Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Determination of elastic constants and rotational viscosity of micellar liquid crystals by conductivity measurements (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 7372-7377 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An experimental study of a lyotropic nematic liquid crystal (CsPFO in a water solution) confined to a cylindrical tube is presented. The structure of the sample is controlled by a magnetic field. A small ac voltage is applied along the tube for conductivity measurements. Elastic constants and conductivity constants of the material are determined from static measurements at different magnetic fields. The method is also used to determine the rotational viscosity γ1 from dynamic response under sudden changes of the magnetic field. The dynamic measurements are analyzed in the framework of the Leslie–Ericksen theory. It is shown that although the dynamic behavior can be qualitatively explained with a single effective rotational viscosity γ1, back flow effects have to be taken into account should the analysis yield consistent values for γ1. The results obtained by this method agree well with other experimental studies. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473698
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Helix deformation and bistable switching of ferroelectric liquid crystals (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1891-1894 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We studied electro-optical properties of 5–13-μm-thick films of a short pitch (0.43 μm) chiral smectic C liquid crystal in bookshelf structure. The anchoring at the silane treated surfaces was relatively weak so that the relaxed bookshelf structure was helical also at the surfaces. Low fields cause only a deformation of the helix. Larger fields unwind the helix and give a quasibistable switching since the helix recovers at zero fields only slowly via a nucleation process. There is an intermediate field range where the sample is in a mixed state: In some areas the helical structure remains stable, while in other areas switching occurs between two unwound states. In the intermediate field range bistable switching with a gray scale is possible. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361091
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Effect of a polymer network on the alignment and the rotational viscosity of a nematic liquid crystal (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3161-3164 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polymer dispersions were made by photoinduced polymerization of 4,4'-bisacryloyl-biphenyl in liquid crystal 4-4'-cyano pentyl biphenyl as nematic solvent. Samples were prepared with 0.5, 1, and 1.5 wt % monomer. The polymerization was done in the isotropic phase. The rotational viscosities of the two lower concentration samples increased only moderately after UV curing (3 mW/cm2, 25 min). The 1.5 wt % sample gave under the same condition a nematic with a fairly rigid anisotropic network that did not realign in magnetic field up to 20 kG. We estimate that the mesh size of the network was in the order of 1 μm, significantly smaller than the magnetic coherence length of the solvent that is in the order of 5 μm. The diamagnetic anisotropies of the aligned samples were not affected significantly by the polymer. We studied electro-optical properties on thin films. The films were strongly light scattering but they could be switched to transparent state. We conclude that the polymer forms a network of loosely connected fibrils that interacts strongly with the director field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351478
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Magnetic birefringence study of isotropic suspensions of tobacco mosaic virus (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 6740-6744 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The magnetic field induced birefringence in isotropic aqueous suspensions of tobacco mosaic virus (TMV) was measured as a function of temperature and concentration in high magnetic fields (100 kG). The temperature range was between 15 and 50 °C and the concentration range was between 4 and 20 mg/cm3. We find that the Cotton–Mouton constant (C) increases with decreasing temperature by 15%–20% over the entire range and extrapolates to infinity at a finite temperature of 110 to 150 K. At constant temperature, the measured ρ/C(ρ=number of TMV particles per cm3 of suspension) can be expanded in a power series of ρ, where the coefficients are expressed by the irreducible cluster integrals. At 20 °C the experimental values can be fitted to the linear form: ρ/λC=(2.09×1030–1.35×1015ρ)G2/cm3. For rigid cylindrical particles with l=3000 A(ring) and d=180 A(ring), and using the rigid hard particle interaction model, we find for the first order coefficient 0.62×1015, i.e., a significant deviation for the rigid hard-rod model. This deviation is also indicated by the variation of C with temperature. We discuss the results on TMV and of similar measurements on phage fd in terms of the interparticle interaction and rigidity of the particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453411
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Measurements of the conductivity and relaxation times for the micellar nematic phase of the system ammonium perfluorononanoate/H2O (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 7467-7471 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Measurements of the electric conductivity for two mixtures of ammonium perfluorononanoate and H2O are presented. The molar ratios for the two mixtures are 0.0159 (sample S2) and 0.0112 (sample S3). The mixtures show a nematic (NL) range about 8 °C wide, between a lamellar smectic and an isotropic micellar solution. The conduction is predominantly due to the NH4+ ions, and it is estimated that about 50% of the NH+4 ions have free mobility. At the same reduced temperature in the NL phase, the lower concentration mixture is more anisotropic, indicating larger micelles for the lower concentration. The reorientation of the director of the NL phase in a magnetic field is also measured. Near the NL to isotropic transition the relaxation times at 10 kG are 30 s for S2 and 80 s for S3. The divergence behavior of the relaxation times at the NL to lamellar transition is different for the two samples. Also, at corresponding temperatures, the relaxation time for the lower concentration is longer than the high concentration mixture. It is also observed that in the lamellar phase, increasing the temperature may lead to undulation of the layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451335
