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Sample records for holographic polymer dispersed

  1. Broadband Wavelength Spanning Holographic Polymer Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Rai, Kashma; Shriyan, Sameet; Fontecchio, Adam

    2008-03-01

    Broadened interaction wavelength of holographic polymer dispersed liquid crystals (HPDLCs) have extensive applications in beam steering for instrument clusters, hyperspectral imaging, wavelength filtering and construction of lightweight optics. A novel simultaneous time and spatial multiplexing formation configuration is proposed here, to increase narrow wavelength reflecting notch to broad range wavelength spanning device. HPDLC films have electro-optic controllability by applying field. No moving parts, light weight, small footprint compared to prisms and lenses, high color purity make the broadband wavelength HPDLCs desirable for the above applications. Varying the incident laser beam exposure angles using motorized rotating stage, during formation is the key step here for their formation in a single medium. The fabricated broadband wavelength sensitive HPDLCs are characterized for the uniformity of the reflected peak and electro optic response. Their output wavefront is analyzed using wavefront analysis technique.

  2. Holographically formed, acoustically switchable gratings based on polymer-dispersed liquid crystals.

    PubMed

    Liu, Yan Jun; Lu, Mengqian; Ding, Xiaoyun; Leong, Eunice S P; Lin, Sz-Chin Steven; Shi, Jinjie; Teng, Jing Hua; Wang, Lin; Bunning, Timothy J; Huang, Tony Jun

    2013-08-01

    We report holographic polymer-dispersed liquid crystal (H-PDLC) gratings driven by surface acoustic waves (SAWs). Our experiments show that upon applying SAWs, the H-PDLC grating exhibited switchable properties: The diffraction of the H-PDLC grating decreased, whereas the transmission increased. This acoustically switchable behavior is due to the acoustic streaming-induced realignment of liquid crystals as well as absorption-resulted thermal diffusion. Such SAW-driven H-PDLC gratings are potentially useful in many photonic applications, such as optical switches, spatial light modulators, and switchable add/drop filters. PMID:22909448

  3. Electro-optical properties of low viscosity driven holographic polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Moon, K. R.; Bae, S. Y.; Kim, B. K.

    2015-04-01

    Relative diffraction efficiency (RDE), operating voltage, and response times are most important performance characteristics of holographic polymer dispersed liquid crystals (HPDLC). Two types of triallyl isocyanurate (TI) having different structures were incorporated into the conventional transmission grating of HPDLC. Premix viscosity decreased by 13-18% with up to 3% TI, beyond which it increased. TI eliminated induction period and augmented initial grating formation rate at all contents. Saturation RDE increased over 200% while threshold voltage and rise time decreased to about half and 2/3, respectively up to 3% TI, beyond which the tendencies were reversed. Among the two TIs, low viscosity monomer (TA) showed high RDE, while high miscibility monomer (TE) low characteristic voltages and short response times. It is concluded that grating formation is largely favored by low viscosity, while interface tensions and electro-optical performances by miscibility at similar viscosities.

  4. Multiplexing studies of holographically-formed polymer-dispersed liquid crystals: Morphology, structure, and device applications

    NASA Astrophysics Data System (ADS)

    Fontecchio, Adam Kent

    Holographically-formed Polymer Dispersed Liquid Crystals (H-PDLC) are phase-segregated liquid crystal/polymer composites which enable electrically switchable holographic recordings. They are formed using a holographic exposure apparatus to create an interference pattern, which is recorded through polymerization to produce Bragg-mode gratings. Application of an electric field eliminates the Bragg grating, and the material appears optically transparent. Optical applications are being evaluated for H-PDLC implementation. Therefore, there is an increasing need to understand the fundamental physics of their formation and operation, and to optimize the electro-optical performance. This work describes H-PDLC formation, characterization, and fundamental investigations into the physics of liquid crystals confined in polymer droplet cavities. Systematic materials studies were performed, and Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) are used to examine morphological details of the polymer. The results indicate a difference in phase-separation between materials sets. Examination of droplet cavities reveals a novel rough texture that is used to explain electro-optic performance differences between materials sets. Solid-state Nuclear Magnetic Resonance (NMR) results are presented for H-PDLC samples formed with deuterated liquid crystal. The findings indicate a change in the nematic temperature range in the confined liquid crystal as compared to bulk. The onset of the nematic phase is found to occur gradually, and the phase transition is non-continuous with regard to the order parameter. Using the electro-optic properties of transmission-mode grating, the size, shape, and distribution of droplets is characterized. These attributes are found to vary with temperature when confined to the small droplets of H-PDLC films, and a coupled-wave theory is used to model these findings. New techniques for H-PDLC formation are reported, including multiplexing

  5. Optically switchable, polarization-independent holographic polymer dispersed liquid crystal (H-PDLC) gratings

    NASA Astrophysics Data System (ADS)

    Hsiao, V. K. S.; Chang, W.-T.

    2010-09-01

    An optically switchable, polarization-independent holographic polymer dispersed liquid crystal (H-PDLC) transmission grating is demonstrated by adding azobenzene-LC and chiral molecules into the H-PDLC formulation. The optical switchable mechanism is from the trans-cis photoisomerization of the doped azobenzene-LC, which modulates the refractive index of the LC rich area. The dependence of the diffraction efficiency of the H-DPLC grating without chiral molecules on light polarization suggests that the orientation of LC directors within the droplet is ellipsoidal and uniaxial. However, the addition of chiral molecules into the H-PDLC formulation helps the formation of isotropic and non-uniaxial LC directors within the droplets. The polarization properties of the grating are investigated and analyzed by the coupled and modified coupled wave theory with a model of sinusoidal dielectric modulation. The results show that the addition of chiral molecules changes the LC phase from nematic to chiral-nematic, where the grating efficiency, which is modulated by the photoinduced phase transition, is independent of the polarization of incident light. Our findings may help improve optical systems that utilize non-polarized light.

  6. Varied-line-spacing switchable holographic grating using polymer-dispersed liquid crystal.

    PubMed

    Wang, Kangni; Zheng, Jihong; Lu, Feiyue; Gao, Hui; Palanisamy, Aswin; Zhuang, Songlin

    2016-06-20

    A varied-line-spacing switchable holographic grating is demonstrated through a changeable interference pattern recorded in polymer-dispersed liquid crystal. The pattern is generated by the interference between one plane wave and another cylindrical wave. The line spacing and the period of grating can be controlled by varying the distance between the cylindrical lens and the grating sample and by changing the exposure angle between the two beams. Experimental period measurements and calculations show good agreement with the theoretical results. High diffraction efficiency of more than 80% for the middle period of the grating has been achieved under appropriate exposure time of 120 s and intensity of 19.1  mW/cm2. In addition, the diffraction can be switched on and off by virtue of the external driving voltage of approximately 120 V. The grating also possesses a fast response with a rise time of 300 μs and a fall time of 750 μs. This grating, which can change the period in the grating structure to allow switchable diffraction of transmitted light, shows great potential application for diffractive optics. PMID:27409124

  7. Effects of multi-context information recorded at different regions in holographic polymer-dispersed liquid crystal on optical reconfiguration

    NASA Astrophysics Data System (ADS)

    Ogiwara, Akifumi; Watanabe, Minoru

    2016-08-01

    A holographic polymer-dispersed liquid crystal (HPDLC) memory to record multi-context information for an optically reconfigurable gate array is formed by constructing a laser illumination system to implement successive laser exposures at different small regions in a glass cell filled with LC composites. The context pattern arrangements for circuit information are designed in a 3 × 3 in.2 photomask by electron beam lithography, and they are recorded as laser interference patterns at nine regions separated in an HPDLC sample by a laser interferometer composed of movable pinhole and photomask plates placed on motorized stages. The multi-context information reconstructed from the different regions in the HPDLC is written to a photodiode array in a gate-array VLSI by switching only the position of laser irradiation using the displacement of the pinhole plate under the control of a personal computer (PC). The effects of multi-context information recorded at different regions in the HPDLC on optical reconfiguration are discussed in terms of the optical system composed of ORGA VLSI and HPDLC memory. The internal structures in the HPDLC memory formed by multi-context recording are investigated by scanning electron microscopy (SEM) observation, and the configurations composed of LC and polymer phases are revealed at various regions in the HPDLC memory.

  8. Holographic polymer-dispersed liquid crystal Bragg grating integrated inside a solid core photonic crystal fiber.

    PubMed

    Zito, Gianluigi; Pissadakis, Stavros

    2013-09-01

    A polymer/liquid crystal-based fiber Bragg grating (PLC-FBG) is fabricated with visible two-beam holography by photo-induced modulation of a prepolymer/liquid crystal solution infiltrated into the hollow channels of a solid core photonic crystal fiber (PCF). The fabrication process and effects related to the photonic bandgap guidance into the infiltrated PCF, and characterization of the PLC-FBG, are discussed. Experimental data presented here demonstrate that the liquid crystal inclusions of the PLC-FBG lead to high thermal and bending sensitivities. The microscopic behavior of the polymer/liquid crystal phase separation inside the PCF capillaries is examined using scanning electron microscopy, and is discussed further. PMID:23988927

  9. Electrically tunable holographic polymer templated blue phase liquid crystal grating

    NASA Astrophysics Data System (ADS)

    He, Zheng-Hong; Chen, Chao-Ping; Zhu, Ji-Liang; Yuan, Ya-Chao; Li, Yan; Hu, Wei; Li, Xiao; Li, Hong-Jing; Lu, Jian-Gang; Su, Yi-Kai

    2015-06-01

    In this paper, we demonstrate an alternative approach to fabricating an electrically tunable holographic polymer templated blue phase liquid crystal grating. This grating is obtained by preforming a polymer template comprised of periodic fringes, and then refilling it with a blue phase liquid crystal. Compared with conventional holographic polymer dispersed liquid crystal gratings, our grating can remarkably reduce its switching voltage from 200 V to 43 V while maintaining a sub-millisecond response time. The holographic polymer templated blue phase liquid crystal (HPTBPLC) grating is free from electrode patterning, thus leading to a lower cost and more flexible applications. Project supported by the National Basic Research Program of China (Grant No. 2013CB328804), the National Natural Science Foundation of China (Grant No. 61307028), the Funds from the Science and Technology Commission of Shanghai Municipality (Grant Nos. 11JC1405300, 13ZR1420000, and 14ZR1422300), and the Fundamental Research Funds for the Central Universities, China (Grant No. XDJK 2011C047).

  10. Holographic Optical Storage Using Photorefractive Polymers

    NASA Technical Reports Server (NTRS)

    Hayden, L. Michael; Strutz, Shane J.; Harris, Kristi; Ayachitula, Rajani

    2000-01-01

    The task for this report is to perform the basic research and develop a prototype benchtop holographic optical storage system based on photochromic and/or photorefractive polymers so that both permanent and erasable images may be stored and retrieved in the same mixed polymer medium. The task consist of: assembly and setup of the benchtop holographic storage system, including lasers, optics, and other ancillary equipment in a laboratory setting; and research and development of a suitable polymer matrix that will allow practical storage and retrieval of digital data. This will necessitate molecular design of the matrices involved and subsequent physics test to verify the characteristics of the matrices provide practical storage and retrieval.

  11. Enhancement of spectrum strength in holographic sensing in nanozeolites dispersed acrylamide photopolymer.

    PubMed

    Yu, Dan; Liu, Hongpeng; Mao, Dongyao; Geng, Yaohui; Wang, Weibo; Sun, Liping; Lv, Jiang

    2015-11-01

    Holographic sensing of organic vapor is characterized at transmission and reflection geometries in ZSM-5 nanozeolites dispersed acrylamide photopolymer. Nano-zeolites as absorption medium are dispersed into the polymer to enhance the absorptivity to organic vapor. Obvious enhancements of spectrum strength are observed during the sensing process. Two primary factors causing the enhancement, absorption of nanozeolites and photopolymerization induced by broadband white light, are analyzed experimentally. Significant increment provides a quick and intuitive identification strategy for holographic sensing. Accompanying with the wavelength blue-shift, the shrinkage of sample is measured quantitatively under homogeneous white light. It is further demonstrated that the significance of nanozeolites absorption. Finally a theoretical model with mutual diffusion is used to simulate the swelling process. This study provides significant foundation for the application of holographic sensor. PMID:26561180

  12. Holographic molecularly imprinted polymers for label-free chemical sensing.

    PubMed

    Fuchs, Yannick; Soppera, Olivier; Mayes, Andrew G; Haupt, Karsten

    2013-01-25

    Holographic molecularly imprinted polymer films for the use in chemical sensors are obtained in one step through photopolymerization with interfering laser beams. This results in hierarchical structuring at four length scales: micrometer-scale patterning of millimeter- to centimeter- size polymer objects with holographic optical properties, exhibiting nanometer-scale porosity and specific molecular recognition properties at the molecular scale through self-assembly. Specific binding of the target analyte testosterone is measured by diffraction analysis. PMID:23080512

  13. Polymer electrolyte membranes with exceptional conductivity anisotropy via holographic polymerization

    NASA Astrophysics Data System (ADS)

    Smith, Derrick M.; Cheng, Shan; Wang, Wenda; Bunning, Timothy J.; Li, Christopher Y.

    2014-12-01

    Polymer electrolyte membranes using an ionic liquid as electrolyte with an ionic conductivity anisotropy of ∼5000 have been fabricated using a holographic polymerization nanomanufacturing technique. The resultant structure is referred to as holographic polymer electrolyte membranes (hPEMs), which are comprised of alternating nanolayers of a room temperature ionic liquid and crosslinked polymer resin, confirmed under TEM imaging. These hPEMs also show no reduction in room temperature conductivity with respect to the loaded ionic liquid when characterized in the plane of ionic liquid nanolayers. At elevated temperatures with the optimal electrolyte volume loading, calculation shows that the free ion concentration is higher than the pure ionic liquid, suggesting that the photopolymer dual-functionalizes as a loadbearing scaffold and an ion-complexing agent, allowing for more ions to participate in charge transfer. These hPEMs provide a promising solution to decoupling mechanical enhancement and ion transport in polymer electrolyte membranes.

  14. Complex Nanoscale-Ordered Liquid Crystal Polymer Film for High Transmittance Holographic Polarizer.

    PubMed

    Du, Tao; Fan, Fan; Tam, Alwin Ming Wai; Sun, Jiatong; Chigrinov, Vladimir G; Sing Kwok, Hoi

    2015-11-25

    A special design of a complex-ordered liquid crystal polymer film is developed into a holographic polarizer. The holographic polarizer shows over 90% transmittance, which provides a simple solution to make LEDs polarized. Furthermore, the holographic polarizer exhibits intensity and polarization maintenance properties, which could be further developed for photonics applications. PMID:26457810

  15. Dispersions of Carbon nanotubes in Polymer Matrices

    NASA Technical Reports Server (NTRS)

    Wise, Kristopher Eric (Inventor); Park, Cheol (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor); Lillehei, Peter T. (Inventor); Lowther, Sharon E. (Inventor)

    2010-01-01

    Dispersions of carbon nanotubes exhibiting long term stability are based on a polymer matrix having moieties therein which are capable of a donor-acceptor complexation with carbon nanotubes. The carbon nanotubes are introduced into the polymer matrix and separated therein by standard means. Nanocomposites produced from these dispersions are useful in the fabrication of structures, e.g., lightweight aerospace structures.

  16. 3D holographic polymer photonic crystal for superprism application

    NASA Astrophysics Data System (ADS)

    Chen, Jiaqi; Jiang, Wei; Chen, Xiaonan; Wang, Li; Zhang, Sasa; Chen, Ray T.

    2007-02-01

    Photonic crystal based superprism offers a new way to design new optical components for beam steering and DWDM application. 3D photonic crystals are especially attractive as they could offer more control of the light beam based on the needs. A polygonal prism based holographic fabrication method has been demonstrated for a three-dimensional face-centered-cubic (FCC)-type submicron polymer photonic crystal using SU8 as the photo-sensitive material. Therefore antivibration equipment and complicated optical alignment system are not needed and the requirement for the coherence of the laser source is relaxed compared with the traditional holographic setup. By changing the top-cut prism structure, the polarization of the laser beam, the exposure and development conditions we can achieve different kinds of triclinic or orthorhombic photonic crystals on demand. Special fabrication treatments have been introduced to ensure the survivability of the fabricated large area (cm2) nano-structures. Scanning electron microscopy and diffraction results proved the good uniformity of the fabricated structures. With the proper design of the refraction prism we have achieved a partial bandgap for S+C band (1460-1565nm) in the [111] direction. The transmission and reflection spectra obtained by Fourier transform infrared spectroscopy (FTIR) are in good agreement with simulated band structure. The superprism effects around 1550nm wavelength for the fabricated 3D polymer photonic crystal have been theoretically calculated and such effects can be used for beam steering purpose.

  17. Two-way shift of wavelength in holographic sensing of organic vapor in nanozeolites dispersed acrylamide photopolymer.

    PubMed

    Mao, Dongyao; Geng, Yaohui; Liu, Hongpeng; Zhou, Ke; Xian, Lihong; Yu, Dan

    2016-08-10

    Holographic sensing of alcohol organic vapor is characterized in detail at transmission and reflection geometries in Y nanozeolites dispersed acrylamide photopolymer. The two-way shift of the diffraction spectrum and its temporal evolution with various vapor concentrations are measured. Obvious blueshifts of diffraction spectrum peaks are observed and analyzed in two recording geometries. The competition mechanism between decreasing the average refractive index and swelling the grating fringe space is proposed for exploring the wavelength shift mechanism. In the reflection grating, as organic vapor increases, the redshift after the blueshift of the wavelength peaks are observed clearly. We further demonstrate the significance of this competition mechanism. In the low concentration region, at transmission <700  ppm and reflection <400  ppm in nanozeolites dispersed polymer, the blueshift of the wavelength is a significant factor in identifying an organic vapor with a low refractive index. These experimental results provide a probability for improving the applicability of a holographic sensor. This work can accelerate the development of the holographic sensing strategy and provide a novel identification method for organic vapor. PMID:27534461

  18. Fast photochromism in polymer matrix with plasticizer and real-time dynamic holographic properties

    NASA Astrophysics Data System (ADS)

    Ishii, Norihito; Abe, Jiro

    2013-04-01

    We have developed a photochromic polymer film for the use of real-time dynamic hologram, fabricated by the plasticized polymer doped with the fast photochromic molecule. The addition of a plasticizer into the conventional polymer is proved to be effective to improve the photochromic performances for the polymer film doped with the fast photochromic molecule that shows instantaneous coloration upon exposure to UV light and rapid fading in the dark. The plasticized photochromic polymers enable the real-time control of the writing and erasing of a holographic grating and show a higher recording sensitivity compared with other organic holographic materials.

  19. Vertically dispersive holographic screens and autostereoscopic displays in 3D medical imaging

    NASA Astrophysics Data System (ADS)

    Magalhães, Daniel S. F.; Serra, Rolando L.; Vannucci, André L.; Moreno, Alfredo B.; Magalhães, Lucas V. B.; Llovera, Juan J.; Li, Li M.

    2011-05-01

    In this work we describe a setup employed for the recording of vertical dispersive holographic screens that can be used for medical applications. We show how to obtain holographic screens with areas up to 1200 cm2, focal length of 25+/-2 cm and diffraction efficiency of 7.2%. We analyze the technique employed and the holographic screens obtained. Using this screen we describe a setup for the projection of Magnetic Resonance or Tomographic Images. We also describe and present the first results of an autostereoscopic system for 3D medical imaging.

  20. Photochromic mesomorphic polymers as holographic data storage materials

    SciTech Connect

    Wuttke, R.; Fischer, K.; Bieringer, T.

    1995-12-01

    Liquid crystalline side chain copolymers containing photochromic azobenzene and mesogenic side groups as well as non-mesogenic comonomer units exhibited distinct changes of the refractive index (RI) upon irradiation. DSC and thermo-optical studies revealed that this phenomenon is linked to the isotropic glass-mesophase transition and was caused by laser-induced trans-cis isomerization of the photochromic side groups. The efficiency of the RI-modulation and thus the writing of holographic patterns changed with copolymer composition and the sample history or thermal treatment, respectively. The results and their implication for the understanding of photochemistry in polymer glasses and mesophases as well as photonic materials will be discussed.

  1. Characterizing SWCNT Dispersion in Polymer Composites

    NASA Technical Reports Server (NTRS)

    Lillehei, Peter T.; Kim, Jae-Woo; Gibbons, Luke; Park, Cheol

    2007-01-01

    The new wave of single wall carbon nanotube (SWCNT) infused composites will yield structurally sound multifunctional nanomaterials. The SWCNT network requires thorough dispersion within the polymer matrix in order to maximize the benefits of the nanomaterial. However, before any nanomaterials can be used in aerospace applications a means of quality assurance and quality control must be certified. Quality control certification requires a means of quantification, however, the measurement protocol mandates a method of seeing the dispersion first. We describe here the new tools that we have developed and implemented to first be able to see carbon nanotubes in polymers and second to measure or quantify the dispersion of the nanotubes.

  2. Holographic interference field-induced localized orientational structures in diacrylate-based polymers

    NASA Astrophysics Data System (ADS)

    Zheng, Wenjun; Su, Meng-Yao

    2014-07-01

    Structures with orientational order were produced in a diacrylate-based polymer by exposing the diacrylate resin to a holographic irradiation created by means of two-beam interferometry. The holographic irradiation acted both as the driving force for the alignment of mesogenic groups and as the optical source that provided energy for generating free radicals for the crosslinking of the acrylate units. In the region exposed to the holographic irradiation, part of the diacrylate resin was aligned, and the alignment state was fixed upon the completion of the crosslink of the acrylic groups, which was initiated by a nonlinear optical process.

  3. Polymer stabilized and dispersed blue phases

    NASA Astrophysics Data System (ADS)

    Kemiklioglu, Emine

    Blue phase liquid crystal (BPLC) materials have potential for advanced applications of display material and technology based on their optical behaviors, such as field-induced birefringence and sub-millisecond response time, which is at least one order of magnitude faster than the present nematic liquid crystal based displays. Since blue phases appear in the narrow temperature range between the chiral nematic and the isotropic phases, there is a temperature range limitation for the application of blue phase liquid crystal. In this dissertation, we have developed blue phase liquid crystal materials with a wide temperature range and low driving voltage. The first goal was to develop wide-temperature range blue phase liquid crystal materials using several stabilization methods notably polymer stabilization, doping of carbon-nanotubes and bent-core molecules. The temperature range could be expanded more than 54°C via the polymer stabilization. The second goal was to explore the polymer dispersed blue phase liquid crystal combining the advantages of the polymer dispersion method and blue phase materials. Polymer encapsulated blue phase films showed a large Kerr constant, low switching voltage and fast response time. Moreover, the temperature range of encapsulated blue phase films were successfully expanded from 9°C to 54°C .

  4. Depth-resolved holographic optical coherence imaging using a high-sensitivity photorefractive polymer device

    NASA Astrophysics Data System (ADS)

    Salvador, M.; Prauzner, J.; Köber, S.; Meerholz, K.; Jeong, K.; Nolte, D. D.

    2008-12-01

    We present coherence-gated holographic imaging using a highly sensitive photorefractive (PR) polymer composite as the recording medium. Due to the high sensitivity of the composite holographic recording at intensities as low as 5 mW/cm2 allowed for a frame exposure time of only 500ms. Motivated by regenerative medical applications, we demonstrate optical depth sectioning of a polymer foam for use as a cell culture matrix. An axial resolution of 18 μm and a transverse resolution of 30 μm up to a depth of 600 μm was obtained using an off-axis recording geometry.

  5. Improving sensitivity of photorefractive polymer composites for holographic display applications

    NASA Astrophysics Data System (ADS)

    Christenson, Cory W.

    This work presents recent progress in the area of organic photorefractive polymer composites. These materials have been previously shown to be a suitable medium for dynamic holographic displays, with multiple colors and single frame writing times on the order of seconds. However, these materials still require large electric fields and high intensity lasers to function effectively. Recent advancements in improving these areas are discussed, including a review of the history and state-of-the-art in photorefractive polymer composites. The addition of electron traps via low loading of the electron-transporting molecule Alq3 is shown to dramatically improve the diffraction efficiency and reduce the required field. The grating formation also proceeds faster by more than one order of magnitude, leading to an increase in sensitivity by a factor of 3. The dynamics of these materials also show evidence of competing gratings indicative of bipolar charge transport and trapping. The addition of an amorphous polycarbonate (APC) buffer layer is reported to have a similar effect on the steady-state diffraction efficiency, and the further doping with a fullerene derivative (PCBM) allows a 3x increase in the efficiency in the reflection geometry, which is normally poor due to the small grating spacing. These composites reveal the fundamental limits of the reflection geometry, based on the physics of high frequency gratings. A reversal in the direction and increase in the magnitude of the two-beam coupling energy transfer is also observed. The use of interdigitated coplanar electrodes, instead of the standard uniform electrodes in a parallel-plate geometry, is shown to result in large diffraction efficiency with symmetric writing beams due to the increased projection field. The efficiency is similar to that achieved in the standard samples with large slant angles and much better than those geometries typically used in applications, with the benefit that the writing beams do not have

  6. Blue-sensitized nanoparticle-(thiol-ene) polymer composites for volume holographic recording

    NASA Astrophysics Data System (ADS)

    Takahashi, Jun-ichiro; Kawana, Masaru; Tomita, Yasuo

    2016-04-01

    We describe an experimental investigation of volume holographic recording in photopolymerizable thiol-ene based nanoparticle-polymer composites (NPCs) at a wavelength of 404 nm. We introduce a new photoinitiator, Irgacure819, for efficient volume holographic recording in the blue-violet spectral region and measure the photopolymerization dynamics and the holographic recording properties at its varying concentrations. It is found that doping of 0.1 wt.% Irgacure 819 provides the saturated refractive index modulation amplitude as large as 9.5×10-3 and the material recording sensitiviey as high as 1800 cm/J. These measured values are much larger than the minimum required values for holographic data storage media. It is also shown that the out-of-plane shrinkage can be suppressed more with decreasing the photoinitiator concentration. We compare these results with another blue sensitizer, Darocur TPO, to evaluate the performance of Irgacure 819.

  7. Diffracting holographic lenses created on azo-polymer films

    NASA Astrophysics Data System (ADS)

    Sabat, Ribal Georges

    2014-02-01

    Various superimposed chirped relief gratings, acting as diffracting holographic lenses, were photo-inscribed on azopolymer films upon exposure to the interference pattern of a plane and a curved laser light wavefronts. Depending on the configuration used, this resulted in incident light being focused independently of polarization along the 0th or 1st diffracted order of the grating. The focal point and focalization angle of the resulting holographic lenses were easily tuned during the fabrication process.

  8. Stable dispersions of polymer-coated graphitic nanoplatelets

    NASA Technical Reports Server (NTRS)

    Stankovich, Sasha (Inventor); Nguyen, Sonbinh T. (Inventor); Ruoff, Rodney S. (Inventor)

    2011-01-01

    A method of making a dispersion of reduced graphite oxide nanoplatelets involves providing a dispersion of graphite oxide nanoplatelets and reducing the graphite oxide nanoplatelets in the dispersion in the presence of a reducing agent and a polymer. The reduced graphite oxide nanoplatelets are reduced to an extent to provide a higher C/O ratio than graphite oxide. A stable dispersion having polymer-treated reduced graphite oxide nanoplatelets dispersed in a dispersing medium, such as water or organic liquid is provided. The polymer-treated, reduced graphite oxide nanoplatelets can be distributed in a polymer matrix to provide a composite material.

  9. IR sensitive photorefractive polymers, the first updateable holographic three-dimensional display

    NASA Astrophysics Data System (ADS)

    Tay, Savas

    This work presents recent advances in the development of infra-red sensitive photorefractive polymers, and updateable near real-time holographic 3D displays based on photorefractive polymers. Theoretical and experimental techniques used for design, fabrication and characterization of photorefractive polymers are outlined. Materials development and technical advances that made possible the use of photorefractive polymers for infra-red free-space optical communications, and 3D holographic displays are presented. Photorefractive polymers are dynamic holographic materials that allow recording of highly efficient reversible holograms. The longest operation wavelength for a photorefractive polymer before this study has been 950nm, far shorter than 1550nm, the wavelength of choice for optical communications and medical imaging. The polymers shown here were sensitized using two-photon absorption, a third order nonlinear effect, beyond the linear absorption spectrum of organic dyes, and reach 40% diffraction efficiency with a 35ms response time at this wavelength. As a consequence of two-photon absorption sensitization they exhibit non-destructive readout, which is an important advantage for applications that require high signal-to-noise ratios. Holographic 3D displays provide highly realistic images without the need for special eyewear, making them valuable tools for applications that require "situational awareness" such as medical, industrial and military imaging. Current commercially available holographic 3D displays employ photopolymers that lack image updating capability, resulting in their restricted use and high cost per 3D image. The holographic 3D display shown here employs photorefractive polymers with nearly 100% diffraction efficiency and fast writing time, hours of image persistence, rapid erasure and large area, a combination of properties that has not been shown before. The 3D display is based on stereography and utilizes world's largest photorefractive

  10. Readout fidelity of coaxial holographic digital data page recording in nanoparticle–(thiol–ene) polymer composites

    NASA Astrophysics Data System (ADS)

    Nagaya, Kohta; Hata, Eiji; Tomita, Yasuo

    2016-09-01

    We report on an experimental investigation of nanoparticle-concentration and thiol-to-ene stoichiometric ratio dependences of symbol error rates (SERs) and signal-to-noise ratios (SNRs) of digital data pages recorded at a wavelength of 532 nm in thiol–ene based nanoparticle–polymer composite (NPC) films by using a coaxial holographic digital data storage method. We show that SERs and SNRs at the optimized material condition can be lower than 1 × 10‑4 and higher than 10, respectively, without error correction coding. These results show the usefulness of thiol–ene based NPCs as coaxial holographic data storage media.

  11. Surface relief gratings on polymer dispersed liquid crystals by polarization holography

    SciTech Connect

    Mazzulla, A.; Pagliusi, P.; Provenzano, C.; Russo, G.; Carbone, G.; Cipparrone, G.

    2004-09-27

    We report the observation of surface relief gratings (SRGs) on polymer dispersed liquid crystal films after polarization holographic recording, demonstrating the formation of SRGs in systems without azo compounds, where photoisomerization and chromophore reorientation processes do not occur. Permanent SRGs, several hundred nanometers deep, are recorded on the surface of a polymeric material containing oriented liquid crystal droplets. The results suggest that SRG growth under uniform intensity irradiation is not exclusively related to the photoisomerization, but is a more general phenomenon which can involve different photoinduced chemical and physical mechanisms sensitive to the light polarization state. These effects contribute to the formation of anisotropic structures during the recording process.

  12. Partially exposed polymer dispersed liquid crystals for boundary layer investigations

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S.; Singh, Jag J.

    1992-01-01

    A new configuration termed partially exposed polymer dispersed liquid crystal in which the liquid crystal microdroplets dispersed in a rigid polymer matrix are partially entrapped on the free surface of the thin film deposited on a glass substrate is reported. Optical transmission characteristics of the partially exposed polymer dispersed liquid crystal thin film in response to an air flow induced shear stress field reveal its potential as a sensor for gas flow and boundary layer investigations.

  13. Holographic three-dimensional telepresence using large-area photorefractive polymer.

    PubMed

    Blanche, P-A; Bablumian, A; Voorakaranam, R; Christenson, C; Lin, W; Gu, T; Flores, D; Wang, P; Hsieh, W-Y; Kathaperumal, M; Rachwal, B; Siddiqui, O; Thomas, J; Norwood, R A; Yamamoto, M; Peyghambarian, N

    2010-11-01

    Holography is a technique that is used to display objects or scenes in three dimensions. Such three-dimensional (3D) images, or holograms, can be seen with the unassisted eye and are very similar to how humans see the actual environment surrounding them. The concept of 3D telepresence, a real-time dynamic hologram depicting a scene occurring in a different location, has attracted considerable public interest since it was depicted in the original Star Wars film in 1977. However, the lack of sufficient computational power to produce realistic computer-generated holograms and the absence of large-area and dynamically updatable holographic recording media have prevented realization of the concept. Here we use a holographic stereographic technique and a photorefractive polymer material as the recording medium to demonstrate a holographic display that can refresh images every two seconds. A 50 Hz nanosecond pulsed laser is used to write the holographic pixels. Multicoloured holographic 3D images are produced by using angular multiplexing, and the full parallax display employs spatial multiplexing. 3D telepresence is demonstrated by taking multiple images from one location and transmitting the information via Ethernet to another location where the hologram is printed with the quasi-real-time dynamic 3D display. Further improvements could bring applications in telemedicine, prototyping, advertising, updatable 3D maps and entertainment. PMID:21048763

  14. Polarization holographic gratings in hybrid solgel films doped with Disperse Red 1.

    PubMed

    Raschellà, Raffaella; Marino, Iari-Gabriel; Lottici, Pier Paolo; Bersani, Danilo

    2003-11-15

    Polarization holographic gratings in sp configuration are written at 488 nm in photorefractive organic-inorganic films based on SiO2. The films, prepared by a solgel technique, contain Disperse Red 1, carbazole units, and 2,4,7-trinitro-9-fluorenone. The gratings are characterized by their diffraction efficiency for a 632.8-nm probe. The polarization gratings act as a half-wave plate, and the diffraction efficiency is independent of the polarization direction of the probe. PMID:14649954

  15. Volume holographic recording in nanoparticle-polymer composites doped with multifunctional chain transfer agents

    NASA Astrophysics Data System (ADS)

    Guo, Jinxin; Fujii, Ryuta; Tomita, Yasuo

    2015-10-01

    We report on an experimental investigation of the properties of volume holographic recording in photopolymerizable nanoparticle-polymer composites (NPCs) doped with chain transferring multifunctional di- and tri-thiols as chain transfer agents. It is shown that the incorporation of the multifunctional thiols into NPCs more strongly influences on volume holographic recording than that doped with mono-thiol since more chemical reactions involve in the polymer network formation. It is found that, as similar to the case of mono-thiol doping, there exist optimum concentrations of di- and tri-thiols for maximizing the saturated refractive index modulation. It is also seen that recording sensitivity monotonically decreases with an increase in multifunctional thiol concentration due to the partial inhibition of the photopolymerization event by excessive thiols.

  16. On the long time holographic grating recording process in azo-polymer

    NASA Astrophysics Data System (ADS)

    Sobolewska, Anna; Bartkiewicz, Stanislaw

    2009-09-01

    The authors report on a complex diffraction efficiency dynamics of the holographic grating recording process in azobenzene-functionalized polymer for a long recording time. The nonexponential dynamics was explain by the mechanism which assumes (i) simultaneous formation of three coupling phase gratings with constant, equal 0 or π, phase shifts between them and (ii) occurrence of gratings erasure processes when the recording time is long. Based on these assumptions and applying the Bessel function, the diffraction efficiency dynamics was calculated.

  17. Performance of 18 polymers in aluminum citrate colloidal dispersion gels

    SciTech Connect

    Smith, J.E.

    1995-11-01

    Colloidal dispersion gels are made up of low concentrations of polymer and aluminum citrate in water. These gels, which are mixed as a homogeneous solution at the surface, provide a valuable tool for in-depth blockage of high permeability regions of rock in heterogeneous reservoirs. Performance of colloidal dispersion gels depends strongly on the type and quality of polymer used. This paper provides an overview of the performance of 18 different polymers in colloidal dispersion gels. 14 of the polymers were partially hydrolyzed polyacrylamides or AMPS polymers in dry crystalline form with varying degrees of hydrolysis and molecular weight. The group also includes one cationic polyacrylamide, one carboxymethyl cellulose, one partially hydrolyzed polyacrylamide in emulsion form and one polysaccharide in dry form. Gels were mixed with the polymers at two polymer concentrations, three polymer:aluminum ratios and in different concentrations of potassium chloride. The gels were quantitatively tested at 1, 7, 14 and 28 days after crosslinking using the transition pressure test, which is a screen flow resistance test. Of the six polymer types tested, only the dry partially hydrolyzed polyacrylamides and AMPS polymers formed colloidal dispersion gels. Gel strength generally increased with increasing anionic charge and molecular weight; however, the manner in which the polymer is manufactured and the impurities present in the polymer also play roles which are more significant than originally expected.

