scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Polarized Fluorescence Studies of Orientational Order in Some Nematic Liquid Crystals Doped with Stilbene Dye

01 Mar 1991-Molecular Crystals and Liquid Crystals (Taylor & Francis Group)-Vol. 197, Iss: 1, pp 1-13
TL;DR: In this paper, the polarized fluorescence intensity for a stilbene guest molecule dissolved in nematic liquid crystals (5CB, 7CB and PCH7) has been used to study the molecular orientational order in thin aligned samples.
Abstract: The measurements of the polarized fluorescence intensity for a stilbene guest molecule dissolved in nematic liquid crystals (5CB, 7CB and PCH7) have been used to study the molecular orientational order in thin aligned samples. The temperature dependence of the order parameters ⟨P2⟩ and ⟨P4⟩ have been investigated. The attempt for the explanation of the different behaviour of ⟨P4⟩ parameter in the various liquid crystals has been undertaken. On the basis of the experimental ⟨P2⟩ and ⟨P4⟩ values some information about the orientational distribution of molecules in guest-host mixture have been obtained.
Citations
More filters
Journal ArticleDOI
TL;DR: In this paper, a conjugated polymers consisting of polythiophene and poly(p-phenylene) backbones carrying cyanobiphenyl and (−)-cholesterol as pendant groups were synthesized and characterized as a new class of optical polymers.
Abstract: Thermotropic nematic and chiral-nematic conjugated polymers consisting of polythiophene and poly(p-phenylene) backbones carrying cyanobiphenyl and (−)-cholesterol as pendant groups were synthesized and characterized as a new class of optical polymers. Spontaneous assembly of the conjugated backbone was promoted by liquid crystalline mesomorphism on the part of the pendants, thereby allowing uniaxially and helically aligned glassy films to be prepared for polarized photoluminescence (PL) studies. In the thiophene series, the conjugated backbone was found to yield an absorption peak red-shifted from those of the monomers and pendant groups. This permitted selective photoexcitation of the polythiophene backbone to be accomplished. In the p-phenylene series, the conjugated backbone did not give rise to a unique absorption peak. However, with excitation at the long wavelength edge of the absorption peak, PL of the poly(p-phenylene) backbone was found to be 1 order of magnitude stronger than that of the pendant...

43 citations

Journal ArticleDOI
TL;DR: In this paper, a theory was formulated for the description of circularly polarized fluorescence from a chiral nematic film in the spectral region outside the selective reflection band, and the experimentally determined dissymmetry factor was found to be in good agreement with the theoretical prediction with all the system parameters determined a priori.
Abstract: A theory was formulated for the description of circularly polarized fluorescence (CPF) from a chiral nematic film in the spectral region outside the selective reflection band. The CPF theory incorporates: (1) the ability of a chiral nematic film to accomplish both circular dichroism and circular polarization and (2) linearly polarized fluorescence from chromophores unaxially aligned in the nematic sublayers comprising the film. Chiral nematic fluid films consisting of a nematic fluid, BDH 18523, and a chiral dopant, cholesteryl oleate, were prepared for hosting 1,6-diphenylhexatriene as a fluorescent dye. The experimentally determined dissymmetry factor using both left- and right-handed circularly polarized excitations was found to be in good agreement with the theoretical prediction with all the system parameters determined a priori. The theory was also employed to furnish insight into the effects of the concentration of the fluorescent dye and chiral nematic film thickness on the dissymmetry factor.

38 citations

Journal ArticleDOI
TL;DR: Fluorescence lifetime in the ps range, polarized absorption, polarized fluorescence spectra and delayed luminescence time resolved spectra were measured for chlorophyll a solutions with and without β-carotene addition in nematic liquid crystal as mentioned in this paper.

