 10 wt % PPI-G2 content), probably caused by the dehydration of monoolein headgroups and subsequent increase of the lipid's critical packing parameter (CPP). In the case of H(II), as a result of the balance between the dehydration of the monoolein headgroups and the significant presence of PPI within the interfacial region, increasing the quantity of hydrogen bonds, no structural transitions occurred. ATR-FTIR analysis demonstrated a downward shift of the H-O-H (water), as a result of PPI-G2 embedment, suggesting an increase in the mean water-water H-bond angle resulting from binding PPI-G2 to the water network. Additionally, the GMO hydroxyl groups at β- and γ-C-OH positions revealed a partial interaction of hydrogen bonds with N-H functional groups of the protonated PPI-G2. Other GMO interfacial functional groups were shown to interact with the PPI-G2, in parallel with the GMO dehydration phenomenon. In the future, these outcomes can be used to design advanced drug delivery systems, allowing administration of

  1. Solvent-responsive floating liquid crystalline-molecularly imprinted polymers for gastroretentive controlled drug release system.

    PubMed

    Zhang, Li-Ping; Wang, Xiao-Lin; Pang, Qian-Qian; Huang, Yan-Ping; Tang, Lei; Chen, Meng; Liu, Zhao-Sheng

    2017-09-06

    Liquid crystalline-molecularly imprinted polymer (LC-MIP) particles was first found to possess the floating behavior on the aqueous medium. Combined with molecular recognition, the LC-MIP was fabricated as a novel class of the controlled-release gastric retentive DDS. The LC-MIP was made using co-polymerization of methacrylic acid, 4-methyl phenyl dicyclohexyl ethylene (LC monomer with vinyl group), and ethylene glycol dimethacrylate with S-amlodipine (S-AML) as model template drug. The optimum condition of the preparation of LC-MIP has been obtained relying on release behaviors of S-AML from the LC-MIP. The surface morphology of LC-MIP and three corresponding control samples, i.e., template-free LC-NIP, LC-free MIP, and LC-free NIP, were studied. Applying the LF model for the binding isotherm, imprinting factors was 2.80 for the LC-MIP with the crosslinking degree of 20.0%, whereas 6.70 for the LC-free MIP with high levels of crosslinker (80.0%). Furthermore, the phase transition behaviors of LC-based particles as well as drug-loaded LC elastomers were measured by a differential scanning calorimeter and the formed hydrogen bonding between S-AML and MI-LCE was demonstrated by FT-IR spectra. In vivo imaging experiment proved that the floating LC-MIP had significantly longer gastric residence time (>60min) than the non-floating MIP reference (<30min). In vivo pharmacokinetic study showed a plateau region between 1.5 and 22hr on the plasma concentration from the LC-MIP. In spite of lower imprinting factor, the relative bioavailability of the gastro-floating LC-MIP was 180.5%, whereas only 111.7% of the LC-free MIP. As a conclusion, the LC-MIPs indicated potentials for oral administration due to the innovative combination of floating and controlled release properties. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Interactions of lipid-based liquid crystalline nanoparticles with model and cell membranes.

    PubMed

    Barauskas, Justas; Cervin, Camilla; Jankunec, Marija; Spandyreva, Marija; Ribokaite, Kristina; Tiberg, Fredrik; Johnsson, Markus

    2010-05-31

    Lipid-based liquid crystalline nanoparticles (LCNPs) are interesting candidates for drug delivery applications, for instance as solubilizing or encapsulating carriers for intravenous (i.v.) drugs. Here it is important that the carriers are safe and tolerable and do not have, e.g. hemolytic activity. In the present study we have studied LCNP particles of different compositions with respect to their mixing behavior and membrane destabilizing effects in model and cell membrane systems. Different types of non-lamellar LCNPs were studied including cubic phase nanoparticles (Cubosome) based on glycerol monooleate (GMO), hexagonal phase nanoparticles (Hexosome) based on diglycerol monooleate (DGMO) and glycerol dioleate (GDO), sponge phase nanoparticles based on DGMO/GDO/polysorbate 80 (P80) and non-lamellar nanoparticles based on soy phosphatidylcholine (SPC)/GDO. Importantly, the LCNPs based on the long-chain monoacyl lipid, GMO, were shown to display a very fast and complete lipid mixing with model membranes composed of multilamellar SPC liposomes as assessed by a fluorescence energy transfer (FRET) assay. The result correlated well with pronounced hemolytic properties observed when the GMO-based LCNPs were mixed with rat whole blood. In sharp contrast, LCNPs based on mixtures of the long-chain diacyl lipids, SPC and GDO, were found to be practically inert towards both hemolysis in rat whole blood as well as lipid mixing with SPC model membranes. The LCNP dispersions based on a mixture of long-chain monoacyl and diacyl lipids, DGMO/GDO, displayed an intermediate behavior compared to the GMO and SPC/GDO-based systems with respect to both hemolysis and lipid mixing. It is concluded that GMO-based LCNPs are unsuitable for parenteral drug delivery applications (e.g. i.v. administration) while the SPC/GDO-based LCNPs exhibit good properties with limited lipid mixing and hemolytic activity. The correlation between results from lipid mixing or FRET experiments and the in

  3. Amphiphilic brush polymers produced using the RAFT polymerisation method stabilise and reduce the cell cytotoxicity of lipid lyotropic liquid crystalline nanoparticles.

    PubMed

    Zhai, Jiali; Suryadinata, Randy; Luan, Bao; Tran, Nhiem; Hinton, Tracey M; Ratcliffe, Julian; Hao, Xiaojuan; Drummond, Calum J

    2016-10-06

    Self-assembled lipid lyotropic liquid crystalline nanoparticles such as hexosomes and cubosomes contain internal anisotropic and isotropic nanostructures, respectively. Despite the remarkable potential of such nanoparticles in various biomedical applications, the stabilisers used in formulating the nanoparticles are often limited to commercially available polymers such as the Pluronic block copolymers. This study explored the potential of using Reversible Addition-Fragmentation chain Transfer (RAFT) technology to design amphiphilic brush-type polymers for the purpose of stabilising phytantriol and monoolein-based lipid dispersions. The synthesised brush-type polymers consisted of a hydrophobic C12 short chain and a hydrophilic poly(ethylene glycol)methyl ether acrylate (PEGA) long chain with multiple 9-unit poly(ethylene oxide) (PEO) brushes with various molecular weights. It was observed that increasing the PEO brush density and thus the length of the hydrophilic component improved the stabilisation effectiveness for phytantriol and monoolein-based cubosomes. Synchrotron small-angle X-ray scattering (SAXS) experiments confirmed that the RAFT polymer-stabilised cubosomes had an internal double-diamond cubic phase with tunable water channel sizes. These properties were dependent on the molecular weight of the polymers, which were considered in some cases to be anisotropically distributed within the cubosomes. The in vitro toxicity of the cubosomes was assessed by cell viability of two human adenocarcinoma cell lines and haemolytic activities to mouse erythrocytes. The results showed that phytantriol cubosomes stabilised by the RAFT polymers were less toxic compared to their Pluronic F127-stabilised analogues. This study provides valuable insight into designing non-linear amphiphilic polymers for the effective stabilisation and cellular toxicity improvement of self-assembled lipid lyotropic liquid crystalline nanoparticles.

  4. Morphology and Ionic Conductivity of Block Copolymer--Ionic Liquid Systems

    NASA Astrophysics Data System (ADS)

    Hoarfrost, M. L.; Virgili, J. M.; Kerr, J. B.; Segalman, R. A.

    2009-03-01

    Block copolymer--ionic liquid systems are of interest for ion exchange membranes due to the ionic conductivity and thermal stability of the ionic liquid combined with the thermal stability and morphological control arising from a structural component in a block copolymer. It is anticipated that the morphology and connectivity of the resulting structural and ionic liquid-containing nanodomains will affect conduction properties. This relationship was investigated for poly(styrene-b-2-vinylpyridine) (S2VP) in ionic liquids composed of varying molar ratios of imidazole and bis(trifluoromethanesulfonyl)imide (Im:TFSI). A stoichiometrically balanced ionic liquid (1:1 Im:TFSI) swells the 2VP lamellar domains for copolymer concentrations as low as 60wt%. With 9:1 Im:TFSI the lamellar structure tolerates more swelling, forming lamellar structures with as little as 30wt% copolymer. Ionic conductivities were derived from AC impedance measurements. The S2VP-Im:TFSI systems, characterized by microphase separated domains, demonstrate ionic conductivities comparable to those of P2VP--ionic liquid systems when normalized by 2VP (monomer) to Im:TFSI ratio.

  5. Interplay of Noncovalent Interactions in Ionic Liquid/Sodium Bis(2-ethylhexyl) Sulfosuccinate Mixtures: From Lamellar to Bicontinuous Cubic Liquid Crystalline Phase.