  18. Hierarchically Ordered Polymer/Block Copolymer/Nanoparticle Systems Enabled via Holographic Photopolymerization

    NASA Astrophysics Data System (ADS)

    Bunning, Timothy

    2010-03-01

    Combining top-down and bottom-up methods in one process step creates novel hierarchical nanostructures with tailored properties. We demonstrate the ability to spatially pattern block copolymers or nanoparticles into periodic volume gratings using a one-step holographic patterning (HP) technique. The confinement of the second phase (e.g. block copolymer or nanoparticle) within the grating results in local preferential ordering of that phase, enabling single-step fabrication of complex hierarchical structures. As an example, this simple interfering photopolymer `writing' technique was utilized to generate a layer-in-layer structure of poly(ethylene oxide-b-epsilon-caprolactone) confined between crosslinked resin. The period of the volume grating was 200 nm, with the BCP occupying 100 nm of the 1-D structure. The BCP crystallized/phase separated to produce a lamellar structure with a 21 nm periodicity. This system exhibits interesting thermo-optical behavior during heating/cooling cycles. Alternatively, a layered polymer/nanoparticle composite was created through a one-step two-beam interference lithographic exposure of a dispersion of silica nanoparticles within a photopolymerizable mixture at a wavelength of 532 nm. The effects of exposure time and power, nanoparticle size, and periodicity on the nanocomposite structure were measured with transmission electron microscopy. The optical properties of the formed gratings were probed in real-time during formation. Collaborators on this work include M. Birnkrant and C. Li from Drexel University, A. Juhl and P. Braun from UIUC, and L. Natarajan, V. Tondiglia, and R. Vaia from AFRL.

  19. Biphotonic holographic grating recordings for different polarization configurations in spirooxazine-doped polymers.

    PubMed

    Zheng, Meiling; Xie, Xin; Zhang, Zhiying; Shi, Feng; Wang, Xiuli; Fu, Shencheng; Liu, Yichun

    2014-09-01

    Spirooxazine-doped polymers exhibit a fast photochromism response and high polarization sensitivity after irradiation in the short-wavelength range. Based on such properties, holographic grating recordings accompanying a linearly polarized blue-violet beam (405 nm) in a photochromic film were performed by two coherent green beams (532 nm) for s-s, p-p, s-p left-to-right circular polarization and right-to-right circular polarization. Under the biphotonic action of 405 and 532 nm, the temporal evolution of the diffraction efficiency was strongly dependent on the polarization configuration of the recording beams. It was found that the blue-violet irradiation plays a dual role in holographic recordings: generation of merocyanine aggregation and induction of anisotropy. The experimental results were precisely fitted with a phenomenological model, assuming the simultaneous formation of one absorption grating induced by the 532 nm light and two coupling phase gratings generated from the refractive index changes by recording and auxiliary beams. The existence of absorption and phase gratings was proved by observing the florescence emission of holographic gratings and testing the dependence of the diffraction efficiency on the reading beam polarization state, respectively. The results provided a good deal of insight into the photochromic behavior of spirooxazine in polymers and created a new range of applications in the field of high-density optical storage. PMID:25321382

  20. Electroacoustics of Particles Dispersed in Polymer Gel

    SciTech Connect

    Bhosale, Prasad S.; Chun, Jaehun; Berg, John C.

    2011-06-27

    This study examines the acoustic electrophoresis of particles dispersed in polymer hydrogels, with the particle size either less than or greater than the gel mesh size. When the particles are smaller than the gel mesh size, their acoustic vibration is resisted by only the background water medium, and the measured dynamic electrophoretic mobility, μd (obtained in terms of colloid vibration current, CVI), is the same as in water. For the case of particles larger than the gel mesh size, μd is decreased due to trapping, and the net decrease depends on the viscoelastic properties of the gel. The gel mesh size was varied by varying its crosslink density, the latter being characterized as the storage modulus, G’. The dependence of mobility on G’, for systems of a given particle size, and on particle size, for gels of a given G’, are investigated. The measured mobility remains constant as G’ is increased (i.e., mesh size is decreased) up to a value of approximately 300 Pa, beyond which it decreases. In the second set of measurements, the trapped particle size was increased in a gel medium of constant mesh size, with G’ approximately 100 Pa. In this case, the measured μd is found to be effectively constant over the particle size range studied (14-120 nm), i.e., it is independent of the degree of trapping as expressed by the ratio of the particle size to the mesh size.

  1. Characterization of volume holographic recording in photopolymerizable nanoparticle-(thiol-ene) polymer composites at 404 nm

    NASA Astrophysics Data System (ADS)

    Kawana, Masaru; Takahashi, Jun-ichiro; Yasui, Satoru; Tomita, Yasuo

    2015-02-01

    We report on the photopolymerization dynamics and the volume holographic recording properties of a thiol-ene based nanoparticle-polymer composite (NPC) doped with a blue-sensitive photoinitiator, Darocur® TPO, by using a highly coherent blue diode laser operating at a wavelength of 404 nm. Our study indicates that volume gratings recorded in the NPC amount to meeting the material requirements of refractive index modulation and material recording sensitivity for holographic data storage media. It is also found that polymerization shrinkage of recorded NPC gratings is higher than that of the same thiol-ene based NPC with a green (523 nm)-sensitive photoinitiator, Irgacure® 784/BzO2. We attribute such a difference in shrinkage to the photopolymerization dynamics at these recording wavelengths. We show that this shrinkage increase at 404 nm can be mitigated to some extent by controlling the thiol-ene stoichiometry in the NPC.

  2. Red light holographic recording and readout on an azobenzene-LC polymer hybrid composite system

    NASA Astrophysics Data System (ADS)

    Mao, Weidong; Sun, Qunhui; Baig, Sarfaraz; Lu, Hui; Wang, Michael R.

    2015-11-01

    We present for the first time stable red light two-dimensional image holographic recording in azobenzene-containing polymer-liquid crystal material following a pre-illumination process. The red light hologram recording is based on cis-to-trans transition of the azobenzene and surrounding LC reorientation. The diffraction efficiency of about 2% has been achieved and clear holograms of a commercial 2D USAF resolution target have been recorded. Using the same readout wavelength as the recording wavelength, color distortion that exists in most hologram researches with azo-containing materials is naturally eliminated. Long-time stabilities such as one-day continuous non-destructive readout and up to 10 weeks hologram storage have been demonstrated. The holographic recording material remains erasable and rewritable.

  3. Holographic digital data storage in a photorefractive polymer.

    PubMed

    Lundquist, P M; Poga, C; Devoe, R G; Jia, Y; Moerner, W E; Bernal, M P; Coufal, H; Grygier, R K; Hoffnagle, J A; Jefferson, C M; Macfarlane, R M; Shelby, R M; Sincerbox, G T

    1996-06-15

    We report high-contrast storage of 64-kbit digital data pages in a photorefractive polymer material. Singlepage writing, reading, and erasing operations were demonstrated with a dual-function-dopant polymeric material having a dark lifetime of several days. Data were reconstructed without error by use of several simple readout algorithms. PMID:19876193

  4. Holographic gratings in photorefractive polymers without external electric field

    NASA Astrophysics Data System (ADS)

    Kukhtarev, Nickolai V.; Lyuksyutov, Sergei F.; Buchhave, Preben; Volodin, Boris L.

    1997-09-01

    Using anomalous large diffusion we report a recording of reflection type gratings in a PVK-based photorefractive polymer without any external electric field. Diffraction efficiency of the gratings was measured to be 7%. An efficient modulation of beams during two-beam coupling up to 12% was demonstrated by using phase mutilation technique. This practical scheme can be used in dynamic vibration measurements.

  5. Dispersing nanoparticles in a polymer film via solvent evaporation

    DOE PAGESBeta

    Cheng, Shengfeng; Grest, Gary S.

    2016-05-19

    Large-scale molecular dynamics simulations are used to study the dispersion of nanoparticles (NPs) in a polymer film during solvent evaporation. As the solvent evaporates, a dense polymer-rich skin layer forms at the liquid/vapor interface, which is either NP rich or poor depending on the strength of the NP/polymer interaction. When the NPs are strongly wet by the polymer, the NPs accumulate at the interface and form layers. However, when the NPs are only partially wet by the polymer, most NPs are uniformly distributed in the bulk of the polymer film, with the dense skin layer serving as a barrier tomore » prevent the NPs from moving to the interface. Furthermore, our results point to a possible route to employ less favorable NP/polymer interactions and fast solvent evaporation to uniformly disperse NPs in a polymer film, contrary to the common belief that strong NP/polymer attractions are needed to make NPs well dispersed in polymer nanocomposites.« less

  6. Interphase and particle dispersion correlations in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Senses, Erkan

    Particle dispersion in polymer matrices is a major parameter governing the mechanical performance of polymer nanocomposites. Controlling particle dispersion and understanding aging of composites under large shear and temperature variations determine the processing conditions and lifetime of composites which are very important for diverse applications in biomedicine, highly reinforced materials and more importantly for the polymer composites with adaptive mechanical responses. This thesis investigates the role of interphase layers between particles and polymer matrices in two bulk systems where particle dispersion is altered upon deformation in repulsive composites, and good-dispersion of particles is retained after multiple oscillatory shearing and aging cycles in attractive composites. We demonstrate that chain desorption and re-adsorption processes in attractive composites under shear can effectively enhance the bulk microscopic mechanical properties, and long chains of adsorbed layers lead to a denser entangled interphase layer. We further designed experiments where particles are physically adsorbed with bimodal lengths of homopolymer chains to underpin the entanglement effect in interphases. Bimodal adsorbed chains are shown to improve the interfacial strength and used to modulate the elastic properties of composites without changing the particle loading, dispersion state or polymer conformation. Finally, the role of dynamic asymmetry (different mobilities in polymer blends) and chemical heterogeneity in the interphase layer are explored in systems of poly(methyl methacrylate) adsorbed silica nanoparticles dispersed in poly(ethylene oxide) matrix. Such nanocomposites are shown to exhibit unique thermal-stiffening behavior at temperatures above glass transitions of both polymers. These interesting findings suggest that the mobility of the surface-bound polymer is essential for reinforcement in polymer nanocomposites, contrary to existing glassy layer theories

  7. Photochromism of spirooxazine-doped polymers studied by monitoring dynamics of holographic gratings

    NASA Astrophysics Data System (ADS)

    Xie, Xin; Zheng, Meiling; Fu, Shencheng; Shi, Feng; Wang, Xiuli; Zhan, Naiyan

    2015-03-01

    As an organic photochromic material, spirooxazine attracted widespread attention because of its high fatigue resistance and thermal stability. In this paper, the photochromism of spirooxazine was studied by monitoring the dynamics of holographic gratings in spirooxazine-doped polymer films. A theoretical description for the transformation of spirooxazine and merocyanine molecules was carried out, which agrees well with the experimental results. The photochromism of spirooxazine-doped different matrixes were studied, the photochromic rate and fatigue resistance of spirooxazine-doped SiO2 films were found to be better than spirooxazine-doped PMMA films.

  8. Shift-multiplexed holographic digital data page storage in a nanoparticle-(thiol-ene) polymer composite film.

    PubMed

    Momose, Keisuke; Takayama, Shingo; Hata, Eiji; Tomita, Yasuo

    2012-06-15

    We demonstrate shift-multiplexed holographic storage of 180 digital data pages with low symbol-error rates in a thick (250 μm) SiO2 nanoparticle-polymer composite film using step-growth thiol-ene photopolymerization. A two-dimensional 2:4 modulation code was employed for formatting digital data pages in order to reduce the average intensity of code block without decreasing the coding efficiency. This study clearly shows the feasibility of the thiol-ene based nanoparticle-polymer composite system as a holographic data storage medium. PMID:22739871

  9. Holographic recording in films of azo-containing LC polymers in the presence of orienting electric field

    SciTech Connect

    Simonov, A N; Larichev, A V; Shibaev, Valerii P

    2000-07-31

    The dynamics of holographic recording in a film of azo-containing liquid-crystal polymer is studied both experimentally and theoretically in the presence of the orienting electric field. The possibility is demonstrated to efficiently control the optical recording regime by varying the applied field. The specificity of hologram formation in the case of different polarisation of the interacting light beams is considered. A theoretical model describing the holographic recording dynamics in a film of azo-containing nematic polymer is presented; numerical simulation of the processes of recording and read-out in anisotropic holograms is carried out as well. (laser applications and other topics in quantum electronics)

  10. Characterization of photopolymerizable nanoparticle-(thiol-ene) polymer composites for volume holographic recording at 404 nm

    NASA Astrophysics Data System (ADS)

    Kawana, Masaru; Takahashi, Jun-ichiro; Yasui, Satoru; Tomita, Yasuo

    2014-05-01

    We report on volume holographic recording in thiol-ene based nanoparticle-polymer composites (NPCs) at a wavelength of 404 nm by using a highly coherent blue diode laser. We study the photopolymerization dynamics of two types of thiol-ene based NPCs doped with different blue-sensitive initiator/sensitizer systems (Darocur ® TPO and Irgacure ® 784/BzO2) at various doping concentrations. We also characterize a volume holographic grating recorded in these two types of thiol-ene based NPCs. Such material characterization includes the refractive index modulation, the material recording sensitivity and polymerization shrinkage. It is shown that Darocur R _ TPO provides larger refractive index modulation and higher material recording sensitivity than those with Irgacure ® 784/BzO2 but these two blue-sensitive initiator/sensitizer systems amount to meeting the requirements of the refractive index modulation and the material recording sensitivity for holographic data storage. However, it is found that shrinkage reduction of a volume grating recorded in these two types of thiol-ene based NPCs at 404 nm is not as effective as the same thiol-ene based NPC doped with Irgacure ® 784/BzO2 at 532 nm.

  11. Two-wavelength exposure enhancement in holographic data storage of spirooxazine-doped polymers

    NASA Astrophysics Data System (ADS)

    Xie, Xin; Zheng, Meiling; Fu, Shencheng; Wang, Xiuli; Li, Ye; Liu, Yichun

    2015-03-01

    Spirooxazine could be used as optical storage medium due to the excellent photochromic characteristic. In this paper, dynamics of holographic grating recording in spirooxazine-doped PMMA polymers was investigated using two coherent green beams (532 nm) and auxiliary blue-violet beam (405 nm) of various powers. The diffraction efficiency and growth rate of holographic gratings as well as the production rate of H-aggregation of merocyanine were strongly dependent on the auxiliary light power. In terms of these effects, an Aggregation Model was proposed, which was found to be in good agreement with the measurements. The corresponding dynamic parameters were obtained by fitting the experimental results, indicating that both the thermal rate constant and the aggregating rate constant increase exponentially versus the auxiliary light power. With the help of this model, the maximum brightness of reconstruction images was calculated and proved experimentally at the blue-violet light power of 57 mW. The results present a new approach to enhance the efficiency in spirooxazine-based films for holographic storage.

  12. Three-dimensional holographic imaging of living tissue using a highly sensitive photorefractive polymer device.

    PubMed

    Salvador, M; Prauzner, J; Köber, S; Meerholz, K; Turek, J J; Jeong, K; Nolte, D D

    2009-07-01

    Photorefractive materials are dynamic holographic storage media that are highly sensitive to coherent light fields and relatively insensitive to a uniform light background. This can be exploited to effectively separate ballistic light from multiply-scattered light when imaging through turbid media. We developed a highly sensitive photorefractive polymer composite and incorporated it into a holographic optical coherence imaging system. This approach combines the advantages of coherence-domain imaging with the benefits of holography to form a high-speed wide-field imaging technique. By using coherence-gated holography, image-bearing ballistic light can be captured in real-time without computed tomography. We analyzed the implications of Fourier-domain and image-domain holography on the field of view and image resolution for a transmission recording geometry, and demonstrate holographic depth-resolved imaging of tumor spheroids with 12 microm axial and 10 microm lateral resolution, achieving a data acquisition speed of 8 x 10(5) voxels/s. PMID:19582098

  13. Magnetic particle dispersion in polymer solution

    NASA Astrophysics Data System (ADS)

    Jeon, Kwang Seoung

    Magnetic particle dispersions were prepared in order to observe the effect of particle surface properties, concentration and functional group of binder, milling time, and solvent on dispersion properties. Rheology and transverse susceptibility measurements were used to characterize the dispersion quality of the magnetic paints macroscopically and microscopically, respectively. In this study, by applying the acid-base concept, methods to optimize magnetic dispersions were established. Initially, interaction between acid-base sites on particles and binder was investigated by poisoning the sites with chemicals, then quantifying each type of adsorption (hydrogen and chemical adsorption) using thermogravimetric analysis. With this fundamental information, effects of typical dispersion parameters were investigated. The acid base interaction between binder solution and particles was related to the magnetic and rheological properties of magnetic inks. The results have significant implications for high density particulate media where dispersion will become increasingly important.

  14. Pattern Polymerization-Induced Phase Separation in a Polymer-Dispersed Liquid Crystal System

    NASA Astrophysics Data System (ADS)

    Kyu, Thein

    2002-03-01

    Liquid crystal (LC)/polymer composite films have gained attention increasingly due to their applications in flat panel displays and shutters. Photopolymerization is a preferred method to produce LC/polymer composite films from mixtures of reactive monomers and LCs. On the basis of the combined Flory-Huggins free energy for isotropic mixing and Maier-Saupe free energy for nematic ordering along with the elastic free energy of the network, phase diagrams have been established by solving self-consistently. A theoretical simulation has been modeled by incorporating the kinetics of crosslinking reaction into the time-dependent Ginzburg-Landau (TDGL-model C) equations to elucidate the emergence of nematic domains during photopolymerization induced phase separation in electrically switchable holographic polymer-dispersed liquid crystals (H-PDLC). The simulated morphological patterns in the concentration and orientation order parameter fields show discrete layers of liquid crystal droplets alternating periodically with polymer network-rich layers. Furthermore, we recognized the potential for producing electrically tunable microlens from PDLC systems through pattern-photopolymerization-induced phase separation by means of the interference of two horizontal waves and two vertical waves. Our simulation revealed that the emerged LC microlens are of the order of a few hundred nanometers. These LC microlens are not only uniformed in size, but also form in regular arrays, reminiscence of the compound eyes found in flies, ants, and wasps. Supported by ALCOM, NSF DMR 99-03519, and OBR.

  15. Efficient configuration transition in a new azobenzene-LC polymer for red light holographic recording

    NASA Astrophysics Data System (ADS)

    Mao, Weidong; Sun, Qunhui; Baig, Sarfaraz; Lu, Hui; Wang, Michael R.

    2012-02-01

    We demonstrate cis-to-trans transition based red light holographic recording in an azobenzene-liquid crystal (LC) polymer material following efficient crucial transition of trans-to-cis, which is prepared by selected wavelength light pre-illumination. The presence and orientation of soft liquid crystal impregnating the polymer backbone allows the cis intermediate states to hold for the stable red hologram recording and non-destructive readout. Using a 50 nm bandwidth light source at the center wavelength of 575 nm, we have efficient pre-illumination on the material. The diffraction efficiency of up to 2% can be achieved by a HeNe laser at 632.8 nm wavelength, and two-dimensional holograms of USAF resolution target are successfully recorded.

  16. Polymers at interfaces and in colloidal dispersions.

    PubMed

    Fleer, Gerard J

    2010-09-15

    This review is an extended version of the Overbeek lecture 2009, given at the occasion of the 23rd Conference of ECIS (European Colloid and Interface Society) in Antalya, where I received the fifth Overbeek Gold Medal awarded by ECIS. I first summarize the basics of numerical SF-SCF: the Scheutjens-Fleer version of Self-Consistent-Field theory for inhomogeneous systems, including polymer adsorption and depletion. The conformational statistics are taken from the (non-SCF) DiMarzio-Rubin lattice model for homopolymer adsorption, which enumerates the conformational details exactly by a discrete propagator for the endpoint distribution but does not account for polymer-solvent interaction and for the volume-filling constraint. SF-SCF corrects for this by adjusting the field such that it becomes self-consistent. The model can be generalized to more complex systems: polydispersity, brushes, random and block copolymers, polyelectrolytes, branching, surfactants, micelles, membranes, vesicles, wetting, etc. On a mean-field level the results are exact; the disadvantage is that only numerical data are obtained. Extensions to excluded-volume polymers are in progress. Analytical approximations for simple systems are based upon solving the Edwards diffusion equation. This equation is the continuum variant of the lattice propagator, but ignores the finite segment size (analogous to the Poisson-Boltzmann equation without a Stern layer). By using the discrete propagator for segments next to the surface as the boundary condition in the continuum model, the finite segment size can be introduced into the continuum description, like the ion size in the Stern-Poisson-Boltzmann model. In most cases a ground-state approximation is needed to find analytical solutions. In this way realistic analytical approximations for simple cases can be found, including depletion effects that occur in mixtures of colloids plus non-adsorbing polymers. In the final part of this review I discuss a

  17. Holographic binary grating liquid crystal cells fabricated by one-step exposure of photocrosslinkable polymer liquid crystalline alignment substrates to a polarization interference ultraviolet beam.

    PubMed

    Kawai, Kotaro; Sasaki, Tomoyuki; Noda, Kohei; Sakamoto, Moritsugu; Kawatsuki, Nobuhiro; Ono, Hiroshi

    2015-07-01

    Holographic binary grating liquid crystal (LC) cells, in which the optical anisotropy was rectangularly modulated even as the grating was fabricated using holographic exposure, were fabricated by one-step polarization holographic exposure of an empty glass cell, the interior of which was coated with a photocrosslinkable polymer LC (PCLC). The present study is of great significance in that three types of holographic binary grating LC cells containing twisted alignments can be fabricated by simultaneous exposure of two PCLC substrates to the UV interference beams, which are sinusoidally modulated. The polarization conversion properties of the diffracted beams are explained well by theoretical analysis based on Jones calculus. PMID:26193145

  18. Nanostructured hybrid materials from aqueous polymer dispersions.

    PubMed

    Castelvetro, Valter; De Vita, Cinzia

    2004-05-20

    Organic-inorganic (O-I) hybrids with well-defined morphology and structure controlled at the nanometric scale represent a very interesting class of materials both for their use as biomimetic composites and because of their potential use in a wide range of technologically advanced as well as more conventional application fields. Their unique features can be exploited or their role envisaged as components of electronic and optoelectronic devices, in controlled release and bioencapsulation, as active substrates for chromatographic separation and catalysis, as nanofillers for composite films in packaging and coating, in nanowriting and nanolithography, etc. A synergistic combination or totally new properties with respect to the two components of the hybrid can arise from nanostructuration, achieved by surface modification of nanostructures, self-assembling or simply heterophase dispersion. In fact, owing to the extremely large total surface area associated with the resulting morphologies, the interfacial interactions can deeply modify the bulk properties of each component. A wide range of starting materials and of production processes have been studied in recent years for the controlled synthesis and characterization of hybrid nanostructures, from nanoparticle or lamellar dispersions to mesoporous materials obtained from templating nanoparticle dispersions in a continuous, e.g. ceramic precursor, matrix. This review is aimed at giving some basic definitions of what is intended as a hybrid (O-I) material and what are the main synthetic routes available. The various methods for preparing hybrid nanostructures and, among them, inorganic-organic or O-I core-shell nanoparticles, are critically analyzed and classified based on the reaction medium (aqueous, non-aqueous), and on the role it plays in directing the final morphology. Particular attention is devoted to aqueous systems and water-borne dispersions which, in addition to being environmentally more acceptable or even a

  19. Dispersion of Soft Nanoparticles in a Chemically Identical Polymer Matrix

    NASA Astrophysics Data System (ADS)

    Ratnaweera, Dilru; Baskaran, D.; Holley, D.; Ruppel, M.; Mays, J.; Urban, V.; Dadmun, Mark

    2013-03-01

    The mechanical, thermal and rheological properties of polymers can be improved by embedding organic nanoparticles (NPs). However, controlling the dispersion of NPs is often challenging due to thermodynamic and kinetic incompatibilities between particles and matrices. The current work focuses on the dispersion of chemically identical NPs in a polystyrene matrix. These NPs were made through a micro-emulsion technique using styrene and divinylbenzene (DVB) monomers. Polystyrene nanoparticles with controlled interfacial roughness and targeted styrene densities were achieved by controlling DVB volume fraction during synthesis. The dispersion of these NPs in deuterated polystyrene matrices was followed by Small Angle Neutron Scattering as a function of NP concentration and matrix molecular weight. At low NP concentrations, individual NPs are well distributed in the matrix, while aggregates were formed at higher concentrations in high molecular weight polymer matrices. Shape of the aggregates as well as the minimum concentration of NPs required to form aggregates were affected by the surface roughness and softness of the NPs.

  20. Correlation measurements of light transmittance in polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Maksimyak, P. P.; Nehrych, A. L.

    2015-11-01

    The methods of correlation optics are for the first time applied to study structure of liquid crystal (LC) - polymer (P) composites at various concentrations of LC and P. Their phase correlation function (PCF) was obtained considering LC-P composite as a random phase screen. The amplitude of PCF contains information about number of LC domains and structure of LC director inside of them, while a half-width of this function is connected with a size of these domains. We studied unpowered and powered composite layers with a thickness of 5 μm. As liquid crystal and polymer were used nematic LC E7 from Merck and photopolymer composition NOA65 from Norland. Concentration of polymer φP was varied in a range 10-55 vol. %. In good agreement with previous studies by SEM technique we detected monotone decrease of LC domains with concentration of polymer. With application of electric field, amplitude of PCF behaves differently for the samples with different polymer content. For the samples with φP>35 vol. % (samples having morphology of polymer dispersed LC), this dependence is monotonic. In turn, if φP<35 vol. % (samples with polymer network LC morphology), the amplitude of PCF non-monotonically depends on the applied voltage going through a maximum. The latter fact is explained by transformation of orientational defects of LC phase with the applied voltage.

  1. Dispersion of Mixed Brush Gold Nanorods in Polymer Matrices

    NASA Astrophysics Data System (ADS)

    Ferrier, Robert; Koski, Jason; Riggleman, Robert; Composto, Russell

    In this work we investigate, both experimentally and through hybrid particle/self-consistent field theoretic (hSCFT) calculations, the dispersion state of gold nanorods (AuNRs) grafted with homopolymer, bidispersed, or mixed polymer brushes. AuNRs are grafted with 11.5 kg/mol PS (HNRs), 11.5 kg/mol PS and 5.3 kg/mol PS (BNRs), or 11.5 kg/mol PS and 5 kg/mol poly(methyl methacrylate) (PMMA) (MBNRs) and cast in PS or PMMA films consisting of short to very long chains compared to the grafted brush. We further investigated the MBNR systems by varying the length of the PS brush. Overall, we find that the MBNRs dispersed markedly better than the other brush types (HNRs or BNRs) in PS matrices. We utilize hSCFT calculations, in particular potential of mean force (PMF) and brush profile calculations, to elucidate the thermodynamics of these systems. The PMFs and brush profiles exhibit similar trends for the BNRs and MBNRs where the short grafted chain forces the longer grafted chain away from the AuNR surface and promotes wetting by the matrix chains. The hSCFT calculations demonstrated qualitative trends consistent with the aggregation observed for AuNRs in PMMA matrices. Therefore, we have demonstrated that MBNR dispersion in polymer matrices is enhanced compared to the HNR and BNR cases, which extends the dispersion window for new combinations of nanorods and polymers.

  2. Effect of pH on the holographic properties of Al2O3 nanoparticle dispersed acrylate photopolymer

    NASA Astrophysics Data System (ADS)

    Li, Yun-Xi; Li, Chun-Liu; Huang, Ming-Ju

    2014-03-01

    Several different pH of Al2O3 nano-fluid were prepared using dispersant and doped into polyvinyl alcohol (PVA)/acrylamide (AA) based photopolymers where the photopolymers were exposed with 647 nm Ar+Kr+ laser to study its holographic properties. The research shows that the incorporation of Al2O3 nanoparticles (NPs) improves the holographic characteristics of sample, where the pH has an effect to the dispersion of Al2O3 NPs in the photopolymer. When the pH of Al2O3 nano-fluid is about 7, the diffraction efficiency of the sample can be raised to 93.8%, the maximum refractive index modulation can be increased to 2.28×10-3, the shrinkage can be depressed to 0.8%, the Bragg mismatch is 0.04°, and the concentration of 10 nm Al2O3 nano-fluid modified by high definition (HD) dispersant must be 1.02×10-3molṡL-1.

  3. Polymer-Particle Nanocomposites: Size and Dispersion Effects

    NASA Astrophysics Data System (ADS)

    Moll, Joseph

    Polymer-particle nanocomposites are used in industrial processes to enhance a broad range of material properties (e.g. mechanical, optical, electrical and gas permeability properties). This dissertation will focus on explanation and quantification of mechanical property improvements upon the addition of nanoparticles to polymeric materials. Nanoparticles, as enhancers of mechanical properties, are ubiquitous in synthetic and natural materials (e.g. automobile tires, packaging, bone), however, to date, there is no thorough understanding of the mechanism of their action. In this dissertation, silica (SiO2) nanoparticles, both bare and grafted with polystyrene (PS), are studied in polymeric matrices. Several variables of interest are considered, including particle dispersion state, particle size, length and density of grafted polymer chains, and volume fraction of SiO2. Polymer grafted nanoparticles behave akin to block copolymers, and this is critically leveraged to systematically vary nanoparticle dispersion and examine its role on the mechanical reinforcement in polymer based nanocomposites in the melt state. Rheology unequivocally shows that reinforcement is maximized by the formation of a transient, but long-lived, percolating polymer-particle network with the particles serving as the network junctions. The effects of dispersion and weight fraction of filler on nanocomposite mechanical properties are also studied in a bare particle system. Due to the interest in directional properties for many different materials, different means of inducing directional ordering of particle structures are also studied. Using a combination of electron microscopy and x-ray scattering, it is shown that shearing anisotropic NP assemblies (sheets or strings) causes them to orient, one in front of the other, into macroscopic two-dimensional structures along the flow direction. In contrast, no such flow-induced ordering occurs for well dispersed NPs or spherical NP aggregates! This work

  4. Modeling swelling and absorption dynamics for holographic sensing in analytes sensitive photopolymer

    NASA Astrophysics Data System (ADS)

    Liu, Hongpeng; Yu, Dan; Mao, Dongyao; Geng, Yaohui; Wang, Weibo

    2016-06-01

    A theoretical model is developed to describe holographic sensing and swelling of grating fringe in photopolymer. In experiments, diffraction spectrum responses of grating are characterized to exhibit holographic sensing processes. Analytic expressions between swelling of grating fringe and environmental factors, such as relative humidity and organic vapor concentrations, are extracted based on experimental results. The primary factors are introduced into the model to simulate the sensing process, including swelling ratio, nanozeolites dispersion, and organic vapor absorption. Finally, numerical results are presented for improving the sensitivity of holographic sensor. This work can accelerate the development of holographic sensor and provide a theoretical base for exploring sensing mechanism of polymer.

  5. Theoretical modeling of the effect of polymer chain immobilization rates on holographic recording in photopolymers.

    PubMed

    Mackey, Dana; O'Reilly, Paul; Naydenova, Izabela

    2016-05-01

    This paper introduces an improved mathematical model for holographic grating formation in an acrylamide-based photopolymer, which consists of partial differential equations derived from physical laws. The model is based on the two-way diffusion theory of [Appl. Opt.43, 2900 (2004)10.1364/AO.43.002900APOPAI1559-128X], which assumes short polymer chains are free to diffuse, and generalizes a similar model presented in [J. Opt. Soc. Am. B27, 197 (2010)10.1364/JOSAB.27.000197JOBPDE0740-3224] by introducing an immobilization rate governed by chain growth and cross-linking. Numerical simulations were carried out in order to investigate the behavior of the photopolymer system for short and long exposures, with particular emphasis on the effect of recording parameters (such as illumination frequency and intensity), as well as material permeability, on refractive index modulation, refractive index profile, and grating distortion. The model reproduces many well-known experimental observations, such as the decrease of refractive index modulation at high spatial frequencies and appearance of higher harmonics in the refractive index profile when the diffusion rate is much slower than the polymerization rate. These properties are supported by a theoretical investigation which uses perturbation techniques to approximate the solution over various time scales. PMID:27140889

  6. Photochemistry of tertiary nitrosoalkanes in solid polymer matrices: a promising new class of organic materials for holographic recording with semiconductor lasers

    SciTech Connect

    Pinsl, J.; Gehrtz, M.; Reggel, A.; Braeuchle, C.

    1987-10-14

    The authors have investigated a new class of photopolymers for near-infrared (near IR) holographic recording: three members of the tertiary nitrosoalkanes (RNO) dissolved in two different poly(alkyl ..cap alpha..-cyanoacrylates) (p-(alkyl-CAc)). Absorption/transmission spectroscopy, a CW holographic technique (PIH), and a newly developed phase-sensitive holographic technique, phase-modulated holography (PMH), were employed in these investigations. The last technique is an ideal tool for the investigation of photopolymer systems because it allows one to monitor separately and simultaneously the amplitude and phase contributions to the holographic grating and thus to monitor simultaneously the photoreaction of the RNO and the resulting holographic recording mechanism. The RNO in p-(alkyl-CAc) undergo a homolytic dissociation after absorption of one photon at wavelengths up to 799 nm. The corresponding photochemical rates, the quantum yields, and the activation energies were determined and were found to depend strongly on the glass transition temperature of the polymer solvent. However, hologram formation arises not only from the photoreaction of the RNO but mainly from a photoinduced expansion of the polymer matrix, i.e., a photomechanical effect. The resulting density change, which is associated with a large change of refractive index, does not depend on the RNO but on the matrix only. The near-IR holographic sensitivities of the new photopolymers were determined. They are high due to the considerable photomechanical effect, allowing one to write holographic gratings with a GaAlAs semiconductor laser at 788 nm.

  7. Analysis of the kinetics of diffraction efficiency during the holographic grating recording in azobenzene functionalized polymers.

    PubMed

    Sobolewska, Anna; Miniewicz, Andrzej

    2007-02-22

    The laser-assisted holographic grating recording process in films of azobenzene functionalized polymers is usually studied by observation of the efficiency of light scattering on a developing in time diffraction grating. Various possible mechanisms contributing to grating formation as well as the bulk or surface origin (bulk refractive index and/or relief grating) of light scattering make the analysis of kinetics of grating recording, from the light scattering data only, difficult and ambiguous. To fully explain experimentally observed various and complex (frequently nonexponential) kinetics of the first-order light diffraction intensity, we considered a simple single-exponential growth of the two phase gratings in the same polymer film. In modeling we assumed that the bulk refractive index grating Deltan(t) and the surface relief grating Deltad(t) differ considerably in their growth rates and we allowed for a nonstationary phase shift Deltaphi(t) between them which was experimentally observed during the recording process. The origin of the nonstationary phase shift is a result of a slow shift of interference pattern due to delicate symmetry breaking in illumination conditions (e.g., difference in beam intensities and deviation of exact symmetrical beam incidence angles on the sample). Changing only such parameters as stationary amplitudes of refractive index and relief gratings for a span of phase shifts (0-pi) between them, we obtained a series of kinetic responses which we discuss and interpret. The various examples of temporal evolution of diffraction efficiency for the same grating formation kinetics, modeled in our work, supply evidence that great care must be taken to properly interpret the experimental results. PMID:17263574

  8. Dispersion of carbon nanotubes in vinyl ester polymer composites

    NASA Astrophysics Data System (ADS)

    Pena-Paras, Laura

    This work focused on a parametric study of dispersions of different types of carbon nanotubes in a polymer resin. Single-walled (SWNTs), double-walled (DWNTs), multi-walled (MWNTs) and XD-grade carbon nanotubes (XD-CNTs) were dispersed in vinyl ester (VE) using an ultra-sonic probe at a fixed frequency. The power, amplitude, and mixing time parameters of sonication were correlated to the electrical and mechanical properties of the composite materials in order to optimize dispersion. The quality of dispersion was quantified by Raman spectroscopy and verified through optical and scanning electron microscopy. By Raman, the CNT distribution, unroping, and damage was monitored and correlated with the composite properties for dispersion optimization. Increasing the ultrasonication energy was found to improve the distribution of all CNT materials and to decrease the size of nanotube ropes, enhancing the electrical conductivity and storage modulus. However, excessive amounts of energy were found to damage CNTs, which negatively affected the properties of the composite. Based on these results the optimum dispersion energy inputs were determined for the different composite materials. The electrical resistivity was lowered by as much as 14, 13, 13, and 11 orders of magnitude for SWNT/VE, DWNT/VE, MWNT/VE, and XD-CNT/VE respectively, compared to the neat resin. The storage modulus was also increased compared to the neat resin by 77%, 82%, 45%, 40% and 85% in SWNT, SAP-f-SWNT, DWNT, MWNT and XD-CNT/VE composites, respectively. This study provides a detailed understanding of how the properties of, nanocomposites are determined by the composite mixing parameters and the distribution, concentration, shape and size of the CNTs. Importantly, it indicates the importance of the need for dispersion metrics to correlate and understand these properties.