27 citations

Journal ArticleDOI
TL;DR: In this article, the authors characterized the dissymmetry factor of circularly polarized photoluminescence (CPPL) for rod-like molecules of Exalite 428 helically arranged in a chiral-nematic liquid crystalline film.
Abstract: Circularly polarized photoluminescence (CPPL) was characterized for rod-like molecules of Exalite 428 helically arranged in a chiral-nematic liquid crystalline film. With an unpolarized excitation at 370nm, CPPL intensities measured at 428nm, and a selective reflection wavelength ranging from 7.2 to 72.6mum, the observed dissymmetry factor, g, was found to be in excellent agreement with theoretical prediction, without resorting to adjustable parameters. As a result, new insight into liquid crystal-induced CPPL has emerged. Specifically, it was found that circular dichroism and circular polarization of the excitation beam prior to inducing linearly polarized photoluminescence (LPPL) at quasi-nematic layers play an insignificant role. The relatively large g value in the spectral region far removed from the selective reflection band was attributed to the circular polarization of LPPL emanating from all quasi-nematic layers comprising the chiral-nematic film. In the absence of a fluorescent dye, the propagati...

22 citations

Journal ArticleDOI
TL;DR: In this article, the nonlinear refractive indices of two dyes (Sudan Black B, Sudan III) doped nematic liquid crystal were measured at low laser powers using moire deflectometry technique.

20 citations

References
More filters
Journal ArticleDOI

16,894 citations

Journal ArticleDOI
TL;DR: In this paper, an extension of the Onsager theory of dielectric polarization is presented, which is applied to liquid water under the assumption of tetrahedral coordination and directed bonds between neighboring molecules.
Abstract: An extension of the Onsager theory of dielectric polarization is presented. The local dielectric constant is approximated by the macroscopic dielectric constant of the fluid in a region outside a molecule and its first shell of neighbors rather than in the entire region exterior to the molecule. In addition to the molecular dipole moment, the average value 〈cosγ〉Av of the cosine of the angle between neighbor dipoles is a determining factor. Hindered relative rotation of neighboring molecules produces a correlation between their orientations and prevents 〈cosγ〉Av from vanishing. The theory is applied to liquid water under the assumption of tetrahedral coordination and directed bonds between neighboring molecules.

1,660 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe a mittlere Innere Feld einer nematischen Molekülanordnung abgeleitet, and gezeigt, daß this Innere Field in einem gewissen Temperaturbereich einen nematicalhen Ordnungszustand bewirken muß and daß dieser ordnung sustand was with einer bestimmten Temperatur diskontinuierlich und unter Energieaufnahme in die isot
Abstract: Mit Beschränkung auf den Dipol-Dipol-Anteil der reinen Dispersionswechselwirkungen als dem für die Existenz einer kristallinflüssigen Phase vermutlich maßgebenden Teil der zwischenmolekularen Kräfte wird durch geeignete Mittelungen ein Ausdruck für das auf das Einzelmolekül wirkende mittlere Innere Feld einer nematischen Molekülanordnung abgeleitet. Es wird gezeigt, daß dieses Innere Feld in einem gewissen Temperaturbereich einen nematischen Ordnungszustand bewirken muß und daß dieser Ordnungszustand bei einer bestimmten Temperatur diskontinuierlich und unter Energieaufnahme in die isotrope Molekülanordnung übergehen muß. Die Theorie liefert also einen Umwandlungspunkt 1. Ordnung, wie er experimentell auch beobachtet wird. Die Umwandlungstemperatur wird im wesentlichen durch die Anisotropie der optischen Übergangsmomente der Moleküle bestimmt.

