Comparative Study of Mixed Monolayers of a Calixarene with a Fatty Acid and a Non-Amphiphilic Nematic Liquid Crystal

Abstract

Many nematic liquid crystals (NLCs) lack a polar headgroup and thus are not able to form stable monolayers at the air/water (a/w) interface. A way to obtain monomolecular films of these compounds is to incorporate them into host monolayers of amphiphilic molecules. We report a comparative investigation of mixed films of Calix[4]resorcinarene O-octacarboxymethylated (CRO) with the non-amphiphilic NLC MBBA and with the amphiphilic stearic acid (SA). The comparative study is useful for a better understanding of the characteristics of the CRO-MBBA mixed films. Surface-pressure and surface-potential measurements on the monolayers at a/w interface, as well as ellipsometric and spectroscopic measurements on transferred Langmuir-Blodgett (LB) films, confirm that MBBA is additively incorporated into CRO films.     

Mixed density wave state in quasi-2D organic conductor

The density wave phase of α-$\alpha \mathrm{-}$(BEDT-TTF)₂KHg(SCN)₄ was investigated by transport properties and magnetic susceptibility. The density wave transition was observed as a broad increase at T_DW$T_{\mathrm{DW}}$=9 K by resistance measurement. Temperature dependence of the static magnetic susceptibility χ$\chi$ shows a large Curie tail below 100 K. By subtracting the Curie component, we found that the magnetic susceptibility increases like weak ferromagnetism with decreasing temperature below 7.4 K. The gradual increase of χ$\chi$ below T_DW$T_{\mathrm{DW}}$ is not expected in simple CDW or SDW, where the magnetic susceptibility decreases with decreasing temperature due to the reduction of Pauli paramagnetic component. To explain the weak ferromagnetic behavior, we consider the coexistence of CDW and SDW. We propose a model of the mixed density wave, where CDW exists with antiferromagnetically coupled canting spins.     

Fluorescence properties of polyamines bearing two terminal quinoline fragments in water

Fluorescence properties of polyamines bearing two terminal quinoline fragments with different polyamine chain length, such as ethylenediamine (L0), diethylenetriamine (L1), and triethylenetetramine (L2), have been studied in water. These ligands show Zn²⁺-induced fluorescence enhancement, while showing almost no enhancement with other cations. However, stability constants for Zn²⁺ coordination and fluorescence response against Zn²⁺ depend strongly on the polyamine chain length. The chain length also affects the fluorescence wavelength. The Zn²⁺-L1 and Zn²⁺-L2 complexes show emission at 410 nm, while Zn²⁺-L0 complexes show a blue-shifted emission at 375 nm due to the partial charge transfer from the excited state quinoline to the Zn²⁺ center.     

Revisit to the photocrosslinking behavior of PVA‐SbQ as a water‐soluble photopolymer with anomalously low contents of quaterized stilbazol side chains

The photocrosslinking behavior of poly(vinyl alcohol) (PVA) substituted with 0.1, 0.3, 1.3, and 4.0 mol % of styrylpyridinium (SbQ) (PVA‐SbQs) side chains was reinvestigated. Even‐order derivative spectra of films of PVAs loaded with 0.1 and 0.3 mol % of SbQ revealed the presence of subpeaks owing to vibrational transitions, whereas PVA bearing 1.3 and 4.0 mol % of SbQ displayed a new blue‐shifted band (H‐band) at 328 nm due to H‐aggregation. Changes in derivative spectra disclosed the rapid disappearance of the H‐band of PVA‐SbQs under UV irradiation within exposure doses of 10 mJ cm^?2. On the other hand, the films of the PVA‐SbQs were insolubilized upon UV irradiation at exposure doses of 2 and 3 mJ cm^?2, respectively, leading to the conclusion that the high photosensitivity comes from the photodimerization of H‐aggregate as a ground‐state dimer. Fluorescence measurements implied the presence of J‐aggregate at 386 nm, but the involvement of the J‐aggregation in photocrosslinking was excluded because of its negligible fraction. A photosensitive emulsion of poly(vinyl acetate) emulsified with PVA‐SbQ exhibited similar changes in higher‐order derivative spectra in film and applied to fabricate a stencil for screen printing with aid of an LED‐emitting 375 nm light. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Movement of Polymer Segments by Exciplex Emission of Pyrene and N,N-Dimethylaniline at the Polymer–Silica Interface

Intermolecular interaction between pyrenyl units linked on the silica surface and N,N-dimethylaniline (DMA) units of polymer segments coated on the silica was investigated. Exciplex emission between these units was observed. The spectral shape and the intensity of the exciplex emission depended on the sample preparative conditions. Emission decay curves had no rise components, which showed that preformed ground-state complexes between pyrene and DMA existed and there were various microenvironmental sites around the preformed complexes just after sample preparation. Annealing of the samples made the exciplex emission wavelength shift and its intensity increase, which meant that polymer segments that contacted with the silica surface moved to make the stable conformations during annealing. It was revealed that DMA units of polymer segments are more stable when they face to the polymer–silica interface than when they become part of the polymer bulk. After the samples were kept at room temperature for 1 month, the spectra of all the samples became the same, which showed that the most stable conformations of the polymer segments were at the polymer–silica interface.     

CALET Observations during the First 5 Years on the ISS

Physics of Atomic Nuclei - The CALorimetric Electron Telescope CALET is collecting science data on the International Space Station since October 2015 with excellent and continuous performance....     

On a Normal Integral Basis Problem over Cyclotomic Zp-extensions, II

Let p be an odd prime number, K an imaginary abelian field with ζ_p∈K^×, and K_∞/K the cyclotomic Z_p-extension with its nth layer K_n. In the previous paper, we showed that for any n and any unramified cyclic extension L/K_n of degree p, LK_n+1/K_n+1 does have a normal integral basis (NIB) even if L/K_n has no NIB, under the assumption that p does not divide the class number of the maximal real subfield K⁺ (and some additional assumptions on K). In this paper, we show that similar but more delicate phenomena occur for a certain class of tamely ramified extensions of degree p.     

Highly sensitive fluorescence microscope system for single biological cell using laser excitation and digital image processing and display

A novel type of laser-excited fluorescence microscope system is reported, which, for the first time, realizes excellent sensitivity and spatial resolution in biological and medical applications using an ultra-high sensitivity image camera and digital image processing technique for three-dimensional display of the detected fluorescence intensity across a single cell. Experimental studies are also presented on the fluorescence intensity distribution of Rhodamine 6G adsorbed in an OH gel as a simple cell model and also of a hematoporphyrin-derivative (HpD) taken up by a cultured esophagus cancer cell.