[en] We report a liquid-crystal (LC) photoalignment material with a high photosensitivity based on the fluorinated poly(arylene ether) containing a chalcone unit in the main chain. The fluorinated poly(arylene ether) exhibited defect-free homogeneous alignment of LCs upon irradiation of linearly polarized UV light for 10 s. Spectroscopic analyses revealed that [2+2] cycloaddition between the chalcone moieties generated the surface anisotropy to induce an efficient alignment of LCs

[en] The pathway producing imide ring closure during the thermal imidization of poly(amic acid) (PAA) was investigated in detail using a new analytical method, two-dimensional (2D) Raman correlation spectroscopy. The signs of the cross peaks in synchronous spectra provided evidence of the thermal imidization of PAA into PI as the heating temperature increased. The signs of the cross peaks in asynchronous spectra suggested that the limide-related modes changed prior to the amide or carboxylic mode, which indicates that cyclization occurred before the amide proton was abstracted

[en] We report a liquid crystal photoalignment material with high photosensitivity and excellent thermal stability. The chloromethylated aromatic polyimide exhibited defect-free homogeneous alignment of liquid crystals upon irradiation of polarized deep ultraviolet (UV) for 50 s. The aligning ability of the film was retained up to 210 deg. C, and the cell containing liquid crystals could be stored at 85 deg. C for more than 14 days without any deterioration. FT-IR and UV-vis spectra confirmed that the alignment was induced by photodecomposition of polyimide, drastically accelerated by the introduction of chloromethyl side group

[en] We reported the first example of the green lyotropic chromonic liquid crystalline compound based on perylene bisimide. The color tuning of perylene bisimide was achieved by introducing electron-donating substituents at the bay area. The syntheses proceeded in good yields via a short and convenient synthetic route. This dye exhibits good thermal stability, solubility in water and organic solvents as well. The structure was characterized by ¹H-NMR, ¹³C-NMR, mass, and UV/Vis spectroscopies. Aqueous solution of hydrochloride salt exhibited lyotropic chromonic liquid crystalline columnar phase at room temperature examined by polarized optical microscopy. Perylene bisimides (PBIs) are widely used as dyes and pigments since they show outstanding chemical, thermal and photochemical stability. Compared to other dyes and pigments, PBIs have advantages such as better solubility, synthetic simplicity, and less trouble in purification. Beside the conventional uses, PBIs are key chromophores for high-tech applications such as re-prographic processes, fluorescent solar collectors, photovoltaic cells, optical switches, and lasers. In this context, PBIs are generally referred to as functional dyes. Especially, PBIs having ionic periphery have attracted much attention because they can form lyotropic chromonic liquid crystal (LCLC) in aqueous solution. The anisotropic orientation of molecules with π-π stacking of aromatic core can exploit their intrinsic properties most efficiently in the potential applications such as coatable polarizers, oriented optical films, and biosensors

[en] A novel tetrathiafulvalene (TTF)-based main-chain polymer (6TTF-polymer) was successfully synthesized via a condensation polymerization between a newly synthesized dihydroxy TTF derivative and a malonyl chloride, and its chemical structure was characterized by spectroscopic techniques. Molecular weight of the 6TTF-polymer (9,030 g/mol by gel permeation chromatography) was large enough to form the ductile film. The electrochemical and optical properties of the 6TTF-polymer were further estimated by cyclic voltammetry, ultraviolet and photoluminescence spectroscopes. The highest occupied molecular orbital level (E_H_O_M_O = .4.79 eV) and band-gap energy (E_g = 1.91 eV) of the 6TTF-polymer suggested that TTF-based polymer could act as a good electron donating material for the optoelectronic applications

[en] A polymer-stabilized vertical alignment (PS-VA) mode using a new type of photoreactive monomer for polymer stabilization of the liquid crystal (LC) director was developed. Conventional reactive mesogens having a higher molecular weight than those of the host LC tend to aggregate and form large-sized polymer grains when exposed to ultraviolet (UV) light, subsequently deteriorating the quality of the dark state. To address these problems, bis(4-hydroxyphenyl) diacrylates were synthesized with four different linking groups as stabilizing monomers (SMs) which have molecular weights similar to that of the host LC. Their stabilizing characteristics with respect to the molecular size and polarity of SMs were evaluated by examining the electro-optic characteristics of LC cells after UV irradiation. The results showed that the SM containing a small linking group in size between biphenyls with high polarity was favored to achieve excellent polymer stabilization. The SM containing an ether linkage showed excellent electro-optic characteristics with no large-sized polymer grains even in the absence of a photo-initiator. Consequently, we anticipate that SMs, polar and smaller in size, can improve the electro-optic characteristics in PS-VA mode. (paper)

[en] 4,4'-Dihydroxychalcone was synthesized under ultrasonic irradiation in the presence of HCl gas as a catalyst. It provided a convenient procedure with shorter reaction time and higher yield compared with conventional methods. The factors influencing the yield were discussed, and the photochemical properties of 4,4'-dihydroxychalcone were also studied.

[en] We have demonstrated cost-effective ITO-free polymer solar cells (PSCs) with ink-jet-printed current collecting Ag grids in combination with highly conductive PEDOT:PSS as a composite transparent electrode. By ink-jetting of Ag nano-particle solution, we were able to obtain ink-jet-printed Ag grids with sheet resistance of 15.8 Ω/square and optical transmittance of 82.51% at 550 nm wavelength. Furthermore, the ITO-free PSC with the composite transparent anode on flexible substrates exhibited excellent cell-performances: fill factor of 64.72%, short-circuit current density (J_sc) of 6.301 mA cm⁻², open-circuit voltage (V_oc) of 0.562 V and power conversion efficiency of 2.292%, indicating the ink-jet-printed grid-based electrode is a visible alternative to cost-intensive sputter-grown ITO electrodes and a promising printing-based electrode for realization of fully printed and flexible ITO-free photovoltaic devices. (paper)

[en] A gel polymer electrolyte (GPE) was successfully prepared by means of an in situ cross-linking reaction of poly(2-vinylpyridine-co-styrene) and oligo(ethylene oxide) with epoxide functional groups at 65 °C without using a polymerization initiator. A stable gel polymer electrolyte could be obtained by adding only 1% of a polymer gelator. The ionic conductivity of the GPE containing 99 wt% of liquid electrolyte was measured to be ca. 10⁻² S/cm at the ambient temperature. The ionic conductivity of the resulting GPE was comparable to that of a pure liquid electrolyte. The electrochemical stability window of the prepared gel polymer electrolytes was measured to be 5.2 V. The test cell carried a discharge capacity of 133.2 mAh/g at 0.1 C and showed good cycling performance with negligible capacity fading after the 200th cycle, maintaining 99.5% coulombic efficiency throughout 200 cycles. The resulting gel polymer electrolyte prepared by in situ thermal cross-linking without a polymerization initiator holds promise for application to on the high power lithium-ion polymer batteries.

[en] There is considerable difficulty in fabricating a reflector with embossing in an array substrate using a conventional single gap transflective fringe-field switching nematic liquid-crystal display. In order to solve this problem, we propose a new structure, which consists of a reflector on a colour filter substrate. The newly proposed structure with a complex field direction has problems such that the voltage-dependent transmittance and reflectance curves do not match each other, which necessitate a dual driving circuit. This paper reports the optimized electrode structure and calculated electro-optical results realizing a single gamma curve and high light efficiency