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Phthalocyanines (Pcs) are organic compounds able to act as chemical recognition systems because of the various physical effects induced in them by interaction with a large number of gases. The gas response, stability and other sensing characteristics of the Pc films are affected by many factors, such as film morphology, molecular orientation and so on. The interaction between the Pc coatings and the gas molecules may be classified in terms of irreversible chemical affinity, reversible (usually charge transfer) chemical reaction or sorption. The nature of the interactions between the coating and vapor molecules determines the selectivity, sensitivity, signal kinetics, and the reversibility of the sensor. The magnitude of these interactions may be conveniently described in the frame of the linear sorption energy relationship (LSER) model that has been shown to be very efficient at predicting the behavior of polymer-based sensors. In this paper, the effect of coating parameters on sensing properties and sensing mechanism are reviewed. We have proposed an alternative way to achieve optimal sensor performance: liquid crystalline Pcs forming self-ordered thin films of defined area and thickness simply by heating the sample over the phase transition temperature and synthetized mesomorphic and functionalized phthalocyanines, to develop sensors based on mass-sensitive transducers (quartz crystal microbalance, QCM). Phthalocyanines used are discussed in terms of their physical and chemical properties, as well as their sensing properties: sensitivity, selectivity and reversibility. We showed our results with LSER and the results are in good agreement with this theory.

We consider a model of liquid crystals, based on a nonlinear hyperbolic system of differential equations, that represents an inviscid version of the model proposed by Qian and Sheng. A new concept of dissipative solution is proposed, for which a global-in-time existence theorem is shown. The dissipative solutions enjoy the following properties:

• (i)they exist globally in time for any finite energy initial data;
• (ii)dissipative solutions enjoying certain smoothness are classical solutions;
• (iii)a dissipative solution coincides with a strong solution originating from the same initial data as long as the latter exists.

We use modulation theory to analyze the interaction of optical solitons and vortices with a dielectric interface between two regions of nematic liquid crystals. In the analysis we consider the role of nonlocality, anisotropy and nonlinear reorientation and compare modulation theory results with numerical results. Upon interacting with the interface, nematicons undergo transverse distortion but remain stable and eventually return to a steady state, whereas vortices experience an enhanced instability and can break up into bright beams or solitary waves.

Inspired by condensed matter physics we propose a new, asymmetric, family of cosmic strings. These strings present a conical curvature singularity plus a surrounding region of alternating positive and negative curvature as the azimuthal angle is changed. Their sources include both positive and negative mass density regions.

In the present work, we report the blue phase (BP) in a binary mixture of cholesteryl nonanoate (CN) and N-(4-ethoxybenzylidene)-4-butylaniline (EBBA). The mixture exhibits BP over a temperature range of 2.3 K at optimum composition (50:50) of liquid crystals (LCs). The effect of silica nanoparticles (SNPs) doping on thermal stability of BPs has also been demonstrated and nearly 6 K wide BP temperature range was achieved at 0.5 wt.% of SNPs. A porous type texture was also observed during the BP formation process in the doped samples.

This paper reports the tunable transmission properties of asymmetric one-dimensional periodic structure (1DPS) composed of SiO₂ and anisotropic metamaterial (AMM) layers with defect of liquid crystal (LC) sandwiched by two SiO₂ layers, i.e., (SiO${}_2|$AMM)${}^3|$SiO${}_2|$LC$|$SiO${}_2|$(SiO${}_2|$AMM)³ using the transfer matrix method (TMM). We have studied the optical properties of the periodic structure (SiO${}_2|$AMM)³$|$SiO${}_2|$LC$|$SiO${}_2|$(SiO${}_2|$AMM)³ with a different incident angle of the electromagnetic wave for particular director angle of LC molecules. The tunability of the transmission property of the considered 1DPS shows that the transmittance depends upon the orientation of LC molecules. Such an asymmetric periodic structure (1DPS) composed of SiO₂ and AMM with a defect of LC sandwiched by two SiO₂ layers, (SiO₂$|$AMM)${}^3|$SiO${}_2|$LC$|$SiO${}_2|$(SiO${}_2|$AMM)³, may be used as a tunable optical filter and bi-stable device.

In this work, the effect of thin films on the thermotropic and thermo-optical properties and peculiarities of the phase transitions between the smectic A and isotropic liquid have been investigated. Peculiarities of the heterophase regions of the straight smectic A-isotropic liquid and reverse isotropic liquid-smectic A phase transitions have been studied.

Change of morphologic properties of the heterophase regions, shift of the phase transition temperatures and the change of temperature widths of these heterophase regions under thin film influence have been observed.

The shear-sensitive liquid crystal coating (SSLCC) technique is investigated in the high-speed jet flow of a micro-wind-tunnel. An approach to measure surface shear stress vector distribution using the SSLCC technique is established, where six synchronous cameras are used to record the coating color at different circumferential view angles. Spatial wall shear stress vector distributions on the test surface are obtained at different velocities. The results are encouraging and demonstrate the great potential of the SSLCC technique in high-speed wind-tunnel measurement.