  9. Chromonic liquid crystals and their dispersion in polymers

    NASA Astrophysics Data System (ADS)

    Park, Jung; Yao, Xuxia; Srinivasarao, Mohan

    2010-03-01

    Chromonic liquid crystals can self-assemble into an ordered complex fluid, potentially applicable for biosensor, polarizers, optical compensetors and organic solar cells. Different from common amphiphilic lyotropic mesophases, aggregation of the chromonic liquid crystals is thought to be isodesmic and without optimum aggregation size. We studied the aggregation behavior by Vis-spectroscopy, and the phase behavior by polarizing optical microscopy and differential scanning calorimetry. We also used capillary flow to achieve uniform planar alignment in a flat capillary, and measured polarized Raman scattering, from which the temperature and concentration dependence of order parameters, both and , and the orientation distribution were deduced. Order parameters increase as concentration increases and decrease as temperature increases. Polymer dispersed chromonic droplets with different director configurations were obtained by using different water soluble polymers and those anchoring phenomena were compared.

  10. Conjugated polymer-assisted dispersion of single-wall carbon nanotubes: the power of polymer wrapping.

    PubMed

    Samanta, Suman Kalyan; Fritsch, Martin; Scherf, Ullrich; Gomulya, Widianta; Bisri, Satria Zulkarnaen; Loi, Maria Antonietta

    2014-08-19

    The future application of single-walled carbon nanotubes (SWNTs) in electronic (nano)devices is closely coupled to the availability of pure, semiconducting SWNTs and preferably, their defined positioning on suited substrates. Commercial carbon nanotube raw mixtures contain metallic as well as semiconducting tubes of different diameter and chirality. Although many techniques such as density gradient ultracentrifugation, dielectrophoresis, and dispersion by surfactants or polar biopolymers have been developed, so-called conjugated polymer wrapping is one of the most promising and powerful purification and discrimination strategies. The procedure involves debundling and dispersion of SWNTs by wrapping semiflexible conjugated polymers, such as poly(9,9-dialkylfluorene)s (PFx) or regioregular poly(3-alkylthiophene)s (P3AT), around the SWNTs, and is accompanied by SWNT discrimination by diameter and chirality. Thereby, the π-conjugated backbone of the conjugated polymers interacts with the two-dimensional, graphene-like π-electron surface of the nanotubes and the solubilizing alkyl side chains of optimal length support debundling and dispersion in organic solvents. Careful structural design of the conjugated polymers allows for a selective and preferential dispersion of both small and large diameter SWNTs or SWNTs of specific chirality. As an example, with polyfluorenes as dispersing agents, it was shown that alkyl chain length of eight carbons are favored for the dispersion of SWNTs with diameters of 0.8-1.2 nm and longer alkyls with 12-15 carbons can efficiently interact with nanotubes of increased diameter up to 1.5 nm. Polar side chains at the PF backbone produce dispersions with increased SWNT concentration but, unfortunately, cause reduction in selectivity. The selectivity of the dispersion process can be monitored by a combination of absorption, photoluminescence, and photoluminescence excitation spectroscopy, allowing identification of nanotubes with specific

  11. Dispersion/Aggregation of polymer grafted nanorods in a polymer matrix studied by Dissipative Particle Dynamics

    NASA Astrophysics Data System (ADS)

    Maia, Joao; Khani, Shaghayegh

    2015-03-01

    Nanorods are incorporated into polymer matrices for fabricating composite materials with enhanced physical and mechanical properties.The final macroscopic properties of the composites are directly related to the dispersion and organization of the nanoparticles in the matrix. For instance, a significant improvement in the mechanical properties of the nanorod-polymer composites is observed upon formation of a percolating network. One way of controlling the assembly of nanorods in the polymer medium is adjusting the chemical interactions which is done through grafting polymer chains on the surface of the rods. The recent developments in the computational techniques have paved the road for further understanding of the controlled dispersion and aggregation of nanorods in polymer matrices. In this study, Dissipative Particle Dynamics (DPD) is employed in order to investigate the effect of enthalpic and entopic variables on the phase behavior of the abovementioned nanocomposites. In DPD, the interaction parameter between the components of the systems can be mapped onto the Flory-Huggins χ-parameter via well-known Groot-Warren expression. This works studies the effect of the enthalpic and entropic variables on phase transitions. The main goal is to provide a phase diagram than can be used to guide the experiments in designing new materials.

  12. Holographic polymer networks formed in liquid crystal phase modulators via a He-Ne laser to achieve ultra-fast optical response.

    PubMed

    Chien, Chun-Yu; Hsu, Che-Ju; Chen, Yu-Wen; Tseng, Sheng-Hao; Sheu, Chia-Rong

    2016-04-01

    The holographic polymer network formed in liquid crystal (LC) phase modulators via a He-Ne laser in this study demonstrates ultra-fast optically response and low light scattering. These advantages are mainly caused by the small LC domains and uniform polymer network when processing LC cells via holographic exposure to a He-Ne laser. The use of this method to fabricate LC cells as phase modulators results in a decay time of 49 μs under 2π phase modulation at room temperature. The predicted fast optical response can be achieved when operating devices at high temperatures. PMID:27137042

  13. Polymer-grafted gold nanorods in polymer thin films: Dispersion and plasmonic coupling

    NASA Astrophysics Data System (ADS)

    Hore, Michael-Jon Ainsley

    This dissertation describes complementary experimental and theoretical studies to deter- mine the thermodynamic factors that affect the dispersion of polymer-grafted Au nanorods within polymer thin films. Au nanorods exhibit a uniform dispersion with a regular spacing for favorable brush / matrix interactions, such as poly(ethylene glycol) (PEG)-Au / poly(methyl methacrylate) (PMMA) and polystyrene (PS)-Au / poly(2,6-dimethyl-p-phenylene oxide) (PPO). For PEG-Au / PMMA, the nanorods are locally oriented and their dispersion is independent of the ratio of the degree of polymerization of the matrix (P) to that of the brush (N), α = P/N, whereas for chemically similar brush / matrix combinations, such as PS-Au / PS and PEG-Au / poly(ethylene oxide) (PEO), nanorods are randomly dispersed for α 2. For aggregated systems (α > 2), nanorods are found primarily within aggregates containing side-by-side aligned nanorods with a spacing that scales with N. UV-visible spectroscopy and discrete dipole approximation (DDA) calculations demonstrate that coupling between surface plasmons within the aggregates leads to a blue shift in the optical absorption as α increases, indicating the sensitivity of spectroscopy for determining nanorod dispersion in polymer nanocomposite films. Self-consistent field theory (SCFT) calculations and Monte Carlo (MC) simulations show that the aggregation of nanorods for α > 2 can be attributed to depletion-attraction forces caused by autophobic dewetting of the brush and matrix. Finally, miscible blends of PS and PPO are investigated as a route to control depletion-attraction interactions between PS-Au nanorods. Initially, nanorods aggregate in matrices having 50 vol. % PPO and then gradually disperse as PPO becomes the majority component. The brush and matrix density profiles, determined by SCFT, show that PPO segregates into the PS brush, and acts as a compatibilizer, which improves dispersion. As dispersion improves, coupling between surface

  14. Digital mirror devices and liquid crystal displays in maskless lithography for fabrication of polymer-based holographic structures

    NASA Astrophysics Data System (ADS)

    Rahlves, Maik; Kelb, Christian; Rezem, Maher; Schlangen, Sebastian; Boroz, Kristian; Gödeke, Dina; Ihme, Maximilian; Roth, Bernhard

    2015-10-01

    Polymer-based holographic and diffractive optical elements have gained increasing interest due to their potential to be used in a broad range of applications, such as illumination technology, micro-optics, and holography. We present a production process to fabricate polymer-based diffractive optical elements and holograms. The process is based on maskless lithography, which is used to fabricate optical elements in photoresist. We discuss several lab-level lithography setups based on digital mirror devices and liquid crystal devices with respect to illumination efficiency, resolution, and contrast. The entire optical setup is designed with emphasis on low-cost components, which can be easily implemented in an optical research lab. In a first step, a copy of the microstructures is replicated into optical polymeric materials by means of a soft stamp hot embossing process. The soft stamp is made from polydimethylsiloxan, which is coated onto the microstructure in the photoresist. The hot embossing process is carried out by a self-made and low-cost hot embossing machine. We present confocal topography measurements to quantify the replication accuracy of the process and demonstrate diffractive optical elements and holographic structures, which were fabricated using the process presented.

  15. Quantifiable Assessment of SWNT Dispersion in Polymer Composites

    NASA Technical Reports Server (NTRS)

    Park, Cheol; Kim, Jae-Woo; Wise, Kristopher E.; Working, Dennis; Siochi, Mia; Harrison, Joycelyn; Gibbons, Luke; Siochi, Emilie J.; Lillehei, Peter T.; Cantrell, Sean; Cantrell, John

    2007-01-01

    NASA LaRC has established a new protocol for visualizing the nanomaterials in structural polymer matrix resins. Using this new technique and reconstructing the 3D distribution of the nanomaterials allows us to compare this distribution against a theoretically perfect distribution. Additional tertiary structural information can now be obtained and quantified with the electron tomography studies. These tools will be necessary to establish the structural-functional relationships between the nano and the bulk. This will also help define the critical length scales needed for functional properties. Field ready tool development and calibration can begin by using these same samples and comparing the response. i.e. gold standards of good and bad dispersion.

  16. Skin friction measurement with partially exposed polymer dispersed liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Holmes, H. K.

    1993-01-01

    Partially exposed polymer dispersed liquid crystal thin film (10-25 microns) deposited on a flat glass substrate has been used for the first time to measure skin friction. Utilizing the shear-stress-induced director reorientation in the partially exposed liquid-crystal droplets, optical transmission under crossed polarization has been measured as a function of the air flow differential pressure. Direct measurement of the skin friction with a skin friction drag balance, under the same aerodynamic conditions, lets us correlate the skin friction with optical transmission. This provides a unique technique for the direct measurement of skin friction from the transmitted light intensity. The results are in excellent agreement with the model suggested in this paper.

  17. Polymer Clad Silica Fibers for Tailoring Modal Area and Dispersion

    PubMed Central

    Rishøj, Lars; Jones, Maxwell; Demas, Jeffrey; Gregg, Patrick; Prabhakar, Gautam; Yan, Lu; Hawkins, Thomas; Ballato, John; Ramachandran, Siddharth

    2016-01-01

    We demonstrate higher-order-mode (Aeff up to ~2000 μm2) propagation in a 100 μm outer diameter pure-silica fiber with a low-index polymer jacket commonly used for fiber-laser pump-guidance. This simple structure obviates the need for complex designs deemed necessary for realizing large-mode-area fibers. Modes ranging from HE1,12 to HE1,22 were found to propagate stably over 15 m in this fiber. The index step is approximately 4 times larger than that obtained with fluorine down doping, thus the fiber supports even higher order modes, which may have implications for building rare earth doped fiber lasers or achieving enhanced dispersion tunability for high-energy fiber nonlinear phenomena. PMID:27472625

  18. Second-order dispersion interactions in π-conjugated polymers

    NASA Astrophysics Data System (ADS)

    Barford, William; Paiboonvorachat, Nattapong; Yaron, David

    2011-06-01

    We calculate the ground state and excited state second-order dispersion interactions between parallel π-conjugated polymers. The unperturbed eigenstates and energies are calculated from the Pariser-Parr-Pople model using CI-singles theory. Based on large-scale calculations using the molecular structure of trans-polyacetylene as a model system and by exploiting dimensional analysis, we find that: (1) For inter-chain separations, R, greater than a few lattice spacings, the ground-state dispersion interaction, Δ E_{GS}, satisfies, Δ E_{GS} ˜ L^2/R^6 for L ≪ R and Δ E_{GS} ˜ L/R^5 for R ≪ L, where L is the chain length. The former is the London fluctuating dipole-dipole interaction while the latter is a fluctuating line dipole-line dipole interaction. (2) The excited state screening interaction exhibits a crossover from fluctuating monopole-line dipole interactions to either fluctuating dipole-dipole or fluctuating line dipole-line dipole interactions when R exceeds a threshold Rc, where Rc is related to the root-mean-square separation of the electron-hole excitation. Specifically, the excited state screening interaction, ΔEn, satisfies, ΔEn ˜ L/R6 for Rc < L ≪ R and ΔEn ˜ L0/R5 for Rc < R ≪ L. For R < Rc < L, ΔEn ˜ R-ν, where ν ≃ 3. We also investigate the relative screening of the primary excited states in conjugated polymers, namely the n = 1, 2, and 3 excitons. We find that a larger value of n corresponds to a larger value of ΔEn. For example, for poly(para-phenylene), ΔEn = 1 ≃ 0.1 eV, ΔEn = 2 ≃ 0.6 eV, and ΔEn = 3 ≃ 1.2 eV (where n = 1 is the 11B1 state, n = 2 is the m1A state, and n = 3 is the n1B1 state). Finally, we find that the strong dependence of ΔEn on inter-chain separation implies a strong dependency of ΔEn on density fluctuations. In particular, a 10% density fluctuation implies a fluctuation of 13 meV, 66 meV, and 120 meV for the 11B1, m1A state, and n1B1 states of poly(para-phenylene), respectively. Our results

  19. Formation and performance of polymer dispersed liquid crystal films

    NASA Astrophysics Data System (ADS)

    Chan, Philip Kwok-Kiou

    Polymer dispersed liquid crystals (PDLC's) are novel composite materials consisting of micron-size liquid crystalline droplets dispersed uniformly in a solid polymer matrix. PDLC's are formed by spinodal decomposition induced by thermal quenching or polymerization. These materials have excellent magneto-optical properties, and have great potential in applications that require efficient light scattering. Present commercial applications include switchable windows for privacy control and large-scale billboards. The optical properties depend on the droplet size, shape and positional order, which are determined during the formation stage, and reorientation dynamics of the liquid crystalline molecules confined within the droplets which occurs during product use. In this thesis, new complex mathematical models that describe the formation and performance of PDLC's are successfully developed, implemented, solved and validated. The nonequilibrium thermodynamic formation model takes into account initial thermal fluctuations computed using Monte Carlo simulations and realistic arbitrary boundary conditions. The performance model is based on classical nematic liquid crystalline magneto-viscoelastic theories, and incorporates transient viscoelastic boundary conditions. The simulations are able to reproduce successfully all the experimentally observed significant dynamical and morphological features of film formation as well as all the dynamical stages observed during the use of these thin optical films. In addition, the sensitivity of the phase separating morphology to processing conditions and material parameters is elucidated. Furthermore, a new scaling method is introduced to describe the phase separation phenomena during the early and intermediate stages of spinodal decomposition induced by thermal quenching. The droplet size selection mechanism for the polymerization-induced phase separation method of forming PDLC films is identified and explained for the first time. Lastly

  20. Measuring the Thickness and Elastic Properties of Electroactive Thin-Film Polymers Using Platewave Dispersion Data

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Lih, Shyh-Shiuh; El-Azab, A.; Mal, Ajit K.

    1996-01-01

    Electroactive thin-film polymers are candidate sensors and actuators materials. They are also finding significant potential in muscle mechanisms and microelectromechanical systems (MEMS). In these applications, polymer thin films of thickness varying between 20 and 300 micrometers are utilized. The authors are currently studying the potential use of platewave dispersion curve measurements as an effective gauging tool for electroactive thin-film polymers.

  1. Does filler surface chemistry impact filler dispersion, polymer dynamics and conductivity in nanofilled solid polymer electrolytes?

    NASA Astrophysics Data System (ADS)

    Ganapatibhotla, Lalitha; Maranas, Janna

    2012-02-01

    We study the impact of nanofiller surface chemistry on filler dispersion, polymer dynamics and ionic conductivity in acidic α-Al2O3 filled PEO+LiClO4 solid polymer electrolytes (SPEs).SPEs are the key to light-weight and high energy density rechargeable Li ion batteries but suffer from low room temperature ionic conductivity. Addition of ceramic nanofillers improves conductivity of SPEs and their surface chemistry influences extent of conductivity enhancement. The ionic conductivity of acidic α-Al2O3 filled SPE is enhanced for salt concentrations at and below eutectic, while neutral γ-Al2O3 filler enhances conductivity only at eutectic composition. Li ion motion is coupled to segmental mobility of polymer and we study how this is affected by addition of α-Al2O3 using quasi-elastic neutron scattering. Aggregation extent of nanoparticles in SPE matrix, a less explored factor in filled SPEs, can affect segmental mobility of polymer. This can vary with surface chemistry of particles and we quantify this using small angle neutron scattering. All measurements are performed as a function of Li concentration, nanoparticle loading and temperature.

  2. Dispersion of carbon nanotubes in organic solvent by commercial polymers with ethylene chains: Experimental and theoretical studies

    NASA Astrophysics Data System (ADS)

    Shigeta, Masahiro; Kamiya, Katsumasa; Uejima, Mitsugu; Okada, Susumu

    2015-03-01

    We demonstrate the possible candidate dispersion agents that can uniformly disperse carbon nanotubes (CNTs) into organic solvent, from among commercially available polymers. We find that CNTs were well dispersed into dimethylacetamide with the use of polystyrene, poly(vinyl chloride), and poly(vinyl pyrrolidone) as dispersion agents. Theoretical calculations revealed that the dispersibility of these polymers arises from the moderate strength and preferential directionality of the interactions between the CNTs and the polymers.

  3. Switchable Solar Window Devices Based on Polymer Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Murray, Joseph; Ma, Dakang; Munday, Jeremy

    Windows are an interesting target for photovoltaics due to the potential for large area of deployment and because glass is already a ubiquitous component of solar cell devices. Many demonstrations of solar windows in recent years have used photovoltaic devices which are semitransparent in the visible region. Much research has focused on enhancing device absorption in the UV and IR ranges as a means to circumvent the basic tradeoff between efficiency and transparency to visible light. Use of switchable solar window is a less investigated alternative approach; these windows utilize the visible spectrum but can toggle between high transparency and high efficiency as needed. We present a novel switchable solar window device based on Polymer Dispersed Liquid Crystals (PDLC). By applying an electric field to the PDLC layer, the device can be switched from an opaque, light diffusing, efficient photovoltaic cell to a clear, transparent window. In the off state (i.e. scattering state), these devices have the added benefits of increased reflectivity for reduced lighting and cooling costs and haze for privacy. Further, we demonstrate that these windows have the potential for self-powering due to the very low power required to maintain the on, or high transparency, state. Support From: University of Maryland and Maryland Nano-center and its Fablab.

  4. Investigation of Polymer-Surfactant and Polymer-Drug-Surfactant Miscibility for Solid Dispersion.

    PubMed

    Gumaste, Suhas G; Gupta, Simerdeep Singh; Serajuddin, Abu T M

    2016-09-01

    In a solid dispersion (SD), the drug is generally dispersed either molecularly or in the amorphous state in polymeric carriers, and the addition of a surfactant is often important to ensure drug release from such a system. The objective of this investigation was to screen systematically polymer-surfactant and polymer-drug-surfactant miscibility by using the film casting method. Miscibility of the crystalline solid surfactant, poloxamer 188, with two commonly used amorphous polymeric carriers, Soluplus® and HPMCAS, was first studied. Then, polymer-drug-surfactant miscibility was determined using itraconazole as the model drug, and ternary phase diagrams were constructed. The casted films were examined by DSC, PXRD and polarized light microscopy for any crystallization or phase separation of surfactant, drug or both in freshly prepared films and after exposure to 40°C/75% RH for 7, 14, and 30 days. The miscibility of poloxamer 188 with Soluplus® was <10% w/w, while its miscibility with HPMCAS was at least 30% w/w. Although itraconazole by itself was miscible with Soluplus® up to 40% w/w, the presence of poloxamer drastically reduced its miscibility to <10%. In contrast, poloxamer 188 had minimal impact on HPMCAS-itraconazole miscibility. For example, the phase diagram showed amorphous miscibility of HPMCAS, itraconazole, and poloxamer 188 at 54, 23, and 23% w/w, respectively, even after exposure to 40°C/75% RH for 1 month. Thus, a relatively simple and practical method of screening miscibility of different components and ultimately physical stability of SD is provided. The results also identify the HPMCAS-poloxamer 188 mixture as an optimal surface-active carrier system for SD. PMID:27301752

  5. Non-covalent polymer wrapping of carbon nanotubes and the role of wrapped polymers as functional dispersants

    NASA Astrophysics Data System (ADS)

    Fujigaya, Tsuyohiko; Nakashima, Naotoshi

    2015-04-01

    Carbon nanotubes (CNTs) have been recognized as a promising material in a wide range of applications from biotechnology to energy-related devices. However, the poor solubility in aqueous and organic solvents hindered the applications of CNTs. As studies have progressed, the methodology for CNT dispersion was established. In this methodology, the key issue is to covalently or non-covalently functionalize the surfaces of the CNTs with a dispersant. Among the various types of dispersions, polymer wrapping through non-covalent interactions is attractive in terms of the stability and homogeneity of the functionalization. Recently, by taking advantage of their stability, the wrapped-polymers have been utilized to support and/or reinforce the unique functionality of the CNTs, leading to the development of high-performance devices. In this review, various polymer wrapping approaches, together with the applications of the polymer-wrapped CNTs, are summarized.

  6. Cascaded holographic polymer reflection grating filters for optical-code-division multiple-access applications.

    PubMed

    Kostuk, Raymond K; Maeda, Wendi; Chen, Chia-Hung; Djordjevic, Ivan; Vasic, Bane

    2005-12-10

    We evaluate the use of edge-illuminated holographic Bragg filters formed in phenanthrenequinone-doped poly(methyl methacrylate) for optical-code-division multiple-access (OCDMA) coding and decoding applications. Experimental cascaded Bragg filters are formed to select two different wavelengths with a fixed distance between the gratings and are directly coupled to a fiber-measurement system. The configuration and tolerances of the cascaded gratings are shown to be practical for time-wavelength OCDMA applications. PMID:16363782

  7. Controlling Non-Covalent Interactions to Modulate the Dispersion of Fullerenes in Polymer Nanocomposites

    SciTech Connect

    Sumpter, Bobby G

    2011-01-01

    Polymer nanocomposites (PNCs) are materials based on a class of filled plastics that contain relatively small amounts of nanoparticles, which can impart improved structural, mechanical, and thermal properties relative to the neat polymer. However, the homogeneous dispersion of the nanoparticles into a polymer matrix is critical and an impeding factor for the controlled enhancement of PNC properties. In this work, we provide new insight into the importance of polymer chain connectivity and nanoparticle shape and curvature on the formation of noncovalent electron donor-acceptor (EDA) interactions between polymers and nanoparticles. This is accomplished by experimentally monitoring the dispersion of nanoparticles in copolymers containing varying amounts of functional moieties that can form noncovalent interactions with carbon nanoparticles with corroboration through density functional calculations. The results show that the presence of a minority of interacting functional groups within a polymer chain leads to an optimum interaction between the polymer and fullerene. Density functional theory calculations that identify the binding energy and geometry of the interaction between the functional monomers and fullerenes correspond very well with the experimental results. Moreover, comparison of these results to similar studies with single-walled carbon nanotubes (SWNT) indicate a distinct difference in the ability of EDA interactions to improve the dispersion of fullerenes relative to their impact on SWNT. Thus, the polymer chain connectivity, the polymer chain conformation, and size and shape of the nanoparticle modulate the formation of intermolecular interactions and directly impact the dispersion of the resultant nanocomposite.

  8. The formation of polymers on the surfaces of disperse carbon materials

    NASA Astrophysics Data System (ADS)

    Bryk, Mikhail T.; Burban, A. F.

    1989-04-01

    The characteristic features of the synthesis of polymers (radical and ionic polymerisation, polyaddition, polycondensation) on the surfaces of disperse carbon materials (graphite, carbon black, and diamond) are examined. The processes involving the formation of polymers, their structures, and their properties are analysed taking into account the chemistry of the surfaces of disperse carbon fillers, which plays an important role in the preparation of filled polymeric materials by the method of polymerisation filling. The bibliography includes 106 references.

  9. Impact of in situ polymer coating on particle dispersion into solid laser-generated nanocomposites.

    PubMed

    Wagener, Philipp; Brandes, Gudrun; Schwenke, Andreas; Barcikowski, Stephan

    2011-03-21

    The crucial step in the production of solid nanocomposites is the uniform embedding of nanoparticles into the polymer matrix, since the colloidal properties or specific physical properties are very sensitive to particle dispersion within the nanocomposite. Therefore, we studied a laser-based generation method of a nanocomposite which enables us to control the agglomeration of nanoparticles and to increase the single particle dispersion within polyurethane. For this purpose, we ablated targets of silver and copper inside a polymer-doped solution of tetrahydrofuran by a picosecond laser (using a pulse energy of 125 μJ at 33.3 kHz repetition rate) and hardened the resulting colloids into solid polymers. Electron microscopy of these nanocomposites revealed that primary particle size, agglomerate size and particle dispersion strongly depend on concentration of the polyurethane added before laser ablation. 0.3 wt% polyurethane is the optimal polymer concentration to produce nanocomposites with improved particle dispersion and adequate productivity. Lower polyurethane concentration results in agglomeration whereas higher concentration reduces the production rate significantly. The following evaporation step did not change the distribution of the nanocomposite inside the polyurethane matrix. Hence, the in situ coating of nanoparticles with polyurethane during laser ablation enables simple integration into the structural analogue polymer matrix without additives. Furthermore, it was possible to injection mold these in situ-stabilized nanocomposites without affecting particle dispersion. This clarifies that sufficient in situ stabilization during laser ablation in polymer solution is able to prevent agglomeration even in a hot polymer melt. PMID:21298127

  10. Mössbauer Investigation of Highly Dispersed Iron Particles in Crazed Porous Polymers

    NASA Astrophysics Data System (ADS)

    Trofimchuk, E. S.; Nikonorova, N. I.; Dedushenko, S. K.; Perfiliev, Y. D.

    2004-12-01

    Formation and stability of highly dispersed iron particles in crazed porous polymer matrices were studied. The iron polymer composites obtained were characterized by different morphologies and dimensions of iron particles. The phase content of the iron constituent in a composite studied by Mössbauer spectroscopy was shown to depend on the type of the iron salt and the method of introduction of the initial reagents into a polymer.

  11. Nanoparticle dispersion in disordered porous media with and without polymer additives.

    PubMed

    Babayekhorasani, Firoozeh; Dunstan, Dave E; Krishnamoorti, Ramanan; Conrad, Jacinta C

    2016-06-29

    In purely viscous Newtonian fluids, mechanical mixing of the fluid stream as it moves through an unstructured porous medium controls the long-time dispersion of molecular tracers. In applications ranging from environmental remediation to materials processing, however, particles are transported through porous media in polymer solutions and melts, for which the fluid properties depend on the shear rate and extent of deformation. How the flow characteristics of polymer solutions affect the spreading of finite-sized particles remains poorly understood - both on the microscopic scale as local velocity profiles, and on the macroscale as dispersion. Here, we show across a range of flow rates and disordered porous media configurations that the long-time transport coefficients of particles flowed in water, in a viscous Newtonian fluid, and in a non-Newtonian shear-thinning polymer solution collapse onto scaling curves, independent of the fluid rheology. Thus the addition of polymer does not impact nanoparticle dispersion through disordered porous media. PMID:27328208

  12. Tailoring Dispersion and Interaction of MWNT in Polymer Nanocomposites, Using Triton X-100 as Nonionic Surfactant

    NASA Astrophysics Data System (ADS)

    Pandey, Priyanka; Mohanty, Smita; Nayak, Sanjay K.

    2014-12-01

    This study reports an investigation on the effect of non-ionic surfactant (Triton X-100) on the dispersion of multiwalled carbon nanotubes (MWNTs) inside the polymer matrix. Adsorption of triton X-100 to the MWNTs was confirmed through FTIR. A reduced bundling of MWNT fibrils were noticed in Triton X-100 modified MWNTs (Tr-MWNTs). The polymer nanocomposites were prepared via melt blending technique. The optimization of loading ratio of the MWNTs and Tr-MWNTs was carried out on the basis of mechanical properties. Dynamic mechanical analysis exhibited the much uniform dispersion of the Tr-MWNT inside polymer matrix as compared to that of MWNTs. A faster rate of crystallization was noticed in case of MWNT reinforced nanocomposites, however, a strong filler-polymer interaction could be seen in case of Tr-MWNT filled nanocomposites. Optical microscopic analysis exhibited similar effect of MWNT and Tr-MWNT on the spherulite size of the polymer.

  13. Theory of polymer-dispersed cholesteric liquid crystals

    SciTech Connect

    Matsuyama, Akihiko

    2013-11-07

    A mean field theory is presented to describe cholesteric phases in mixtures of a polymer and a cholesteric liquid crystal. Taking into account an anisotropic coupling between a polymer and a liquid crystal, we examine the helical pitch, twist elastic constant, and phase separations. Analytical expressions of the helical pitch of a cholesteric phase and the twist elastic constant are derived as a function of the orientational order parameters of a polymer and a liquid crystal and two intermolecular interaction parameters. We also find isotropic-cholesteric, cholesteric-cholesteric phase separations, and polymer-induced cholesteric phase on the temperature-concentration plane. We demonstrate that an anisotropic coupling between a polymer and a liquid crystal can stabilize a cholesteric phase in the mixtures. Our theory can also apply to mixtures of a nematic liquid crystal and a chiral dopant. We discuss the helical twisting power, which depends on temperature, concentration, and orientational order parameters. It is shown that our theory can qualitatively explain experimental observations.

  14. How Fast Should Polymer/Drug Nanocrystal Dispersions Be Frozen?

    NASA Astrophysics Data System (ADS)

    Lee, Jonghwi; Park, Chul Ho

    2006-03-01

    Recent advances in nanoparticle technologies have significantly enhanced the oral and parenteral delivery of poorly water-soluble active pharmaceutical ingredients (APIs). However, reports have been limited on the various drying procedures to convert a liquid nanocrystal dispersions into solid dosage forms. The solid dosage form should consist of nanocrystals that can readily reconstitute into their original size upon dissolution in water. Herein, the freeze drying process of nanocrystal dispersions was examined at varying freezing rates (speed of freezing interface). As freezing rate decreases, more particle-particle aggregation developed. A critical freezing rate, below which the dried nanocrystals cannot be re-dispersed, was identified based on the plot of the particle size of reconstituted nanocrystals versus freezing rate. Freeze drying at a freezing rate near the critical value produces dry powders of bimodal particle size distribution after re-dispersion. In addition, API concentration was found to significantly affect the critical freezing rate and therefore the re-dispersibility of dry powders. The concept of critical freezing rate is critical for the development of solid dosage forms of liquid nanocrystal dispersions. [1] J. Lee, Drug nano- and microparticles processed into solid dosage forms: physical properties, J. Pharm. Sci., 92(10) (2003) 2057-2068.

  15. Holographic vector-wave femtosecond laser processing

    NASA Astrophysics Data System (ADS)

    Hayasaki, Yoshio; Hasegawa, Satoshi

    2016-03-01

    Arbitrary and variable beam shaping of femtosecond pulses by a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM) have been applied to femtosecond laser processing. The holographic femtosecond laser processing has been widely used in many applications such as two-photon polymerization, optical waveguide fabrication, fabrication of volume phase gratings in polymers, and surface nanostructuring. A vector wave that has a spatial distribution of polarization states control of femtosecond pulses gives good performances for the femtosecond laser processing. In this paper, an in- system optimization of a CGH for massively-parallel femtosecond laser processing, a dynamic control of spatial spectral dispersion to improve the focal spot shape, and the holographic vector-wave femtosecond laser processing are demonstrated.

  16. Anionic surfactant with hydrophobic and hydrophilic chains for nanoparticle dispersion and shape memory polymer nanocomposites.

    PubMed

    Iijima, Motoyuki; Kobayakawa, Murino; Yamazaki, Miwa; Ohta, Yasuhiro; Kamiya, Hidehiro

    2009-11-18

    An anionic surfactant comprising a hydrophilic poly(ethylene glycol) (PEG) chain, hydrophobic alkyl chain, and polymerizable vinyl group was synthesized as a capping agent of nanoparticles. TiO(2) nanoparticles modified by this surfactant were completely dispersible in various organic solvents with a wide range of polarities, such as nitriles, alcohols, ketones, and acetates. Furthermore, these particles were found to be dispersible in various polymers with different properties, such as thermosetting epoxy resins and radical polymerized poly(methylmethacrylate) (PMMA). A polymer composite of surface-modified TiO(2) nanoparticles in epoxy resins prepared by using the developed surfactant also possessed temperature-induced shape memory properties. PMID:19852463

  17. Tuning the wetting-dewetting and dispersion-aggregation transitions in polymer nanocomposites using composition of graft and matrix polymers

    NASA Astrophysics Data System (ADS)

    Martin, Tyler B.; Jayaraman, Arthi

    2016-03-01

    Recent simulation and experimental work on polymer nanocomposites composed of polymer grafted particles and free matrix polymers, where the graft and matrix homopolymers are chemically dissimilar and exhibit lower critical solution temperature behavior with temperature, has shown that wetting to dewetting is a gradual and distinct transition from the sharp particle dispersion-aggregation transition. In this study, using coarse-grained molecular simulations, we demonstrate that the extent of wetting of the grafted polymer layer and the particle dispersion-aggregation transition are tuned using the composition of graft and matrix polymers. Specifically, we study composites where the graft and matrix chains are random copolymers composed of attractive and athermal monomers. We maintain a dense grafting density on the spherical particles of diameter five times the monomer diameter and study matrix lengths five times that of the graft chain length or equal graft and matrix chain lengths. We vary the fraction of attractive monomers in the graft ({f}{{G}}) and matrix ({f}{{M}}) chains, graft-matrix chain composition ratio ({f}{{G}}/{f}{{M}}), and the graft-matrix interaction strength, as characterized by the Flory-Huggins interaction parameter between graft and matrix attractive monomers: {χ }{{GM}}. When {χ }{{GM}} is negative, decreasing {f}{{G}} and/or {f}{{M}} decreases the extent of grafted layer wetting by matrix chains because the enthalpic driving force for wetting is reduced. As the {χ }{{GM}} increases and becomes positive, the extent of wetting decreases gradually till it reaches the wetting of analogous athermal composites. That value of {χ }{{GM}} where the extent of wetting is the same as that of an analogous athermal polymer nanocomposite marks the onset of dispersion-aggregation transition. For symmetric graft and matrix chain compositions ({f}{{G}}={f}{{M}}), the magnitude of {f}{{G}} and {f}{{M}} tunes the overall extent of wetting of the grafted

  18. Holographic Optical Elements with Electro-optic Control

    NASA Astrophysics Data System (ADS)

    Ermold, Michael Leigh

    Although polymeric and liquid crystalline materials have been separately studied for many years, optical devices based the interaction between these two materials in a composite device have come to the forefront of technology in recent years. Liquid crystals typically have strong interactions with the surfaces with which they make contact, with the dominant effects arising from geometrical and chemical contributions. It is this surface interaction that allows the construction of thin, flat liquid crystal displays that now can be found in almost every type of portable electronic device requiring information display. Instead of the liquid crystals lying on a polymer surface, they can be embedded within a thin film. In this format, the liquid crystal will assume the shape of ellipsoidal cavities, forming the so-called polymer dispersed liquid crystals. The index mismatch between the liquid crystal and the surrounding polymer matrix creates a highly efficient scattering device. This index mismatch can be modulated by applied electric fields, facilitating electronic grayscale control of the scattering efficiency. With a sufficiently high applied field, the device can be made transparent. Utilizing the holographic techniques developed by Gabor, Leith, and Upatnieks, polymer dispersed liquid crystals can be formed under holographic conditions to produce holographic polymer dispersed liquid crystals (H-PDLC). The resulting stratified structure is composed of layers of hardened polymer separated by layers of liquid crystal droplet-rich planes. Optical structures in this form also possess the same electro-optic properties as their unstructured predecessors. A whole host of diffractive optical devices can be created via holographic means, which includes, but is not limited to transmission gratings, reflection gratings, 2D and 3D photonic crystals and holographic optical elements. In this work, I have examined the role of H-PLDC gratings that function as holographic focusing

  19. Balanced charge injection in multilayer polymer light-emitting diode with water soluble nonconjugated polymer dispersed by ionic compounds

    NASA Astrophysics Data System (ADS)

    Park, Dong-Kyu; Chun, A.-Rum; Kim, Soo-Hong; Kim, Min-Sook; Kim, Choong-Gi; Kwon, Tae-Woo; Cho, Seong-Jin; Woo, Hyung-Suk; Lee, Jae-Gyoung; Lee, Suck-Hyun; Guo, Zhi-Xin

    2007-07-01

    The authors have fabricated highly efficient polymeric light-emitting diode (PLED) from ionic compound dispersed water soluble nonconjugated polymer, polyurethane (PU), which was used as an ultrathin hole blocking and electron injection layer (HB-EIL) on the top of commercially available blue-emitting polymer, polyfluorene. The device with HB-EIL showed a maximum quantum efficiency of 1.7%, while the one without HB-EIL showed an efficiency of 0.6%. They propose that the better performance in PLED with PU layer was due to a well balanced charge injection in emitting layer after the enhanced electron injection due to ionic compound in the insulating PU layer.