    PubMed

    Novak, Sanja; Morasi Piperčić, Sara; Makarić, Sandro; Primožič, Ines; Ćurlin, Marija; Štefanić, Zoran; Domazet Jurašin, Darija

    2016-12-15

    Phase transitions in mixtures of imidazolium based ionic liquid ([C12mim]Br) and anionic double tail surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT), were studied using a multitechnique approach. The system was primarily chosen for its expected ability to form a variety of lamellar and nonlamellar liquid crystalline phases which can transform into each other via different mechanisms. Depending on the bulk composition and total surfactant concentration, mixed micelles, coacervates, and lamellar and inverse bicontinuous cubic liquid crystalline phase were observed. Along with electrostatic attractions and geometric packing constraints, additional noncovalent interactions (hydrogen bonding, π-π stacking) enhanced attractive interactions and stabilized low curvature aggregates. At stoichiometric conditions, coexistence of coacervates and vesicles was found at lower, while bicontinuous cubic phase and vesicles were present at higher total surfactant concentrations. The phase transitions from a dispersed lamellar to inverse cubic bicontinuous phase occur as a consequence of charge shielding and closer packing of oppositely charged headgroups followed by a change in bilayer curvature. Transition is continuous with both phases coexisting over a relatively broad range of concentrations and very likely involves a sponge-like phase as a structural intermediate. To the best of our knowledge, this type of phase transition has not been observed before in surface active ionic liquid/surfactant mixtures.

  6. Nonlinear seismic response of a partially-filled rectangular liquid tank with a submerged block

    NASA Astrophysics Data System (ADS)

    Nayak, Santosh Kumar; Biswal, Kishore Chandra

    2016-04-01

    The seismic response of partially-filled two-dimensional rigid rectangular liquid tanks with a bottom-mounted submerged block is numerically simulated. The Galerkin-weighted-residual based finite element method (FEM) is used for solving the governing Laplace equation with fully nonlinear free surface boundary conditions and also for velocity recovery. Based on the mixed Eulerian-Lagrangian (MEL) method, a fourth order explicit Runge-Kutta scheme is used for the time-stepping integration of free surface boundary conditions. A cubic-spline fitted regridding technique is used at every time step to eliminate possible numerical instabilities on account of Lagrangian node induced mesh distortion. An artificial surface damping term is used to mimic the viscosity induced damping. Three different earthquake motions characterized on the basis of low, intermediate and high frequency contents are used to study the effect of frequency content on the nonlinear dynamic response of this tank-liquid-submerged block system. The effect of the submerged block on the impulsive and convective response components of the hydrodynamic forces manifested in terms of base shear, overturning base moment and pressure distribution along the tank wall as well as the block wall has been quantified vis-a-vis frequency content of ground motions. It is observed that the convective response of this tank-liquid system is highly sensitive to the frequency content of the ground motion.

  7. Induced liquid-crystalline ordering in solutions of stiff and flexible amphiphilic macromolecules: Effect of mixture composition

    NASA Astrophysics Data System (ADS)

    Glagolev, Mikhail K.; Vasilevskaya, Valentina V.; Khokhlov, Alexei R.

    2016-07-01

    Impact of mixture composition on self-organization in concentrated solutions of stiff helical and flexible macromolecules was studied by means of molecular dynamics simulation. The macromolecules were composed of identical amphiphilic monomer units but a fraction f of macromolecules had stiff helical backbones and the remaining chains were flexible. In poor solvents the compacted flexible macromolecules coexist with bundles or filament clusters from few intertwined stiff helical macromolecules. The increase of relative content f of helical macromolecules leads to increase of the length of helical clusters, to alignment of clusters with each other, and then to liquid-crystalline-like ordering along a single direction. The formation of filament clusters causes segregation of helical and flexible macromolecules and the alignment of the filaments induces effective liquid-like ordering of flexible macromolecules. A visual analysis and calculation of order parameter relaying the anisotropy of diffraction allow concluding that transition from disordered to liquid-crystalline state proceeds sharply at relatively low content of stiff components.

  8. Induced liquid-crystalline ordering in solutions of stiff and flexible amphiphilic macromolecules: Effect of mixture composition.

    PubMed

    Glagolev, Mikhail K; Vasilevskaya, Valentina V; Khokhlov, Alexei R

    2016-07-28

    Impact of mixture composition on self-organization in concentrated solutions of stiff helical and flexible macromolecules was studied by means of molecular dynamics simulation. The macromolecules were composed of identical amphiphilic monomer units but a fraction f of macromolecules had stiff helical backbones and the remaining chains were flexible. In poor solvents the compacted flexible macromolecules coexist with bundles or filament clusters from few intertwined stiff helical macromolecules. The increase of relative content f of helical macromolecules leads to increase of the length of helical clusters, to alignment of clusters with each other, and then to liquid-crystalline-like ordering along a single direction. The formation of filament clusters causes segregation of helical and flexible macromolecules and the alignment of the filaments induces effective liquid-like ordering of flexible macromolecules. A visual analysis and calculation of order parameter relaying the anisotropy of diffraction allow concluding that transition from disordered to liquid-crystalline state proceeds sharply at relatively low content of stiff components.

  9. Evaporative Self-Assembly and Formation of the Lyotropic Liquid Crystalline Phase of Poly(3-hexyl thiophene)

    NASA Astrophysics Data System (ADS)

    Park, Min Sang; Aiyar, Avishek; Park, Jung Ok; Reichmanis, Elsa; Srinivasarao, Mohan

    2011-03-01

    In this study, we electrically and optically interrogated the evolution of the thin film structure in conjugated systems using poly(3-hexylthiphene) (P3HT) as a model semiconducting polymer. In an effort to understand the electrical properties of the conducting channel in terms of polymer chain orientation and relaxation in solution, we performed in-situ micro-Raman measurements using polarized incident light. We measured the extent of molecular chain alignment during the process of film formation and showed the existence of a lyotropic liquid crystal phase at the three-phase contact line. The variation of frequency dispersion and the shift of position for Raman active mode, combined with the structural anisotropy of P3HT films, suggest a phase transition to the lyotropic liquid crystalline phase. The orientational order of P3HT chains in the liquid crystalline phase was quantified as a function of evaporation time using solidified solvent, 1,3,5-triclorobenzene (1,3,5-TCB). This work was supported, in part, by the Office of Basic Energy Science, Department of Energy, Grant No. DESC0001412 and by an NSF, Grant No. DMR0706235.

  10. Chiral front propagation in liquid-crystalline materials: Formation of the planar monodomain twisted plywood architecture of biological fibrous composites.

    PubMed

    De Luca, Gino; Rey, Alejandro D

    2004-01-01

    Biological fibrous composites commonly exhibit an architecture known as twisted plywood, which is similar to that of the cholesteric liquid-crystalline mesophases. The explanation for the structural similarity is that biological fibrous composites adopt a lyotropic cholesteric liquid-crystalline phase during their formation process. In this work, a mathematical model based on the Landau-de Gennes theory of liquid crystals has been developed to reproduce the process by which long chiral fibrous molecules form the twisted plywood structures observed in biological composites. The dynamics of the process was then further investigated by analytically solving a simplified version of the governing equations. Results obtained from the model are in good qualitative agreement with the theory of Neville [Biology of Fibrous Composites (Cambridge University Press, Cambridge, England, 1993)] who hypothesized the necessity of a constraining layer to lock the direction of the helical axis of the plywood in order to create a monodomain structure. Computational results indicate that the plywood architecture is obtained by a chiral front propagation process with a fully relaxed wake. The effects of chirality and concentration on the formation process kinetics are characterized.

  11. Photochromic hybrid organic-inorganic liquid-crystalline materials built from nonionic surfactants and polyoxometalates: elaboration and structural study.

    PubMed

    Poulos, Andreas S; Constantin, Doru; Davidson, Patrick; Impéror, Marianne; Pansu, Brigitte; Panine, Pierre; Nicole, Lionel; Sanchez, Clément

    2008-06-17

    This work reports the elaboration and structural study of new hybrid organic-inorganic materials constructed via the coupling of liquid-crystalline nonionic surfactants and polyoxometalates (POMs). X-ray scattering and polarized light microscopy demonstrate that these hybrid materials, highly loaded with POMs (up to 18 wt %), are nanocomposites of liquid-crystalline lamellar structure (Lalpha), with viscoelastic properties close to those of gels. The interpretation of X-ray scattering data strongly suggests that the POMs are located close to the terminal -OH groups of the nonionic surfactants, within the aqueous sublayers. Moreover, these materials exhibit a reversible photochromism associated to the photoreduction of the polyanion. The photoinduced mixed-valence behavior has been characterized through ESR and UV-visible-near-IR spectroscopies that demonstrate the presence of W(V) metal cations and of the characteristic intervalence charge transfer band in the near-IR region, respectively. These hybrid nanocomposites exhibit optical properties that may be useful for applications involving UV-light-sensitive coatings or liquid-crystal-based photochromic switches. From a more fundamental point of view, these hybrid materials should be very helpful models for the study of both the static and dynamic properties of nano-objects confined within soft lamellar structures.

  12. Liquid-crystalline phases of cholesterol/lipid bilayers as revealed by the fluorescence of trans-parinaric acid.

    PubMed Central

    Reyes Mateo, C; Ulises Acuña, A; Brochon, J C

    1995-01-01

    The presence of two liquid-crystalline phases, alpha and beta, in mixed bilayers of dimyristoylphosphatidylcholine/cholesterol was detected by the changes in the distribution of the fluorescence lifetimes of t-PnA, as analyzed by the Maximum Entropy Method. The formation of the liquid-ordered beta-phase, in the 30-40 degrees C temperature range as a function of cholesterol concentration (0-40 mol%), could be related quantitatively to the relative amplitude of a long lifetime component of the probe (10-14 ns). Based on this evidence, the phase behavior of mixtures of the unsaturated lipid palmitoyloleoylphosphatidylcholine and cholesterol was determined using the same technique, for cholesterol concentrations in the 0-50 mol% range, between 10 and 40 degrees C. It was found that two liquid-crystalline phases are also formed in this system, with physical properties reminiscent of the alpha- and beta-phases formed with saturated lipids. However, in this case it was determined that, for temperatures in the physiological range, the alpha- and beta-phases coexist up to 40 mol% cholesterol. This finding may be of significant biological relevance, because it supports the long held notion that cholesterol is responsible for the lipid packing heterogeneity of several natural membranes rich in unsaturated lipid components. PMID:7756560

  13. Microfluidic synthesis of highly shape-anisotropic particles from liquid crystalline elastomers with defined director field configurations.