A comparative study on the optical, morphological and laser-induced damage characteristics of rubbed polyimide, SiO₂ thin films by glancing angle deposition, and the corresponding liquid crystal (LC) retarders, is presented in this paper. SiO₂ inorganic thin films were prepared with a deposition angle of 45${}^{\circ }$, and traditional polyimide (PI) films were prepared by spin coating and rubbing. The experimental results indicate that the SiO₂ thin films have a good transmittance and resistance to laser damage. The transmittance of the SiO₂ thin films was above 92% in the wavelength range 400–1200 nm, and that of the corresponding LC retarder was approximately 90% in the wavelength range 800–1200 nm. The laser-induced damage threshold of the SiO₂ thin films reached 32.6 J/cm², and that of the corresponding LC retarder was 1.84 J/cm². These results are better than those of the PI alignment films. SiO₂ thin films have potential for use in the LC optical devices for laser applications.

In this paper, a device and technique for circular dichroism (CD) recording in the fixed spectral range and in real time are developed. In CD spectroscopy the requirement for precision measurements of the light intensity is one thousandth of a percent. In order to expand the dynamic range the control of data accumulation time is provided. Two NMOS sensor linear arrays provide an excellent linearity of response. The basic functional unit of the proposed device is a circular diffraction waveplate (CDW). CDW analytical and numerical models are given.

A density functional theory (DFT) based multi-step simulation method is used to characterize the detailed molecular structure and inter/intra- molecular interactions of two benchmark liquid crystals (LC) 5CB, 8CB and a novel tri-biphenyl ring bent core LC material. The method uses hybrid DFT at the B3LYP/6-31G* level to obtain molecular structure and Raman data. These results are fed to a crystal packing simulation to find possible crystal structures. A pico-second quantum mechanics/molecular mechanics (QM/MM) simulation model is built for the selected structures with lower overall energy as well as optimal density. The stabilized crystal structures are then extended into a super cell, heated and simulated using a mixed force field and nano-second molecular dynamics (MD). The described simulation process sequence provides predictions of molecular Raman spectrum, LC density, isotropic depolarization ratio, ratio of differential polarizability, order parameters, molecular structures, and rotating Raman spectrum of the different mesophases. The Raman spectra, order parameters and depolarization ratios all agree well with existing experimental and previous simulation results. The study of the novel tri-biphenyl ring bent core LC system shows that the ratio of differential polarizability depends on intra-molecular interactions. The findings presented in this manuscript contribute to the on-going efforts to establish links between LC molecular structures and their properties, including optical behavior.

Two series of porphyrin liquid crystalline compounds, meso-tetra-[(p-alkacyloxy-m-ethyloxy)phenyl]porphyrin (TPAMEP), and [5-(p-alkacyloxy) phenyl-10,15,20-tri-phenyl] porphyrin (APTPP) are synthesized and display a hexagonal columnar discotic columnar (Col_h) phase. Their structure and properties were studied by elemental analysis, molar conductance, UV-visible and infrared spectra. Luminescence spectra of the compounds were discussed. Quantum yields of the Q band are in the region 0.007935-0.05847. The electrochemical studies show that the redox potentials do not change with the variation of the chain length. The surface photovoltage (SPV) response of the compounds was investigated by means of surface photovoltage spectroscopy (SPS) and field-induced surface photovoltage spectroscopy (FISPS), and the bands are analogous with the UV-visible absorption spectra.

A series of tris[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] rare earth(III) complexes M₂[Pc(OC₈H₁₇)₈]₃ [M = Eu, Gd, Y, Lu] has been prepared by the reaction of corresponding bis[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] rare earth complexes with M(acac)₃·nH₂O in refluxing 1,2,4-trichlorobenzene. These liquid crystalline sandwich, triple-decker complexes were characterized by elemental analysis and various spectroscopic methods including ¹H NMR, UV-vis, IR and mass spectroscopies. Their liquid crystal phase transition behavior was studied by Polarized Optical Microscope, Differential Scanning Calorimeter and X-ray diffraction. The complexes, with octyloxy attached as side chains, showed rectangular columnar liquid crystal phases in a liquid crystal temperature range between 83 and 305°C. In addition to the rare earth contraction, both the transition temperature and the wide temperature range of the mesophase show a slight but obvious trend to decrease, respectively, in the same order. In contrast, the molecular packing of these complexes as revealed by X-ray diffraction was found to be almost independent of the ionic size of the central rare earth.

Dielectric spectroscopy, at room temperature (20°C), is used to study the dielectric response of ternary mixtures of commercial nematic liquid crystal mixtures E7 and E33, an organic solvent N-Methyl-2-Pyrrolidone (NMP) and a triblock polymers in the frequency range from 0.01 Hz to 1 MHz. The results indicate a dielectric relaxation in the hectohertz region. Individually, both E7 and NMP have rather large low frequency conductivities; however, the low frequency (0.01–10 Hz) behavior of the mixtures has no such behavior. We attribute this behavior to an ion getter effect of the triblock polymer surfactant. Optimized ternary mixtures obtain a real dielectric constant near 230, and loss tangent less than 0.05 at frequencies near 10 mHz.