  20. Trypsin coatings on electrospun and alcohol-dispersed polymer nanofibers for trypsin digestion column

    SciTech Connect

    Jun, Seung-Hyun; Chang, Mun Seock; Kim, Byoung Chan; An, Hyo Jin; Lopez-Ferrer, Daniel; Zhao, Rui; Smith, Richard D.; Lee, Sang-Won; Kim, Jungbae

    2010-09-15

    The construction of a trypsin reactor in a chromatography column for rapid and efficient protein digestion in proteomics is described. Electrospun and alcohol-dispersed polymer nanofibers were used for the fabrication of highly stable trypsin coating, which was prepared by a two-step process of covalent attachment and enzyme crosslinking. In a comparative study with the trypsin coatings on asspun and non-dispersed nanofibers, it has been observed that a simple step of alcohol dispersion improved not only the enzyme loading but also the performance of protein digestion. In-column digestion of enolase was successfully performed in less than twenty minutes. By applying the alcohol dispersion of polymer nanofibers, the bypass of samples was reduced by filling up the column with well-dispersed nanofibers, and subsequently, interactions between the protein and the enzymes were improved yielding more complete and reproducible digestions. Regardless of alcohol-dispersion or not, trypsin coating showed better digestion performance and improved performance stability under recycled uses than covalently-attached trypsin. The combination of highly stable trypsin coating and alcoholdispersion of polymer nanofibers has opened up a new potential to develop a trypsin column for on-line and automated protein digestion.

  1. Three-port beam splitter for slow neutrons using holographic nanoparticle-polymer composite diffraction gratings

    SciTech Connect

    Klepp, J.; Fally, M.; Tomita, Y.; Pruner, C.; Kohlbrecher, J.

    2012-10-08

    Diffraction of slow neutrons by nanoparticle-polymer composite gratings has been observed. By carefully choosing grating parameters such as grating thickness and spacing, a three-port beam splitter operation for slow neutrons - splitting the incident neutron intensity equally into the {+-}1st and the 0th diffraction orders - has been realized. As a possible application, a Zernike three-path interferometer is briefly discussed.

  2. Orthogonal Double View Digital Holographic Diagnostics for Random Motion of Micro Polymer Jet by Electrospinning

    NASA Astrophysics Data System (ADS)

    Lee, Jaiho; Sallam, Khaled

    2008-11-01

    An experimental investigation of three-dimensional random behavior of polymer micro jet generated by electrospinning is described. Two frequency doubled Nd:YAG lasers were used as the light source and a commercial grade CCD sensor (Nikon D-70) was used for holograms recording. The two lasers could be fired with a pulse separation as small as 100 ns, and the two laser beams were aligned with three polarized beam splitter cubes. Orthogonal double-view and double-pulses were recorded on the same camera frame. The camera frame was split into two, and both of the halves of the frame were used for each view. Two objective lenses (M 5x) and two spatial filters (Pinhole ˜ 5μm) were used to generate expanding laser beams in the digital microscopic holography (DMH) optical setup. As the electric field (˜20 kV) was intensified, the polymer solution formed a charged filament (or multiple filaments) from the tip of the Taylor cone. As the filament was accelerated toward the collector, its diameter was shrunk and axisymmetric disturbances grew further away from the exit. The polymer was randomly deposited on the collector as non woven microfiber.

  3. Reduced Crystallization Temperature Methodology for Polymer Selection in Amorphous Solid Dispersions: Stability Perspective.

    PubMed

    Bhugra, Chandan; Telang, Chitra; Schwabe, Robert; Zhong, Li

    2016-09-01

    API-polymer interactions, used to select the right polymeric matrix with an aim to stabilize an amorphous dispersion, are routinely studied using spectroscopic and/or calorimetric techniques (i.e., melting point depression). An alternate selection tool has been explored to rank order polymers for formation of stable amorphous dispersions as a pragmatic method for polymer selection. Reduced crystallization temperature of API, a parameter introduced by Zhou et al.,1 was utilized in this study for rank ordering interactions in API-polymeric systems. The trends in reduced crystallization temperature monitored over polymer concentration range of up to 20% polymer loading were utilized to calculate "crystallization parameter" or CP for two model systems (nifedipine and BI ABC). The rank order of CP, i.e., a measure of API-polymer interaction, for nifedipine followed the order PVP > PVP-VA > Soluplus > HPMCAS > PV Ac > PAA. This rank ordering was correlated to published results of molecular interactions and physical stability for nifedipine. A different rank ordering was observed for BI ABC: PAA > PVP > HPMCAS > Soluplus > PVPV-VA > PVAc. Interactions for BI ABC were not as differentiated when compared to nifedipine based on CP trends. BI ABC dispersions at drug loadings between 40 and 60% were physically stable for prolonged periods under ICH conditions as well as accelerated stress. We propose that large CP differences among polymers could be predictive of stability outcomes. Acceptable stability at pharmaceutically relevant drug loadings would suggest that the relative influence of downstream processes, such as polymer solubility in various solvents, process suitability and selection, and more importantly supersaturation potential, should be higher compared to stability considerations while developing compounds like BI ABC. PMID:27414755

  4. Synthesis of well dispersed polymer grafted metal-organic framework nanoparticles.

    PubMed

    Xie, K; Fu, Q; He, Y; Kim, J; Goh, S J; Nam, E; Qiao, G G; Webley, P A

    2015-11-01

    Novel polymer grafted metal-organic framework (MOF) nanoparticles were synthesized. The formed core/shell nanoparticles exhibit outstanding water dispersity and pH sensitivity, and show their catalytic effect for the reduction reaction of 4-nitrophenol (NP) to 4-aminophenol (AP) when loaded with Pd(0) catalyst. PMID:26355917

  5. Ultra-high dispersion of graphene in polymer composite via solvent free fabrication and functionalization

    PubMed Central

    Noh, Ye Ji; Joh, Han-Ik; Yu, Jaesang; Hwang, Soon Hyoun; Lee, Sungho; Lee, Cheol Ho; Kim, Seong Yun; Youn, Jae Ryoun

    2015-01-01

    The drying process of graphene-polymer composites fabricated by solution-processing for excellent dispersion is time consuming and suffers from a restacking problem. Here, we have developed an innovative method to fabricate polymer composites with well dispersed graphene particles in the matrix resin by using solvent free powder mixing and in-situ polymerization of a low viscosity oligomer resin. We also prepared composites filled with up to 20 wt% of graphene particles by the solvent free process while maintaining a high degree of dispersion. The electrical conductivity of the composite, one of the most significant properties affected by the dispersion, was consistent with the theoretically obtained effective electrical conductivity based on the mean field micromechanical analysis with the Mori-Tanaka model assuming ideal dispersion. It can be confirmed by looking at the statistical results of the filler-to-filler distance obtained from the digital processing of the fracture surface images that the various oxygenated functional groups of graphene oxide can help improve the dispersion of the filler and that the introduction of large phenyl groups to the graphene basal plane has a positive effect on the dispersion. PMID:25771823

  6. Development of a Reflective Polymer-Dispersed Liquid Crystal Shear Measurement System

    NASA Astrophysics Data System (ADS)

    DeBenedictis, Gina

    Polymer-dispersed liquid crystals as a shear force measurement system offer many advantages over conventional single-point measurement systems. They are non-intrusive while offering ideal 2-dimensional mapping of shear stresses across a surface. Furthermore, the inclusion of the liquid crystals within a polymer matrix allows for a reversible sensor that is self-adherent to testing surfaces. Previous testing has examined small-scale surface mapping and clear samples through which light may pass. This paper examines the expansion of polymer-dispersed liquid crystals to larger area mapping as well as reflective measurements, with measurements taken in multiple shear force configurations, confirming the validity of the reflective data.

  7. Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal

    NASA Astrophysics Data System (ADS)

    Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

    2016-07-01

    Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm‑2, which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm‑2). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE.

  8. Enhancing Dispersion and Properties of SWNT-polymer Nanocomposites by Controlled Non-covalent Interactions

    NASA Astrophysics Data System (ADS)

    Linton, Dias

    2008-03-01

    The enhancement of the dispersion and properties of singlewalled carbon nanotubes in a polymer nanocomposite via non-covalent interaction is studied. 1% w/w SWNT are dispersed in random copolymers of methyl methacrylate and 2-(dimethylamino)ethyl methacrylate (DMAEMA), where the composition of the copolymer varies from 0% to 50% DMAEMA. The resulting nanocomposites indicate the existence of interactions between the carbon nanotube and polymer matrix by a shift of the D* peak position (˜2600-2700 cm-1) of the polymer nanocomposite. The copolymer with 30% DMAEMA shows the smallest shift, suggesting that the nanotubes are debundled, where it is expected that this non-covalent interaction originate from the tertiary amino group in DMAEMA by formation of an electron-donor interaction with the SWNT.

  9. Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal.

    PubMed

    Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

    2016-07-01

    Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm(-2), which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm(-2)). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE. PMID:27196786

  10. Improving Dispersion of Single-Walled Carbon Nanotubes in a Polymer Matrix Using Specific Interactions

    SciTech Connect

    Rasheed, Asif; Dadmun, Mark D; Ivanov, Ilia N; Britt, Phillip F; Geohegan, David B

    2006-01-01

    A novel approach is presented to improve the dispersion of oxidized single-walled carbon nanotubes (SWNTs) in a copolymer matrix by tuning hydrogen-bonding interactions to enhance dispersion. Nanocomposites of single-walled carbon nanotubes and copolymers of styrene and vinyl phenol (PSVPh) with varying vinyl phenol content were produced and examined. The dispersion of the SWNT in the polymer matrix is quantified by optical microscopy and Raman spectroscopy. Raman spectroscopy is also used to investigate preferred interactions between the SWNTs and the copolymers via the shift in the D* Raman band of the SWNTs in the composites. All composites show regions of SWNT aggregates; however, the aggregate size varies with composition of the PSVPh copolymer and the amount of SWNT oxidation. Optimal dispersion of the SWNT is observed in PSVPh with 20% vinyl phenol and oxidized nanotubes, which correlates with spectroscopic evidence that indicates that this system also incorporates the most interactions between SWNT and polymer matrix. These results are in agreement with previous studies that indicate that optimizing the extent of specific interactions between a polymer matrix and nanoscale filler enables the efficient dispersion of the nanofillers.

  11. Dispersion of PMMA-grafted, mesoscopic iron-oxide rods in polymer films.

    PubMed

    Ferrier, Robert C; Huang, Yun; Ohno, Kohji; Composto, Russell J

    2016-03-01

    This study investigates the parameters that affect the dispersion of polymer grafted mesoscopic iron-oxide rods (FeMRs) in polymer matrices. FeMRs (212 nm long by 36 nm in diameter) are grafted with poly(methyl methacrylate) (PMMA) at three different brush molecular weights: 3.7 kg mol(-1), 32 kg mol(-1), and 160 kg mol(-1). Each FeMR sample was cast in a polymer thin film consisting of either PMMA or poly(ethylene oxide) (PEO) each at a molecular weight much higher or much lower than the brush molecular weight. We find that the FeMRs with 160 kg mol(-1) brush disperse in all matrices while the FeMRs with 32 kg mol(-1) and 3.7 kg mol(-1) brushes aggregate in all matrices. We perform simple free energy calculations, taking into account steric repulsion from the brush and van der Waals attraction between FeMRs. We find that there is a barrier for aggregation for the FeMRs with the largest brush, while there is no barrier for the other FeMRs. Therefore, for these mesoscopic particles, the brush size is the main factor that determines the dispersion state of FeMRs in polymer matrices with athermal or weakly attractive brush-matrix interactions. These studies provide new insight into the mechanisms that affect dispersion in polymer matrices of mesoscopic particles and therefore guide the design of composite films with well-dispersed mesoscopic particles. PMID:26908174

  12. Problem of hydroxyapatite dispersion in polymer matrices: a review.

    PubMed

    Supová, Monika

    2009-06-01

    This review summarizes recent work on manufacturing biocomposites suitable for bone tissue engineering. There is a great need to engineer multi-phase (i.e. composite) materials that combine the advantages exhibited by each component of the material, with a structure and composition similar to that of natural bone. The discussion concentrates on the preparation of nanocomposites containing hydroxyapatite particles (one of the most widely used bioceramics materials) with polymer matrices. Special attention is paid to the preparation of nanocomposites with individual (non-aggregated) nanoparticles because this is a key problem in nanotechnology industrialization. Controlling the mixing between so two dissimilar phases is a critical challenge in the design of these inorganic-organic systems. Several approaches that may be applied to overcome this problem will be described in this review. PMID:19225871

  13. Amorphous stabilization and dissolution enhancement of amorphous ternary solid dispersions: combination of polymers showing drug-polymer interaction for synergistic effects.

    PubMed

    Prasad, Dev; Chauhan, Harsh; Atef, Eman

    2014-11-01

    The purpose of this study was to understand the combined effect of two polymers showing drug-polymer interactions on amorphous stabilization and dissolution enhancement of indomethacin (IND) in amorphous ternary solid dispersions. The mechanism responsible for the enhanced stability and dissolution of IND in amorphous ternary systems was studied by exploring the miscibility and intermolecular interactions between IND and polymers through thermal and spectroscopic analysis. Eudragit E100 and PVP K90 at low concentrations (2.5%-40%, w/w) were used to prepare amorphous binary and ternary solid dispersions by solvent evaporation. Stability results showed that amorphous ternary solid dispersions have better stability compared with amorphous binary solid dispersions. The dissolution of IND from the ternary dispersion was substantially higher than the binary dispersions as well as amorphous drug. Melting point depression of physical mixtures reveals that the drug was miscible in both the polymers; however, greater miscibility was observed in ternary physical mixtures. The IR analysis confirmed intermolecular interactions between IND and individual polymers. These interactions were found to be intact in ternary systems. These results suggest that the combination of two polymers showing drug-polymer interaction offers synergistic enhancement in amorphous stability and dissolution in ternary solid dispersions. PMID:25196860

  14. Novel Thermogelling Dispersions of Polymer Nanoparticles for Controlled Protein Release

    PubMed Central

    Cai, Tong; Hu, Peter D.; Sun, Manwu; Zhou, Jun; Tsai, Yi-Ting; Baker, David; Tang, Liping

    2012-01-01

    A novel poly(oligo(ethylene glycol) methyl ether methacrylate-co-oligo(ethylene glycol) ethyl ether methacrylate)/ poly(acrylic acid) interpenetrating network (IPN) nanoparticle was synthesized. The temperature-responsive properties of the IPN nanoparticles were investigated by dynamic light scattering method. Atomic force microscopic images confirm the homogenous and mono-disperse morphology of the IPN nanoparticles. Both visual observation and viscosity testing demonstrated that the IPN nanoparticles exhibit thermogelling properties at body temperature, 37°C. Subsequent studies verified that such temperature sensitive properties of IPN nanoparticles allow their ease of injection and then slow release of model proteins, both in vitro and in vivo. Histological analysis showed that our IPN implants exerted minimal inflammation following subcutaneous implantation. Our results support that, by simply mixing with proteins of interest, the novel IPN nanoparticles can be used to form in situ thermogelling devices for controlled protein release. PMID:22349097

  15. Stabile, thermoresponsive colloidal clusters: an unusual morphology of polymer dispersions.

    PubMed

    Yu, Ran; Hartmann, Jürgen; Tauer, Klaus

    2013-10-01

    A new class of colloidal polymeric particles consisting of polystyrene spheres grown in a poly(N-isopropyl acrylamide) precursor scaffold is synthesized via redox-initiated heterophase polymerization. The morphology and thermoresponsiveness of these assemblies is proven by electron microscopy investigations and temperature-dependent measurements of the change of both the speed of sound travelling through the dispersion and the hydrodynamic particle size. Electron microscopy (EM) micrographs (transmission and scanning EM as well cryo-scanning EM) prove the existence of colloidal clusters when the freeze-dried copolymer is redispersed in pure water. The clusters have a size of several micrometers, contain about 800 polystyrene particles with diameter below 100 nm, and show a highly reproducible thermoresponsive behavior with a lower critical solution temperature corresponding to that of pure poly(N-isopropyl acrylamide). PMID:24023043

  16. Orientational photorefractive properties in polymer-dispersed liquid crystals with different polymer matrixes

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Saito, Isao; Kawatsuki, Nobuhiro

    1998-10-01

    We report orientational photorefractive effects observed in photoconductive liquid crystals (LCs) contained with three kinds of polymer, i.e., poly(methyl methacrylate) (PMMA), poly(vinyl alcohol) (PVA) and a side-chain liquid crystalline polymer (SLCP1). The morphology of the photorefractive composites depended on the kind of polymer strongly. In both PMMA and PVA cases, LC and polymer were phase-separated and the composite showed memory effects. In SLCP1 case, the phase-separation in the composite dose not occur and the high resolution could be achieved. In this case, the photorefractive Bragg gratings were generated and a high two-beam coupling gain coefficient with a low applied field of 4 V/micrometers was observed.

  17. Holographic Photopolymer Linear Variable Filter with Enhanced Blue Reflection

    PubMed Central

    2015-01-01

    A single beam one-step holographic interferometry method was developed to fabricate porous polymer structures with controllable pore size and location to produce compact graded photonic bandgap structures for linear variable optical filters. This technology is based on holographic polymer dispersed liquid crystal materials. By introducing a forced internal reflection, the optical reflection throughout the visible spectral region, from blue to red, is high and uniform. In addition, the control of the bandwidth of the reflection resonance, related to the light intensity and spatial porosity distributions, was investigated to optimize the optical performance. The development of portable and inexpensive personal health-care and environmental multispectral sensing/imaging devices will be possible using these filters. PMID:24517443

  18. Holographic photopolymer linear variable filter with enhanced blue reflection.

    PubMed

    Moein, Tania; Ji, Dengxin; Zeng, Xie; Liu, Ke; Gan, Qiaoqiang; Cartwright, Alexander N

    2014-03-12

    A single beam one-step holographic interferometry method was developed to fabricate porous polymer structures with controllable pore size and location to produce compact graded photonic bandgap structures for linear variable optical filters. This technology is based on holographic polymer dispersed liquid crystal materials. By introducing a forced internal reflection, the optical reflection throughout the visible spectral region, from blue to red, is high and uniform. In addition, the control of the bandwidth of the reflection resonance, related to the light intensity and spatial porosity distributions, was investigated to optimize the optical performance. The development of portable and inexpensive personal health-care and environmental multispectral sensing/imaging devices will be possible using these filters. PMID:24517443

  19. Holographic recording medium

    NASA Technical Reports Server (NTRS)

    Gange, Robert Allen (Inventor)

    1977-01-01

    A holographic recording medium comprising a conductive substrate, a photoconductive layer and an electrically alterable layer of a linear, low molecular weight hydrocarbon polymer has improved fatigue resistance. An acrylic barrier layer can be interposed between the photoconductive and electrically alterable layers.

  20. Yielding and flow of cellulose microfibril dispersions in the presence of a charged polymer.

    PubMed

    de Kort, Daan W; Veen, Sandra J; Van As, Henk; Bonn, Daniel; Velikov, Krassimir P; van Duynhoven, John P M

    2016-05-25

    The shear flow of microfibrillated cellulose dispersions is still not wholly understood as a consequence of their multi-length-scale heterogeneity. We added carboxymethyl cellulose, a charged polymer, that makes cellulose microfibril dispersions more homogeneous at the submicron and macro scales. We then compared the yielding and flow behavior of these dispersions to that of typical thixotropic yield-stress fluids. Despite the apparent homogeneity of the dispersions, their flow velocity profiles in cone-plate geometry, as measured by rheo-MRI velocimetry, differ strongly from those observed for typical thixotropic model systems: the viscosity across the gap is not uniform, despite a flat stress field across the gap. We describe these velocity profiles with a nonlocal model, and attribute the non-locality to persistent micron-scale structural heterogeneity. PMID:27120969

  1. The role of the polymer host on reversible photodegradation in Disperse Orange 11 dye

    NASA Astrophysics Data System (ADS)

    Hung, Sheng-Ting; Ramini, Shiva K.; Wyrick, David G.; Clays, Koen; Kuzyk, Mark G.

    2012-10-01

    The photodegradation and recovery process in anthraquinone chromophores have been characterized using am­ plified spontaneous emission (ASE) in several Anthraquinone derivatives doped in poly(methyl methacrylate) (PMMA). To understand the mechanisms of self healing in disperse orange 11 (DOll) doped in PMMA and the role of the host polymer, we investigated reversible photodegradation in DOll doped in copolymer composed of different percentages of methyl methacrylate (MMA) and Styrene. The results suggest that the host polymer is an important factor in determining the distribution of domain sizes of dye molecules.

  2. Enhanced electrical transport in ionic liquid dispersed TMAI-PEO solid polymer electrolyte

    SciTech Connect

    Gupta, Neha; Rathore, Munesh Dalvi, Anshuman; Kumar, Anil

    2014-04-24

    A polymer composite is prepared by dispersing ionic liquid [Bmim][BF{sub 4}] in Polyethylene oxide-tetra methyl ammonium iodide composite and subsequent microwave treatment. X-ray diffraction patterns confirm the composite nature. To explore possibility of proton conductivity in these films, electrical transport is studied by impedance spectroscopy and DC polarization. It is revealed that addition of ionic liquid in host TMAI-PEO solid polymer electrolyte enhances the conductivity by ∼ 2 orders of magnitude. Polarization measurements suggest that composites are essentially ion conducting in nature. The maximum ionic conductivity is found to be ∼2 × 10{sup −5} for 10 wt % ionic liquid.

  3. Role of Polymer Segment-Particle Surface Interactions in Controlling Nanoparticle Dispersions in Concentrated Polymer Solutions

    SciTech Connect

    Kim, So Youn; Zukoski, Charles F.

    2014-09-24

    The microstructure of particles suspended in concentrated polymer solutions is examined with small-angle X-ray scattering and small-angle neutron scattering. Of interest are changes to long wavelength particle density fluctuations in ternary mixtures of silica nanoparticles suspended in concentrated solutions of poly(ethylene glycol). The results are understood in terms of application of the pseudo-two-component polymer reference interaction site model (PRISM) theory modified to account for solvent addition via effective contact strength of interfacial attraction, εpc, in an implicit manner. The combined experimental-theoretical study emphasizes the complex interactions between solvent, polymer, and particle surface that control particle miscibility but also demonstrate that these factors can all be understood in terms of variations of εpc.

  4. Enhanced nanoflow behaviors of polymer melts using dispersed nanoparticles and ultrasonic vibration.

    PubMed

    Tian, Wei; Yung, Kai Leung; Xu, Yan; Huang, Longbiao; Kong, Jie; Xie, Yunchuan

    2011-10-01

    In the micro/nano fabrication of polymer nanostructures, a key factor is the favorable nanoflow behavior of polymer melts. Compared with the fluidic hydrodynamics of simple liquids through micro- or macrochannels, the nanoflow behavior of polymer melts, however, is affected much more by nanoscale effects and surface interactions. Therefore, achieving a favorable nanoflow of polymer melts in nanochannels is the key to fabricate high quality polymer nanoproducts. In this paper, the improved nanoflow behaviors of polystyrene melts in ordered porous alumina templates with the addition of nanoparticles and ultrasonic vibration were reported for the first time. Compared with bulk polystyrene (PS), the nanoflow rate of PS melts was enhanced when nanoparticles, such as surface-modified nano-silica (nano-SiO(2)) or β-cyclodextrin (β-CD), were added in a dispersed phase into a polystyrene matrix due to the decrease of the melts' viscosity caused by interactions between nanoparticles and PS segments. The enhancement action of β-CD was observed to be more significant than that of nano-SiO(2) based on the adsorption and the supramolecular self-assembly interactions between PS segments and β-CD. The enhanced nanoflow rate has shown to be more pronounced under ultrasonic vibration than those of the static condition and the low frequency vibration attributed to the synergetic effects of mechanical vibration and ultrasonic oscillation. The nanoflow rate of polymer melts increases with the gradual increase of vibration frequency. The optimal nanoflow behavior can be obtained by simultaneously adding β-CD as dispersed phase into PS matrix and applying ultrasonic vibration in one nanoflow system. These new findings will help the preparation of polymer-based functional nanocomposites, ultrasonic vibration-assisted nanofluidics, and micro/nano injection molding etc. PMID:21901225

  5. Application of spherical silicate to prepare solid dispersion dosage forms with aqueous polymers.

    PubMed

    Nagane, Kentaro; Kimura, Susumu; Ukai, Koji; Takahashi, Chisato; Ogawa, Noriko; Yamamoto, Hiromitsu

    2015-09-30

    The objective of this study is to prepare and characterize solid dispersions of nifedipine (NP) using porous spherical silicate micro beads (MB) that were approximately 100 μm in diameter with vinylpyrrolidone/vinyl acetate copolymer (PVP/VA) and a Wurster-type fluidized bed granulator. Compared with previously reported solid dispersion using only MB, the supersaturation of NP dissolved from the proposed system of MB and PVP/VA was maintained during dissolution tests. The proposed system produced a solid dispersion product coated on MB, and morphology was maintained after the coating process to prepare solid dispersion; therefore, the powder characteristics, such as flowability of the proposed solid dispersion product, was tremendously preferable to that of the conventional spray-dried solid dispersions of NP with PVP/VA, expecting to make the consequent manufacturing processes easy for development. Another advantage in the terms of manufacturing is its simple process to prepare solid dispersion by spraying the drug and polymer that were dissolved in an organic solvent onto a MB in a Wurster-type fluidized bed granulator, thus, simplifying the optimization and scale-up with ease. PMID:26200750

  6. Water transport in cement-in-polymer dispersions at variable temperature studied by magnetic resonance imaging

    SciTech Connect

    Olaru, A.M. Bluemich, B.; Adams, A.

    2013-02-15

    The hydration of recently developed cement-in-polymer dispersions (c/p) containing 30% and 40% poly (vinyl acetate) [PVAc] and 30% poly(vinyl alcohol) [PVA] was monitored on-line at various temperatures using {sup 1}H Single Point Imaging (SPI). The physical changes undergone by the materials as well as the complex manner in which the absorption process takes place and the evolution of the spin density were characterized and were found to be strongly dependent on the nature and amount of polymer and on the temperature. Based on the results obtained we propose a simple mathematical model which can be used to characterize the behaviour of the c/p dispersions exposed to hydration at variable temperature.

  7. Dispersion of dielectric characteristics of polymer structures based on the Cu(II) complex

    NASA Astrophysics Data System (ADS)

    Avanesyan, V. T.; Vodkaĭlo, E. G.

    2010-10-01

    The results of the study of the dielectric response of thin-layer polymer films based on [Cum-Salpn-1,3] monomers and the H2mSalpn-1,3 ligand synthesized by electrochemical polymerization are presented. A frequency dispersion of dielectric characteristics that corresponds to the distribution of a set of relaxors is revealed. The role of a metal center, i.e., divalent copper, and the azomethine group during dielectric polarization is discussed.

  8. Phonon Dispersion and Electron--Phonon Interaction in Peanut-Shaped Fullerene Polymers

    NASA Astrophysics Data System (ADS)

    Ono, Shota; Shima, Hiroyuki

    2011-06-01

    We reveal that the periodic radius modulation peculiar to one-dimensional (1D) peanut-shaped fullerene (C60) polymers exerts a strong influence on their low-frequency phonon states and their interactions with mobile electrons. The continuum approximation is employed to show the zone-folding of phonon dispersion curves, which leads to fast relaxation of a radial breathing mode in the 1D C60 polymers. We also formulate the electron--phonon interaction along the deformation potential theory, demonstrating that only a few set of electron and phonon modes yields a significant magnitude of the interaction relevant to the low-temperature physics of the system. The latter finding gives an important implication for the possible Peierls instability of the C60 polymers suggested in the earlier experiment.

  9. Modelling drug degradation in a spray dried polymer dispersion using a modified Arrhenius equation.

    PubMed

    Patterson, Adele; Ferreira, Ana P; Banks, Elizabeth; Skeene, Kirsty; Clarke, Graham; Nicholson, Sarah; Rawlinson-Malone, Clare

    2015-01-15

    The Pharmaceutical industry is increasingly utilizing amorphous technologies to overcome solubility challenges. A common approach is the use of drug in polymer dispersions to prevent recrystallization of the amorphous drug. Understanding the factors affecting chemical and physical degradation of the drug within these complex systems, e.g., temperature and relative humidity, is an important step in the selection of a lead formulation, and development of appropriate packaging/storage control strategies. The Arrhenius equation has been used as the basis of a number of models to predict the chemical stability of formulated product. In this work, we investigate the increase in chemical degradation seen for one particular spray dried dispersion formulation using hydroxypropyl methylcellulose acetate succinate (HPMC-AS). Samples, prepared using polymers with different substitution levels, were placed on storage for 6 months under a range of different temperature and relative humidity conditions and the degradant level monitored using high-performance liquid chromatography (HPLC). While the data clearly illustrates the impact of temperature and relative humidity on the degradant levels detected, it also highlighted that these terms do not account for all the variability in the data. An extension of the Arrhenius equation to include a term for the polymer chemistry, specifically the degree of succinoyl substitution on the polymer backbone, was shown to improve the fit of the model to the data. PMID:25450477

  10. Carbon nanotubes filled polymer composites: A comprehensive study on improving dispersion, network formation and electrical conductivity

    NASA Astrophysics Data System (ADS)

    Chakravarthi, Divya Kannan

    In this dissertation, we determine how the dispersion, network formation and alignment of carbon nanotubes in polymer nanocomposites affect the electrical properties of two different polymer composite systems: high temperature bismaleimide (BMI) and polyethylene. The knowledge gained from this study will facilitate optimization of the above mentioned parameters, which would further enhance the electrical properties of polymer nanocomposites. BMI carbon fiber composites filled with nickel-coated single walled carbon nanotubes (Ni-SWNTs) were processed using high temperature vacuum assisted resin transfer molding (VARTM) to study the effect of lightning strike mitigation. Coating the SWNTs with nickel resulted in enhanced dispersions confirmed by atomic force microscopy (AFM) and dynamic light scattering (DLS). An improved interface between the carbon fiber and Ni-SWNTs resulted in better surface coverage on the carbon plies. These hybrid composites were tested for Zone 2A lightning strike mitigation. The electrical resistivity of the composite system was reduced by ten orders of magnitude with the addition of 4 weight percent Ni-SWNTs (calculated with respect to the weight of a single carbon ply). The Ni-SWNTs - filled composites showed a reduced amount of damage to simulated lightning strike compared to their unfilled counterparts indicated by the minimal carbon fiber pull out. Methods to reduce the electrical resistivity of 10 weight percent SWNTs --- medium density polyethylene (MDPE) composites were studied. The composites processed by hot coagulation method were subjected to low DC electric fields (10 V) at polymer melt temperatures to study the effect of viscosity, nanotube welding, dispersion and, resultant changes in electrical resistivity. The electrical resistivity of the composites was reduced by two orders of magnitude compared to 10 wt% CNT-MDPE baseline. For effective alignment of SWNTs, a new process called Electric field Vacuum Spray was devised to

  11. Dispersion-Aggregation and Wetting-Dewetting Phase Transitions in Mixtures of Polymer Grafted Nanoparticles and a Chemically Dissimilar Polymer Matrix

    NASA Astrophysics Data System (ADS)

    Martin, Tyler; Mongcopa, Katrina; Ashkar, Rana; Butler, Paul; Krishnamoorti, Ramanan; Jayaraman, Arthi

    Significant efforts have been focused towards controlling morphology of the nanoscale fillers and matrix polymer in polymer nanocomposites as the composite morphology is directly related to the macroscopic properties of that material. For nanocomposites with chemically identical graft and matrix polymers, it is well understood that the polymer grafted particle dispersion to aggregation transition is directly linked to and synonymous with wetting/dewetting of the graft and matrix polymer. Our recent work has focused on exploring composites with chemically different graft and matrix polymers, specifically those with attractive graft-matrix interactions that lead to a dispersed filler state at low temperature and aggregated filler state at high temperatures. We show, using coarse-grained molecular simulations, that the sharp phase transition from dispersed to aggregated states is distinct from the continuous wetting-dewetting transition. The onset of wetting to dewetting occurs at temperatures lower than the dispersion to aggregation transition, and dewetting continues at temperatures above the transition temperature in the aggregated state. Furthermore, the graft and matrix chain composition can be varied to tune the dispersion-aggregation transition temperature and the degree of wetting of the grafted layer. Experiments using SANS and SAXS of deuterated poly(styrene) grafted silica particles in a poly(vinyl methyl ether) matrix show remarkable agreement with our simulations.

  12. Nanotube dispersion and polymer conformational confinement in a nanocomposite fiber: a joint computational experimental study.