    PubMed

    Ohm, Christian; Kapernaum, Nadia; Nonnenmacher, Dorothee; Giesselmann, Frank; Serra, Christophe; Zentel, Rudolf

    2011-04-13

    In this article, we present the synthesis of highly shape-anisotropic, micrometer-sized particles from liquid crystalline elastomers, which have the ability to reversibly change their shape in response to a certain external stimulus. For their preparation, we utilized a microfluidic setup. We succeeded in preparing sets of particles with differing degrees of shape anisotropy in their ground state including highly anisotropic fiber-like objects. All samples produced movement during the phase transition from the nematic to the isotropic phase of the liquid crystal. Depending on the direction of this shape change, we classified the samples in two groups. One type showed a contraction, while the other showed an expansion during the actuation, generating displacements of 60% and 80%, respectively. Using X-ray diffraction experiments, we could show that the different actuation properties arise from different director patterns of the liquid crystalline moieties in the microparticles. While the weakly shape-anisotropic microparticles possess a concentric director field (director perpendicular to the symmetry axis), the highly anisotropic fiber-like particles show an alignment of the director along the fiber axis. We present an explanation, claiming that this is the result of two different orientation mechanisms involving elongational flow on the one side and "log-rolling" on the other. © 2011 American Chemical Society

  14. Analysis of liquid crystalline nanoparticles by small angle X-ray diffraction: evaluation of drug and pharmaceutical additives influence on the internal structure.

    PubMed

    Rossetti, Fábia Cristina; Fantini, Márcia C A; Carollo, Aline Regina H; Tedesco, Antônio Cláudio; Bentley, Maria Vitória Lopes Badra

    2011-07-01

    The goal of this work was to study the liquid crystalline structure of a nanodispersion delivery system intended to be used in photodynamic therapy after loading with photosensitizers (PSs) and additives such as preservatives and thickening polymers. Polarized light microscopy and light scattering were performed on a standard nanodispersion in order to determine the anisotropy of the liquid crystalline structure and the mean diameter of the nanoparticles, respectively. Small angle X-ray diffraction (SAXRD) was used to verify the influence of drug loading and additives on the liquid crystalline structure of the nanodispersions. The samples, before and after the addition of PSs and additives, were stable over 90 days, as verified by dynamic light scattering. SAXRD revealed that despite the alteration observed in some of the samples analyzed in the presence of photosensitizing drugs and additives, the hexagonal phase still remained in the crystalline phase. Copyright © 2011 Wiley-Liss, Inc. and the American Pharmacists Association

  15. Quasi-Liquid Crystalline Materials with Special Electro-Optic Properties.

    DTIC Science & Technology

    1987-11-01

    of the US Army we have described a new type of organic material, quasi- liquid crystals (QLC’s) obtained by us from thermochromic spiropyrans with...is intended only for the internal management use of the Contractor and the U.S. Government". ABSTRACT Photo/ thermochromic liquid crystals and liquid ...34. During the past four months the studies on the project have been concentrated on examination of nonlinear optical properties of Quasi- liquid crystals

  16. Tilted Orientation of Photochromic Dyes with Guest-Host Effect of Liquid Crystalline Polymer Matrix for Electrical UV Sensing

    PubMed Central

    Ranjkesh, Amid; Park, Min-Kyu; Park, Do Hyuk; Park, Ji-Sub; Choi, Jun-Chan; Kim, Sung-Hoon; Kim, Hak-Rin

    2015-01-01

    We propose a highly oriented photochromic dye film for an ultraviolet (UV)-sensing layer, where spirooxazine (SO) derivatives are aligned with the liquid crystalline UV-curable reactive mesogens (RM) using a guest-host effect. For effective electrical UV sensing with a simple metal-insulator-metal structure, our results show that the UV-induced switchable dipole moment amount of the SO derivatives is high; however, their tilting orientation should be controlled. Compared to the dielectric layer with the nearly planar SO dye orientation, the photochromic dielectric layer with the moderately tilted dye orientation shows more than seven times higher the UV-induced capacitance variation. PMID:26729116

  17. One-step facile synthesis of noble metal nanocrystals with tunable morphology in a nematic liquid crystalline medium

    SciTech Connect

    Dan, Kaustabh; Satpati, Biswarup; Datta, Alokmay

    2016-05-23

    The present study describes in-situ synthesis of noble metal nano structures (MNCs) (Au and Ag) within a nematic liquid crystalline medium MBBA [N-(4-methoxybenzylidene)-4-butylaniline] without using any seed mediated growth protocol or without using any external stabilizing or reducing agent. Detailed Transmission Electron Microscopy (TEM) study indicates that apart from Kinetic based mechanism, the thermodynamical parameters also influence greatly the morphological evolution of these MNCs. The MNCs are of diverse shapes including nano prisms, hexagons, urchins, cubes, and rods which depend on the time of reaction and the choice of nanoparticle precursor.

  18. Tilted Orientation of Photochromic Dyes with Guest-Host Effect of Liquid Crystalline Polymer Matrix for Electrical UV Sensing.

    PubMed

    Ranjkesh, Amid; Park, Min-Kyu; Park, Do Hyuk; Park, Ji-Sub; Choi, Jun-Chan; Kim, Sung-Hoon; Kim, Hak-Rin

    2015-12-29

    We propose a highly oriented photochromic dye film for an ultraviolet (UV)-sensing layer, where spirooxazine (SO) derivatives are aligned with the liquid crystalline UV-curable reactive mesogens (RM) using a guest-host effect. For effective electrical UV sensing with a simple metal-insulator-metal structure, our results show that the UV-induced switchable dipole moment amount of the SO derivatives is high; however, their tilting orientation should be controlled. Compared to the dielectric layer with the nearly planar SO dye orientation, the photochromic dielectric layer with the moderately tilted dye orientation shows more than seven times higher the UV-induced capacitance variation.

  19. One-step facile synthesis of noble metal nanocrystals with tunable morphology in a nematic liquid crystalline medium

    NASA Astrophysics Data System (ADS)

    Dan, Kaustabh; Satpati, Biswarup; Datta, Alokmay

    2016-05-01

    The present study describes in-situ synthesis of noble metal nano structures (MNCs) (Au and Ag) within a nematic liquid crystalline medium MBBA [N-(4-methoxybenzylidene)-4-butylaniline] without using any seed mediated growth protocol or without using any external stabilizing or reducing agent. Detailed Transmission Electron Microscopy (TEM) study indicates that apart from Kinetic based mechanism, the thermodynamical parameters also influence greatly the morphological evolution of these MNCs. The MNCs are of diverse shapes including nano prisms, hexagons, urchins, cubes, and rods which depend on the time of reaction and the choice of nanoparticle precursor.

  20. Alternation of Side-Chain Mesogen Orientation Caused by the Backbone Structure in Liquid-Crystalline Polymer Thin Films.

    PubMed

    Tanaka, Daisuke; Nagashima, Yuki; Hara, Mitsuo; Nagano, Shusaku; Seki, Takahiro

    2015-10-27

    In side-chain-type liquid-crystalline (LC) polymers, the main chain rigidity significantly affects the LC structure and properties. We show herein a relevant new effect regarding the orientation of side-chain mesogenic groups of LC polymers in a thin-film state. A subtle change in the main chain structure, i.e., polyacrylate and polymethacrylate, leads to a clear alternation of mesogens in the homeotropic and planar modes, respectively. This orientational discrimination is triggered from the free surface region (film-air interface) as revealed by surface micropatterning via inkjet printing.

  1. Effect of Morphology on Ion Transport in Polymerized Ionic Liquid Block Copolymers

    NASA Astrophysics Data System (ADS)

    Choi, Jae-Hong; Ye, Yuesheng; Elabd, Yossef; Winey, Karen

    2013-03-01

    We investigate the impact of morphology on ion transport in single-ion conductor polymerized ionic liquid (PIL) diblock copolymers. The morphology for two types of PIL block copolymers with different degrees of miscibility between blocks was studied using small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). For poly(methyl methacrylate-b-1-[(2-methacryloyloxy)ethyl]-3-butylimidazolium-bis(trifluoromethylsulfonyl)imide) (MMA-b-MEBIm-TFSI) PIL diblock copolymers, the partial miscibility between the MEBIm-TFSI and MMA blocks resulted in a weakly microphase-separated morphology without long-range order. In poly(styrene-b-1-[(2-acryloyloxy)ethyl]-3-butylimidazolium-TFSI) (S-b-AEBIm-TFSI) PIL block copolymers, a variety of self-assembled nanostructures including hexagonally packed cylinders, lamellae, and coexisting lamellae and network morphologies were observed by varying PIL composition. A comparison of ionic conductivity between PMMA- and PS-based PIL block copolymers suggests that strong microphase separation with well-defined structures can improve ionic conductivity. The local ion concentration and connectivity of the conducting microdomains also play an important role in ion conduction in these PIL block copolymers.