1,328 citations

BookDOI
01 Jan 1970
TL;DR: In this paper, the authors present a NMR study of the transition of a mixture of two Isomeric Cyano-Ester homologous series, showing that the phase transition of one of the two isomeric versions of this series is a transition of the other.
Abstract: Some Novel Ferroelectric Smectic Liquid Crystals.- Liquid Crystalline Esters of Phenylhydroquinone and 3-Phenyl 4-Hydroxybenzoic Acid.- The Synthesis and Characterization of Some Perylene and Anthraquinoic Dichroic Dyes for Liquid Crystal Display Applications.- Some New Thermotropic Discogens.- Syntheses and Properties of Liquid Crystalline Heterocycloalkanes.- Characterization of Two Isomeric Cyano-Ester Homologous Series -I.- Effects of Molecular Length on Nematic Mixtures - IV: Structure Effects on Viscosity of Ester Mixtures.- Orientational Disorder in Smectic Liquid Crystals: An Aspect of Structure that has to be Included.- Effect of Molecular Structure of Rigid - Flexible Polyesters on Their Thermotropic Liquid Crystalline Properties.- Relationships Between Molecular Structure and the Incidence of Crystal B and Hexatic B Phases.- Characterization of the Phases of Two Isomeric Cyano-Ester Homologous Series - II.- Unusual Glass Transition of Smectic Liquid Crystal in p-n-Hexyloxybenzylidene-p'-Butylaniline.- Some High Electric Field Effects in Nematic Liquid Crystals.- Application of Generalized Van Der Waals Theory of Homologous Nematogens - Part 1: Trans-4-Ethoxy-4'-N-Alkanoyloxyazobenzenes..- Application of Regular Solution Theory to Discotic Mesophases: Calculation of Phase Diagrams Exhibiting Minima.- Extension of McMillan's Model to Liquid Crystals of Disc-Like Molecules.- Thermotropic Liquid-Crystalline Polymers with Mesogenic Groups and Flexible Spacers in the Main Chain.- Effect of Mesogenic Unit and Spacer Structures on the Thermotropic Properties of Main Chain Liquid Crystal Polyesters.- The Role of Sequence Distribution on Liquid Crystalline Properties of Aromatic Copolyesters.- Diffusion of Rigid Polyamides Through Swollen Gel of Same.- The Molecular Weight Dependence of the Splay and Bend Elastic Constants of a Polymer Liquid Crystal.- DSC, Miscibility and X-ray Studies of the Thermotropic Liquid Crystalline Polyesters with Aromatic Moieties and Flexible Spacers in the Main Chain.- Influence of the Leprosy Drug, Dapsone, on the Phase Transitions of the Lyotropic, Dipalmitoy1 Phosphatidylcholine (DPPC).- Nonaqueous Lyotropic Liquid Crystals of Lecithin and Oligomers of Polyethylene Glycols.- The Diamagnetic Anisotropy of Lyotropic Nematic Mesophases.- Physical Models of Lipid Membranes in Latent Cancer Cells: Ordering Effects of Petroleum Hydrocarbons.- Adiabatic Compression: A New Method to Measure Latent Heats in Phospholipid Bilayers.- Anisotropy of the Electric Conductivity in Amphiphilic Liquid Crystals.- Phase Transition Properties of Bilayers of Mixed Lipids and Their Covalent Analogs.- On The Orientation of Liquid Crystals by Monolayers of Amphiphilic Molecules.- Refractive Index Measurements Using a Double Arm Converging Beam Interferometer.- A Pulsed NMR Study of Transient and Persistent Molecular Order in Nematic Liquid Crystals.- The Effect of Twist on Biaxial Ordering in the Cholesteric Phase.- Deuteron Magnetic Relaxation and Molecular Dynamics in Thermotropic Liquid Crystals.- An Effective Proton Hyperfine Tensor for Di-Tertbutylnitroxide.- Alkyl Chain Flexibility in Liquid Crystals.- Orientational Order in Binary Mixtures of Nematic Liquid Crystals.- The Effect of the Tricritical Region on the Smectic A - Smectic C Transition.- Spatial Correlations in Nematic Liquid Crystals.- Molecular Structure and Ordering in Liquid Crystals.- New Liquid Crystals, Polymeric and Monomeric, Derived From Binaphthyl.- Ioneneomeric Liquid Crystals.- Mesomorphic Properties of an Homologous Series of Alkyl-Terminated Enamine-Ketone Containing Liquid Crystals.- Liquid Crystalline Polymers with Amphiphilic and Non Amphiphilic Side Chains - Effect of the Main Chain on the Phase Behaviour.- The Fluid Mesophases of Polar Rods.- The Nematogeneity of Some Hydrocarbons.- Some Heterocyclic Analogues of Biphenyl Mesogens.- Alignment of Liquid Crystal Molecules on Various Surfaces: Myths, Theories, Facts.- Development of Dual-Frequency Addressable Liquid Crystals.- Dielectric Studies of Monoester and Diester Nematogens.- Intermolecular Guest-Host Interactions and the Optical Order Parameter of Pleochroic Dyes.- Liquid Crystal Alignment on Substrate Surfaces, A Collective Phenomenon.- Alignment of Liquid Crystals in the Vicinity of the SmA-N Transition.- Nematic-Substrate Interaction and the Boundary Layer Phase Transition.- Optical Properties of the Blue Phase of Cholesteric Liquid Crystals.- Lattice Parameters in Blue Phase Mixtures.- Blue Phase Structure Analysis by Optical Bragg Diffractions.- Mesomorphic Polymers as Three Component Systems.- Colloidal Crystals and Glasses.- Self Diffusion Constant and Viscosity of Charged Polystyrene Colloids.- Influence of Molecular Conformation on the Helical Twisting Power of Terpenes in Nematic Liquid Crystals.- Vibrational Spectra of Liquid Crystals XIII: Crystallization Kinetics Study of 4, Octyloxy, 4', Cyano Biphenyl by Rapid Raman Spectroscopy..- Nuclear Spin-Lattice Relaxation Due to Orientational Fluctuation in Smectic Liquid Crystals.- NMR Studies of Molecules Oriented in Mixed Thermotropic Liquid Crystals of Opposite Diamagnetic Anisotropies.- Discotic Mesophase: A Complementary Review.- Identification of the Structure of Mesomorphic Polymers by Means of their Miscibility.- Effect of Molecular Structure on Mesomorphism: Difluorinated Siamese Twin Mesogens.- Anisotropy Induced in a Semi-Flexible Polymer by a Liquid-Crystalline Solvent.- Electrooptical Behaviour of a Novel Strong-Weak Anchored Nematic Layer: First Measurements of MBBA Flexoelectric Coefficient of Splay elz.- On Thermotropic Disc-Like Mesogens.- On The Nature of the Smectic-C Phase.- Contributors.