    PubMed

    Meng, Jiangsha; Zhang, Yiying; Cranford, Steven W; Minus, Marilyn L

    2014-08-01

    A combination of computational and experimental methods was implemented to understand and confirm that conformational changes of a polymer [specifically polyacrylonitrile (PAN)] vary with the dispersion quality and confinement between single-wall carbon nanotubes (SWNT) in the composite fibers. A shear-flow gel-spinning approach was utilized to produce PAN-based composite fibers with high concentration (i.e., loading of 10 wt %) of SWNT. Dispersion qualities of SWNT ranging from low to high were identified in the fibers, and their effects on the structural morphologies and mechanical properties of the composites were examined. These results show that, as the SWNT dispersion quality in terms of distribution in the fiber and exfoliation increases, PAN conformations were confined to the extended-chain form. Full atomistic computational results show that the surface interaction energy between isolated PAN and SWNT was not preferred, leading to the self-agglomeration of PAN. However, confinement of the polymer chains between SWNT bundles or individual tubes (i.e., molecular crowding) resulted in large increases in the PAN-SWNT interaction energy. In other words, the crowding of polymer chains by the SWNT at high concentrations can promote extended-chain conformational development during fiber spinning. This was also evidenced experimentally by the observance of significantly improved PAN orientation and crystallization in the composite. Ultimately this work provides fundamental insight toward the specific structural changes capable at the polymer/nanotube interface which are important toward improvement of the effective contribution of the SWNT to the mechanical performance of the composite. PMID:25011016

  13. Light scattering characterization of carbon nanotube dispersions and reinforcement of polymer composites

    NASA Astrophysics Data System (ADS)

    Zhao, Jian

    Dispersion and morphology of carbon nanotubes as well as enhancement for rubber reinforcement are studied. Several approaches including surfactant aids, functionalization and plasma treatment are used to assist dispersion. Several characterization methods are used to assess both the degree of dispersion and the level of reinforcement. Small angle light scattering is carried out as a primary tool to assess structure and dispersion of nanotubes treated through these approaches Stress-strain measurement and dynamic mechanical analysis are performed on elastomeric composites to study polymer reinforcement. These results are divided into five sections. The first section focuses on dispersion of untreated and acid-treated multi-walled carbon nanofibers (MWNF) suspended in water. Light scattering data provide the first insights into the mechanism by which surface treatment promotes dispersion. Both acid-treated and untreated nanofibers exhibit hierarchical morphology consisting of small-scale aggregates (bundles) that agglomerate to form fractal clusters that eventually precipitate. Although the morphology of the aggregates and agglomerates is nearly independent of surface treatment, their time evolution is quite different. Acid oxidation has little effect on bundle morphology. Rather acid treatment inhibits agglomeration of the bundles. The second section focuses on dispersion of the solubilized nanofibers. Light scattering data indicate that PEG-functionalized sample is dispersed at small rod-like bundle (side-by-side aggregate) level. Solubilization is achieved not by disrupting small-scale size-by-side bundles, but mainly by completely inhibiting large-scale agglomeration. The third section focuses on dispersion of plasma-treated carbon nanofibers. Comparison of untreated and plasma-treated nanofibers indicates that plasma treatment facilitates dispersion of nanofibers. The fourth section focuses on dispersion and structure of single-walled carbon nanotubes (SWNTs

  14. Effect of solvent quality on the dispersibility of polymer-grafted spherical nanoparticles in polymer solutions

    NASA Astrophysics Data System (ADS)

    Egorov, S. A.; Binder, K.

    2012-09-01

    In this work, lattice-based self consistent field theory is used to study the structural properties of individual polymer-grafted spherical nanopartices and particle-particle interactions in polymer melts and solutions under variable solvent conditions. Our study has focused on the depth of the minimum in the potential of mean force between the two brush-coated nanoparticles, if such a minimum occurs, and we have also addressed the corresponding radial density profiles of free and grafted chains around a single nanoparticle, in an attempt to clarify the extent of correlation between the depth of the minimum, Wmin, and the parameter δ characterizing the interpenetration between the profiles of free and grafted chains. Although one cannot establish a simple one-to-one correspondence between Wmin and δ, we do find common trends, in particular, if the solvent conditions for free and grafted chains differ: varying the volume fraction of the free chains, δ typically exhibits a broad minimum, corresponding to a region where the magnitude of Wmin exceeds thermal energy kBT, leading to particle aggregation.

  15. Effects of symbol modulation coding on readout fidelity of shift-multiplexed holographic digital data page storage in a photopolymerizable nanoparticle-(thiol-ene)polymer composite film.

    PubMed

    Takayama, Shingo; Nagaya, Kohta; Momose, Keisuke; Tomita, Yasuo

    2014-04-01

    We report on shift-multiplexed holographic storage of 250 digital data pages in a photopolymerizable SiO₂ nanoparticle-polymer composite film being capable of step-growth thiol-ene polymerization in the green. Various two-dimensional symbol modulation codes for the digital data page format were employed to examine the dependence of the readout fidelity on modulation coding schemes. It is found that, as compared to 1:2 and 2:4 modulation codes, higher-order 5:9, 9:16, and 13:25 modulation codes possessing reduced white rates and higher coding efficiencies give lower symbol-error rates of ~1×10⁻³ and higher signal-to-noise ratios (>4). PMID:24787217

  16. Plasma - enhanced dispersion of metal and ceramic nanoparticles in polymer nanocomposite films

    NASA Astrophysics Data System (ADS)

    Maguire, Paul; Liu, Yazi; Askari, Sadegh; Patel, Jenish; Macia-Montero, Manuel; Mitra, Somak; Zhang, Richao; Sun, Dan; Mariotti, Davide

    2015-09-01

    In this work we demonstrate a facile method to synthesize a nanoparticle/PEDOT:PSS hybrid nanocomposite material in aqueous solution through atmospheric pressure direct current (DC) plasma processing at room temperature. Both metal (Au) and ceramic (TiO2) nanoparticle composite films have been fabricated. Nanoparticle dispersion is enhanced considerable and remains stable. TiO2/polymer hybrid nanoparticles with a distinct core shell structure have been obtained. Increased nanoparticle/PEDOT:PSS nanocomposite electrical conductivity has been observed. The improvement in nanocomposite properties is due to the enhanced dispersion and stability in liquid polymer of microplasma processed Au or TiO2 nanoparticles. Both plasma induced surface charge and nanoparticle surface termination with specific plasma chemical species are thought to provide an enhanced barrier to nanoparticle agglomeration and promote nanoparticle-polymer bonding. This is expected to have a significant benefit in materials processing with inorganic nanoparticles for applications in energy storage, photocatalysis and biomedical sensors. Engineering and Physical Sciences Research Council (EPSRC: EP/K006088/1, EP/K006142, Nos. EP/K022237/1).

  17. In situ growth of well-dispersed CdS nanocrystals in semiconducting polymers

    PubMed Central

    2013-01-01

    A straight synthetic route to fabricate hybrid nanocomposite films of well-dispersed CdS nanocrystals (NCs) in poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) is reported. A soluble cadmium complex [Cd(SBz)2]2·MI, obtained by incorporating a Lewis base (1-methylimidazole, MI) on the cadmium bis(benzyl)thiol, is used as starting reagent in an in situ thermolytic process. CdS NCs with spherical shape nucleate and grow well below 200°C in a relatively short time (30 min). Photoluminescence spectroscopy measurements performed on CdS/MEH-PPV nanocomposites show that CdS photoluminescence peaks are totally quenched inside MEH-PPV, if compared to CdS/PMMA nanocomposites, as expected due to overlapping of the polymer absorption and CdS emission spectra. The CdS NCs are well-dispersed in size and homogeneously distributed within MEH-PPV matrix as proved by transmission electron microscopy. Nanocomposites with different precursor/polymer weight ratios were prepared in the range from 1:4 to 4:1. Highly dense materials, without NCs clustering, were obtained for a weight/weight ratio of 2:3 between precursor and polymer, making these nanocomposites particularly suitable for optoelectronic and solar energy conversion applications. PMID:24015753

  18. Nanocomposites of polymers with layered inorganic nanofillers: Antimicrobial activity, thermo-mechanical properties, morphology, and dispersion

    NASA Astrophysics Data System (ADS)

    Songtipya, Ponusa

    In the first part of the thesis, polyethylene/layered silicate nanocomposites that exhibit an antimicrobial activity were synthesized and studied. Their antimicrobial activity was designed to originate from non-leaching, novel cationic modifiers---amine-based surfactants---used as the organic-modification of the fillers. Specifically, PE/organically-modified montmorillonite ( mmt) nanocomposites were prepared via melt-processing, and simultaneous dispersion and antimicrobial activity was designed by proper choice of the fillers' organic modification. The antimicrobial activity was measured against three micotoxinogen fungal strains (Penicillium roqueforti and claviforme, and Fusarium graminearum ). Various mmt-based organofillers, which only differ in the type or amount of their organic modification, were used to exemplify how these surfactants can be designed to render antifungal activity to the fillers themselves and the respective nanocomposites. A comparative discussion of the growth of fungi on unfilled PE and nanocomposite PE films is used to demonstrate how the antimicrobial efficacy is dictated by the surfactant chemistry and, further, how the nanocomposites' inhibitory activity compares to that of the organo-fillers and the surfactants. An attempt to improve the thermomechanical reinforcement of PE/mmt nanocomposites while maintaining their antimicrobial activity, was also carried out by combining two different organically modified montmorillonites. However, a uniform microscopic dispersion could not be achieved through this approach. In the second part of this thesis, a number of fundamental studies relating to structure-property relations in nanocomposites were carried out, towards unveiling strategies that can concurrently optimize selected properties of polymers by the addition of nanofillers. Specifically, the dispersion-crystallinity-reinforcement relations in HDPE/mmt nanocomposites was investigated. The influence of a functional HDPE compatibilizer

  19. Light transmission of polymer-dispersed liquid crystal layer composed of droplets with inhomogeneous surface anchoring

    NASA Astrophysics Data System (ADS)

    Loiko, V. A.; Zyryanov, V. Ya.; Konkolovich, A. V.; Miskevich, A. A.

    2016-01-01

    We have developed a model and realized an algorithm for the calculation of the coefficient of coherent (direct) transmission of light through a layer of liquid crystal (LC) droplets in a polymer matrix. The model is based on the Hulst anomalous diffraction approximation for describing the scattering by an individual particle and the Foldy-Twersky approximation for a coherent field. It allows one to investigate polymer dispersed LC (PDLC) materials with homogeneous and inhomogeneous interphase surface anchoring on the droplet surface. In order to calculate the configuration of the field of the local director in the droplet, the relaxation method of solving the problem of minimization of the free energy volume density has been used. We have verified the model by comparison with experiment under the inverse regime of the ionic modification of the LC-polymer interphase boundary. The model makes it possible to solve problems of optimization of the optical response of PDLC films in relation to their thickness and optical characteristics of the polymer matrix, sizes, polydispersity, concentration, and anisometry parameters of droplets. Based on this model, we have proposed a technique for estimating the size of LC droplets from the data on the dependence of the transmission coefficient on the applied voltage.

  20. Three-Dimensional Microstructure of a Polymer-Dispersed Liquid Crystal Observed by Transmission Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Pierron, Jean; Tournier-Lasserve, Valérie; Sopena, Pierre; Boudet, Alain; Sixou, Pierre; Mitov, Michel

    1995-11-01

    A film consisting of an amorphous photo-crosslinkable polymer matrix and a dispersion of microinclusions of a cholesteric polymer was investigated by transmission electron microscopy (TEM). The polymerization procedure of the blend provides a composite with many small nodules of spherical or ellipsoidal shapes, with sizes between 0.4 and 6 μm. The cholesteric stratification is well evidenced in transmission electron microscopy by dark lines due to diffraction contrast. The 3D organization was reconstructed by the observation of successive ultramicrotomed sections. Six types of nodules were distinguished according to the number of defects (foci or disclination lines), among which only three had already been observed and theoretically calculated. The confined geometry inherent in the size of the nodules, close to the cholesteric pitch, is responsible of these unexpected structures. In these conditions, the surface forces are in tight competition with the cholesteric elastic forces.

  1. Photomechanical response of disperse red 1 azobenzene dye-doped PMMA polymer fiber

    NASA Astrophysics Data System (ADS)

    Ye, Xianjun; Kuzyk, Mark G.

    2014-02-01

    Disperse red 1 azobenzene (DR1) doped poly(methyl methacrylate) (PMMA) optical fiber has been shown to have a fast photomechanical response upon 633 nm laser irradiation originating in photo-isomerization of the dopants between the cis and trans forms. In this work, laser light of 355 nm wavelength is used to investigate the trans to cis isomerization process, which should result in length contraction. A three-point-contact optically actuated beam-controlling mount is made of dye doped polymer fiber segments and metal-coated microscope coverslips to measure the photomechanical response. The length change of the fiber is determined from a quadrant photodetector reading upon beam deflection. The fiber is observed to elongate upon UV irradiation. We find that for DR1 dye in PMMA polymer, the dominant mechanism of the photomechanical effect is photo-thermally stimulated isomerization rather than direct photoisomerization.

  2. Polymer adsorption and electrokinetic potential of dispersed particles in weak and strong electric fields.

    PubMed

    Barany, Sandor

    2015-08-01

    A review on the effects of adsorbed non-ionic polymers and polyelectrolytes on the electrophoresis of dispersed particles is given. The variety of changes in the electrical double layer (EDL) structure and, in particular, electrokinetic potential in weak electric fields as a result of polymer adsorption is discussed. Examples on the dependence of zeta potential of particles on the adsorbed amount of polymers are described. An analysis of the influence of various complicating factors, namely polarization of the EDL, curvature of the surface and the presence of electrolytes, on the calculation of polymer layer thickness from electrophoretic data has been performed. Results of electrophoretic measurements in suspensions of non-conventional particles (TiC, SiC and Si3N4) having adsorbed polyethylene oxide are presented. Regularities of the effect of anionic and cationic polyelectrolytes (PEs) and their binary mixtures on the electrokinetic potential of dispersed particles (polystyrene, silica, bentonite and kaolin) as a function of the polymer dose, pH, charge density (CD) of the polyelectrolyte, as well as the mixture composition and the sequence of component addition are described. It has been shown that addition of increasing amount of anionic PEs increases the absolute value of the negative zeta potential of particles, while adsorption of cationic PEs results in a significant decrease in the negative ζ-potential and overcharging the particle surface; changes in the ζ-potential are more pronounced for samples with higher CD. In mixtures of cationic and anionic PEs, in a wide range of their composition, the ζ-potential of negatively charged particles is determined by the adsorbed amount of the anionic polymer independently of the CD of polyelectrolyte and the sequence of the mixture component addition. The role of coulombic and non-coulombic forces in the mechanism of polyelectrolyte adsorption and structure of adsorbed layers formed is discussed. The results of

  3. High transmittance optical films based on quantum dot doped nanoscale polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Gandhi, Sahil Sandesh; Chien, Liang-Chy

    2016-04-01

    We propose a simple way to fabricate highly transparent nanoscale polymer dispersed liquid crystal (nano-PDLC) films between glass substrates and investigate their incident angle dependent optical transmittance properties with both collimated and Lambertian intensity distribution light sources. We also demonstrate that doping nano-PDLC films with 0.1% InP/ZnS core/shell quantum dots (QD) results in a higher optical transmittance. This work lays the foundation for such nanostructured composites to potentially serve as roll-to-roll coatable light extraction or brightness enhancement films in emissive display applications, superior to complex nanocorrugation techniques proposed in the past.

  4. Shear-induced surface alignment of polymer dispersed liquid crystal microdroplets on the boundary layer

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Singh, J. J.

    1993-01-01

    Polymer dispersed liquid crystal thin films have been deposited on a glass substrate, utilizing the processes of polymerization and solvent evaporation induced phase separation. Liquid crystal microdroplets trapped on the upper surface of the thin film respond to the shear stress due to air or gas flow on the surface layer. Response to an applied step shear stress input on the surface layer has been measured by measuring the time response of the transmitted light intensity. Initial results on the measurements of the light transmission as a function of the air flow differential pressure indicate that these systems offer features suitable for boundary layer and gas flow sensors.

  5. Low switching voltage ZnO quantum dots doped polymer-dispersed liquid crystal film.

    PubMed

    Hsu, Chuan-Chun; Chen, Yi-Xuan; Li, Hui-Wen; Hsu, Jy-Shan

    2016-04-01

    This paper investigates the effects of ZnO nanoparticles (NPs) on the switching voltages of polymer dispersed liquid crystal (PDLC) films. The threshold and driving electric fields of PDLC film doped with 2.44 wt% ZnO NPs were 0.13 and 0.31 V/μm, respectively, with a contrast ratio of 26. The results of field emission scanning electron microscopy show that the size of the droplets in doped PDLC films increases with the doping concentration. The development of ZnO-doped PDLC films with low driving voltages greatly broadens the applicability of these devices. PMID:27137000

  6. Electro-optic system for online light transmission control of polymer-dispersed liquid crystal windows

    NASA Astrophysics Data System (ADS)

    Sanchez-Pena, Jose M.; Vazquez, Carmen; Perez, I.; Rodriguez, Inmaculada; Oton, Jose M.

    2002-07-01

    Polymer-dispersed liquid crystals (PDLCs) are formed by microdroplets of liquid crystal embedded in a flexible matrix and sandwiched between transparent electrodes. Large area units (several square meters) can be easily prepared. Opaque, transparent, and intermediate light transmission states can be achieved by applying appropriate electric fields. These features allow their use in active windows for illumination, greenhouse regulation, and privacy, both on buildings and vehicles. An electro-optic system based on a microcontrolled driver was implemented for on-line control of PDLC windows. The system may self-regulate daylight or may be used as remote control.

  7. Evaluation of polyvinyl acetate dispersion as a sustained release polymer for tablets.

    PubMed

    Bordaweka, M S; Zia, H; Quadir, A

    2006-01-01

    Kollicoat SR 30D is a unique 30% aqueous dispersion of polyvinvyl acetate stabilized by polyvinyl-pyrrolidone intended for preparation of sustained release products. Detailed evaluation of this polymer dispersion as a sustained release coating for active pharmaceutical ingredients of two diverse classes of drugs was studied. A water insoluble drug (ibuprofen) and a water soluble drug (ascorbic acid) were selected as model active drugs. Ibuprofen was granulated using a GPCG-1 fluid bed processor prior to tableting, to improve the particle size and particle flow properties. In this process a 2(3) factorial design was implemented to evaluate the optimum process parameters such as spray rate, inlet air temperature and the inlet air velocity. The statistical model selected was Y(ijkl) = mu + tau(i) + beta(j) + theta(k) + (taubeta)ij + (betatheta)jk + (tautheta)ik + (taubetatheta)ijk + epsilon(ijkl). The factorial design showed that the spray rate, inlet air temperature, and inlet air velocity had a significant effect (p value <0.05) on the particle size. Significant improvement was observed in the flow properties of the granules. The granules were coated with Kollicoat SR30D dispersion using top spray method in the fluid bed processor. The dissolution studies showed that the release of ibuprofen decreased with an increase in the coating levels of Kollicoat SR 30 D. In the case of ascorbic acid, preparation of sustained release coated commercial granules was not possible due to the difficulty in coating a highly soluble drug particle. However, the coated granules when compressed into tablets showed some sustainability. Ibuprofen tablets manufactured with coated granules with a 15 g polymer for 300 g batch showed dissolution parameters of t50 and t90 at 4.2 hr and 7.5 hr, respectively. An approximate zero-type of release was observed when the polymer content was increased to 45 g for 300 g batch. Ascorbic acid tablets made with coated commercial granules having a total

  8. Frequency doubling in poled polymers using anomalous dispersion phase-matching

    SciTech Connect

    Kowalczyk, T.C.; Singer, K.D.; Cahill, P.A.

    1995-10-01

    The authors report on a second harmonic generation in a poled polymer waveguide using anomalous dispersion phase-matching. Blue light ({lambda} = 407 nm) was produced by phase-matching the lowest order fundamental and harmonic modes over a distance of 32 {micro}m. The experimental conversion efficiency was {eta} = 1.2 {times} 10{sup {minus}4}, in agreement with theory. Additionally, they discuss a method of enhancing the conversion efficiency for second harmonic generation using anomalous dispersion phase-matching to optimize Cerenkov second harmonic generation. The modeling shows that a combination of phase-matching techniques creates larger conversion efficiencies and reduces critical fabrication requirements of the individual phase-matching techniques.

  9. A polarization independent liquid crystal phase modulation adopting surface pinning effect of polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Tsou, Yu-Shih

    2011-12-01

    A polarization-independent liquid crystal (LC) phase modulation using the surface pinning effect of polymer dispersed liquid crystals (SP-PDLC) is demonstrated. In the bulk region of the SP-PDLC, the orientations of LC directors are randomly dispersed; thus, any polarization of incident light experiences the same averaged refractive index. In the regions near glass substrates, the LC droplets are pinned. The orientations of top and bottom droplets are orthogonal. Two eigen-polarizations of an incident light experience the same phase shift. As a result, the SP-PDLC is polarization independent. Polarizer-free microlens arrays of SP-PDLC are also demonstrated. The SP-PDLC has potential for application in spatial light modulators, laser beam steering, and electrically tunable microprisms.

  10. Dispersion strategies and role of interfacial phenomena in dielectric polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Khodaparast, Payam

    Owing to unique characteristics of nanoparticles such as high surface to volume ratio, it is postulated that nanoparticle-modified polymers exhibit properties beyond those predicted by effective media theories. In the case of dielectric nanoparticles in a polymer, it is expected that dielectric properties of the nanocomposite are dominated by the expansive interface rather than anticipated by the inherent properties of individual components. An in-depth review of dielectric polymer nanocomposites shows conflicting trends where addition of nano-sized particles resulted in increase or decrease in dielectric properties. This contradictory behavior could mainly stem from 1- the state of dispersion of nanoparticles and 2-The unique nature of interface based on the particle-polymer system. The hypothesis of the proposed research is that the role of the interfacial region is not only influenced by its expansive nature but is also governed by their interaction at nanoscale regime. In order to achieve a high internal surface area, the first important challenge to address is controlling the state of dispersion and disaggregation of nanoparticles. Therefore the first goal of this research is studying the effectiveness of different processing methods in achieving uniform nanoscale dispersion in dielectric polymer nanocomposites. Silane functionalization of titania nanoparticles is investigated as one possible solution of better dispersion of titania in PVDF polymer where two coupling agents namely, aminopropyltriethoxy silane called as APS, and Nonafluorohexyltriethoxysilane called as FHES, are studied. FHES is shown to be more effective in reducing the average aggregate size of titania nanoparticles in PVDF matrix to below 100nm, whereas the average aggregate size in untreated and APS-functionalized TiO2/PVDF nanocomposite was approximately one to two orders of magnitude higher than that. Dielectric permittivity of FHES-functionalized TiO2/PVDF nanocomposite, showed

  11. The hydration of reactive cement-in-polymer dispersions studied by nuclear magnetic resonance

    SciTech Connect

    Olaru, A.M.; Weichold, O.; Adams, A.

    2011-11-15

    The behaviour of two novel cement-in-polymer (c/p) dispersions, namely cement-in-poly(vinyl acetate) and cement-in-poly(vinyl alcohol) upon exposure to water at room temperature was investigated by a combination of various NMR methods. The swelling, cracking, and the water ingress were monitored non-destructively using {sup 1}H single point imaging. The hydration of the cement matrix was investigated using {sup 29}Si NMR whilst {sup 13}C CPMAS NMR spectra allowed the quantification of the kinetics of the hydrolysis reaction of poly(vinyl acetate) into poly(vinyl alcohol). The polymer controls the rate of water ingress and swelling which in turn determines the behaviour of the c/p dispersions upon exposure to water. For the cement-in-poly(vinyl alcohol), the rates of water ingress and swelling are much faster than the hydration of the clinker whilst for the cement-in-poly(vinyl acetate) the slow rates of the two processes allow the formation of a cementious matrix which assures the stability of the sample.

  12. Investigation of intermolecular interactions between fluorene-based conjugated polymers using the dispersion-corrected DFT

    NASA Astrophysics Data System (ADS)

    Ayoub, Sarah; Lagowski, Jolanta B.

    2015-03-01

    Alternating triphenylamine-fluorene, TPAFn (n=1-3), and fluorene-oxadiazole OxFn (n=1-3) conjugated copolymers are important components of novel high-efficiency multi-layer organic light-emitting diodes (OLEDs). In this work, we investigate the intermolecular interactions between the various combinations of monomers of OxFn-TPAFn (n=1-3) copolymers using the dispersion-corrected density functional theory (B97D) method. The monomer combinations are taken with and without the presence of long alkyl chains in order to study the effect of side-chains on the polymer backbone intermolecular interactions. The dispersion effect is studied by comparing the structures of the interacting monomers with those in vacuum. In addition, we calculate intermolecular distances, energy gaps and binding energies of monomer dimers corresponding to different pairings of OxFn-TPAFn (n=1-3) monomers. Our results show that the combination of OxF3-TPAF2 monomers exhibites the highest binding energy, closest intermolecular distance, and the best matching of chain lengths amongst all of the combinations of OxFn-TPAFn (n=1-3) monomers. Experiments have shown that OxF3-TPAF2 combination gives the best performance for OLEDS made of OxF-TPAF polymer layers.

  13. Reducing the Cation Exchange Capacity of Lithium Clay to Form Better Dispersed Polymer-Clay Nanocomposites

    NASA Technical Reports Server (NTRS)

    Liang, Maggie

    2004-01-01

    Polymer-clay nanocomposites have exhibited superior strength and thermo- oxidative properties as compared to pure polymers for use in air and space craft; however, there has often been difficulty completely dispersing the clay within the matrices of the polymer. In order to improve this process, the cation exchange capacity of lithium clay is first lowered using twenty-four hour heat treatments of no heat, 130 C, 150 C, or 170 C to fixate the lithium ions within the clay layers so that they are unexchangeable. Generally, higher temperatures have generated lower cation exchange capacities. An ion exchange involving dodecylamine, octadecylamine, or dimethyl benzidine (DMBZ) is then employed to actually expand the clay galleries. X-ray diffraction and transmission electron microscopy can be used to determine whether the clay has been successfully exfoliated. Finally, resins of DMBZ with clay are then pressed into disks for characterization using dynamic mechanical analyzer and oven- aging techniques in order to evaluate their glass transition, modulus strength, and thermal-oxidative stability in comparison to neat DMBZ. In the future, they may also be tested as composites for flexural and laminar shear strength.

  14. Topological polymer dispersed liquid crystals with bulk nematic defect lines pinned to handlebody surfaces.

    PubMed

    Campbell, Michael G; Tasinkevych, Mykola; Smalyukh, Ivan I

    2014-05-16

    Polymer dispersed liquid crystals are a useful model system for studying the relationship between surface topology and defect structures. They are comprised of a polymer matrix with suspended spherical nematic drops and are topologically constrained to host defects of an elementary hedgehog charge per droplet, such as bulk or surface point defects or closed disclination loops. We control the genus of the closed surfaces confining such micrometer-sized nematic drops with tangential boundary conditions for molecular alignment imposed by the polymer matrix, allowing us to avoid defects or, on the contrary, to generate them in a controlled way. We show, both experimentally and through numerical modeling, that topological constraints in nematic microdrops can be satisfied by hosting topologically stable half-integer bulk defect lines anchored to opposite sides of handlebody surfaces. This enriches the interplay of topologies of closed surfaces and fields with nonpolar symmetry, yielding new unexpected configurations that cannot be realized in vector fields, having potential implications for topologically similar defects in cosmology and other fields. PMID:24877965

  15. Micro and nano composites composed of a polymer matrix and a metal disperse phase

    NASA Astrophysics Data System (ADS)

    Olea Mejia, Oscar Fernando

    Low density polyethylene (LDPE) and Hytrel (a thermoplastic elastomer) were used as polymeric matrices in polymer + metal composites. The concentration of micrometric (Al, Ag and Ni) as well as nanometric particles (Al and Ag) was varied from 0 to 10%. Composites were prepared by blending followed by injection molding. The resulting samples were analyzed by scanning electron microscopy (SEM) and focused ion beam (FIB) in order to determine their microstructure. Certain mechanical properties of the composites were also determined. Static and dynamic friction was measured. The scratch resistance of the specimens was determined. A study of the wear mechanisms in the samples was performed. The Al micro- and nanoparticles as well as Ni microparticles are well dispersed throughout the material while Ag micro and nanoparticles tend to form agglomerates. Generally the presence of microcomposites affects negatively the mechanical properties. For the nanoparticles, composites with a higher elastic modulus than that of the neat materials are achievable. For both micro- and nanocomposites it is feasible to lower the friction values with respective to the neat polymers. The addition of metal particles to polymers also improves the scratch resistance of the composites, particularly so for microcomposites. The inclusion of Ag and Ni particles causes an increase in the wear loss volume while Al can reduce the wear for both polymeric matrices.

  16. Topological Polymer Dispersed Liquid Crystals with Bulk Nematic Defect Lines Pinned to Handlebody Surfaces

    NASA Astrophysics Data System (ADS)

    Campbell, Michael G.; Tasinkevych, Mykola; Smalyukh, Ivan I.

    2014-05-01

    Polymer dispersed liquid crystals are a useful model system for studying the relationship between surface topology and defect structures. They are comprised of a polymer matrix with suspended spherical nematic drops and are topologically constrained to host defects of an elementary hedgehog charge per droplet, such as bulk or surface point defects or closed disclination loops. We control the genus of the closed surfaces confining such micrometer-sized nematic drops with tangential boundary conditions for molecular alignment imposed by the polymer matrix, allowing us to avoid defects or, on the contrary, to generate them in a controlled way. We show, both experimentally and through numerical modeling, that topological constraints in nematic microdrops can be satisfied by hosting topologically stable half-integer bulk defect lines anchored to opposite sides of handlebody surfaces. This enriches the interplay of topologies of closed surfaces and fields with nonpolar symmetry, yielding new unexpected configurations that cannot be realized in vector fields, having potential implications for topologically similar defects in cosmology and other fields.

  17. Dispersion and self-assembly of nanospheres and nanorods in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Deshmukh, Ranjan Deepak

    2007-12-01

    Polymer nanocomposites are hybrid nanomaterials in which electrical, opto-electronic, magnetic, mechanical and other properties can be precisely tuned by choosing an appropriate combination of nanoparticle (NP) and polymer. This dissertation explores in-situ and ex-situ routes to disperse metal NP in polymers as well as the fundamental thermodynamic and dynamic principles underlying the NP dispersion in polymers. "In-situ" silver NP are prepared by the thermal decomposition of an organometallic precursor (1,1,1,5,5,5-hexafluoroacetylacetonato)silver(I) or (AgHFA) in homopolymer poly(methyl methactyalate), PMMA and block copolymer poly(MMA-b-styrene), PS-b-PMMA films. A range of complementary characterization techniques including Rutherford backscattering spectrometry (RBS), scanning force microscopy (SFM), transmission electron microscopy (TEM), and UV-visible spectroscopy are used to characterize the polymer nanocomposites. The in-situ formed "spherical" silver NP are observed to segregate to the surface and the substrate regions in PMMA and PS-b-PMMA films. By showing that the precursor organizes into aggregates in as-cast films, our experiments uncover the mechanism of NP segregation. Upon annealing, diffusion of the precursor to the surface and substrate occurs concurrently with NP formation resulting in enrichment of Ag at both interfaces. In PS-b-PMMA films, the Ag NP form during the self-assembly of the block copolymer. At the surface, NP organize into well-defined arrays that are guided by the PMMA domains. For the first time, our experiments also show that the kinetics of block copolymer reorganization is slowed down by the incorporation of NP. This dissertation also explores the self-assembly of "ex-situ" synthesized NP with aspect ratio > 1, namely gold nanorods functionalized with poly(ethylene glycol), PEG. After solvent annealing PS-b-PMMA with 5-vol% Au, the nanorods are selectively located and confined in the "lamellar" PMMA domains due to favorable

  18. A novel structure and photochromism of heteropolyoxometalates dispersed in polymer networks

    SciTech Connect

    Bao Xinjian; Feng Wei; Chen Jie; Liu Xiaoyang

    2012-07-15

    Nanocomposites based on Keggin structure tungstophosphate acid (PWA) with 'branch-like' nanometer well dispersed in poly(acrylamide-co-vinylamine) (PAM-co-PVAm) were fabricated. The microstructure and photochromic properties were studied via Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), ultraviolet-visible spectra (UV-vis) and electron resonance spectra (ESR). FT-IR results showed that the Keggin geometry of polyoxometalates was still preserved inside the composites and hydrogen bonding and salt formation were built between PWA and polymer matrix. SEM and TEM images showed that PWA nanoparticles were finely dispersed in polymer matrix with 'branch-like' shape. Under UV irradiation, the film was reduced photochemically to yield a glaucous species. After UV light turned off, the color of film became green. Two photo-reduction processes (one was between acylamino and heteropoly acid, another was between amidocyanogen and heteropoly acid) occurred at the same time in PWA/PAM-co-PVAm system, which resulted in the formation of heteropolygreen. - Graphical abstract: Two absorption bands appeared after UV irradiated. In bleaching process, the peaks at 620-820 nm disappeared and those at 420 nm still presented. Due to synergies happened between heteropolyacid and PAM-co-PVAm, heteropolygreen was formed. Highlights: Black-Right-Pointing-Pointer 'Branch-like' composites were fabricated by dispersed PWA into PAM-co-PVAm system. Black-Right-Pointing-Pointer Two photo-reduction processes occurred simultaneously in PWA/PAM-co-PVAm system. Black-Right-Pointing-Pointer Heteropolygreen was formed by synergies of hydrogen bonding and salt formation.

  19. Holographic microscopy studies of emulsions

    NASA Technical Reports Server (NTRS)

    Witherow, W. K.

    1981-01-01

    A holographic microscopy system that records and observes the dynamic properties of separation of dispersed immiscible fluids is described. The holographic construction system and reconstruction system that were used to obtain particle size and distribution information from the holograms are discussed. The holographic microscopy system is used to observed the phase separating processes in immiscible fluids that were isothermally cooled into the two phase region. Nucleation, growth rates, coalescence, and particle motion are successfully demonstrated with this system. Thus a holographic particle sizing system with a resolution of 2 micrometers and a field of view of 100 cu cm was developed that provides the capability of testing the theories of separating immiscible fluids for particle number densities in the range of 10 to 10 to the 7th power particles.

  20. Holographic Recording Materials Development

    NASA Technical Reports Server (NTRS)

    Verber, C. M.; Schwerzel, R. E.; Perry, P. J.; Craig, R. A.

    1976-01-01

    Organic photorefractive materials were evaluated for application in a reversible holographic memory system. Representative indigo and thioindigo derivatives and several stilbene derivatives were studied as well as 15, 16-dialkyldihydropyrene derivatives the following goals were achieved: (1) the successful writing of phase holograms in a thioindigo/polymer gel system, (2) the successful writing and erasing of phase holograms in a variety of indigo/polymer gel and indigo/solid polymer systems, and (3) the identification of indigoid dyes and 15, 16-dialkyldihydropyrene derivatives as materials potentially suitable for utilization in an operational system. Photochemical studies of the stilbene, indigo, thioindigo, and dialkyldihydropyrene derivatives in solution and in a variety of polymer matrix materials were conducted with the goal of optimizing the photorefractive behavior of the chemical system as a whole. The spectroscopic properties required of optimal photorefractive materials were identified, and it was shown that both the indigoid dyes and the dialkyldihydropyrenes closely match the required properties.

  1. Formulation and Characterization of Solid Dispersion Prepared by Hot Melt Mixing: A Fast Screening Approach for Polymer Selection

    PubMed Central

    Enose, Arno A.; Dasan, Priya K.; Sivaramakrishnan, H.; Shah, Sanket M.

    2014-01-01

    Solid dispersion is molecular dispersion of drug in a polymer matrix which leads to improved solubility and hence better bioavailability. Solvent evaporation technique was employed to prepare films of different combinations of polymers, plasticizer, and a modal drug sulindac to narrow down on a few polymer-plasticizer-sulindac combinations. The sulindac-polymer-plasticizer combination that was stable with good film forming properties was processed by hot melt mixing, a technique close to hot melt extrusion, to predict its behavior in a hot melt extrusion process. Hot melt mixing is not a substitute to hot melt extrusion but is an aid in predicting the formation of molecularly dispersed form of a given set of drug-polymer-plasticizer combination in a hot melt extrusion process. The formulations were characterized by advanced techniques like optical microscopy, differential scanning calorimetry, hot stage microscopy, dynamic vapor sorption, and X-ray diffraction. Subsequently, the best drug-polymer-plasticizer combination obtained by hot melt mixing was subjected to hot melt extrusion process to validate the usefulness of hot melt mixing as a predictive tool in hot melt extrusion process. PMID:26556187

  2. Physicochemical properties of tadalafil solid dispersions - Impact of polymer on the apparent solubility and dissolution rate of tadalafil.