  2. Evidence for phospholipid microdomain formation in liquid crystalline liposomes reconstituted with Escherichia coli lactose permease.

    PubMed Central

    Lehtonen, J Y; Kinnunen, P K

    1997-01-01

    vesicles lacking the reconstituted protein only 40% quenching was evident. The addition of 1,2-dipalmitoyl-sn-glycero-3-phospho-rac'-glycerol (DPPG) decreased IE/IM for PPDPC, revealing the driving force for the lateral segregation of this probe to become attenuated. More specifically for protein-free bilayers at XDPPG = 0.10 the rate of lateral diffusion of PPDPC in POPG is diminished, as evidenced by the 24% decrement in IE/IM, under these conditions the increase in IE/IM due to lac permease was strongly reduced, by approximately 84%. The present data are interpreted in terms of the hydrophobic mismatch theory, which predicts that integral membrane proteins will draw lipids of similar hydrophobic thickness into their vicinity. In brief, the approximate lengths of most of the predicted 12 hydrophobic, membrane-spanning alpha-helical segments of lactose permease range between 28.5 and 37.5 A and thus exceed the hydrophobic thickness of POPG of approximately 25.8 A. Therefore, to reduce the free energy of the assembly, longer lipids such as PPDPC and DPPF are accumulated in the immediate vicinity of lactose permease in fluid, liquid crystalline POPG bilayers. PMID:9138570

  3. Mechanically Tunable, Readily Processable Ion Gels by Self-Assembly of Block Copolymers in Ionic Liquids.

    PubMed

    Lodge, Timothy P; Ueki, Takeshi

    2016-10-05

    Room temperature ionic liquids are of great interest for many advanced applications, due to the combination of attractive physical properties with essentially unlimited tunability of chemical structure. High chemical and thermal stability, favorable ionic conductivity, and complete nonvolatility are just some of the most important physical characteristics that make ionic liquids promising candidates for emerging technologies. Examples include separation membranes, actuators, polymer gel electrolytes, supercapacitors, ion batteries, fuel cell membranes, sensors, printable plastic electronics, and flexible displays. However, in these and other applications, it is essential to solidify the ionic liquid, while retaining the liquid state properties of interest. A broadly applicable solidification strategy relies on gelation by addition of suitable triblock copolymers with the ABA architecture, producing ion gels or ionogels. In this paradigm, the A end blocks are immiscible with the ionic liquid, and consequently self-assemble into micellar cores, while some fraction of the well-solvated B midblocks bridge between micelles, forming a percolating network. The chemical structures of the A and B repeat units, the molar mass of the blocks, and the concentration of the copolymer in the ionic liquid are all independently tunable to attain desired property combinations. In particular, the modulus of the resulting ion gel can be readily varied between 100 Pa and 1 MPa, with little sacrifice of the transport properties of the ionic liquid, such as ionic conductivity or gas diffusivity. Suitable A blocks can impart thermoreversible gelation (with solidification either on heating or cooling) or even photoreversible gelation. By virtue of the nonvolatility of ionic liquids, a wide range of processing strategies can be employed directly to prepare ion gels in thin or thick film forms, including solvent casting, spin coating, aerosol jet printing, photopatterning, and transfer

  4. Three-dimensional patterning of solid microstructures through laser reduction of colloidal graphene oxide in liquid-crystalline dispersions.

    PubMed

    Senyuk, Bohdan; Behabtu, Natnael; Martinez, Angel; Lee, Taewoo; Tsentalovich, Dmitri E; Ceriotti, Gabriel; Tour, James M; Pasquali, Matteo; Smalyukh, Ivan I

    2015-05-21

    Graphene materials and structures have become an essential part of modern electronics and photovoltaics. However, despite many production methods, applications of graphene-based structures are hindered by high costs, lack of scalability and limitations in spatial patterning. Here we fabricate three-dimensional functional solid microstructures of reduced graphene oxide in a lyotropic nematic liquid crystal of graphene oxide flakes using a pulsed near-infrared laser. This reliable, scalable approach is mask-free, does not require special chemical reduction agents, and can be implemented at ambient conditions starting from aqueous graphene oxide flakes. Orientational ordering of graphene oxide flakes in self-assembled liquid-crystalline phases enables laser patterning of complex, three-dimensional reduced graphene oxide structures and colloidal particles, such as trefoil knots, with 'frozen' orientational order of flakes. These structures and particles are mechanically rigid and range from hundreds of nanometres to millimetres in size, as needed for applications in colloids, electronics, photonics and display technology.

  5. Ionic liquid, glass or crystalline solid? Structures and thermal behaviour of (C4mim)2CuCl3.

    PubMed

    Zürner, Philipp; Schmidt, Horst; Bette, Sebastian; Wagler, Jörg; Frisch, Gero

    2016-02-28

    The ionic liquid (C4mim)2CuCl3 was synthesised from a mixture of copper(i) chloride and 1-butyl-3-methylimidazolium chloride (C4mimCl) and investigated using crystallographic and thermoanalytical methods. In the crystalline state, the compound consists of C4mim(+) cations and triangular [CuCl3](2-) anions and forms three different modifications, which are connected through phase transitions at 227 and 203 K. The high and intermediate temperature phases crystallise in the space group C2, whereas the low temperature phase exhibits the space group P21. The three crystal structures are related through an isomorphic and a klassengleiche symmetry transition, respectively. The solid undergoes congruent melting at 320 K. The enthalpy of fusion was determined to be 25.7 kJ mol(-1). The melting process is irreversible and the ionic liquid can be supercooled to its glass transition at 221 K.

  6. The Distribution of Crystalline Hematite on Mars from the Thermal Emission Spectrometer: Evidence for Liquid Water

    NASA Technical Reports Server (NTRS)

    Christensen, P. R.; Malin, M.; Morris, D.; Bandfield, J.; Lane, M.; Edgett, K.

    2000-01-01

    Crystalline hematite on Mars has been mapped using the MGS TES. Two major, and several minor areas of significant accumulation are identified. We favor precipitation models involving Fe-rich water, providing direct mineralogic evidence for large-scale water interactions.

  7. Presence of retained crystalline seed necessary for bicrystal-liquid-bicrystal phase transformation

    NASA Astrophysics Data System (ADS)

    Vijay Reddy, K.; Meraj, Md.; Pal, Snehanshu

    2017-10-01

    Regaining of the original bicrystal structure during solidification after melting is found to be possible only if a fraction of crystalline seed is retained in the melt as per this molecular dynamics study. The effect of cooling rate on retaining the crystalline seed is also investigated. The bicrystal specimen is heated up to 1850 K with a constant heating rate of 3.5 K ps-1 and instantly cooled with different cooling rates i.e. 1 K ps-1, 5 K ps-1, 10 K ps-1, 15 K ps-1 and 20 K ps-1. It has been observed through total energy analysis that specimen cooled with 1 K ps-1 cooling rate dissipates the energy throughout the specimen causing randomization of atoms resulting into disappearance of the crystalline seed and formation of nanocrystalline structure. Whereas comparatively higher cooling rates does not allow complete dissipation of energy and retain the crystalline seed thus transform into bicrystal. It has been found through Voronoi polyhedra analysis that during slower cooling rate, icosahedral clusters are formed which play a vital role in formation of nanocrystalline structure.

  8. The Distribution of Crystalline Hematite on Mars from the Thermal Emission Spectrometer: Evidence for Liquid Water

    NASA Technical Reports Server (NTRS)

    Christensen, P. R.; Malin, M.; Morris, D.; Bandfield, J.; Lane, M.; Edgett, K.

    2000-01-01

    Crystalline hematite on Mars has been mapped using the MGS TES. Two major, and several minor areas of significant accumulation are identified. We favor precipitation models involving Fe-rich water, providing direct mineralogic evidence for large-scale water interactions.

  9. Thermal Properties and Crystallite Morphology of Nylon 66 Modified with a Novel Biphenyl Aromatic Liquid Crystalline Epoxy Resin

    PubMed Central

    Cai, Zhiqi; Mei, Shuang; Lu, Yuan; He, Yuanqi; Pi, Pihui; Cheng, Jiang; Qian, Yu; Wen, Xiufang

    2013-01-01

    In order to improve the thermal properties of important engineering plastics, a novel kind of liquid crystalline epoxy resin (LCER), 3,3′,5,5′-Tetramethylbiphenyl-4,4′-diyl bis(4-(oxiran-2-ylmethoxy)benzoate) (M1) was introduced to blend with nylon 66 (M2) at high temperature. The effects of M1 on chemical modification and crystallite morphology of M2 were investigated by rheometry, thermo gravimetric analysis (TGA), dynamic differential scanning calorimetry (DSC) and polarized optical microscopy (POM). TGA results showed that the initial decomposition temperature of M2 increased by about 8 °C by adding 7% wt M1, indicating the improvement of thermal stability. DSC results illustrated that the melting point of composites decreased by 12 °C compared to M2 as the content of M1 increased, showing the improvement of processing property. POM measurements confirmed that dimension of nylon-66 spherulites and crystallization region decreased because of the addition of liquid crystalline epoxy M1. PMID:24132153

  10. Thermal properties and crystallite morphology of nylon 66 modified with a novel biphenyl aromatic liquid crystalline epoxy resin.