1,036 citations

Journal ArticleDOI
TL;DR: Evidence is presented indicating that the site of iodoacetamide inhibition in photosynthesis is solely the photosynthetic carbon cycle since the synthesis of reducing power and reduced triphosphopyridine nucleotide and the evolution of O2 is not impaired.
Abstract: An attempt has been made to determine why iodoacetamide at certain concentrations inhibits photosynthesis but does not affect respiration if the site of inhibition of both processes is considered to be the same enzyme, namely, ᴅ-glyceraldehyde-3-phosphate dehydrogenase. Evidence is presented indicating that the site of iodoacetamide inhibition in photosynthesis is solely the photosynthetic carbon cycle since the synthesis of reducing power (adenosine triphosphate and reduced triphosphopyridine nucleotide) and the evolution of O₂ is not impaired. At a concentration of 5·10⁻⁵ M, iodoacetamide is a strong inhibitor of CO₂ fixation by the isolated spinach chloroplast and by the reconstituted system as defined by ARNON. At this concentration glyceraldehyde-3-phosphate dehydrogenase is not affected. Phosphoribulokinase, an enzyme considered to be exclusively concerned with photosynthesis is sensitive in this range of inhibitor. It was concluded that at low concentrations of iodoacetamide, this phosphorylation is blocked thus stopping photosynthesis while at this same concentration all enzymes of respiration are unaffected. The significance of the lack of accumulation of ribulose-5-phosphate in poisoned intact cells is discussed.

291 citations