    PubMed

    Wlodarski, K; Sawicki, W; Haber, K; Knapik, J; Wojnarowska, Z; Paluch, M; Lepek, P; Hawelek, L; Tajber, L

    2015-08-01

    To improve solubility of tadalafil (Td), a poorly soluble drug substance (3μg/ml) belonging to the II class of the Biopharmaceutical Classification System, its six different solid dispersions (1:1, w/w) in the following polymers: HPMC, MC, PVP, PVP-VA, Kollicoat IR and Soluplus were successfully produced by freeze-drying. Scanning electron microscopy showed a morphological structure of solid dispersions typical of lyophilisates. Apparent solubility and intrinsic dissolution rate studies revealed the greatest, a 16-fold, increase in drug solubility (50μg/ml) and a significant, 20-fold, dissolution rate enhancement for the Td/PVP-VA solid dispersion in comparison with crystalline Td. However, the longest duration of the supersaturation state in water (27μg/ml) over 24h was observed for the Td solid dispersion in HPMC. The improved dissolution of Td from Td/PVP-VA was confirmed in the standard dissolution test of capsules filled with solid dispersions. Powder X-ray diffraction and thermal analysis showed the amorphous nature of these binary systems and indicated the existence of dispersion at the molecular level and its supersaturated character, respectively. Nevertheless, as evidenced by film casting, the greatest ability to dissolve Td in polymer was determined for PVP-VA. The crystallization tendency of Td dispersed in Kollicoat IR could be explained by the low Tg (113°C) of the solid dispersion and the highest difference in Hansen solubility parameters (6.8MPa(0.5)) between Td and the polymer, although this relationship was not satisfied for the partially crystalline dispersion in PVP. Similarly, no correlation was found between the strength of hydrogen bonds investigated using infrared spectroscopy and the physical stability of solid dispersions or the level of supersaturation in aqueous solution. PMID:25998701

  3. Holographic diffusers

    NASA Astrophysics Data System (ADS)

    Wadle, Stephen; Wuest, Daniel; Cantalupo, John; Lakes, Roderic S.

    1994-01-01

    Holographic diffusers are prepared using silver halide (Agfa 8E75 and Kodak 649F) and photopolymer (Polaroid DMP 128 and DuPont 600, 705, and 150 series) media. It is possible to control the diffusion angle in three ways: by selection of the properties of the source diffuser, by control of its subtended angle, and by selection of the holographic medium. Several conventional diffusers based on refraction or scattering of light are examined for comparison.

  4. Heat transport in polymer-dispersed liquid crystals under electric field

    NASA Astrophysics Data System (ADS)

    Hadj Sahraoui, Abdelhak; Delenclos, Sylvain; Longuemart, Stéphane; Dadarlat, Dorin

    2011-08-01

    The concepts of effective thermal conductivity and interfacial thermal contact resistance in composite media are applied to study heat transport in polymer-dispersed liquid crystals (PDLC). In these systems, the thermal properties of liquid crystal inclusions are changed by an imposed electric field. The photopyroelectric (PPE) technique with a cell allowing the application of an electric field to the sample is used to measure the thermal parameters. A model based on effective medium approximation is used to assess the impact of interfaces on the flow of heat through the determination of the Kapitza radius. It was found that the effect of interfaces becomes dominant compared to the volume conduction of the droplet when the liquid crystal (LC) droplet radius becomes smaller than 1 micron. The comparison of the thermal behavior of LC in the droplets with that of bulk liquid crystal allowed to evaluate the effect of confinement on the LC nematic phase.

  5. Mechanisms of reversible photodegradation in disperse orange 11 dye doped in PMMA polymer

    NASA Astrophysics Data System (ADS)

    Embaye, Natnael B.; Ramini, Shiva K.; Kuzyk, Mark G.

    2008-08-01

    We use amplified spontaneous emission (ASE) and linear absorption spectroscopy to study the mechanisms of reversible photodegradation of 1-amino-2-methylanthraquinone (disperse orange 11-DO11) in solid poly(methyl methacrylate). Measurements as a function of intensity, concentration, and time suggest that ASE originates in a state (be it a tautomer or a vibronic level) that can form a dimer or some other aggregate upon relaxation, which through fluorescence quenching leads to degradation of the ASE signal. Whatever the degradation route, a high concentration of DO11 is required and the polymer plays a key role in the process of opening a new reversible degradation pathway that is not available at lower concentrations or in liquid solutions. We construct an energy level diagram that describes all measured quantities in the decay and recovery processes and propose a hypothesis of the nature of the associated states.

  6. Fabrication of Microcapsules for Dye-Doped Polymer-Dispersed Liquid Crystal-Based Smart Windows.

    PubMed

    Kim, Mingyun; Park, Kyun Joo; Seok, Seunghwan; Ok, Jong Min; Jung, Hee-Tae; Choe, Jaehoon; Kim, Do Hyun

    2015-08-19

    A dye-doped polymer-dispersed liquid crystal (PDLC) is an attractive material for application in smart windows. Smart windows using a PDLC can be operated simply and have a high contrast ratio compared to those of other devices that employed photochromic or thermochromic material. However, in conventional dye-doped PDLC methods, dye contamination can cause problems and has a limited degree of commercialization of electric smart windows. Here, we report on an approach to resolve dye-related problems by encapsulating the dye in monodispersed capsules. By encapsulation, a fabricated dye-doped PDLC had a contrast ratio of >120 at 600 nm. This fabrication method of encapsulating the dye in a core-shell structured microcapsule in a dye-doped PDLC device provides a practical platform for dye-doped PDLC-based smart windows. PMID:26192469

  7. Light sensitive polymer obtained by dispersion of azo-functionalized POSS nanoparticles

    NASA Astrophysics Data System (ADS)

    Miniewicz, A.; Tomkowicz, M.; Karpinski, P.; Sznitko, L.; Mossety-Leszczak, B.; Dutkiewicz, M.

    2015-07-01

    Hybrid inorganic-organic nanoparticles based on cubic siloxane cage (RSiO3/2)8, known as polyhedral oligosilsesquioxane (POSS), have been functionalized by eight groups of azo-benzene mesogens and dispersed in poly(methyl methacrylate) PMMA matrix. Presence of azo-benzene units adds an important light-driven functionality to the system due to their photoisomerization resulting in refractive index and/or absorption changes of the whole system. The polymer films containing various concentrations of azo-POSS nanoparticles show remarkable changes of surface morphology being either transparent (at low POSS concentration) or highly scattering (at high POSS concentration) for visible light. Surface structures were examined by optical microscopy as well as by atomic force microscopy (AFM). Results of photoinduced alignment are discussed in the framework of light-induced modification of the aliphatic chains containing azo-benzene photoisomerizing moieties and self-organization process.

  8. Polymer-clad silica fibers for tailoring modal area and dispersion.

    PubMed

    Rishøj, L; Jones, M; Demas, J; Gregg, P; Prabhakar, G; Yan, L; Hawkins, T; Ballato, J; Ramachandran, S

    2016-08-01

    We demonstrate higher-order-mode (Aeff up to ∼2000  μm2) propagation in a 100 μm outer diameter pure-silica fiber with a low-index polymer jacket commonly used for fiber laser pump guidance. This simple structure obviates the need for complex designs deemed necessary for realizing large-mode-area fibers. Modes ranging from HE1,12 to HE1,22 were found to propagate stably over 15 m in this fiber. The index step is approximately 4 times larger than that obtained with fluorine down doping; thus the fiber supports even higher-order modes, which may have implications for building rare-earth-doped fiber lasers or achieving enhanced dispersion tunability for high-energy fiber nonlinear phenomena. PMID:27472625

  9. Rheology of a viscoelastic emulsion with a liquid crystalline polymer dispersed phase

    SciTech Connect

    Lee, H.S.; Denn, M.M. |

    1999-11-01

    The steady-shear viscosity and first normal stress difference and the dynamic storage and loss moduli have been measured for a blend consisting of a thermotropic liquid crystalline polymer dispersed in a thermoplastic fluoropolymer matrix. The components are immiscible and nonreacting. Consistency with the Palierne emulsion theory for viscoelastic blends is possible if and only if the interfacial tension contribution is negligible for droplets that are comparable in size to a liquid crystalline domain or smaller, while retaining the effect for larger droplets. Steady shear results are approximately described by the scaling of the Doi{endash}Ohta theory, but there is a significant reduction in the excess shear stress over a finite shear-rate range for the lowest concentration, which contains the smallest droplets. {copyright} {ital 1999 Society of Rheology.}

  10. Mechanisms of reversible photodegradation in disperse orange 11 dye doped in PMMA polymer

    SciTech Connect

    Embaye, Natnael B.; Ramini, Shiva K.; Kuzyk, Mark G.

    2008-08-07

    We use amplified spontaneous emission (ASE) and linear absorption spectroscopy to study the mechanisms of reversible photodegradation of 1-amino-2-methylanthraquinone (disperse orange 11-DO11) in solid poly(methyl methacrylate). Measurements as a function of intensity, concentration, and time suggest that ASE originates in a state (be it a tautomer or a vibronic level) that can form a dimer or some other aggregate upon relaxation, which through fluorescence quenching leads to degradation of the ASE signal. Whatever the degradation route, a high concentration of DO11 is required and the polymer plays a key role in the process of opening a new reversible degradation pathway that is not available at lower concentrations or in liquid solutions. We construct an energy level diagram that describes all measured quantities in the decay and recovery processes and propose a hypothesis of the nature of the associated states.

  11. Surface morphology control of cross-linked polymer particles via dispersion polymerization.

    PubMed

    Peng, Bo; Imhof, Arnout

    2015-05-14

    Cross-linked polymer colloids (poly(methyl methacrylate) and polystyrene) with diverse shapes were prepared in polar solvents (ethanol, methanol and water) via dispersion polymerization, in which a linear addition of the cross-linker was used during reaction. Apart from spherical particles we found dented spheres or particles covered with nodules, or a combination of both. A comprehensive investigation was carried out, mainly concentrating on the effect of the experimental conditions (e.g., the addition start time and total addition time, cross-linker density and the solvency of the solvents) on particle morphologies. Consequently, we suggest a number of effective ways for the synthesis of regular (spherical) colloidal particles through maintaining a relatively low concentration of the cross-linker during the entire reaction, or forcing the co-polymerization (of monomer and cross-linker) locus to the continuous medium, or using a high quality or quantity of the stabilizer. Moreover, the size of the particles was also precisely manipulated by varying the polarity of the solvents, the concentration of the cross-linker, and the amount and average molecular weight of the stabilizer. In addition, the formation of the heavily dented particles with a very rough surface prepared under a pure or oxygen-'contaminated' nitrogen environment was monitored over time. The results accumulated in this article are of use for a better understanding of the mechanism of the polymerization and control over the structure and property of polymer particles. PMID:25793973

  12. Dispersion and Alignment of CdSe Nanorods in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Rasin, Boris; Frischknecht, Amalie; Diroll, Benjamin; Tsai, Lindsay; Murray, Christopher; Composto, Russell

    2014-03-01

    The thermodynamic factors that affect the dispersion of polymer-brush grafted nanorods (NR) added to homopolymer matrix films have been studied by both experiments and theory. Whereas prior studies have focused on gold nanorods with fixed diameter (12nm-16nm) and varying length (37nm to 98 nm), these studies investigate the smaller diameter (4 nm) CdSe nanorods with length 27 nm to determine if nanorod curvature increases wetting between brush and matrix chains. Here we investigate two chemically similar brush / matrix systems polystyrene (PS)-NR / PS and poly(ethylene oxide) (PEO)-NR/PEO as a function of matrix to brush degree of polymerization, P/N. For the PS-NR / PS system for P/N =.5 the nanorods observed in the polymer matrix are primarily either individual nanorods or individual chains of end to end positioned nanorods. For P/N =13 aggregates consisting of side to side positioned nanorods and side to side positioned nanorod chains are observed. Individual nanorods and individual nanorod chains are also observed. The transition from wet to dry brush is explored and compared with the gold NR studies as well as density functional theory calculations. The effect of electrical field alignment on nanorod orientation is also presented.

  13. Optimising Drug Solubilisation in Amorphous Polymer Dispersions: Rational Selection of Hot-melt Extrusion Processing Parameters.

    PubMed

    Li, Shu; Tian, Yiwei; Jones, David S; Andrews, Gavin P

    2016-02-01

    The aim of this article was to construct a T-ϕ phase diagram for a model drug (FD) and amorphous polymer (Eudragit® EPO) and to use this information to understand the impact of how temperature-composition coordinates influenced the final properties of the extrudate. Defining process boundaries and understanding drug solubility in polymeric carriers is of utmost importance and will help in the successful manufacture of new delivery platforms for BCS class II drugs. Physically mixed felodipine (FD)-Eudragit(®) EPO (EPO) binary mixtures with pre-determined weight fractions were analysed using DSC to measure the endset of melting and glass transition temperature. Extrudates of 10 wt% FD-EPO were processed using temperatures (110°C, 126°C, 140°C and 150°C) selected from the temperature-composition (T-ϕ) phase diagrams and processing screw speed of 20, 100 and 200rpm. Extrudates were characterised using powder X-ray diffraction (PXRD), optical, polarised light and Raman microscopy. To ensure formation of a binary amorphous drug dispersion (ADD) at a specific composition, HME processing temperatures should at least be equal to, or exceed, the corresponding temperature value on the liquid-solid curve in a F-H T-ϕ phase diagram. If extruded between the spinodal and liquid-solid curve, the lack of thermodynamic forces to attain complete drug amorphisation may be compensated for through the use of an increased screw speed. Constructing F-H T-ϕ phase diagrams are valuable not only in the understanding drug-polymer miscibility behaviour but also in rationalising the selection of important processing parameters for HME to ensure miscibility of drug and polymer. PMID:26729536

  14. Solid polymer electrolyte composite membrane comprising a porous support and a solid polymer electrolyte including a dispersed reduced noble metal or noble metal oxide

    SciTech Connect

    Liu, Han; Mittelsteadt, Cortney K; Norman, Timothy J; Griffith, Arthur E; LaConti, Anthony B

    2015-02-24

    A solid polymer electrolyte composite membrane and method of manufacturing the same. According to one embodiment, the composite membrane comprises a thin, rigid, dimensionally-stable, non-electrically-conducting support, the support having a plurality of cylindrical, straight-through pores extending perpendicularly between opposing top and bottom surfaces of the support. The pores are unevenly distributed, with some or no pores located along the periphery and more pores located centrally. The pores are completely filled with a solid polymer electrolyte, the solid polymer electrolyte including a dispersed reduced noble metal or noble metal oxide. The solid polymer electrolyte may also be deposited over the top and/or bottom surfaces of the support.

  15. X-ray Scattering Measurements of Particle Orientation in a Sheared Polymer/Clay Dispersion

    SciTech Connect

    Pujari, Saswati; Dougherty, Leah; Mobuchon, Christoph; Carreau, Pierre J.; Heuzey, Marie-Claude; Burghardt, Wesley R.

    2012-01-20

    We report steady and transient measurements of particle orientation in a clay dispersion subjected to shear flow. An organically modified clay is dispersed in a Newtonian polymer matrix at a volume fraction of 0.02, using methods previously reported by Mobuchon et al. (Rheol Acta 46: 1045, 2007). In accord with prior studies, mechanical rheometry shows yield stress-like behavior in steady shear, while time dependent growth of modulus is observed following flow cessation. Measurements of flow-induced orientation in the flow-gradient plane of simple shear flow using small-angle and wide-angle X-ray scattering (SAXS and WAXS) are reported. Both SAXS and WAXS reveal increasing particle orientation as shear rate is increased. Partial relaxation of nanoparticle orientation upon flow cessation is well correlated with time-dependent changes in complex modulus. SAXS and WAXS data provide qualitatively similar results; however, some quantitative differences are attributed to differences in the length scales probed by these techniques.

  16. Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend

    NASA Astrophysics Data System (ADS)

    Kurpiers, Jona; Neher, Dieter

    2016-05-01

    Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer:fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions.

  17. Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend

    PubMed Central

    Kurpiers, Jona; Neher, Dieter

    2016-01-01

    Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer:fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions. PMID:27225584

  18. Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend.

    PubMed

    Kurpiers, Jona; Neher, Dieter

    2016-01-01

    Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer:fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions. PMID:27225584

  19. A stable silicon anode based on the uniform dispersion of quantum dots in a polymer matrix

    NASA Astrophysics Data System (ADS)

    Zhong, Lanlan; Guo, Juchen; Mangolini, Lorenzo

    2015-01-01

    We propose a novel approach to the fabrication of silicon-containing anodes for lithium-ion batteries. Our approach is based on a liquid dispersion comprising of silicon quantum dots, carbon nanotubes and polyvinylpirrolidone (PVP) as a polymer additive. Coating of this dispersion onto copper foil followed by annealing in inert atmosphere allows the realization of a structure with good electrical conductivity, high specific surface area and with a carbon-based coating preventing the direct contact between the silicon particles and the electrolyte. This structure maintains a specific charge capacity of approximately 1000 mAh g-1 for 200 cycles and reaches a coulombic efficiency of 99.8%. The addition of PVP is a simple and scalable way of realizing, after annealing, a carbon-based matrix which surrounds the silicon particles and which greatly enhances the stability of the battery. The proposed process is based on commercially available carbon nanotubes, on silicon quantum dots which are produced using a scalable plasma-enhanced chemical vapour deposition technique, and is compatible with large area coating and processing techniques. The fabrication protocol described in this contribution represents a step towards the successful commercial utilization of silicon-based nanomaterials for energy storage applications.

  20. Dispersal

    USGS Publications Warehouse

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  1. H-bonded supramolecular polymer for the selective dispersion and subsequent release of large-diameter semiconducting single-walled carbon nanotubes.

    PubMed

    Pochorovski, Igor; Wang, Huiliang; Feldblyum, Jeremy I; Zhang, Xiaodong; Antaris, Alexander L; Bao, Zhenan

    2015-04-01

    Semiconducting, single-walled carbon nanotubes (SWNTs) are promising candidates for applications in thin-film transistors, solar cells, and biological imaging. To harness their full potential, however, it is necessary to separate the semiconducting from the metallic SWNTs present in the as-synthesized SWNT mixture. While various polymers are able to selectively disperse semiconducting SWNTs, the subsequent removal of the polymer is challenging. However, many applications require semiconducting SWNTs in their pure form. Toward this goal, we have designed a 2-ureido-6[1H]-pyrimidinone (UPy)-based H-bonded supramolecular polymer that can selectively disperse semiconducting SWNTs. The dispersion purity is inversely related to the dispersion yield. In contrast to conventional polymers, the polymer described herein was shown to disassemble into monomeric units upon addition of an H-bond-disrupting agent, enabling isolation of dispersant-free, semiconducting SWNTs. PMID:25815604

  2. Formation of holographic memory for optically reconfigurable gate array by angle-multiplexing recording of multi-circuit information in liquid crystal composites

    NASA Astrophysics Data System (ADS)

    Ogiwara, Akifumi; Maekawa, Hikaru; Watanabe, Minoru; Moriwaki, Retsu

    2014-02-01

    A holographic polymer-dispersed liquid crystal (HPDLC) memory to record multi-context information for an optically reconfigurable gate array is formed by the angle-multiplexing recording using a successive laser exposure in liquid crystal (LC) composites. The laser illumination system is constructed using the half mirror and photomask written by the different configuration contexts placed on the motorized stages under the control of a personal computer. The fabricated holographic memory implements a precise reconstruction of configuration contexts corresponding to the various logical circuits such as OR circuit and NOR circuit by the laser illumination at different incident angle in the HPDLC memory.

  3. Evaluation of a molecularly imprinted polymer for determination of steroids in goat milk by matrix solid phase dispersion.

    PubMed

    Gañán, Judith; Morante-Zarcero, Sonia; Gallego-Picó, Alejandrina; Garcinuño, Rosa María; Fernández-Hernando, Pilar; Sierra, Isabel

    2014-08-01

    A molecularly imprinted polymer-matrix solid-phase dispersion methodology for simultaneous determination of five steroids in goat milk samples was proposed. Factors affecting the extraction recovery such as sample/dispersant ratio and washing and elution solvents were investigated. The molecularly imprinted polymer used as dispersant in the matrix solid-phase dispersion procedure showed high affinity to steroids, and the obtained extracts were sufficiently cleaned to be directly analyzed. Analytical separation was performed by micellar electrokinetic chromatography using a capillary electrophoresis system equipped with a diode array detector. A background electrolyte composed of borate buffer (25mM, pH 9.3), sodium dodecyl sulfate (10mM) and acetonitrile (20%) was used. The developed MIP-MSPD methodology was applied for direct determination of testosterone (T), estrone (E1), 17β-estradiol (17β-E2), 17α-ethinylestradiol (EE2) and progesterone (P) in different goat milk samples. Mean recoveries obtained ranged from 81% to 110%, with relative standard deviations (RSD)≤12%. The molecularly imprinted polymer-matrix solid-phase dispersion method is fast, selective, cost-effective and environment-friendly compared with other pretreatment methods used for extraction of steroids in milk. PMID:24881547

  4. Large birefringence and polarization holographic gratings formed in photocross-linkable polymer liquid crystals comprising bistolane mesogenic side groups

    SciTech Connect

    Emoto, Akira; Matsumoto, Taro; Shioda, Tatsutoshi; Ono, Hiroshi; Yamashita, Ayumi; Kawatsuki, Nobuhiro

    2009-10-01

    Polarization gratings with large birefringence are formed in photoreactive polymer liquid crystals with bistolane moiety and terminal cinnamic acid moiety by the use of polarized ultraviolet interference light and subsequent annealing. The polarized ultraviolet light causes the axis-selective photoreaction between the cinnamic acid groups and subsequent annealing induce the reorientation of peripheral molecules without cross-linking along the cross-linked groups. Long bistolane mesogenic moiety exhibits large birefringence in comparison with a biphenyl mesogenic moiety, the value of the induced birefringence in the bistolane mesogenic liquid crystalline (LC) polymer is strongly dependent on both the grating constant and the wavelength of the reconstruction light.

  5. Molecular simulation of dispersion and mechanical stability of organically modified layered silicates in polymer matrices

    NASA Astrophysics Data System (ADS)

    Fu, Yao-Tsung

    The experimental analysis of nanometer-scale separation processes and mechanical properties at buried interfaces in nanocomposites has remained difficult. We have employed molecular dynamics simulation in relation to available experimental data to alleviate such limitations and gain insight into the dispersion and mechanical stability of organically modified layered silicates in hydrophobic polymer matrices. We analyzed cleavage energies of various organically modified silicates as a function of the cation exchange capacity, surfactant head group chemistry, and chain length using MD simulations with the PCFF-PHYLLOSILICATE force field. The range of the cleavage energy is between 25 and 210 mJ/m2 upon the molecular structures and packing of surfactants. As a function of chain length, the cleavage energy indicates local minima for interlayer structures comprised of loosely packed layers of alkyl chains and local maxima for interlayer structures comprised of densely packed layers of alkyl chains between the layers. In addition, the distribution of cationic head groups between the layers in the equilibrium state determines whether large increases in cleavage energy due to Coulomb attraction. We have also examined mechanical bending and failure mechanisms of layered silicates on the nanometer scale using molecular dynamics simulation in comparison to a library of TEM data of polymer nanocomposites. We investigated the energy of single clay lamellae as a function of bending radius and different cation density. The layer energy increases particularly for bending radii below 20 nm and is largely independent of cation exchange capacity. The analysis of TEM images of agglomerated and exfoliated aluminosilicates of different CEC in polymer matrices at small volume fractions showed bending radii in excess of 100 nm due to free volumes in the polymer matrix. At a volume fraction >5%, however, bent clay layers were found with bending radii <20 nm and kinks as a failure mechanism

  6. Effects of dispersion and interfacial modification on the macroscale properties of TiO2 polymer matrix nanocomposites

    PubMed Central

    Hamming, Lesley M.; Qiao, Rui; Messersmith, Phillip B.; Brinson, L. Catherine

    2009-01-01

    This paper quantifies how the quality of dispersion and the quality of the interfacial interaction between TiO2 nanoparticles and host polymer independently affect benchmark properties such as glass transition temperature (Tg), elastic modulus and loss modulus. By examining these composites with differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM), we were able to demonstrate changes in properties depending on the adhesive/wetting or repulsive/dewetting interactions the nanoparticles have with the bulk polymer. We further quantified the dispersion of TiO2 nanoparticles in polymethylmethacrylate (PMMA) matrices by a digital-optical method and correlated those values to the degree of Tg depression compared to neat PMMA. Samples with the same weight percent of nanoparticles but better dispersion showed larger shifts in Tg. PMID:20161273

  7. The influence of dispersed state on the structure and capability of the polymer electrolytes based on PVDF/PMMA

    NASA Astrophysics Data System (ADS)

    Yang, S. T.; Chen, H. J.; Jia, J. H.

    2002-12-01

    The polymer electrolyte which is firstly made by micro-wave inter-connect method and based on blended PVDF/PMMA and its conductivity is exceeding 10-3S · cm at room temperature. The result of polymer electrolytes that is dispersed by sub-micron SiO2 indicate that the mechanic intension is improved and the conductivity also improved. There is a new state with the test of the SEM and XRD and the non-crystal state of the polymer electrolytes have been improved after system adulteration which are favorable for the migration of Li+ and this is the expiation of the improvement of the conductivity of the polymer electrolytes.

  8. Preparation and characterization of tablet formulation based on solid dispersion of glimepiride and poly(ester amide) hyperbranched polymer.

    PubMed

    Reven, Sebastjan; Homar, Miha; Peternel, Luka; Kristl, Julijana; Žagar, Ema

    2013-01-01

    The feasibility of incorporating a solid dispersion containing poorly soluble antidiabetic drug glimepiride and poly(ester amide) hyperbranched polymer into a tablet using a direct-compression tabletting technique was investigated. Tablet cores were additionally coated with hydroxypropyl methylcellulose phthalate in order to protect the extremely hygroscopic solid dispersion from atmospheric moisture. Preliminary stability studies show that glimepiride, which is in amorphous form within solid dispersion, is chemically stable, even if tablets are exposed to elevated temperature and/or moisture. In-vitro dissolution studies show some impact of storage conditions on the tablet cores disintegration time and, consequently, drug release rate. Glimepiride solubility also deteriorates somewhat, most probably due to its partial recrystallization. Storage conditions much less affect the physical stability of coated tablets, which was ascribed to reduced tablet hygroscopicity due to the presence of protecting coating. The hyperbranched polymers are rather new and complex macromolecules. Therefore, we addressed also the biocompatibility of hyperbranched polymer, i.e., its impact on haemolysis of the red blood cells. The concentration required for the haemolytic effect on the red blood cells is around 100-times higher than its expected gastrointestinal luminal concentration, which makes the occurrence of hyperbranched polymer mediated cytotoxicity very unlikely. PMID:21812524

  9. Poly(N-isopropylacrylamide)-tethered silicate platelets for colloidal dispersion of conjugated polymers with thermoresponsive and photoluminescence properties.

    PubMed

    Lan, Yi-Fen; Hsieh, Bi-Zen; Lin, Hsiao-Chu; Su, Yu-An; Chan, Ying-Nan; Lin, Jiang-Jen

    2010-07-01

    Poly(N-isopropylacrylamide)-tethered nanosilicate platelets (NSP-PNiPAAm) have been synthesized by covalently bonding the polymer onto the surfaces of silicate platelets of nanometer dimension, and this class of nanohybrids has proved to be effective for dispersing water-insoluble conjugated polymers (CPs). Simple pulverization of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) with NSP-PNiPAAm rendered the powder material dispersible in water, whereupon it displayed thermoresponsive properties at 37.5 degrees C and CP particle size variation between ca. 50 and 100 nm by SEM observation. The same dispersion had a maximum UV-vis absorption at 524 nm and PL emission at 605 nm. The PL emission was significantly higher at 4 degrees C than at 45 degrees C. Being coated as a film, it showed an orange emission under an ultraviolet lamp, consistent with the PL measurement. The water-borne process of dispersing the CP in aqueous media by the presence of NSP-PNiPAAm and followed by film formation to demonstrate a unique method of manipulating hydrophobic conjugated polymers in a facile manner. PMID:20302288

  10. Dispersion and shear-induced orientation of anisotropic nanoparticle filled polymer nanocomposites: insights from molecular dynamics simulation.

    PubMed

    Zheng, Zijian; Wang, Zixuan; Wang, Lu; Liu, Jun; Wu, Youping; Zhang, Liqun

    2016-07-01

    Although a large number of studies have been performed to study the dispersion behavior of spherical nanoparticles (NPs) in the polymer matrix, little effort has been directed to anisotropic NPs via simulation, which is convenient for controlling the physical parameters compared to experiment. In this work we adopt molecular dynamics simulation to study polymer nanocomposites filled with anisotropic NPs such as graphene and carbon nanotubes (CNTs). We investigate the effects of the grafting position, grafting density, the length and flexibility of the grafted chains on the dispersion of graphene and CNTs. In particular, we find that when the grafting position is located on the surface center of the graphene or the middle of the CNT, the dispersion state is the best, leading to the greatest stress-strain behavior. Meanwhile, the mechanical property can be further strengthened by introducing chemical couplings in the interfacial region, by chemically tethering the grafted chains to the matrix chains. To monitor the processing effect, we exert a dynamic periodic shear deformation in the x direction with its gradient in the y direction. Polymer chains are found to align in the x direction, graphene sheets align in the xoz plane and CNTs orientate in the z direction. We study the effects of the shear amplitude, the shear frequency, polymer-NP interaction strength and volume fraction of NPs on the stress-strain behavior. We also observe that the relaxation process following the shear deformation deteriorates the mechanical performance, resulting from the disorientation of polymer chains and NPs. In general, this work could provide valuable guidance in manipulating the distribution and alignment of graphene and CNTs in the polymer matrix. PMID:27196704

  11. Photochromic liquid hydrogels as hosts for holographic materials

    SciTech Connect

    White, R.L.; Hsu, Y.Y.; Cooper, T.M.; Gresser, J.D.; Wise, D.L.; Trantolo, D.J.

    1998-07-01

    The goal of this project is to develop, fabricate, and test advanced optical materials for potential applications to real-time holography based on liquid crystalline polymer hydrogels. In this project, the authors are investigating the feasibility of increasing holographic capacity and lifetime by coupling a photochromic spyropyan dye to a liquid crystalline polymer in which cholesteric order has been captured. Capture is being approached using a unique in-plane poling process with the helical polypeptide poly({alpha}-benzyl-L-glutamate), PBLG, a biopolymer which is capable of maintaining cholesteric order in a liquid crystalline state. Subsequent in situ crosslinking of this aligned biopolymer is projected to offer increased birefringence of the host in the writing of a hologram. Given that a key issue is the magnitude of the real component of the refractive index, increasing the birefringence may be a useful approach. In writing the hologram, the liquid crystals (LC's) go from isotropic to an ordered dispersion, a property which can be captured via crosslinking to improve holographic lifetime. In the following, the characterization of an aligned host LC system based on the biopolymer poly({alpha}-benzyl-L-glutamate), PBLG, is presented. In-plane alignment is shown to depend on a number of variables, most notably the choice of solvent, polymer molecular weight, and field strength. The results show that optimal alignment of the PBLG LC is achieved with a 2.5% (w/w) concentration of a 118kD biopolymer in methylene chloride in an applied field of 10 kV/cm. Subsequent work will exploit this system as a host for a spiropyran dye for improved holographics.

  12. Drug-polymer miscibility across a spray dryer: a case study of naproxen and miconazole solid dispersions.

    PubMed

    Worku, Zelalem Ayenew; Aarts, Jolie; Singh, Abhishek; Van den Mooter, Guy

    2014-04-01

    The structural and physical stability of solid dispersions have not been adequately explored during spray drying manufacturing processes. In this study a wide range of compositions of naproxen/PVP-VA 64 (poly(1-vinylpyrrolidone-co-vinyl acetate)) and miconazole/PVP-VA 64 solid dispersions prepared by different laboratory spray dryers were collected from various selected locations and used to investigate the drug-polymer mixing across spray dryers. Spray-dried dispersions with 30% (w/w) naproxen collected from the transport tube of the Pro-C-epT Microspray dryer showed the narrowest glass transition width, which apparently indicates the highest degree of drug-polymer mixing compared to the other locations. The intensity of the naproxen-PVP-VA 64 interaction peak at 1654 cm(-1) of IR spectra differs for solid dispersions (SDs) from the collector and transport tube of Pro-C-epT Microspray dryer with a higher intensity for the latter. Samples with 50% (w/w) naproxen loading collected from the cyclone and the cyclone steel part of the Buchi mini spray dryer showed a melting endotherm (Tm at 112.2 ± 0.8 °C and ΔHf between 0.7 and 1.8 J/g), whereas samples from the cyclone tube to the drying chamber were devoid of crystalline material. The variations in drug-polymer mixing extend to miconazole/PVP-VA solid dispersions where 20% drug loading showed location-dependent drug-polymer mixing. This study clearly showed that the variation in drug-polymer miscibility and solid form of the drug in solid dispersions can occur across spray dryer in small-scale manufacturing processes. The optimization of formulation parameters and spray drying process parameters is imperative to diminish these variations to enhance homogeneity of solid dispersions in laboratory scale spray dryers. The same problem can occur in geometrically large spray drying manufacturing equipment, and the robustness of the processes should be carefully assessed. PMID:24533891

  13. Thermo-Optical Effects and Fiber Optic Sensing Device Based on Polymer Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Sirleto, L.; Righini, G. C.; Mahmoud, Aburish; Simoni, F.

    In this article, the thermo-optical properties of polymer dispersed liquid crystals (PDLCs) in confined geometry are experimentally investigated to demonstrate the feasibility of a fiber optic sensing device based on PDLCsE Since an unexpected behavior of PDLCs in confined geometry has been experienced, a systematic study of PDLCs' thermo-optical properties in bulk is presented also to point out principal differences. Finally, bistable all fiber optic temperature sensors, in which a PDLC permits at the same time the opto-mechanical interconnection of two fibers and the modulation of light crossing the device, has been realized and characterized, for the first time. Being the modulation controlled by external temperature, the device has been proven to be suitable for the realization of a heat flow sensor. The sensor presents the typical advantages of both fiber optic sensors and liquid crystal technology. Moreover, due to its small thermal capacity, it should exhibit little influence on thermal equilibrium and, above all, it represents a significant improvement compared to a temperature fiber optic sensor based on liquid crystals (presented in the literature).

  14. Non-dispersive carrier transport in molecularly doped polymers and the convection-diffusion equation

    NASA Astrophysics Data System (ADS)

    Tyutnev, A. P.; Parris, P. E.; Saenko, V. S.

    2015-08-01

    We reinvestigate the applicability of the concept of trap-free carrier transport in molecularly doped polymers and the possibility of realistically describing time-of-flight (TOF) current transients in these materials using the classical convection-diffusion equation (CDE). The problem is treated as rigorously as possible using boundary conditions appropriate to conventional time of flight experiments. Two types of pulsed carrier generation are considered. In addition to the traditional case of surface excitation, we also consider the case where carrier generation is spatially uniform. In our analysis, the front electrode is treated as a reflecting boundary, while the counter electrode is assumed to act either as a neutral contact (not disturbing the current flow) or as an absorbing boundary at which the carrier concentration vanishes. As expected, at low fields transient currents exhibit unusual behavior, as diffusion currents overwhelm drift currents to such an extent that it becomes impossible to determine transit times (and hence, carrier mobilities). At high fields, computed transients are more like those typically observed, with well-defined plateaus and sharp transit times. Careful analysis, however, reveals that the non-dispersive picture, and predictions of the CDE contradict both experiment and existing disorder-based theories in important ways, and that the CDE should be applied rather cautiously, and even then only for engineering purposes.