    PubMed

    Cai, Zhiqi; Mei, Shuang; Lu, Yuan; He, Yuanqi; Pi, Pihui; Cheng, Jiang; Qian, Yu; Wen, Xiufang

    2013-10-15

    In order to improve the thermal properties of important engineering plastics, a novel kind of liquid crystalline epoxy resin (LCER), 3,3',5,5' -Tetramethylbiphenyl-4,4' -diyl bis(4-(oxiran-2-ylmethoxy)benzoate) (M1) was introduced to blend with nylon 66 (M2) at high temperature. The effects of M1 on chemical modification and crystallite morphology of M2 were investigated by rheometry, thermo gravimetric analysis (TGA), dynamic differential scanning calorimetry (DSC) and polarized optical microscopy (POM). TGA results showed that the initial decomposition temperature of M2 increased by about 8 °C by adding 7% wt M1, indicating the improvement of thermal stability. DSC results illustrated that the melting point of composites decreased by 12 °C compared to M2 as the content of M1 increased, showing the improvement of processing property. POM measurements confirmed that dimension of nylon-66 spherulites and crystallization region decreased because of the addition of liquid crystalline epoxy M1.

  11. Design and Characterization of a Novel p1025 Peptide-Loaded Liquid Crystalline System for the Treatment of Dental Caries.

    PubMed

    Calixto, Giovana Maria Fioramonti; Garcia, Matheus Henrique; Cilli, Eduardo Maffud; Chiavacci, Leila Aparecida; Chorilli, Marlus

    2016-01-28

    Dental caries, mainly caused by the adhesion of Streptococcus mutans to pellicle-coated tooth surfaces, is an important public health problem worldwide. A synthetic peptide (p1025) corresponding to residues 1025-1044 of the adhesin can inhibit this binding. Peptides are particularly susceptible to the biological environment; therefore, a p1025 peptide-loaded liquid crystalline system (LCS) consisting of tea tree oil as the oil phase, polyoxypropylene-(5)-polyoxyethylene-(20)-cetyl alcohol as the surfactant, and water or 0.5% polycarbophil polymer dispersions as the aqueous phase was employed as a drug delivery platform. This system exhibited anticaries and bioadhesive properties and provided a protective environment to p1025 at the site of action, thereby modulating its action, prolonging its contact with the teeth, and decreasing the frequency of administration. LCSs were characterized by polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), and rheological, texture, and bioadhesive tests. PLM and SAXS revealed the presence of hexagonal liquid crystalline phases and microemulsions. Rheological analyses demonstrated that the addition of polymer dispersions favored characteristics such as shear thinning and thixotropy, hence improving buccal application. Bioadhesion tests showed that polymer dispersions contributed to the adhesion onto the teeth. Taken together, LCS could provide a novel pharmaceutical nanotechnology platform for dental caries treatment.

  12. Gold Nanoparticle Clusters in Quasinematic Layers of Liquid-Crystalline Dispersion Particles of Double-Stranded Nucleic Acids

    PubMed Central

    Yevdokimov, Yu.M.; Salyanov, V.I.; Katz, E.I.; Skuridin, S.G.

    2012-01-01

    The interaction between gold nanoparticles and particles of cholesteric liquid-crystalline dispersions formed by double-stranded DNA and poly(I)×poly(C) molecules is considered. It is shown that small-sized (~ 2 nm) gold nanoparticles induce two different structural processes. First, they facilitate the reorganization of the spatial cholesteric structure of the particles into a nematic one. This process is accompanied by a fast decrease in the amplitude of an abnormal band in the CD spectrum. Second, they induce cluster formation in a “free space” between neighboring nucleic acid molecules fixed in the structure of the quasinematic layers of liquid-crystalline particles. This process is accompanied by slow development of the surface plasmon resonance band in the visible region of the absorption spectrum. Various factors influencing these processes are outlined. Some assumptions concerning the possible mechanism(s) of fixation of gold nanoparticles between the neighboring double-stranded nucleic acid molecules in quasinematic layers are formulated. PMID:23346383

  13. Ionic liquid and plastic crystalline phases of pyrazolium imide salts as electrolytes for rechargeable lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Abu-Lebdeh, Yaser; Abouimrane, Ali; Alarco, Pierre-Jean; Armand, Michel

    A new member of the plastic crystal, pyrazolium imide family, N, N‧-diethyl-3-methylpyrazolium bis-(trifluoromethanesulfonyl)imide (DEMPyr123) was prepared. It showed a single, plastic crystalline phase that extends from 4.2 °C to its melting at 11.3 °C. When 10 mol% LiTFSI salt was added, the mixture showed ionic conductivities reaching 1.7 × 10 -3 S cm -1 at 20 °C, in the liquid state and 6.9 × 10 -4 S cm -1 at 5 °C, in the solid, plastic phase. A wide electrochemical stability window's of 5.5 V was observed by cyclic voltammetry of the molten salt mixture. Batteries were assembled with LiFePO 4/Li 4Ti 5O 12 electrodes and the salt mixture as an electrolyte. They showed a charge/discharge efficiency of 93% and 87% in the liquid and the plastic phase, respectively. The capacity retention was very good in both states with 90% of the initial capacity still available after 40 cycles. In general, the batteries showed good rate capability and cycle life performance in the ionic liquid phase that were sustained when the electrolyte transformed to the plastic phase. Comparison of the battery results with those of a classic (non-plastic crystal) ionic liquid has proven the advantage of the dual state of matter character in this electrolyte.

  14. Photochromic Composite for Random Lasing Based on Porous Polypropylene Infiltrated with Azobenzene-Containing Liquid Crystalline Mixture.

    PubMed

    Lisinetskii, Victor; Ryabchun, Alexander; Bobrovsky, Alexey; Schrader, Sigurd

    2015-12-09

    We report on a new low-cost and easily fabricated type of liquid crystalline polymer composites demonstrating low threshold random lasing, which can be used as a cheap and simple mirror-less laser source. The composite is based on mass-producible commercially available porous polypropylene (Celgard 2500) infiltrated with low-molar-mass liquid crystal material doped with Rhodamine 800 laser dye. Excitation with red nanosecond laser (630 nm) induces random lasing with the emission peak in NIR spectral range (804 nm) with noticeable degree of linear polarization. The possibility to control the lasing threshold and polarization of the output light with UV radiation through photoswitching of liquid crystal phase from nematic to isotropic is demonstrated. The photocontrollable phase switching is achieved by reversible E/Z isomerization of the azobenzene dopant introduced to the nematic host matrix. It is revealed that the isotropic state of liquid crystal provides more efficient random lasing with lower threshold due to significant scattering of the ordinary wave.

  15. Light chain crystalline kidney disease: diagnostic urine microscopy as the "liquid kidney biopsy".

    PubMed

    Luciano, Randy L; Castano, Ekaterina; Fogazzi, Giovanni B; Perazella, Mark A

    2014-12-01

    Multiple myeloma (MM) is a plasma cell disorder, which often causes parenchymal kidney disease. Light chain (LC) cast nephropathy represents the most common renal lesion. In some instances, LC crystals precipitate within renal tubular lumens and deposit within proximal tubular cell cytoplasms. Importantly, urine microscopy in such patients can provide insight into the underlying LC-related lesion. Here we present two patients with MM complicated by acute kidney injury (AKI) where LC crystalline casts were observed on urinary sediment analysis. Kidney biopsy revealed acute tubular injury with LC crystal casts within both tubular lumens and renal tubular epithelial cell cytoplasms. These findings suggest that the urinary sediment may be a non-invasive way to diagnose LC crystalline-induced AKI in patients with MM.

  16. Minimalistic Liquid-Assisted Route to Highly Crystalline α-Zirconium Phosphate.

    PubMed

    Cheng, Yu; Wang, Xiaodong Tony; Jaenicke, Stephan; Chuah, Gaik-Khuan

    2017-08-24

    Zirconium phosphates have potential applications in areas of ion exchange, catalysis, photochemistry, and biotechnology. However, synthesis methodologies to form crystalline α-zirconium phosphate (Zr(HPO4 )2 ⋅H2 O) typically involve the use of excess phosphoric acid, addition of HF or oxalic acid and long reflux times or hydrothermal conditions. A minimalistic sustainable route to its synthesis has been developed by using only zirconium oxychloride and concentrated phosphoric acid to form highly crystalline α-zirconium phosphate within hours. The morphology can be changed from platelets to rod-shaped particles by fluoride addition. By varying the temperature and time, α-zirconium phosphate with particle sizes from nanometers to microns can be obtained. Key features of this minimal solvent synthesis are the excellent yields obtained with high atom economy under mild conditions and ease of scalability. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Three-dimensional positioning and control of colloidal objects utilizing engineered liquid crystalline defect networks

    PubMed Central

    Yoshida, H.; Asakura, K.; Fukuda, J.; Ozaki, M.