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    The electric conductivity of the lamellar smectic, the micellar nematic, and the isotropic micellar solution of ammonium perfluorononanoate in water (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 517-521 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present electric conductivity measurements on a mixture of 25 wt. % ammonium perfluorononanoate in H2O. The system shows a lamellar smectic phase up to 26.3 °C, followed by a nematic phase consisting of disk-like aggregates, which at 34.2 °C transforms to an isotropic micellar solution. The relative anisotropy of the conductivity increases from ∼0.07 at 34 °C to ∼0.29 at 26.3 °C. There is no discontinuity, but a small change in slope occurs at the nematic–smectic transition. The experimental results, interpreted in terms of structural models for the two anisotropic phases, shows that the aggregates in the nematic phase have diameter to thickness ratios, decreasing from about 8.3 at the lamellar to nematic transition, to about 4.0 at the transition to the isotropic phase. We estimate that about 30% of the total area are disrupted by holes or channel-like defects. The results are in agreement with previous studies on a mixture of decylammonium chloride/NH4Cl/H2O. It is also indicated that increasing the size of the aggregates increases the binding of the counterions to the aggregates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450117
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Electric conductivity measurements on the nematic states of a micellar solution of potassium laurate/1-decanol/D2O (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 6928-6932 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present electric conductivity measurements on a mixture of 25.15 potassium laurate/6.33 1-decanol/68.52 D2O by weight. The mixture shows two isotropic phases, two uniaxial nematics, and a biaxial nematic phase. The variation of the conductivities with temperature shows the phase transitions, which were also optically verified. The average conductivity does not change at the phase transitions. It shows a temperature dependence that is almost fully due to the effect of the viscosity of the aqueous phase on the ion mobility. The anisotropy of the conductivity in the uniaxial nematic phase is relatively weak. An analysis of the conductivity in terms of micellar structures suggests relatively small micelles of ellipsoidal shape. The reorientation of NC in magnetic fields of 10 kG has relaxation times of 20–40 s. The rotational viscosity is in the order of 10 P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450612
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Curvature elasticity and rotational viscosity of the nematic decylammonium chloride system (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5137-5142 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Experimental data are reported on curvature elasticity and rotational viscosity of micellar nematics formed in the decylammonium chloride/NH4Cl/H2O system. Two mixtures of different salt concentrations were studied (DACl:NH4Cl=10:1 and 20:1 by weight). The constants for the bend elasticity and the rotational viscosity were found to vary over nearly three orders of magnitude from 0.2×10−6 to 150×10−6 dyn and from 1 to about 1000 P, respectively. The large range is due to the divergence at the nematic–smectic transition. Both constants diverge with the same exponent. We obtained an exponent of 1.07±0.05 for a weight ratio DACl/NH4Cl of 20 and 0.87±0.02 for a ratio of 10, but an unexpected thermal hysteresis interfered with a reliable determination of the critical properties. Overall, the elastic properties and the divergence is this micellar nematic are similar to those observed in thermotropic nematics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454667
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Measurements of density and expansion coefficient for the nematic, lamellar smectic, and isotropic phase of micellar systems (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5011-5015 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Measurements of the density and expansion coefficient as a function of temperature are presented for two micellar systems, namely, decylammonium chloride/NH4Cl/water, and cesium perfluorooctanoate/water. The measurements cover the lamellar smectic, the nematic, and the isotropic micellar solution. The measurements show that away from the phase transitions, the density decreases smoothly with increasing temperature. At the nematic-to-isotropic transition the density shows steplike features, indicating a change in the micellar structure at the transition, with denser packing of the amphiphiles in the micelles of the isotropic phase. A similar change is observed in the lamellar to nematic transition, however, the detailed behavior at this transition showed some dependence on the history of the sample. The expansion coefficients decrease at the transitions. Considerable pretransitional behavior is observed about the lamellar-to-nematic transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456570
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    pH-based enzyme potentiometric sensors. Part 1. Theory (1985)
    s.l. : American Chemical Society
    Analytical chemistry 57 (1985), S. 1917-1920 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00286a027
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...