  15. Thermo-optical effects and fiber optic sensing device based on polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Sirleto, Luigi; Righini, Giancarlo C.; Ciaccheri, Leonardo; Rish, Mahmoud A.; Simoni, Francesco F.

    2001-05-01

    In this paper an experimental study of thermo-optical properties of polymer dispersed liquid crystals (PDLC), prepared by PIPS in bulk and in confined cylindrical geometry, is presented. The transmissivity of PDLC In bulk as a function of temperature proves the existence of temperature optical switching. We have also demonstrated the existence of optical bistability, which could be interesting in develop of logical optical devices as optical memory elements. A bistable al fiber optic sensors based on PDLC is also presented. In this device PDLC permits at the same time the optomechanical interconnection of tow fibers and the modulation of the light crossing the device. As the modulation can be controlled by external temperature, the device has been proved to be suitable for the realization of a heat flow sensor. Without any optimization of the device we have obtained an ON-OFF contrast of 8 dB and a response time comparable with other conventional device using nematic LCs. This sensor is compact, rugged and is cheap, because it does not require a complex fabrication and alignment technology. It presents the typical advantages of both the fiber optic sensor and the liquid crystal technology. We note that its main advantage is a small thermal capacity, which is comparable with electronic device as thermistors, and it represents a significant improvement for the sensor based on liquid crystals. Further theoretical studies are necessary in order to understand in depth it thermo-optical characteristics.

  16. Micro-molding with ultrasonic vibration energy: new method to disperse nanoclays in polymer matrices.

    PubMed

    Planellas, Marc; Sacristán, Matías; Rey, Lorena; Olmo, Cristian; Aymamí, Joan; Casas, María T; del Valle, Luis J; Franco, Lourdes; Puiggalí, Jordi

    2014-07-01

    Ultrasound technology was proved as an efficient processing technique to obtain micro-molded specimens of polylactide (PLA) and polybutylene succinate (PBS), which were selected as examples of biodegradable polyesters widely employed in commodity and specialty applications. Operational parameters such as amplitude, molding force and processing time were successfully optimized to prepare samples with a decrease in the number average molecular weight lower than 6%. Ultrasonic waves also seemed an ideal energy source to provide effective disaggregation of clay silicate layers, and therefore exfoliated nanocomposites. X-ray diffraction patterns of nanocomposites prepared by direct micro-molding of PLA or PBS powder mixtures with natural montmorillonite or different organo-modified clays showed the disappearance of the 001 silicate reflection for specimens having up to 6 wt.% clay content. All electron micrographs revealed relatively homogeneous dispersion and sheet nanostructures oriented in the direction of the melt flow. Incorporation of clay particles during processing had practically no influence on PLA characteristics but enhanced PBS degradation when an organo-modifier was employed. This was in agreement with thermal stability data deduced from thermogravimetric analysis. Cold crystallization experiments directly performed on micro-molded PLA specimens pointed to a complex influence of clay particles reflected by the increase or decrease of the overall non-isothermal crystallization rate when compared to the neat polymer. In all cases, the addition of clay led to a clear decrease in the Avrami exponent. PMID:24457002

  17. Lanthanide-Containing Polymer Microspheres by Multiple-Stage Dispersion Polymerization for Highly Multiplexed Bioassays

    PubMed Central

    Abdelrahman, Ahmed I.; Dai, Sheng; Thickett, Stuart C.; Ornatsky, Olga; Bandura, Dmitry; Baranov, Vladimir; Winnik, Mitchell A.

    2009-01-01

    We describe the synthesis and characterization of metal-encoded polystyrene microspheres by multiple-stage dispersion polymerization with diameters on the order of 2 µm and a very narrow size distribution. Different lanthanides were loaded into these microspheres through the addition of a mixture of LnCl3 salts and excess acrylic acid or acetoacetylethyl methacrylate (AAEM) dissolved in ethanol to the reaction after about 10% conversion of styrene, i.e., well after the particle nucleation stage was complete. Individual microspheres contain ca. 106 – 108 chelated lanthanide ions, of either a single element or a mixture of elements. These microspheres were characterized one-by-one utilizing a novel mass cytometer with an inductively coupled plasma (ICP) ionization source and time-of-flight (TOF) mass spectrometry detection. Microspheres containing a range of different metals at different levels of concentration were synthesized to meet the requirements of binary encoding and enumeration encoding protocols. With four different metals at five levels of concentration, we could achieve a variability of 624, and the strategy we report should allow one to obtain much larger variability. To demonstrate the usefulness of element-encoded beads for highly multiplexed immunoassays, we carried out a proof-of-principle model bioassay involving conjugation of mouse IgG to the surface of La and Tm containing particles, and its detection by an anti-mouse IgG bearing a metal-chelating polymer with Pr. PMID:19807075

  18. Toward measuring concentration gradients in polymer-dispersed liquid crystals with secondary ion mass spectrometry

    NASA Astrophysics Data System (ADS)

    Kjellander, B. K. Charlotte; van IJzendoorn, Leo J.; de Jong, Arthur M.; Broer, Dirk J.; van Gennip, Wouter J. H.; de Voigt, Martien J. A.; Niemantsverdriet, Hans J. W.

    2004-05-01

    Dynamic secondary ion mass spectrometry (SIMS) is usually applied to measure depth profiles in inorganic multi-layer systems. SIMS on organic multi-layer samples is highly complicated due to the complex fragmentation of the sample which results in fingerprint of masses representing the components in the sample. Using multivariate statistics, we succeeded to interpret the SIMS spectra and were able to identify layers with different compositions in artificially produced two-layer samples. The method is demonstrated for samples of a poly(isobornylmethacrylate) coating on a polymer dispersed liquid crystal consisting of the nematic liquid crystal (E7) and poly(isobornylmethacrylate). Quantification of the E7 concentration is complicated by evaporation in the vacuum system. Infrared spectroscopy proved that the loss of E7 from poly(isobornylmethacrylate) can be prevented by capping the sample with poly(vinyl alcohol). Cooling to cryogenic temperatures will be required to suppress further evaporation during SIMS analysis. The SIMS depth resolution of a two-layered sample was determined by discriminant function analysis to be 130 nm at a depth of one micrometer, which allows the application of SIMS for a typical optical grating.

  19. Effect of UV intensity on the electro-optical properties of polymer dispersed liquid crystal lens for smart electronic glasses

    NASA Astrophysics Data System (ADS)

    Kim, Jaeyong; Han, Jeong In

    2014-05-01

    Polymer dispersed liquid crystal (PDLC) lenses were made from a mixture of prepolymer (NOA 65) and E7 liquid crystal (LC). The mixture of polymer dispersed in LC was polymerized by ultraviolet (UV) irradiation in the polymerization induced phase separation process. With varying UV curing intensity in this process, the electrooptical properties of PDLC lens device such as transmittance, driving voltage, response times, contrast ratio (C/R) and slope of the linear region of the transmittance-voltage were measured and optimized for application to smart electronic glasses with auto-shading and auto-focusing functions. The optimum UV intensity for the PDLC lenses was more than 580 µW/cm2. These results were improved compared to our previously reported data[1] for the application of these PDLC lenses to smart electronic glasses with auto-shading and/or auto-focusing functions.

  20. Effect of polymer type and drug dose on the in vitro and in vivo behavior of amorphous solid dispersions.

    PubMed

    Knopp, Matthias Manne; Chourak, Nabil; Khan, Fauzan; Wendelboe, Johan; Langguth, Peter; Rades, Thomas; Holm, René

    2016-08-01

    This study investigated the non-sink in vitro dissolution behavior and in vivo performance in rats of celecoxib (CCX) amorphous solid dispersions with polyvinyl acetate (PVA), polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) at different drug doses. Both in vitro and in vivo, the amorphous solid dispersions with the hydrophilic polymers PVP and HPMC led to higher areas under both, the in vitro dissolution and the plasma concentration-time curves (AUC) compared to crystalline and amorphous CCX for all doses. In contrast, the amorphous solid dispersion with the hydrophobic polymer PVA showed a lower AUC both in vitro and in vivo than crystalline CCX. For crystalline CCX and CCX:PVA, the in vitro AUC was limited by the low solubility of the drug and the slow release of the drug from the hydrophobic polymer, respectively. For the supersaturating formulations, amorphous CCX, CCX:PVP and CCX:HPMC, the in vitro performance was mainly dependent on the dissolution rate and precipitation/crystallization inhibition of the polymer. As expected, the crystallization tendency increased with increasing dose, and therefore the in vitro AUCs did not increase proportionally with dose. Even though the in vivo AUC for all formulations increased with increasing dose, the relative bioavailability decreased significantly, indicating that the supersaturating formulations also crystallized in vivo and that the absorption of CCX was solubility-limited. These findings underline the importance of evaluating relevant in vitro doses, in order to rationally assess the performance of amorphous solid dispersions and avoid confusion in early in vivo studies. PMID:27212472

  1. Monolithically integrated, flexible display of polymer-dispersed liquid crystal driven by rubber-stamped organic thin-film transistors

    SciTech Connect

    Mach, P.; Rodriguez, S. J.; Nortrup, R.; Wiltzius, P.; Rogers, J. A.

    2001-06-04

    This letter describes the monolithic integration of rubber-stamped thin-film organic transistors with polymer-dispersed liquid crystals (PDLCs) to create a multipixel, flexible display with plastic substrates. We report the electro-optic switching behavior of the PDLCs as driven by the organic transistors, and we show that our displays operate robustly under flexing and have a contrast comparable to that of newsprint. {copyright} 2001 American Institute of Physics.

  2. Dispersion and shear-induced orientation of anisotropic nanoparticle filled polymer nanocomposites: insights from molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Zheng, Zijian; Wang, Zixuan; Wang, Lu; Liu, Jun; Wu, Youping; Zhang, Liqun

    2016-07-01

    Although a large number of studies have been performed to study the dispersion behavior of spherical nanoparticles (NPs) in the polymer matrix, little effort has been directed to anisotropic NPs via simulation, which is convenient for controlling the physical parameters compared to experiment. In this work we adopt molecular dynamics simulation to study polymer nanocomposites filled with anisotropic NPs such as graphene and carbon nanotubes (CNTs). We investigate the effects of the grafting position, grafting density, the length and flexibility of the grafted chains on the dispersion of graphene and CNTs. In particular, we find that when the grafting position is located on the surface center of the graphene or the middle of the CNT, the dispersion state is the best, leading to the greatest stress–strain behavior. Meanwhile, the mechanical property can be further strengthened by introducing chemical couplings in the interfacial region, by chemically tethering the grafted chains to the matrix chains. To monitor the processing effect, we exert a dynamic periodic shear deformation in the x direction with its gradient in the y direction. Polymer chains are found to align in the x direction, graphene sheets align in the xoz plane and CNTs orientate in the z direction. We study the effects of the shear amplitude, the shear frequency, polymer–NP interaction strength and volume fraction of NPs on the stress–strain behavior. We also observe that the relaxation process following the shear deformation deteriorates the mechanical performance, resulting from the disorientation of polymer chains and NPs. In general, this work could provide valuable guidance in manipulating the distribution and alignment of graphene and CNTs in the polymer matrix.

  3. Control of the anchoring behavior of polymer-dispersed liquid crystals: effect of branching in the side chains of polyacrylates.

    PubMed

    Zhou, Jian; Collard, David M; Park, Jung O; Srinivasarao, Mohan

    2002-08-28

    A temperature-driven anchoring transition in a polymer/nematic fluid composite that is far from the bulk nematic-isotropic transition temperature is reported. A series of poly(methylheptyl acrylates) were studied to probe the subtle effects of the side chain structure of the polymer on control of the anchoring. A polymer-dispersed liquid crystal film made from TL205 and 1-methylheptyl acrylate shows only planar anchoring over the temperature range studied, while the films made from TL205 and each of the other methylheptyl acrylates or n-heptyl acrylate show the homeotropic-to-planar anchoring transition at temperatures between 70 and 78 degrees C. An interfacial model is proposed in which the different conformation of the side chains is suggested as the cause for the dramatic difference in the observed anchoring behavior. PMID:12188649

  4. Probing dispersion and re-agglomeration phenomena upon melt-mixing of polymer-functionalized graphite nanoplates.

    PubMed

    Santos, R M; Vilaverde, C; Cunha, E; Paiva, M C; Covas, J A

    2016-01-01

    A one-step melt-mixing method is proposed to study dispersion and re-agglomeration phenomena of the as-received and functionalized graphite nanoplates in polypropylene melts. Graphite nanoplates were chemically modified via 1,3-dipolar cycloaddition of an azomethine ylide and then grafted with polypropylene-graft-maleic anhydride. The effect of surface functionalization on the dispersion kinetics, nanoparticle re-agglomeration and interface bonding with the polymer is investigated. Nanocomposites with 2 or 10 wt% of as-received and functionalized graphite nanoplates were prepared in a small-scale prototype mixer coupled to a capillary rheometer. Samples were collected along the flow axis and characterized by optical microscopy, scanning electron microscopy and electrical conductivity measurements. The as-received graphite nanoplates tend to re-agglomerate upon stress relaxation of the polymer melt. The covalent attachment of a polymer to the nanoparticle surface enhances the stability of dispersion, delaying the re-agglomeration. Surface modification also improves interfacial interactions and the resulting composites presented improved electrical conductivity. PMID:26439171

  5. Ionic liquids as lubricants of metal-polymer contacts. Preparation and properties of the first dispersions of ionic liquids and nanoparticles in polymers

    NASA Astrophysics Data System (ADS)

    Sanes Molina, Jose

    Room-temperature ionic liquids (ILs) are high performance fluids that stand out because of a wide range of functional properties and exhibit a great potential for engineering applications. Although they have been employed as lubricants in metal-metal, metal-ceramic and ceramic-ceramic contacts, in this thesis we present the first study about the use of ILs as pure lubricants in polymer/steel contacts. The tests have established the efficacy of the ILs to reduce friction coefficient and wear rates in a variety of kinds of contacts, and criogenic to high temperature performance. Novel dispersions of ILs in polymers have been obtained with epoxy resin and thermoplastics as matrix. Therefore, the thermal, mechanical and tribological properties of the materials have studied and are discussed in the present thesis. Furthermore, the contents of ILs in the polymer matrix have been studied in relation to the tribological properties using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectrometry (EDS), the wear mechanisms that operated in the contacts were established. The novel dispersions showed a reduction in the friction coefficient and wear in comparison with neat polymers, reaching in some cases a decrease of 79%. In the case of thermoplastics such as polystyrene and polyamide 6, the new dispersions showed a reduction in friction coefficient and wear in the same range as that of the ILs when used as external lubricants in the steel/polymer contact. In addition nanoparticles of zinc oxide were used to obtain polycarbonate based nanohybrids with the purpose of improving the tribological properties. Novel nanohybrids of zinc oxide and modified zinc oxide were obtained. The mechanical, thermal and tribological properties were studied. The results of experiments clearly demonstrated that the use of ILs modifies the shape and size of the ZnO nanoparticles, increasing the tribological properties of the novel nanohybrids. Different techniques such as EDS

  6. Nanoparticle dispersion in polymer nanocomposites by spin-diffusion-averaged paramagnetic enhanced NMR relaxometry: scaling relations and applications.

    PubMed

    Xu, Bo; Leisen, Johannes; Beckham, Haskell W

    2014-08-21

    Scaling relationships are identified between NMR longitudinal relaxation times and clay dispersion quality in polymer-paramagnetic clay nanocomposites. Derived from a previously published analytical relationship developed from a lamella-based model, the scaling relationships are based on the enhancement of NMR relaxation rates with increasing exfoliation and dispersion homogeneity. The paramagnetic contribution to the NMR relaxation rate is inversely proportional to the square of the clay interparticle spacing, and directly proportional to the square of the clay weight fraction. These scaling relationships allow the prediction of relative exfoliation of clay particles for a given series of polymer-clay nanocomposites. With independent knowledge of clay exfoliation in a single sample (e.g., from transmission electron microscopy), NMR relaxometry data may be converted into absolute measures of exfoliation. These scaling relations are confirmed with samples of fully exfoliated poly(vinyl alcohol)-montmorillonite nanocomposites, and then used to reveal exfoliation and dispersion quality in a series of nylon-6-montmorillonite nanocomposites. This characterization route is advantageous because NMR relaxometry can more rapidly provide clay dispersion information that is averaged over larger sample volumes than transmission electron microscopy. PMID:25000915

  7. Holographic vitrification

    NASA Astrophysics Data System (ADS)

    Anninos, Dionysios; Anous, Tarek; Denef, Frederik; Peeters, Lucas

    2015-04-01

    We establish the existence of stable and metastable stationary black hole bound states at finite temperature and chemical potentials in global and planar four-dimensional asymptotically anti-de Sitter space. We determine a number of features of their holographic duals and argue they represent structural glasses. We map out their thermodynamic landscape in the probe approximation, and show their relaxation dynamics exhibits logarithmic aging, with aging rates determined by the distribution of barriers.

  8. Holographic Spacetime

    NASA Astrophysics Data System (ADS)

    Banks, Tom

    2012-10-01

    The theory of holographic spacetime (HST) generalizes both string theory and quantum field theory (QFT). It provides a geometric rationale for supersymmetry (SUSY) and a formalism in which super-Poincare invariance follows from Poincare invariance. HST unifies particles and black holes, realizing both as excitations of noncommutative geometrical variables on a holographic screen. Compact extra dimensions are interpreted as finite-dimensional unitary representations of super-algebras, and have no moduli. Full field theoretic Fock spaces, and continuous moduli are both emergent phenomena of super-Poincare invariant limits in which the number of holographic degrees of freedom goes to infinity. Finite radius de Sitter (dS) spaces have no moduli, and break SUSY with a gravitino mass scaling like Λ1/4. In regimes where the Covariant Entropy Bound is saturated, QFT is not a good description in HST, and inflation is such a regime. Following ideas of Jacobson, the gravitational and inflaton fields are emergent classical variables, describing the geometry of an underlying HST model, rather than "fields associated with a microscopic string theory". The phrase in quotes is meaningless in the HST formalism, except in asymptotically flat and AdS spacetimes, and some relatives of these.

  9. Dispersing Zwitterions into Comb Polymers for Nonviral Transfection: Experiments and Molecular Simulation.

    PubMed

    Ghobadi, Ahmadreza F; Letteri, Rachel; Parelkar, Sangram S; Zhao, Yue; Chan-Seng, Delphine; Emrick, Todd; Jayaraman, Arthi

    2016-02-01

    Polymer-based gene delivery vehicles benefit from the presence of hydrophilic groups that mitigate the inherent toxicity of polycations and that provide tunable polymer-DNA binding strength and stable complexes (polyplexes). However, hydrophilic groups screen charge, and as such can reduce cell uptake and transfection efficiency. We report the effect of embedding zwitterionic sulfobetaine (SB) groups in cationic comb polymers, using a combination of experiments and molecular simulations. Ring-opening metathesis polymerization (ROMP) produced comb polymers with tetralysine (K4) and SB pendent groups. Dynamic light scattering, zeta potential measurements, and fluorescence-based experiments, together with coarse-grained molecular dynamics simulations, described the effect of SB groups on the size, shape, surface charge, composition, and DNA binding strength of polyplexes formed using these comb polymers. Experiments and simulations showed that increasing SB composition in the comb polymers decreased polymer-DNA binding strength, while simulations indicated that the SB groups distributed throughout the polyplex. This allows polyplexes to maintain a positive surface charge and provide high levels of gene expression in live cells. Notably, comb polymers with nearly 50 mol % SB form polyplexes that exhibit positive surface charge similarly as polyplexes formed from purely cationic comb polymers, indicating the ability to introduce an appreciable amount of SB functionality without screening surface charge. This integrated simulation-experimental study demonstrates the effectiveness of incorporating zwitterions in polyplexes, while guiding the design of new and effective gene delivery vectors. PMID:26741292

  10. Shrinkage during holographic recording in photopolymer films determined by holographic interferometry.

    PubMed

    Moothanchery, Mohesh; Bavigadda, Viswanath; Toal, Vincent; Naydenova, Izabela

    2013-12-10

    Shrinkage of photopolymer materials is an important factor for their use in holographic data storage and for fabrication of holographic optical elements. Dimensional change in the holographic element leads to a requirement for compensation in the reading angle and/or wavelength. Normally, shrinkage is studied at the end of the polymerization process and no information about the dynamics is obtained. The aim of this study was to use holographic interferometry to measure the shrinkage that occurs during holographic recording of transmission diffraction gratings in acrylamide photopolymer layers. Shrinkage in photopolymer layers can be measured over the whole recorded area by real-time capture of holographic interferograms at regular intervals during holographic recording using a complimentary metal-oxide-semiconductor camera. The optical path length change, and hence the shrinkage, are determined from the captured fringe patterns. Through analysis of the real-time shrinkage curves, it is possible to distinguish two processes that determine the value of shrinkage in the photopolymer layer. These processes are ascribed to monomer polymerization and crosslinking of polymer chains. The dependence of shrinkage of the layers on the conditions of recording such as recording intensity, single or double beam exposure, and the physical properties of the layers, such as thickness, were studied. Higher shrinkage was observed with recordings at lower intensities and in thinner layers. Increased shrinkage was also observed in the case of single beam polymerization in comparison to the case of double beam holographic exposure. PMID:24513896

  11. Impact of particle size on interaction forces between ettringite and dispersing comb-polymers in various electrolyte solutions.

    PubMed

    Ferrari, Lucia; Kaufmann, Josef; Winnefeld, Frank; Plank, Johann

    2014-04-01

    The inter-particle forces play a fundamental role for the flow properties of a particle suspension in response to shear stresses. In concrete applications, cement admixtures based on comb-polymers like polycarboxylate-ether-based superplasticizer (PCE) are used to control the rheological behavior of the fresh mixtures, as it is negatively impacted by certain early hydration products, like the mineral ettringite. In this work, dispersion forces due to PCE were measured directly at the surface of ettringite crystals in different electrolyte solutions by the means of atomic force microscopy (AFM) applying spherical and sharp silicon dioxide tips. Results show an effective repulsion between ettringite surface and AFM tips for solutions above the IEP of ettringite (pH∼12) and significant attraction in solution at lower pH. The addition of polyelectrolytes in solution provides dispersion forces exclusively between the sharp tips (radius ≈ 10 nm) and the ettringite surface, whereas the polymer layer at the ettringite surface results to be unable to disperse large colloidal probes (radius ≈ 10 μm). A simple modeling of the inter-particle forces explains that, for large particles, the steric hindrance of the studied PCE molecules is not high enough to compensate for the Van der Waals and the attractive electrostatic contributions. Therefore, in cement suspensions the impact of ettringite on rheology is probably not only related to the particle charge, but also related to the involved particle sizes. PMID:24491324

  12. Controlled Dissolution of Griseofulvin Solid Dispersions from Electrosprayed Enteric Polymer Micromatrix Particles: Physicochemical Characterization and in Vitro Evaluation.

    PubMed

    Roine, Jorma; Kaasalainen, Martti; Peurla, Markus; Correia, Alexandra; Araújo, Francisca; Santos, Hélder A; Murtomaa, Matti; Salonen, Jarno

    2015-07-01

    The oral bioavailability of a poorly water-soluble drug is often inadequate for the desired therapeutic effect. The bioavailability can be improved by enhancing the physicochemical properties of the drug (e.g., dissolution rate, permeation across the gastrointestinal tract). Other approach include shielding the drug from the gastric metabolism and targeted drug release to obtain optimal drug absorption. In this study, a poorly water-soluble model drug, griseofulvin, was encapsulated as disordered solid dispersions into Eudragit L 100-55 enteric polymer micromatrix particles, which were produced by electrospraying. Similar micromatrix particles were also produced with griseofulvin-loaded thermally oxidized mesoporous silicon (TOPSi) nanoparticles dispersed to the polymer micromatrices. The in vitro drug dissolution at pH 1.2 and 6.8, and permeation at pH 7.4 across Caco-2/HT29 cell monolayers from the micromatrix particles, were investigated. The micromatrix particles were found to be gastro-resistant, while at pH 6.8 the griseofulvin was released very rapidly in a fast-dissolving form. Compared to free griseofulvin, the permeability of encapsulated griseofulvin across the intestinal cell monolayers was greatly improved, particularly for the TOPSi-doped micromatrix particles. The griseofulvin solid dispersions were stable during storage for 6 months at accelerated conditions. Overall, the method developed here could prove to be a useful oral drug delivery solution for improving the bioavailability of poorly water-soluble or otherwise problematic drugs. PMID:26035734

  13. The structure of a polymer blend in a volume grating

    NASA Astrophysics Data System (ADS)

    Birnkrant, Michael; Li, Christopher; Natarajan, Lalgudi V.; Tondiglia, Vincent P.; Sutherland, Richard L.; Lloyd, Pamela F.; Jakubiak, Rachel; Bunning, Timothy J.

    2008-08-01

    Holographic polymerization (H-P) has been used to fabricate polymer-dispersed liquid crystals, block copolymers and pattern inert nanoparticles. In this article, one-dimensional grating structures of Norland resin and a polymer blend were achieved using the H-P technique. A reflection grating structure known as a Bragg reflector (BR) was fabricated. The hierarchical structure and morphology of the BR were studied using synchrotron X-ray, polarized light microscopy and transmission electron microscopy. The structure of the BR containing a polymer blend displayed lamellae structures formed with periodicity of 200 nm. Polycaprolactone and Poly(L-lactide) crystals were found to be confined in ~ 60 nm thick layers in the BR. The polymer chains tended to orient themselves parallel to the grating when the two polymers where blended together. The phase separation and structure of the polymer blend inside the H-P grating could be of great interest for multifunctional optical sensors or devices.

  14. Holographic turbulence.

    PubMed

    Adams, Allan; Chesler, Paul M; Liu, Hong

    2014-04-18

    We construct turbulent black holes in asymptotically AdS4 spacetime by numerically solving Einstein's equations. Using the AdS/CFT correspondence we find that both the dual holographic fluid and bulk geometry display signatures of an inverse cascade with the bulk geometry being well approximated by the fluid-gravity gradient expansion. We argue that statistically steady-state black holes dual to d dimensional turbulent flows have horizons whose area growth has a fractal-like structure with fractal dimension D=d+4/3. PMID:24785028

  15. Characterization of solid dispersions of Patchouli alcohol with different polymers: effects on the inhibition of reprecipitation and the improvement of dissolution rate.

    PubMed

    Chen, Yun Long; Liao, Jin Bin; Liang, Yong Zhuo; Xie, Jian Hui; Wu, Qiong; Lai, Xiao Ping; Chen, Jian Nan; Su, Zi Ren; Lin, Zhi Xiu

    2015-03-01

    Solid dispersion technique is known to be an effective approach for the polymer to keep drugs stable in the solid state, thereby improving the dissolution rate and oral bioavailability through inhibiting reprecipitation in supersaturated solution. In this study, to evaluate the inhibitory effect of polyethylene glycol-6000 (PEG), Polyvinylpyrrolidone K30 (PVP) and Aminoalkyl methacrylate copolymer (Eudragit), the reprecipitation profiles were observed from supersaturated solutions of Patchouli alcohol (PA) in the presence and absence of the polymers. Furthermore, the dissolution profiles of PA solid dispersions formulated with PEG, PVP or Eudragit were compared for investigating the effect on improving dissolution of each polymer. Solid dispersions formulated with Eudragit were found to result in solution with the highest extent of supersaturation. By contrast, PEG and PVP were less effective. At equivalent supersaturation, all three polymers are capable of mitigating reprecipitation relative to that of PA alone. In addition, in the PA solid dispersion with Eudragit (E-SD (1/3)), the highest concentration of supersaturation of PA was maintained for prolonged time. These results unambiguously indicate that it is imperative to select the appropriate polymer and drug/polymer ratio in addition to considering the stability of the supersaturated solution, which was generated following dissolution of amorphous solid dispersion. PMID:24410045

  16. Comparative study of the electrochemical behavior and analytical applications of (bio)sensing platforms based on the use of multi-walled carbon nanotubes dispersed in different polymers.

    PubMed

    Primo, E N; Gutierrez, F A; Luque, G L; Dalmasso, P R; Gasnier, A; Jalit, Y; Moreno, M; Bracamonte, M V; Rubio, M Eguílaz; Pedano, M L; Rodríguez, M C; Ferreyra, N F; Rubianes, M D; Bollo, S; Rivas, G A

    2013-12-17

    This review present a critical comparison of the electrochemical behavior and analytical performance of glassy carbon electrodes (GCE) modified with carbon nanotubes (CNTs) dispersed in different polymers: polyethylenimine (PEI), PEI functionalized with dopamine (PEI-Do), polyhistidine (Polyhis), polylysine (Polylys), glucose oxidase (GOx) and double stranded calf-thymus DNA (dsDNA). The comparison is focused on the analysis of the influence of the sonication time, solvent, polymer/CNT ratio, and nature of the polymer on the efficiency of the dispersions and on the electrochemical behavior of the resulting modified electrodes. The results allow to conclude that an adequate selection of the polymers makes possible not only an efficient dispersion of CNTs but also, and even more important, the building of successful analytical platforms for the detection of different bioanalytes like NADH, glucose, DNA and dopamine. PMID:24296140

  17. Enhanced photorefractive performance in CdSe quantum-dot-dispersed poly(styrene-co-acrylonitrile) polymers

    SciTech Connect

    Li Xiangping; Embden, Joel van; Chon, James W. M.; Gu Min; Evans, Richard A.

    2010-06-21

    This paper reports on the enhanced photorefractive behavior of a CdSe quantum-dot-dispersed less expensive polymer of poly(styrene-co-acrylonitrile). The capability of CdSe quantum dots used as photosensitizers and the associated photorefractive performance are characterized through a photocurrent experiment and a two-beam coupling experiment, respectively. An enhanced two-beam coupling gain coefficient of 12.2 cm{sup -1} at 46 V/mum was observed owning to the reduced potential barrier. The photorefractive performance per CdSe quantum dot is three orders of magnitude higher than that in the sample sensitized by trinitrofluorenone in poly(styrene-co-acrylonitrile), and almost ten times higher than that in the CdSe quantum-dot-sensitized poly(N-vinylcarbazole) polymers.

  18. Water-in-water emulsions stabilized by non-amphiphilic interactions: polymer-dispersed lyotropic liquid crystals.

    PubMed

    Simon, Karen A; Sejwal, Preeti; Gerecht, Ryan B; Luk, Yan-Yeung

    2007-01-30

    Emulsion systems involving surfactants are mainly driven by the separation of the hydrophobic interactions of the aliphatic chains from the hydrophilic interactions of amphiphilic molecules in water. In this study, we report an emulsion system that does not include amphiphilic molecules but molecules with functional groups that are completely solvated in water. These functional groups give rise to molecular interactions including hydrogen bonding, pi stacking, and salt bridging and are segregated into a dispersion of droplets forming a water-in-water emulsion. This water-in-water emulsion consists of dispersing droplets of a water-solvated biocompatible liquid crystal--disodium cromoglycate (DSCG)--in a continuous aqueous solution containing specific classes of water-soluble polymers. Whereas aqueous solutions of polyols support the formation of emulsions of spherical droplets consisting of lyotropic liquid crystal DSCG with long-term stability (for at least 30 days), aqueous solutions of polyamides afford droplets of DSCG in the shape of prolate ellipsoids that are stable for only 2 days. The DSCG liquid crystal in spherical droplets assumes a radial configuration in which the optical axis of the liquid crystal aligns perpendicular to the surface of the droplets but assumes a tangential configuration in prolate ellipsoids in which the optical axis of the liquid crystal aligns parallel to the surface of the droplet. Other classes of water-soluble polymers including polyethers, polycations, and polyanions do not afford a stable emulsion of DSCG droplets. Both the occurrence and the stability of this unique emulsion system can be rationalized on the basis of the functional groups of the polymer. The different configurations of the liquid crystal (DSCG) droplets were also found to correlate with the strength of the hydrogen bonding that can be formed by the functional groups on the polymer. PMID:17241072

  19. Nanoscale Infrared, Thermal, and Mechanical Characterization of Telaprevir-Polymer Miscibility in Amorphous Solid Dispersions Prepared by Solvent Evaporation.

    PubMed

    Li, Na; Taylor, Lynne S

    2016-03-01

    Miscibility is of great interest for pharmaceutical systems, in particular, for amorphous solid dispersions, as phase separation can lead to a higher tendency to crystallize, resulting in a loss in solubility, decreased dissolution rate, and compromised bioavailability. The purpose of this study was to investigate the miscibility behavior of a model poorly water-soluble drug, telaprevir (TPV), with three different polymers using atomic force microscopy-based infrared, thermal, and mechanical analysis. Standard atomic force microscopy (AFM) imaging together with nanoscale infrared spectroscopy (AFM-IR), nanoscale thermal analysis (nanoTA), and Lorentz contact resonance (LCR) measurements were used to evaluate the miscibility behavior of TPV with three polymers, hydroxypropyl methylcellulose (HPMC), HPMC acetate succinate (HPMCAS), and poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA), at different drug to polymer ratios. Phase separation was observed with HPMC and PVPVA at drug loadings above 10%. For HPMCAS, a smaller miscibility gap was observed, with phase separation being observed at drug loadings higher than ∼30-40%. The domain size of phase-separated regions varied from below 50 nm to a few hundred nanometers. Localized infrared spectra, nano-TA measurements, images from AFM-based IR, and LCR measurements showed clear contrast between the continuous and discrete domains for these phase-separated systems, whereby the discrete domains were drug-rich. Fluorescence microscopy provided additional evidence for phase separation. These methods appear to be promising to evaluate miscibility in drug-polymer systems with similar Tgs and submicron domain sizes. Furthermore, such findings are of obvious importance in the context of contributing to a mechanistic understanding of amorphous solid dispersion phase behavior. PMID:26859046

  20. Characterization of solid polymer dispersions of active pharmaceutical ingredients by 19F MAS NMR and factor analysis

    NASA Astrophysics Data System (ADS)

    Urbanova, Martina; Brus, Jiri; Sedenkova, Ivana; Policianova, Olivia; Kobera, Libor

    In this contribution the ability of 19F MAS NMR spectroscopy to probe structural variability of poorly water-soluble drugs formulated as solid dispersions in polymer matrices is discussed. The application potentiality of the proposed approach is demonstrated on a moderately sized active pharmaceutical ingredient (API, Atorvastatin) exhibiting extensive polymorphism. In this respect, a range of model systems with the API incorporated in the matrix of polvinylpyrrolidone (PVP) was prepared. The extent of mixing of both components was determined by T1(1H) and T1ρ(1H) relaxation experiments, and it was found that the API forms nanosized domains. Subsequently it was found out that the polymer matrix induces two kinds of changes in 19F MAS NMR spectra. At first, this is a high-frequency shift reaching 2-3 ppm which is independent on molecular structure of the API and which results from the long-range polarization of the electron cloud around 19F nucleus induced by electrostatic fields of the polymer matrix. At second, this is broadening of the signals and formation of shoulders reflecting changes in molecular arrangement of the API. To avoid misleading in the interpretation of the recorded 19F MAS NMR spectra, because both the contributions act simultaneously, we applied chemometric approach based on multivariate analysis. It is demonstrated that factor analysis of the recorded spectra can separate both these spectral contributions, and the subtle structural differences in the molecular arrangement of the API in the nanosized domains can be traced. In this way 19F MAS NMR spectra of both pure APIs and APIs in solid dispersions can be directly compared. The proposed strategy thus provides a powerful tool for the analysis of new formulations of fluorinated pharmaceutical substances in polymer matrices.

  1. Pressure dependence of the electro-optic response function in partially exposed polymer dispersed ferroelectric liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Holmes, H. K.