    2015-01-01

    Topological defects in liquid crystals not only affect the optical and rheological properties of the host, but can also act as scaffolds in which to trap nano or micro-sized colloidal objects. The creation of complex defect shapes, however, often involves confining the liquid crystals in curved geometries or adds complex-shaped colloidal objects, which are unsuitable for device applications. Using topologically patterned substrates, here we demonstrate the controlled generation of three-dimensional defect lines with non-trivial shapes and even chirality, in a flat slab of nematic liquid crystal. By using the defect lines as templates and the electric response of the liquid crystals, colloidal superstructures are constructed, which can be reversibly reconfigured at a voltage as low as 1.3 V. Three-dimensional engineering of the defect shapes in liquid crystals is potentially useful in the fabrication of self-healing composites and in stabilizing artificial frustrated phases. PMID:25994837

  18. Three-dimensional positioning and control of colloidal objects utilizing engineered liquid crystalline defect networks.

    PubMed

    Yoshida, H; Asakura, K; Fukuda, J; Ozaki, M

    2015-05-21

    Topological defects in liquid crystals not only affect the optical and rheological properties of the host, but can also act as scaffolds in which to trap nano or micro-sized colloidal objects. The creation of complex defect shapes, however, often involves confining the liquid crystals in curved geometries or adds complex-shaped colloidal objects, which are unsuitable for device applications. Using topologically patterned substrates, here we demonstrate the controlled generation of three-dimensional defect lines with non-trivial shapes and even chirality, in a flat slab of nematic liquid crystal. By using the defect lines as templates and the electric response of the liquid crystals, colloidal superstructures are constructed, which can be reversibly reconfigured at a voltage as low as 1.3 V. Three-dimensional engineering of the defect shapes in liquid crystals is potentially useful in the fabrication of self-healing composites and in stabilizing artificial frustrated phases.

  19. Confined Discotic Liquid Crystalline Self-Assembly in a Novel Coil-Coil-Disk Triblock Oligomer

    NASA Astrophysics Data System (ADS)

    Cui, Li; Sics, Igors

    2005-03-01

    An asymmetric ABC coil-coil-disk triblock oligomer, based on polyethylene-block-poly(ethylene oxide)-block-pentakis(pentyloxy)triphenylene (PE-b-PEO-b-P5T or EEO-P5T), was successfully synthesized by coupling a hydroxyl group terminated PE-b-PEO diblock oligomer and 2-hydroxy-3,6,7,10,11-pentakis(pentyloxy)triphenylene using oxalyl chloride. The structure and morphology of supramolecular self-assembly in bulk EEO-P5T was studied by small- and wide-angle X-ray scatterings and transmission electron microscopy. The PE block was found to crystallize into interdigitated, extended chain crystals with a chain-tilting angle of 23^o from the lamellar normal, where their melting temperature (Tm) was at 93.8^o C. The PEO block remained in the amorphous state because both its ends were tethered to other two blocks. Bilayer P5Ts, sandwiched between amorphous PEO layers, exhibited a nematic columnar (Ncol) to nematic discotic (ND) transition at ca. 23^o C. Intriguingly, the ND to isotropic (or vise versa) transition was observed to coincide with the melting (or crystallization) of the PE block.

  20. Examination of the electronic structure of crystalline and liquid Al versus temperature by in situ electron energy-loss spectroscopy (EELS).

    PubMed

    Palanisamy, Prakash; Jong, Maarten de; Asta, Mark; Howe, James M

    2015-09-01

    Electron energy-loss near-edge structure (ELNES) analysis using in situ heating in a transmission electron microscope (TEM) was performed to compare the electronic structure of crystalline and liquid Al versus temperature. It was found that the ELNES features in the L2,3 edges of crystalline and liquid Al are qualitatively similar, but that the edge threshold is modified and certain features in the energy range between 102 and 115eV vanish in the liquid, indicating that partial DOS is quantitatively different. Broadening of the L2,3 edge maximum for Al with temperature indicates a decay in the centrifugal barrier for the 2p electrons with increasing temperature. Comparison between the ELNES edge in supercooled liquid and crystalline Al at the same temperature of 600°C shows that the degree of order, i.e., crystallinity, plays an important role in determining the DOS. The ELNES edge of supercooled liquid Al closely resembles that of superheated liquid Al. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Ionothermal synthesis--ionic liquids as functional solvents in the preparation of crystalline materials.

    PubMed

    Morris, Russell E

    2009-06-07

    Ionothermal synthesis is the use of ionic liquids simultaneously as both the solvent and potential template or structure directing agent in the formation of solids. It directly parallels hydrothermal synthesis where the solvent is water. In this feature article I discuss the general features of ionothermal synthesis and how the properties of the synthesis differ from those of other synthetic methodologies. In particular, I will discuss the role of the ionic liquid anion in determining the structure of the synthesised solid, the role of mineralisers such as water and fluoride, and the targeted use of unstable ionic liquids to produce new inorganic and inorganic-organic hybrid materials.

  2. Synthesis and Characterization of Liquid Crystalline Poly((N-acylethyleneimine)s.

    DTIC Science & Technology

    1986-10-01

    8217%-,% , . . . % .% . . " ’% ’ # ./ / ." ’ z ’%’z . ’’ .’ ’ ’ 4. Ethyl-5-(4-phenylphenoxy)Valerate (BiPh-4-COO~t) 4- Phenylphenol (8g, 0.04 mol) and 1.656g (0.04...vacuum. The sodium salt of 4- phenylphenol was put Into 120 al of dried dimethylformamide and 8.5 .l (0.054 mol) of ethyl-5-bromovalerate and l.4g (10...that poly(BiPh-4-Oxz) is crystalline. This is not an unexpected result. The insertion of 4- phenylphenol as side group in polymers before, did give

  3. Ionic Conductivity and Gas Permeability of Polymerized Ionic Liquid Block Copolymer Membranes

    NASA Astrophysics Data System (ADS)

    Evans, Christopher; Sanoja, Gabriel; Schneider, Yanika; Modestino, Miguel; Segalman, Rachel; Joint CenterArtificial Photosynthesis Team

    2014-03-01

    Polymer membranes for many energy applications, such as solar-to-hydrogen fuel production, require ionic conductivity while acting as gas diffusion barriers. We have synthesized a diblock copolymer consisting of poly(styrene-block-(4-(2-methacrylamidoethyl)-imidazolium trifluoroacetate) by treating poly(styrene-block-histamine methacrylamide) (PS- b-PHMA) with trifluoroacetic acid. The PS block serves as the structural support while the imidazolium derivative is an ion conducting polymerized ionic liquid (PIL). Small angle X-ray scattering and transmission electron microscopy demonstrate that the block copolymer self-assembles into well-ordered nanostructures, with lamellae and hexagonally packed cylindrical morphologies. The ionic conductivities of the PS-b-PHMA materials were as high as 2 x 10-4 S/cm while an order of magnitude increase in conductivity was observed upon conversion to PS-b-PIL. The ionic conductivity of the PS-b-PIL increased by a factor of ~ 4 up to 1.2 x 10-3 S/cm as the PIL domain size increased from 20 to 40 nm. These insights allow for the rational design of high performance ion conducting membranes with even greater conductivities via precise morphological control. Additionally, the role of thermal annealing on the ionic conductivity and gas permeability of copolymer membranes was investigated.

  4. Effect of emulsifiers and their liquid crystalline structures in emulsions on dermal and transdermal delivery of hydroquinone, salicylic acid and octadecenedioic acid.

    PubMed

    Otto, A; Wiechers, J W; Kelly, C L; Dederen, J C; Hadgraft, J; du Plessis, J

    2010-01-01

    This study investigated the effect of emulsifiers and their liquid crystalline structures on the dermal and transdermal delivery of hydroquinone (HQ), salicylic acid (SA) and octadecenedioic acid (DIOIC). Emulsions containing liquid crystalline phases were compared with an emulsion without liquid crystals. Skin permeation experiments were performed using Franz-type diffusion cells and human abdominal skin dermatomed to a thickness of 400 mum. The results indicate that emulsifiers arranging in liquid crystalline structures in the water phase of the emulsion enhanced the skin penetration of the active ingredients with the exception of SA. SA showed a different pattern of percutaneous absorption, and no difference in dermal and transdermal delivery was observed between the emulsions with and without liquid crystalline phases. The increase in skin penetration of HQ and DIOIC could be attributed to an increased partitioning of the actives into the skin. It was hypothesized that the interaction between the different emulsifiers and active ingredients in the formulations varied and, therefore, the solubilization capacities of the various emulsifiers and their association structures.

  5. Modulatory effect of human plasma on the internal nanostructure and size characteristics of liquid-crystalline nanocarriers.

    PubMed

    Azmi, Intan Diana Mat; Wu, Linping; Wibroe, Peter Popp; Nilsson, Christa; Østergaard, Jesper; Stürup, Stefan; Gammelgaard, Bente; Urtti, Arto; Moghimi, Seyed Moein; Yaghmur, Anan

    2015-05-12

    The inverted-type liquid-crystalline dispersions comprising cubosomes and hexosomes hold much potential for drug solubilization and site-specific targeting on intravenous administration. Limited information, however, is available on the influence of plasma components on nanostructural and morphological features of cubosome and hexosome dispersions, which may modulate their stability in the blood and their overall biological performance. Through an integrated approach involving SAXS, cryo-TEM, and nanoparticle tracking analysis (NTA) we have studied the time-dependent effect of human plasma (and the plasma complement system) on the integrity of the internal nanostructure, morphology, and fluctuation in size distribution of phytantriol (PHYT)-based nonlamellar crystalline dispersions. The results indicate that in the presence of plasma the internal nanostructure undergoes a transition from the biphasic phase (a bicontinuous cubic phase with symmetry Pn3m coexisting with an inverted-type hexagonal (H2) phase) to a neat hexagonal (H2) phase, which decreases the median particle size. These observations were independent of a direct effect by serum albumin and dispersion-mediated complement activation. The implication of these observations in relation to soft nanocarrier design for intravenous drug delivery is discussed.

  6. Comparison of drug release from liquid crystalline monoolein dispersions and solid lipid nanoparticles using a flow cytometric technique

    PubMed Central

    Dawoud, Mohamed Z.; Nasr, Mohamed

    2016-01-01

    Colloidal lipid particles such as solid lipid nanoparticles and liquid crystalline nanoparticles have great opportunities as drug carriers especially for lipophilic drugs intended for intravenous administration. In order to evaluate drug release from these nanoparticles and determine their behavior after administration, emulsion droplets were used as a lipophilic compartment to which the transfer of a model drug was measured. The detection of the model drug transferred from monoolein cubic particles and trimyristin solid lipid nanoparticles into emulsion droplets was performed using a flow cytometric technique. A higher rate and amount of porphyrin transfer from the solid lipid nanoparticles compared to the monoolein cubic particles was observed. This difference might be attributed to the formation of a highly ordered particle which leads to the expulsion of drug to the surface of the crystalline particle. Furthermore, the sponge-like structure of the monoolein cubic particles decreases the rate and amount of drug transferred. In conclusion, the flow cytometric technique is a suitable technique to study drug transfer from these carriers to large lipophilic acceptors. Monoolein cubic particles with their unique structure can be used successfully as a drug carrier with slow drug release compared with trimyristin nanoparticles. PMID:27006901

  7. Titanium dioxide/silicon hole-blocking selective contact to enable double-heterojunction crystalline silicon-based solar cell

    NASA Astrophysics Data System (ADS)

    Nagamatsu, Ken A.; Avasthi, Sushobhan; Sahasrabudhe, Girija; Man, Gabriel; Jhaveri, Janam; Berg, Alexander H.; Schwartz, Jeffrey; Kahn, Antoine; Wagner, Sigurd; Sturm, James C.

    2015-03-01

    In this work, we use an electron-selective titanium dioxide (TiO2) heterojunction contact to silicon to block minority carrier holes in the silicon from recombining at the cathode contact of a silicon-based photovoltaic device. We present four pieces of evidence demonstrating the beneficial effect of adding the TiO2 hole-blocking layer: reduced dark current, increased open circuit voltage (VOC), increased quantum efficiency at longer wavelengths, and increased stored minority carrier charge under forward bias. The importance of a low rate of recombination of minority carriers at the Si/TiO2 interface for effective blocking of minority carriers is quantitatively described. The anode is made of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) heterojunction to silicon which forms a hole selective contact, so that the entire device is made at a maximum temperature of 100 °C, with no doping gradients or junctions in the silicon. A low rate of recombination of minority carriers at the Si/TiO2 interface is crucial for effective blocking of minority carriers. Such a pair of complementary carrier-selective heterojunctions offers a path towards high-efficiency silicon solar cells using relatively simple and near-room temperature fabrication techniques.

  8. Titanium dioxide/silicon hole-blocking selective contact to enable double-heterojunction crystalline silicon-based solar cell

    SciTech Connect

    Nagamatsu, Ken A. Man, Gabriel; Jhaveri, Janam; Berg, Alexander H.; Kahn, Antoine; Wagner, Sigurd; Sturm, James C.; Avasthi, Sushobhan; Sahasrabudhe, Girija; Schwartz, Jeffrey

    2015-03-23

    In this work, we use an electron-selective titanium dioxide (TiO{sub 2}) heterojunction contact to silicon to block minority carrier holes in the silicon from recombining at the cathode contact of a silicon-based photovoltaic device. We present four pieces of evidence demonstrating the beneficial effect of adding the TiO{sub 2} hole-blocking layer: reduced dark current, increased open circuit voltage (V{sub OC}), increased quantum efficiency at longer wavelengths, and increased stored minority carrier charge under forward bias. The importance of a low rate of recombination of minority carriers at the Si/TiO{sub 2} interface for effective blocking of minority carriers is quantitatively described. The anode is made of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) heterojunction to silicon which forms a hole selective contact, so that the entire device is made at a maximum temperature of 100 °C, with no doping gradients or junctions in the silicon. A low rate of recombination of minority carriers at the Si/TiO{sub 2} interface is crucial for effective blocking of minority carriers. Such a pair of complementary carrier-selective heterojunctions offers a path towards high-efficiency silicon solar cells using relatively simple and near-room temperature fabrication techniques.

  9. Reinfiltration through liquid bridges formed between two matrix blocks in fractured rocks

    NASA Astrophysics Data System (ADS)

    Dejam, Morteza; Hassanzadeh, Hassan; Chen, Zhangxin

    2014-11-01

    Liquid reinfiltration is a significant process, which can considerably retard and slowdown the transport of oil, water and contaminants in fractured subsurface formations. However, accurate modeling of the reinfiltration via liquid bridges formed in a horizontal fracture or space between two rock porous blocks remains a controversial topic. In an attempt to improve an understanding of the problem, the reinfiltration from upper to lower matrix blocks through formation of liquid bridges is theoretically modeled by using generalization of the Lucas-Washburn theory for a porous medium, which takes into account pressure differences due to matrix capillary, gravity, inertia, viscous, and fracture capillary forces. The developed model results in a second-order nonlinear ordinary differential equation (ODE), which is solved numerically to obtain depth and rate of the reinfiltrated liquid versus time. The results showed that three reinfiltration regimes: including Early Time Regime (ETR) (z ∼ t, q = constant), Middle Time Regime (MTR) (z ∼ √{ t } , q ∼ 1 /√{ t }) and Late Time Regime (LTR) (z ∼ t, q = constant) can be observed, where the inertia, viscous, and gravity forces are dominant, respectively. The results also indicated that by increasing the permeability of the porous medium, the durations of the ETR (z ∼ t, q = constant) and the LTR (z ∼ t, q = constant) are prolonged while the duration of the MTR (z ∼ √{ t } , q ∼ 1 /√{ t }) is reduced. Moreover, the results revealed that by increasing the liquid viscosity, the durations of the ETR (z ∼ t, q = constant) and LTR (z ∼ t, q = constant) are reduced whereas the duration of the MTR (z ∼ √{ t } , q ∼ 1 /√{ t }) is prolonged. In addition, the results showed that in the case of high permeability of the porous medium when the fracture capillary pressure is strong enough only the LTR (z ∼ t, q = constant) can be observed. The MTR (z ∼ √{ t } , q ∼ 1 /√{ t }) and the LTR (z ∼ t

  10. Block Copolymers and Ionic Liquids: A New Class of Functional Nanocomposites

    NASA Astrophysics Data System (ADS)

    Lodge, Timothy

    2009-03-01

    Block copolymers provide a remarkably versatile platform for achieving desired nanostructures by self-assembly, with lengthscales varying from a few nanometers up to several hundred nanometers. Ionic liquids are an emerging class of solvents, with an appealing set of physical attributes. These include negligible vapor pressure, high chemical and thermal stability, tunable solvation properties, high ionic conductivity, and wide electrochemical windows. For various applications it will be necessary to solidify the ionic liquid into particular spatial arrangements, such as membranes or gels, or to partition the ionic liquid in coexisting phases, such as microemulsions and micelles. One example includes formation of spherical, cylindrical, and vesicular micelles by poly(butadiene-b-ethylene oxide) and poly(styrene-b-methylmethacrylate) in the common hydrophobic ionic liquids [BMI][PF6] and [EMI][TFSI]. This work has been extended to the formation of reversible micelle shuttles between ionic liquids and water, whereby entire micelles transfer from one phase to the other, reversibly, depending on temperature and solvent quality. Formation of ion gels has been achieved by self-assembly of poly(styrene-b-ethylene oxide-b-styrene) triblocks in ionic liquids, and by the thermoreversible system poly(N-isopropylacrylamide-b-ethylene oxide-b-N-isopropylacrylamide), using as little as 4% copolymer. Further, these gels have been shown to be remarkably effective as gate dielectrics in organic thin film transistors. The remarkably high capacitance of the ion gels (> 10 μF/cm^2) supports a very high carrier density in an organic semiconductor such as poly(3-hexylthiophene), leading to milliamp currents for low applied voltages. Furthermore, the rapid mobility of the ions enables switching speeds approaching 10 kHz, orders of magnitude higher than achievable with other polymer-based dielectrics such as PEO/LiClO4. Finally, we have shown that ordered nanostructures of block

  11. Controlling the intermediate structure of an ionic liquid for f-block element separations

    DOE PAGES

    Abney, Carter W.; Do, Changwoo; Luo, Huimin; ...