    1993-01-01

    Ferroelectric liquid crystals in a new configuration, termed partially exposed polymer dispersed ferroelectric liquid crystal (PEPDFLC), respond to external pressures and demonstrate pressure-induced electro-optic switching response. When the PEPDFLC thin film is sandwiched between two transparent conducting electrodes, one a glass plate and the other a flexible sheet such as polyvenylidene fluoride, the switching characteristics of the thin film are a function of the pressure applied to the flexible transparent electrode and the bias voltage across the electrodes. Response time measurements reveal a linear dependence of the change in electric field with external pressure.

  2. Holographic Aquaculture

    NASA Astrophysics Data System (ADS)

    Ian, Richard; King, Elisabeth

    1988-01-01

    Proposed is an exploratory study to verify the feasibility of an inexpensive micro-climate control system for both marine and freshwater pond and tank aquaculture, offering good control over water temperature, incident light flux, and bandwidth, combined with good energy efficiency. The proposed control system utilizes some familiar components of passive solar design, together with a new holographic glazing system which is currently being developed by, and proprietary to Advanced Environmental Research Group (AERG). The use of solar algae ponds and tanks to warm and purify water for fish and attached macroscopic marine algae culture is an ancient and effective technique, but limited seasonally and geographically by the availability of sunlight. Holographic Diffracting Structures (HDSs) can be made which passively track, accept and/or reject sunlight from a wide range of altitude and azimuth angles, and redirect and distribute light energy as desired (either directly or indirectly over water surface in an enclosed, insulated structure), effectively increasing insolation values by accepting sunlight which would not otherwise enter the structure.

  3. Quantifying the Heterogeneity of Chemical Structures in Complex Charged Polymers through the Dispersity of Their Distributions of Electrophoretic Mobilities or of Compositions.

    PubMed

    Thevarajah, Joel J; Sutton, Adam T; Maniego, Alison R; Whitty, Elizabeth G; Harrisson, Simon; Cottet, Hervé; Castignolles, Patrice; Gaborieau, Marianne

    2016-02-01

    The complexity of synthetic and natural polymers used in industrial and medical applications is expanding; thus, it becomes increasingly important to improve and develop methods for their molecular characterization. Free-solution capillary electrophoresis is a robust technique for the separation and characterization of both natural and synthetic complex charged polymers. In the case of polyelectrolytes, free-solution capillary electrophoresis is in the "critical conditions" (CE-CC): it allows their separation by factors other than molar mass for molar masses typically higher than 20000 g/mol. This method is thus complementary to size-exclusion chromatography (SEC). SEC is widely used to determine molar mass distributions and their dispersities. Utilizing CE-CC, an analogous calculation of dispersity based on the distributions of electrophoretic mobilities was derived and the heterogeneity of composition or branching in different polysaccharides or synthetic polymers was obtained in a number of experimental cases. Calculations are based on a ratio of moments and could therefore be compared to simulations of polymerization processes, in analogy to the work performed on molar mass distributions. Among four possible types of dispersity, the most precise values were obtained with the calculation analogous with the dispersity of molar mass distribution Mw/Mn. In addition, the dispersity value allows conclusions based on a single value: the closer the dispersity is to 1, the more homogeneous the polymer is in terms of composition or branching. This approach allows the analysis of dispersity of important molecular attributes of polymers other than molar mass and aims at improving the overall molecular characterization of both synthetic and natural polymers. The dispersity can also be monitored online while performing a chemical reaction within the CE instrument. PMID:26674535

  4. Measuring the Thickness and Elastic Properties of Electroactive Thin-film Polymers Using Platewave Dispersion Data

    NASA Technical Reports Server (NTRS)

    El-Azab, A.; Mal, A. K.; Bar-Cohen, Y.; Lih, S.

    1996-01-01

    Electroactive thin-film polymers are candidate sensors and actuators materials [1,2]. They are also finding a significant potential for applications in muscle mechanisms and micro-electro-mechanical systems (MEMS).

  5. Thermal Conductivity of 3D CNT-Polymer Composites with Controlled Dispersion

    NASA Astrophysics Data System (ADS)

    Klittich, Mena; Wang, Xue; Dhinojwala, Ali

    The high thermal conductivity of isolated carbon nanotubes (CNTs) has inspired its use as a thermal filler for insulative polymers. However, the performance of these composites has consistently been sub par. Extensive analyses of these complex systems have resulted in the conclusion that resistance at the CNT/polymer interface due to phonon mismatch and poor physical binding, as well as the weakly bonded tube-tube interactions restrict the effectiveness of CNTs in practice. Experimental comparisons of CNT treatments, coatings, functionalization, and interactions with various polymers have proved challenging, due to the interconnected nature of the composite properties. Here, we have reversed the paradigm and used a constant CNT structure that is then modified post-growth to allow for direct comparisons of polymer composites.

  6. Optical properties of a photopolymer film for digital holographic storage

    NASA Astrophysics Data System (ADS)

    Shin, Changwon; Kim, Junghoi; Kim, Nam; Lee, Hyojin; Kim, Eunkyoung

    2005-09-01

    Tir- and mono functional monomers were dispersed in a solution of polysulfone in organic solvent containing a photo initiator and other additives. New photopolymer film was prepared by dispersing acrylic monomer in a polysulfone matrix. The Polysulfone was adopted as a binder since it affords transparent thick films with low dimensional changes during holographic recording. Optical property of the photopolymer showed high diffraction efficiency (>90%) under an optimized optical condition at 532nm laser. The angular selectivity for angular multiplexing page oriented holographic memories (POHMs), the maximum diffraction efficiency of the material during holographic recording, the diffraction efficiency of the films as a function of an incident angle of two beams, exposure energy for saturation of the holographic material and application for holographic data storage will be discussed.

  7. Hot Melt Extruded Amorphous Solid Dispersion of Posaconazole with Improved Bioavailability: Investigating Drug-Polymer Miscibility with Advanced Characterisation

    PubMed Central

    Amin, Purnima

    2014-01-01

    Invasive antifungal infections are reasons for morbidity and mortality in immunogenic patients worldwide. Posaconazole is a most promising antifungal agent against all types of invasive infections with high % of cure rate. The marketed suspension formulation has low bioavailability and is needed to be taken with food. In this paper, PCZ hot melt extruded amorphous solid dispersion (SD) with immediate release and improved bioavailability was prepared using Soluplus (Sol) as primary carrier for solubilization. Surfactants such as PEG 400, Lutrol F27, Lutrol F68, and TPGS are also used in combination with Soluplus to improve the physicochemical performance of the formulation when it comes in contact with GI (gastrointestinal) fluid. Drug-polymer miscibility of SD was investigated using advanced techniques. In the in vivo study, the AUC(0–72) and Cmax of PCZ/Soluplus were 11.5 and 11.74 time higher than those of pure PCZ. The formulation of the extrudate SD had an AUC(0–72) and Cmax higher than those with the commercial capsule (Noxafil). Molecular dynamic (MD) simulation studies were carried out using in silico molecular modelling to understand the drug-polymer intermolecular behaviour. The results of this research ensure enhanced dissolution and bioavailability of the solid dispersion of PCZ prepared by HME compared with the PCZ suspension. PMID:25143935

  8. Enhanced dissolution and oral bioavailability of valsartan solid dispersions prepared by a freeze-drying technique using hydrophilic polymers.

    PubMed

    Xu, Wei-Juan; Xie, Hong-Juan; Cao, Qing-Ri; Shi, Li-Li; Cao, Yue; Zhu, Xiao-Yin; Cui, Jing-Hao

    2016-01-01

    This study aimed to improve the dissolution rate and oral bioavailability of valsartan (VAL), a poorly soluble drug using solid dispersions (SDs). The SDs were prepared by a freeze-drying technique with polyethylene glycol 6000 (PEG6000) and hydroxypropylmethylcellulose (HPMC 100KV) as hydrophilic polymers, sodium hydroxide (NaOH) as an alkalizer, and poloxamer 188 as a surfactant without using any organic solvents. In vitro dissolution rate and physicochemical properties of the SDs were characterized using the USP paddle method, differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and Fourier transform-infrared (FT-IR) spectroscopy, respectively. In addition, the oral bioavailability of SDs in rats was evaluated by using VAL (pure drug) as a reference. The dissolution rates of the SDs were significantly improved at pH 1.2 and pH 6.8 compared to those of the pure drug. The results from DSC, XRD showed that VAL was molecularly dispersed in the SDs as an amorphous form. The FT-IR results suggested that intermolecular hydrogen bonding had formed between VAL and its carriers. The SDs exhibited significantly higher values of AUC 0-24 h and Cmax in comparison with the pure drug. In conclusion, hydrophilic polymer-based SDs prepared by a freeze-drying technique can be a promising method to enhance dissolution rate and oral bioavailability of VAL. PMID:24735247

  9. Holographic Vortex Coronagraph

    NASA Technical Reports Server (NTRS)

    Palacios, David

    2010-01-01

    A holographic vortex coronagraph (HVC) has been proposed as an improvement over conventional coronagraphs for use in high-contrast astronomical imaging for detecting planets, dust disks, and other broadband light scatterers in the vicinities of stars other than the Sun. Because such light scatterers are so faint relative to their parent stars, in order to be able to detect them, it is necessary to effect ultra-high-contrast (typically by a factor of the order of 1010) suppression of broadband light from the stars. Unfortunately, the performances of conventional coronagraphs are limited by low throughput, dispersion, and difficulty of satisfying challenging manufacturing requirements. The HVC concept offers the potential to overcome these limitations.

  10. Application of film-casting technique to investigate drug-polymer miscibility in solid dispersion and hot-melt extrudate.

    PubMed

    Parikh, Tapan; Gupta, Simerdeep Singh; Meena, Anuprabha K; Vitez, Imre; Mahajan, Nidhi; Serajuddin, Abu T M

    2015-07-01

    Determination of drug-polymer miscibility is critical for successful development of solid dispersions. This report details a practical method to predict miscibility and physical stability of drug with various polymers in solid dispersion and, especially, in melt extrudates by applying a film-casting technique. Mixtures of itraconazole (ITZ) with hydroxypropylmethylcellulose phthalate (HPMCP), Kollidon(®) VA 64, Eudragit(®) E PO, and Soluplus(®) were film-casted, exposed to 40°C/75% RH for 1 month and then analyzed using differential scanning calorimetry (DSC), powder X-ray diffractometry, and polarized light microscopy (PLM). ITZ had the highest miscibility with HPMCP, being miscible at drug to polymer ratio of 6:4 (w/w). There was a downward trend of lower miscibility with Soluplus(®) (miscible at 3:7, w/w, and a few microcrystals present at 4:6, w/w), Kollidon(®) VA 64 (2:8, w/w) and Eudragit(®) E PO (<1:9, w/w). PLM was found more sensitive to detect drug crystallization than DSC and powder X-ray diffractometry. There was general correlation between results of film casting and hot-melt extrusion (HME) using a twin screw extruder. For ITZ-Soluplus(®) mixtures, HME at 4:6 (w/w) resulted in a single phase, whereas drug crystallization was observed at higher drug load. HME of ITZ-Kollidon(®) VA 64 mixtures also correlated well with the miscibility predicted by film casting. PMID:25917333

  11. Polymer swelling, drug mobilization and drug recrystallization in hydrating solid dispersion tablets studied by multinuclear NMR microimaging and spectroscopy.

    PubMed

    Dahlberg, Carina; Dvinskikh, Sergey V; Schuleit, Michael; Furó, István

    2011-08-01

    Despite the advantages offered by solid dispersions, the marketed products based on this technology are few. The most frequent concern is the stability of the amorphous drug. The state of the drug in solid dispersions is, in general, poorly characterized as the number of characterization techniques available to monitor nanometer-sized drug particles embedded in a matrix are limited. Here we present a combination of localized NMR spectroscopic and NMR imaging techniques which allow in situ monitoring of the state of the drug during tablet disintegration and dissolution. (19)F NMR relaxation is shown to be sensitive to both the crystalline/amorphous state and the size of the model nanoparticles made of the drug substance flutamide. The time course of drug mobilization and recrystallization is detected with spatial resolution within swelling solid dispersion tablets. Comparing results from spatially resolved (19)F, (2)H and (1)H NMR experiments, recrystallization is related to its enabling factors such as local hydration level and local mobility of the polymer matrix. The initially amorphous drug may recrystallize either by nanoparticle coalescence or by ripening of crystalline grains. PMID:21696185

  12. Tailoring dispersion and aggregation of Au nanoparticles in the BHJ layer of polymer solar cells: plasmon effects versus electrical effects.

    PubMed

    Kim, Wanjung; Cha, Bong Geun; Kim, Jung Kyu; Kang, Woonggi; Kim, Eunchul; Ahn, Tae Kyu; Wang, Dong Hwan; Du, Qing Guo; Cho, Jeong Ho; Kim, Jaeyun; Park, Jong Hyeok

    2014-12-01

    Plasmonic effects that arise from embedding metallic nanoparticles (NPs) in polymer solar cells (PSCs) have been extensively studied. Many researchers have utilized metallic NPs in PSCs by either incorporating them into the PSC interlayers (e.g., the hole extraction and electron extraction layers) or blending them into the bulk heterojunction (BHJ) active layer. In such studies, the dispersity of the metallic NPs in each layer may vary due to both the different nature of the ligands and the amount of ligands on the metallic NPs. This in turn can produce different PSC performance parameters. Here, we systematically control the amount of attached organic ligands on Au NPs to control their dispersion behavior in the BHJ active layer of PSCs. By controlling the number of capping organic ligands on the Au NPs, the dispersity of the NPs in the BHJ layer is also controlled and the positive effects (particularly the plasmonic and electrical effects) of the Au NPs in the PSCs are investigated. From the obtained results, we find that the electrical contribution of the Au NPs is a more dominant factor for enhancing cell efficiency when compared to the plasmonic effect. PMID:25333870

  13. Molecularly designed lipid microdomains for solid dispersions using a polymer/inorganic carrier matrix produced by hot-melt extrusion.

    PubMed

    Adler, Camille; Schönenberger, Monica; Teleki, Alexandra; Kuentz, Martin

    2016-02-29

    Amorphous solid dispersions have for many years been a focus in oral formulations, especially in combination with a hot-melt extrusion process. The present work targets a novel approach with a system based on a fatty acid, a polymer and an inorganic carrier. It was intended to adsorb the acidic lipid by specific molecular interactions onto the solid carrier to design disorder in the alkyl chains of the lipid. Such designed lipid microdomains (DLM) were created as a new microstructure to accommodate a compound in a solid dispersion. Vibrational spectroscopy, X-ray powder diffraction, atomic force microscopy as well as electron microscopic imaging were employed to study a system of stearic acid, hydroxypropylcellulose and aluminum magnesium silicate. β-carotene was used as a poorly water-soluble model substance that is difficult to formulate with conventional solid dispersion formulations. The results indicated that the targeted molecular excipient interactions indeed led to DLMs for specific compositions. The different methods provided complementary aspects and important insights into the created microstructure. The novel delivery system appeared to be especially promising for the formulation of oral compounds that exhibit both high crystal energy and lipophilicity. PMID:26721729

  14. Study of anchoring behavior of nematic fluids at the interface of polymer-dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Zhou, Jian

    A liquid crystal (LC) at its boundary surface adopts a preferential alignment, which is referred to as anchoring. The direction of this alignment (i.e., anchoring direction) may be perpendicular, parallel or tilted with respect to the surface. Transitions from one anchoring condition to another may occur when the parameters (e.g., temperature) charactering the surface change, as referred to as anchoring transitions. In the LC-polymer composite systems under our study, the anchoring and temperature-driven anchoring transitions of nematic fluids is very sensitive to the structure of the side chain of poly (alkyl acrylate) matrixes that encapsulate the LC. We have shown that the anchoring transition temperature of these systems can be tuned far below the nematic-to-isotropic transition temperature, by varying either the length, branching structure of the side chains of homopolymers, or the composition of copolymer of two dissimilar monomers. Both sharp and broad anchoring transitions with respect to the temperature range over which a transition occurs were observed. It is postulated that microscopic interactions between the polymer side chains and LC molecules play an important role in determining the anchoring. In particular, the conformation of the polymer side chain is proposed to have important control over the anchoring. Anchoring strength and tilt angle as a function of temperature during the anchoring transitions were also experimentally investigated, which contribute to understanding of the microscopic mechanism for such transitions. Based on the LC-polymer composites with controlled anchoring, a LC display with reverse switching mode and a novel electrically switchable diffraction grating have been demonstrated. The advantages of these devices are ease of manufacturing, low operation voltage, and mechanical stability offered by polymer matrix. Moreover, a detailed study of the director configuration of wall defects found in these composite films was carried

  15. Increase in the coercivity of an ensemble of (DyPr)-(CoFe)-B microparticles during their dispersion in a polymer matrix

    NASA Astrophysics Data System (ADS)

    Kablov, E. N.; Ospennikova, O. G.; Kablov, D. E.; Piskorskii, V. P.; Korolev, D. V.; Kurochkin, S. A.; Kunitsyna, E. I.; Talantsev, A. D.; Morgunov, R. B.

    2016-07-01

    In ensembles of annealed ferrimagnetic alloy (DyPr)-(CoFe)-B microparticles in the free state and fixed in polymer, the coercivity differs more than by an order of magnitude. The contributions of orientation locking of magnetic axes of particles and the dipole magnetic interaction between particles to the coercivity and saturation magnetization field of an ensemble are discussed. In ensembles of unannealed microparticles, the effect of their locking and dispersing in polymer is significantly weaker.

  16. Solvent-shift strategy to identify suitable polymers to inhibit humidity-induced solid-state crystallization of lacidipine amorphous solid dispersions.

    PubMed

    Sun, Mengchi; Wu, Chunnuan; Fu, Qiang; Di, Donghua; Kuang, Xiao; Wang, Chao; He, Zhonggui; Wang, Jian; Sun, Jin

    2016-04-30

    The solvent-shift strategy was used to identify appropriate polymers that inhibit humidity-induced solid-state crystallization of amorphous solid dispersions (ASDs). Lacidipine with the polymers, PVP-K30, HPMC-E5 or Soluplus, were combined to form amorphous solid dispersions prepared by solvent evaporation. The formulations were characterized by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and Fourier-transform infrared spectroscopy (FT-IR) and were subjected to in vitro dissolution testing. The moisture had a significant impact on the amount dissolved for the solid dispersions. Molecular docking studies established that hydrogen bonding was critical for the stabilization of the solid dispersions. The rank order of the binding energy of the drug-polymer association was Soluplus (-6.21kcal/mol)>HPMC-E5 (-3.21kcal/mol)>PVP-K30 (-2.31kcal/mol). PVP-K30 had the highest water uptake among the polymers, as did ASD system of lacidipine-PVP-K30 ASDs. In the Soluplus ASDs, with its strong drug-polymer interactions and low water uptake, moisture-induced solid-state crystallization was not observed. PMID:26869398

  17. Investigation of phase diagrams and physical stability of drug-polymer solid dispersions.

    PubMed

    Lu, Jiannan; Shah, Sejal; Jo, Seongbong; Majumdar, Soumyajit; Gryczke, Andreas; Kolter, Karl; Langley, Nigel; Repka, Michael A

    2015-01-01

    Solid dispersion technology has been widely explored to improve the solubility and bioavailability of poorly water-soluble compounds. One of the critical drawbacks associated with this technology is the lack of physical stability, i.e. the solid dispersion would undergo recrystallization or phase separation thus limiting a product's shelf life. In the current study, the melting point depression method was utilized to construct a complete phase diagram for felodipine (FEL)-Soluplus® (SOL) and ketoconazole (KTZ)-Soluplus® (SOL) binary systems, respectively, based on the Flory-Huggins theory. The miscibility or solubility of the two compounds in SOL was also determined. The Flory-Huggins interaction parameter χ values of both systems were calculated as positive at room temperature (25 °C), indicating either compound was miscible with SOL. In addition, the glass transition temperatures of both solid dispersion systems were theoretically predicted using three empirical equations and compared with the practical values. Furthermore, the FEL-SOL solid dispersions were subjected to accelerated stability studies for up to 3 months. PMID:25113671

  18. Polar Laser Dyes Dispersed in Polymer Matrices: Reverification of Charge Transfer Character and New Optical Functions

    NASA Astrophysics Data System (ADS)

    Kwak, Giseop; Okada, Chisato; Fujiki, Michiya; Takeda, Hiroaki; Nishida, Takashi; Shiosaki, Tadashi

    2008-03-01

    In this paper, we describe the photophysical properties and new functions of 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) and its derivative, 2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j]quinolizin-9-yl)-ethenyl]-4H-pyran-4-ylidene)propane dinitrile (DCM2) in various polymer matrices, with respect to intramolecular charge transfer (ICT). The maximum fluorescence wavelengths of DCM and DCM2 shifted to red with an increase in the dielectric constant of the polymer matrix. The fluorescence lifetime shortened according to the matrix polarity. When a polymer with a dielectric constant varying according to its crystalline structure, poly(vinylidenefluoride-co-trifluoroethylene) (PVdF-co-TrFE), was used as a matrix, we were able to thermally tune the fluorescence wavelength as well as the fluorescence intensity of DCM2. The locked molecular structure of DCM2 was very effective for maintaining the charge transfer character during thermal stimulation.

  19. Effect of hydrophilic additives on the dissolution and pharmacokinetic properties of itraconazole-enteric polymer hot-melt extruded amorphous solid dispersions.

    PubMed

    Lang, Bo; Liu, Sha; McGinity, James W; Williams, Robert O

    2016-01-01

    Hot-melt extrusion technology has been widely reported for producing amorphous solid dispersions of poorly water-soluble compounds. A number of studies revealed that enteric polymers containing ionizable groups are able to improve the physical stability and maintain drug supersaturation, thereby enhancing oral bioavailability. However, our previous studies found that itraconazole (ITZ)-enteric polymer amorphous solid dispersions are hydrophobic and poorly wettable. Moreover, drug release in an acidic environment (i.e. stomach) is very limited, indicating a narrow absorption window. In the present study, we investigated the effect of hydrophilic additives on the in vitro and in vivo performance of ITZ-enteric polymer amorphous solid dispersions. Incorporating Vitamin E TPGS into ITZ-HPMCAS amorphous solid dispersions significantly improved drug release in the acidic media. Surprisingly, a low concentration of Vitamin E TPGS also enhanced the degree of drug supersaturation in neutral pH media, which is unique as compared with other tested hydrophilic additives. This effect is not due to the solubilization of the surfactant. We further formulated the amorphous solid dispersions into tablet dosage forms and evaluated their performance in a bio-relevant dissolution media. Our optimized formulations exhibited drastically enhanced dissolution profiles as compared with the commercial ITZ product and ITZ amorphous solid dispersion without hydrophilic additive. In vivo study showed that Vitamin E TPGS induced rapid drug absorption after oral administration. Moreover, the elimination half-life of ITZ was prolonged due to the enzyme inhibition effect of Vitamin E TPGS. PMID:26355819

  20. Gas flow-field induced director alignment in polymer dispersed liquid crystal microdroplets deposited on a glass substrate

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Singh, J. J.

    1993-01-01

    Polymer dispersed liquid crystal thin films have been deposited on glass substrates by the processes of polymerization and solvent evaporation induced phase separation. The electron and the optical polarization microscopies of the films reveal that PDLC microdroplets formed during the process of phase separation near the top surface of the film remain exposed and respond to shear stress due to air or gas flow on the surface. Optical response of the film to an air flow-induced shear stress input on the free surface has been measured. Director orientation in the droplets changes with the applied shear stress leading to time varying transmitted light intensity. Director dynamics of the droplet for an applied step shear stress has been discussed from free energy considerations. Results on the measurement of light transmission as a function of the gas flow parameter unambiguously demonstrate the potential of these systems for use as boundary layer and gas flow sensors.

  1. Electrically tunable microlens arrays based on polarization-independent optical phase of nano liquid crystal droplets dispersed in polymer matrix.

    PubMed

    Yu, Ji Hoon; Chen, Hung-Shan; Chen, Po-Ju; Song, Ki Hoon; Noh, Seong Cheol; Lee, Jae Myeong; Ren, Hongwen; Lin, Yi-Hsin; Lee, Seung Hee

    2015-06-29

    Electrically tunable focusing microlens arrays based on polarization independent optical phase of nano liquid crystal droplets dispersed in polymer matrix are demonstrated. Such an optical medium is optically isotropic which is so-called an optically isotropic liquid crystals (OILC). We not only discuss the optical theory of OILC, but also demonstrate polarization independent optical phase modulation based on the OILC. The experimental results and analytical discussion show that the optical phase of OILC microlens arrays results from mainly orientational birefringence which is much larger than the electric-field-induced birefringence (or Kerr effect). The response time of OILC microlens arrays is fast~5.3ms and the tunable focal length ranges from 3.4 mm to 3.8 mm. The potential applications are light field imaging systems, 3D integrating imaging systems and devices for augment reality. PMID:26191743

  2. Near-infrared sensitive photorefractive device using polymer dispersed liquid crystal and BSO:Ru hybrid structure.

    PubMed

    Liu, Ren Chung; Marinova, Vera; Lin, Shiuan Huei; Chen, Ming-Syuan; Lin, Yi-Hsin; Hsu, Ken Yuh

    2014-06-01

    A near-infrared sensitive hybrid device, based on a Ru-doped BSO photorefractive substrate and polymer dispersed liquid crystal (PDLC) layer, is reported. It is found that the photoexcited charge carriers generated in the BSO:Ru substrate create an optically induced space charge field, sufficient to penetrate into the PDLC layer and to re-orient the LC molecules inside the droplets. Beam-coupling measurements at the Bragg regime are performed showing prospective amplification values and high spatial resolution. The proposed structure does not require indium tin oxide (ITO) contacts and alignment layers. Such a device allows all the processes to be controlled by light, thus opening further potential for real-time image processing at the near-infrared range. PMID:24876043

  3. Coding in 2D: Using Intentional Dispersity to Enhance the Information Capacity of Sequence-Coded Polymer Barcodes.

    PubMed

    Laure, Chloé; Karamessini, Denise; Milenkovic, Olgica; Charles, Laurence; Lutz, Jean-François

    2016-08-26

    A 2D approach was studied for the design of polymer-based molecular barcodes. Uniform oligo(alkoxyamine amide)s, containing a monomer-coded binary message, were synthesized by orthogonal solid-phase chemistry. Sets of oligomers with different chain-lengths were prepared. The physical mixture of these uniform oligomers leads to an intentional dispersity (1st dimension fingerprint), which is measured by electrospray mass spectrometry. Furthermore, the monomer sequence of each component of the mass distribution can be analyzed by tandem mass spectrometry (2nd dimension sequencing). By summing the sequence information of all components, a binary message can be read. A 4-bytes extended ASCII-coded message was written on a set of six uniform oligomers. Alternatively, a 3-bytes sequence was written on a set of five oligomers. In both cases, the coded binary information was recovered. PMID:27484303

  4. Current trends in studies on reverse-mode polymer dispersed liquid-crystal films — A review

    NASA Astrophysics Data System (ADS)

    Ahmad, Farzana; Jamil, M.; Jeon, Y. J.

    2014-07-01

    Reverse-mode polymer dispersed liquid crystals (PDLCs) comprise an important new class of materials for optical device applications. Generally reverse-mode PDLCs are transparent and opaque in the absence and presence of an external field, respectively. Display devices based on reverse-mode PDLC technology are useful for large-area displays; because their fabrication for manufacturing shutters is considered to be easier and faster, they are also employed for automotive technology and smart windows. These devices can be operated at a low voltage, which conserves energy in intelligent-device applications. This work presents a comprehensive review of past research regarding reverse-mode PDLCs and includes the advantageous features, applications, and various fabrication methods of reverse-mode PDLCs and photo-chromic reverse-mode PDLCs. In addition, some new features of this technology that have recently been reported and future investigations by a variety of research groups are presented.

  5. The effects of nanoparticles and organic additives with controlled dispersion on dielectric properties of polymers: Charge trapping and impact excitation

    NASA Astrophysics Data System (ADS)

    Huang, Yanhui; Wu, Ke; Bell, Michael; Oakes, Andrew; Ratcliff, Tyree; Lanzillo, Nicholas A.; Breneman, Curt; Benicewicz, Brian C.; Schadler, Linda S.

    2016-08-01

    This work presents a comprehensive investigation into the effects of nanoparticles and organic additives on the dielectric properties of insulating polymers using reinforced silicone rubber as a model system. TiO2 and ZrO2 nanoparticles (d = 5 nm) were well dispersed into the polymer via a bimodal surface modification approach. Organic molecules with the potential of voltage stabilization were further grafted to the nanoparticle to ensure their dispersion. These extrinsic species were found to provide deep traps for charge carriers and exhibited effective charge trapping properties at a rather small concentration (˜1017 cm-3). The charge trapping is found to have the most significant effect on breakdown strength when the electrical stressing time is long enough that most charges are trapped in the deep states. To establish a quantitative correlation between the trap depth and the molecular properties, the electron affinity and ionization energy of each species were calculated by an ab initio method and were compared with the experimentally measured values. The correlation however remains elusive and is possibly complicated by the field effect and the electronic interactions between different species that are not considered in this computation. At high field, a super-linear increase of current density was observed for TiO2 filled composites and is likely caused by impact excitation due to the low excitation energy of TiO2 compared to ZrO2. It is reasoned that the hot charge carriers with energies greater than the excitation energy of TiO2 may excite an electron-hole pair upon collision with the NP, which later will be dissociated and contribute to free charge carriers. This mechanism can enhance the energy dissipation and may account for the retarded electrical degradation and breakdown of TiO2 composites.

  6. Initial Droplet Size Impacts pH-Induced Structural Changes in Phase-Separated Polymer Dispersions.

    PubMed

    Thongkaew, Chutima; Zeeb, Benjamin; Gibis, Monika; Hinrichs, Jörg; Weiss, Jochen

    2016-05-01

    The effect of pH change on the morphology of whey protein isolate (WPI)-pectin dispersions obtained from phase-separated systems after mild shear was studied. The purpose of this study was to examine the impact of mixing speed on the initial particle size of biopolymer complexes and their structure morphology after sequentially changing the pH. Therefore, solutions of WPI and pectin were combined at pH 6.1, allowed to phase separate and were then mildly homogenized at 50, 100, and 150 rpm, respectively, to form a dispersion containing differently sized WPI droplets in a surrounding pectin-rich phase. Each dispersion was then subjected to a pH change, such as 6.1 to 5.2 and 3.2, by slowly adding hydrochloric acid. The systems morphology, size, appearance, rheology, and storage stability was then characterized by optical microscopy, static light scattering, visual inspections, and steady shear rheometry to gain insights into the structural rearrangements. Results indicated substantial changes in the structure of the dispersion when the pH was changed. Formation of core-shell structures from the WPI droplets was observed at an intermediate pH. There, initial droplet size was found to affect structures formed, that is, core-shell type particles would only form if droplets were large (>1.5 μm) prior to pH change. Insights gained may be of importance to food manufacturers intending to create new structures from mixtures of proteins and carbohydrates. PMID:27061600

  7. Effect of TiO2 dispersion on mechanical properties of epoxy polymer

    NASA Astrophysics Data System (ADS)

    Singh, Sushil Kumar; Singh, Samarjit; Kohli, Raunak; Jain, Anuj; Kumar, Abhishek

    2016-05-01

    This study is focused to assess reinforcing effects of TiO2 particles on the mechanical properties of epoxy resins, particularly with regards to fracture and toughening mechanisms. An experimental study has been carried out on series of composites containing varying amount of micro size titanium dioxide (TiO2) up to 8 wt.%. The particles were dispersed via mixing with mechanical stirrer at 1000 rpm for 2 hours to ensure a well-dispersed phase of the particles. The epoxy resin with the dispersed particle has been cured with hardener at 40 °C for 16 hours. Test reveals improvement in up to 4 wt.% of the particles and decrease in the mechanical properties beyond 4 wt. %. This may be attributed to the significant increase in clustering and settlement of the particles during long curing time. The tensile strength increases by 32 % and fracture toughness (K1C) by 44.95 % and the fracture energy (G1C) by 150.29 % with particle loading of 4 wt. % TiO2.

  8. A recombinant triblock protein polymer with dispersant and binding properties for digital printing.

    PubMed

    Qi, Min; O'Brien, John P; Yang, Jianjun

    2008-01-01

    A structured triblock protein was designed to explore the potential of engineered peptides to function as high-performance ink dispersants and binders. The protein consists of three functional elements, including a pigment binding domain, a hydrophilic linker, and a printing surface binding domain. To construct such a chimeric protein, a carbon black binding peptide, FHENWPS, and a cellulose binding peptide, THKTSTQRLLAA, were identified from phage display libraries through biopanning, based on their strong and specific binding affinities to carbon black and cellulose. They were used as carbon black and cellulose binding domains, respectively, in a recombinant triblock protein. A linker sequence, PTPTPTPTPTPTPTPTPTPTPTP, was adapted from endoglucanase A of the bacterium Cellulomonas fimi, as a small, rigid, and hydrophilic interdomain linker. When incorporated into the triblock structure between the carbon black and cellulose binding sequences, the linker sufficiently isolates these two elements and allows dual binding activity. The structured triblock protein was shown to disperse carbon black particles and attach it to paper surfaces. Thus, the utility of structured proteins having useful dispersant and binding properties for digital printing inks was demonstrated. PMID:17972282

  9. Imaging studies of temperature dependent photodegradation and self-healing in disperse orange 11 dye-doped polymers

    NASA Astrophysics Data System (ADS)

    Anderson, Benjamin R.; Hung, Sheng-Ting; Kuzyk, Mark G.

    2016-07-01

    Using confocal transmission imaging microscopy, we measure the temperature dependence of photodegradation and self-healing in disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate (PMMA) and polystyrene (PS). In both dye-doped polymers, an increase in sample temperature results in a greater photodegradation rate and degree of degradation, while also resulting in a slower recovery rate and larger recovery fraction. These results confirm the temperature dependence predictions of the modified correlated chromophore domain model (mCCDM) [B. R. Anderson and M. G. Kuzyk, Phys. Rev. E 89, 032601 (2014)]. Additionally, using quantitative fitting of the imaging data for DO11/PMMA, we determine the domain density parameter to be ρ = 1.19 (±0.25) × 10-2 and the domain free energy advantage to be λ = 0.282 ± 0.015 eV, which are within the uncertainty of the values previously determined using amplified spontaneous emission as the probe method [S. K. Ramini et al., Polym. Chem. 4, 4948 (2013)]. Finally, while we find photodegradation and self-healing of DO11/PS to be qualitatively consistent with the mCCDM, we find that it is quantitatively incompatible with the mCCDM as recovery in DO11/PS is found to behave as a stretched (or double) exponential as a function of time.

  10. Imaging studies of temperature dependent photodegradation and self-healing in disperse orange 11 dye-doped polymers.

    PubMed

    Anderson, Benjamin R; Hung, Sheng-Ting; Kuzyk, Mark G

    2016-07-14

    Using confocal transmission imaging microscopy, we measure the temperature dependence of photodegradation and self-healing in disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate (PMMA) and polystyrene (PS). In both dye-doped polymers, an increase in sample temperature results in a greater photodegradation rate and degree of degradation, while also resulting in a slower recovery rate and larger recovery fraction. These results confirm the temperature dependence predictions of the modified correlated chromophore domain model (mCCDM) [B. R. Anderson and M. G. Kuzyk, Phys. Rev. E 89, 032601 (2014)]. Additionally, using quantitative fitting of the imaging data for DO11/PMMA, we determine the domain density parameter to be ρ = 1.19 (±0.25) × 10(-2) and the domain free energy advantage to be λ = 0.282 ± 0.015 eV, which are within the uncertainty of the values previously determined using amplified spontaneous emission as the probe method [S. K. Ramini et al., Polym. Chem. 4, 4948 (2013)]. Finally, while we find photodegradation and self-healing of DO11/PS to be qualitatively consistent with the mCCDM, we find that it is quantitatively incompatible with the mCCDM as recovery in DO11/PS is found to behave as a stretched (or double) exponential as a function of time. PMID:27421424