    2017-04-19

    Recent research has revealed molecular structure beyond the inner coordination sphere is essential in defining the performance of separations processes, but nevertheless remains largely unexplored. Here we apply small angle neutron scattering (SANS) and x-ray absorption fine structure (XAFS) spectroscopy to investigate the structure of an ionic liquid system studied for f-block element separations. SANS data reveal dramatic changes in the ionic liquid microstructure (~150 Å) which we demonstrate can be controlled by judicious selection of counter ion. Mesoscale structural features (> 500 Å) are also observed as a function of metal concentration. XAFS analysis supports formation of extended aggregatemore » structures, similar to those observed in traditional solvent extraction processes, and suggest additional parallels may be drawn from further study. As a result, achieving precise tunability over the intermediate features is an important development in controlling mesoscale structure and realizing advanced new forms of soft matter.« less

  12. Luminescence and scintillation properties of liquid phase epitaxy grown Y2SiO5:Ce single crystalline films

    NASA Astrophysics Data System (ADS)

    Wantong, Kriangkrai; Yawai, Nattasuda; Chewpraditkul, Weerapong; Kucera, Miroslav; Hanus, Martin; Nikl, Martin

    2017-06-01

    Luminescence and scintillation properties of Y2SiO5:Ce single crystalline film (YSO:Ce-LPE) grown by the liquid phase epitaxy technique are investigated and compared to the bulk Czochralski-grown YSO:Ce single crystal (YSO:Ce-SC). The light yield (LY) and energy resolution are measured using an R6231 photomultiplier under excitation with α - and γ- rays. At 662 keV γ- rays, the LY value of 12,410 ph/MeV obtained for YSO:Ce -LPE is lower than that of 20,150 ph/MeV for YSO:Ce -SC whereas the comparable LY value and energy resolution are obtained under excitation with 5.5 MeV α- rays. The ratio of LY under excitation with α- and γ- rays (α/γ ratio) is determined. Dependence of LY on an amplifier shaping time (0.5-12 μs) is also measured.

  13. Evaluation of preservative effectiveness of liquid crystalline systems with retynil palmitate by the challenge test and D-value.

    PubMed

    Chorilli, Marlus; Leonardi, Gislaine Ricci; Salgado, Hérida Regina Nunes; Scarpa, Maria Virgínia

    2011-01-01

    The objective of this work was to evaluate the preservative effectiveness of liquid crystalline systems containing retynil palmitate (RP) by the challenge test (CT) and D-value. A system was developed containing water, silicon glycol copolymer, and polyether functional siloxane with 1% RP added. The analyses were carried out by methods in the U.S. Pharmacopeia (USP 31, 2008) using the microorganisms Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger. The CT showed that after 7 days, all microorganisms were eliminated except A. niger, which maintained viability for at least 28 days after inoculation. Moreover, the microorganisms E. coli, P. aeruginosa, S. aureus, C. albicans, and A. niger presented different growth behaviors, evidenced by differences among the D-values calculated. It was concluded that the CT and D-value were efficient methods for evaluation of the preservative property of these formulations.

  14. Aerogels with 3D ordered nanofiber skeletons of liquid-crystalline nanocellulose derivatives as tough and transparent insulators.

    PubMed

    Kobayashi, Yuri; Saito, Tsuguyuki; Isogai, Akira

    2014-09-22

    Aerogels of high porosity and with a large internal surface area exhibit outstanding performances as thermal, acoustic, or electrical insulators. However, most aerogels are mechanically brittle and optically opaque, and the structural and physical properties of aerogels strongly depend on their densities. The unfavorable characteristics of aerogels are intrinsic to their skeletal structures consisting of randomly interconnected spherical nanoparticles. A structurally new type of aerogel with a three-dimensionally ordered nanofiber skeleton of liquid-crystalline nanocellulose (LC-NCell) is now reported. This LC-NCell material is composed of mechanically strong, surface-carboxylated cellulose nanofibers dispersed in a nematic LC order. The LC-NCell aerogels are transparent and combine mechanical toughness and good insulation properties. These properties of the LC-NCell aerogels could also be readily controlled. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. In-situ synthesis of Au nano particles of co-existing morphologies in liquid crystalline matrix

    SciTech Connect

    Dan, Kaustabh Datta, Alokmay

    2015-06-24

    The present study describes the in-situ synthesis of Au nano particles (Au-NP) in the room temperature nematic liquid crystalline (LC) substance MBBA (N-4 methoxybenzylidene 4 butylaniline) without any external reducing or stabilizing agents. UV-Visible absorption and fluorescence spectroscopy clearly show formation of Au-NP within the LC matrix through the plasmon resonance peak for the NPs and EDAX measurements confirm this formation. Transmission electron Microscopy shows co-existence of spherical and prismatic NPs. FTIR spectroscopy shows a considerable shift in the C=N stretch band pointing to the location of the growth centre of the NPs. Polarization microscopy data indicates a definite phase ordering and texture transformation from Nematic to highly ordered smectic mesophase.

  16. Experimental realization of hyperbolic dispersion metamaterial for the whole visible spectrum based on liquid crystalline phase soft template.

    PubMed

    Xiang, Xiangjun; Yang, Chengliang; Zhang, Ying; Peng, Zenghui; Cao, Zhaoliang; Zhao, Haifeng; Zhang, Peiguang; Xuan, Li

    2015-08-10

    We experimentally demonstrated a metamaterial composed of hexagonal arrays of silver nanowires that exhibits hyperbolic dispersion and negative refraction in the entire visual wavelength range. The nanowires with extremely small size of 10 nm diameter and 15 nm center-to-center distance were fabricated using the reverse hexagonal liquid crystalline phase template containing AgNO(3) solution. Through the experiments of angle dependent reflectance for s-polarization and p-polarization, the dielectric constants were measured in several wavelengths. Calculations and experiments both show hyperbolic dispersion relations from 370 nm to 750 nm which indicates the presence of all-angle negative refraction. For all the experimental wavelengths, the permittivities of the material are in good agreement with the theoretical calculations.

  17. Thermotropic and lyotropic behaviour of new liquid-crystalline materials with different hydrophilic groups: synthesis and mesomorphic properties.

    PubMed

    Bubnov, Alexej; Kašpar, Miroslav; Hamplová, Věra; Dawin, Ute; Giesselmann, Frank

    2013-01-01

    Several new calamitic liquid-crystalline (LC) materials with flexible hydrophilic chains, namely either hydroxy groups or ethylene glycol units, or both types together, have been synthesized in order to look for new functional LC materials exhibiting both, thermotropic and lyotropic behaviour. Such materials are of high potential interest for challenging issues such as the self-organization of carbon nanotubes or various nanoparticles. Thermotropic mesomorphic properties have been studied by using polarizing optical microscopy, differential scanning calorimetry and X-ray scattering. Four of these nonchiral and chiral materials exhibit nematic and chiral nematic phases, respectively. For some molecular structures, smectic phases have also been detected. A contact sample of one of the prepared compounds with diethylene glycol clearly shows the lyotropic behaviour; namely a lamellar phase was observed. The relationship between the molecular structure and mesomorphic properties of these new LCs with hydrophilic chains is discussed.

  18. Thermotropic and lyotropic behaviour of new liquid-crystalline materials with different hydrophilic groups: synthesis and mesomorphic properties

    PubMed Central

    Kašpar, Miroslav; Hamplová, Věra; Dawin, Ute; Giesselmann, Frank

    2013-01-01

    Summary Several new calamitic liquid-crystalline (LC) materials with flexible hydrophilic chains, namely either hydroxy groups or ethylene glycol units, or both types together, have been synthesized in order to look for new functional LC materials exhibiting both, thermotropic and lyotropic behaviour. Such materials are of high potential interest for challenging issues such as the self-organization of carbon nanotubes or various nanoparticles. Thermotropic mesomorphic properties have been studied by using polarizing optical microscopy, differential scanning calorimetry and X-ray scattering. Four of these nonchiral and chiral materials exhibit nematic and chiral nematic phases, respectively. For some molecular structures, smectic phases have also been detected. A contact sample of one of the prepared compounds with diethylene glycol clearly shows the lyotropic behaviour; namely a lamellar phase was observed. The relationship between the molecular structure and mesomorphic properties of these new LCs with hydrophilic chains is discussed. PMID:23504455

  19. X-ray Scattering Measurements of Molecular Orientation in Channel Flows of a Thermotropic Liquid Crystalline Polymer

    NASA Astrophysics Data System (ADS)

    Cinader, D., Jr.; Burghardt, W.

    1998-03-01

    We have constructed an extrusion die which allows collection of x-ray scattering patterns(Experiments performed at DND-CAT at the APS) as a function of position in channel flows. A single-screw extruder is used to pump the melt, while interchangeable spacers allow the channel flow geometry to be altered. Available geometries include contractions and expansions of sharp and gradual character, as well as a simple slit flow. We present studies of a commercial liquid crystalline polymer (Xydar resin supplied by Amoco), emphasizing results from expansion flow experiments. A sharp decrease in orientation is observed at the expansion, followed by a recovery in the straight downstream channel. Scattering patterns reveal orientation transverse to the flow direction induced by unfavorable extensional gradients. This mixed orientation state manifests itself as a Rfour spotS scattering pattern consisting of two sets of nematic peaks with axes aligned perpendicular to one another.(Work sponsored by an AFOSR MURI)

  20. Quasi-liquid crystalline materials with special electro-optic properties

    NASA Astrophysics Data System (ADS)

    Krongauz, Valeri

    1987-11-01

    During the past six months we have completed synthesis and investigation of side chain liquid crystal polysiloxanes containing photochromic spiropyran side groups (Item C, Section 4 of the Research Proposal). The polymers exhibit both thermo- and photochromic properties. By changing temperature and wavelength of light we could control the polymer color. Three primary colors (yellow, blue and red) were obtained. The color changes stemmed from spiropyran-merocyanine conversion and aggregation of the merocyanine side groups. Our research plans include further examination of optical properties of the photo-thermochromic liquid crystal polymers, including laser irradiation effects.