Molecular design,synthesis, and properties of Y‐type nonlinear optical polyester containing tricyanovinylthiophene with enhanced thermal stability of second harmonic generation

1‐{3,4‐Di‐(2‐hydroxyethoxy)phenyl}‐2‐(2‐thiophenyl)ethene (5) was prepared and condensed with terephthaloyl chloride to yield polyester (6). Polymer 6 was reacted with tetracyanoethylene to give a new Y‐type polyester (7) containing 1‐(3,4‐dioxyethoxy)phenyl‐2‐{5‐(2,2,3‐tricyanovinyl)‐2‐thiophenyl)}ethenyl groups as NLO‐chromophores, which are components of the polymer backbones. Polyester 7 is soluble in common organic solvents such as N,N‐dimethylformamide and acetone. Polymer 7 showed a thermal stability up to 300 °C in thermogravimetric analysis with glass transition temperature (T_g) obtained from differential scanning calorimetry near 126 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at the 1560 nm fundamental wavelength was around 6.57 × 10^?9 esu. The dipole alignment exhibited high thermal stability up to the T_g, and there was no SHG decay below 125 °C due to the partial main‐chain character of polymer structure, which is acceptable for NLO device applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1911–1919, 2009     

Studies on organo-phosphorus, -arsenic,and -antimony polytungstates and polymolybdates: V. Syntheses and structures of benzylarsonic polymolybdates

In order to investigate the influence of organic groups on the structural types of organoarsenic polymolybdates, benzylarsonic acid has been selected to react with sodium molybdate. Three new complexes have been synthesized and characterized: [C(NH₂)₃]₄ [(C₆H₅CH₂As)₂Mo₆O₂₄] (1), Cs₄[(C₆H₅CH₂AS)₂Mo₆O₂₄]·5H₂O ( 2 ) and [(n-C₄H₉)₄N]₃Na[(C₆H₅CH₂As)₂Mo₆O₂₄] · 6H_aO( 3 ). Molecular structure of compound 1 has been determined by means of single-crystal X-ray diffraction studies. It is monoclinic, space group P 2 ₁/n with cell dimensions of a = 12 . 342( 2 ), b = 18.621( 2 ), c = 10.042( 2 )Å, β = 105.80(1)°, V = 2220.5 ų, z = 2, μ = 15.854 cm^?1, R = 0.023. It is demonstrated that the structural types of benzylarsonic polymolybdates are the same as those for alkylarsonic polymolybdates but different from those for arylarsonic polymolybdates. Their elemental analyses, IR and UV spectra and electrochemical behaviors in aqueous solution have been reported. It is suggested that the arsenic—carbon bond has great influence on the structural types of organoarsenic polymolybdates.     

Spatial inhomogeneity of the interaction between bistable ferromagnetic wires

An experimental study and a theoretical calculation are presented of the hysteresis loop of two bistable ferromagnetic wires. A new effect—an asymmetry of the shift of the switching field at the first and the second Barkhausen jump—is found experimentally. The effect is explained as a consequence of the spatial dependence of the stray field. It is also reproduced within our recent calculation of the stray field from the magnetisation profile. Theoretical results qualitatively agree with the experimental data.     

Removal of acidic dyestuffs in aqueous solution by nanofiltration

Separation of acidic dyestuffs, including Acid red 4, Acid orange 10, and Acid red 27, from aqueous solution by nanofiltration (NF) was shown to be a feasible process to accomplish an effective removal over a broad operational range. For most experiments conducted in this study, dyestuff rejections of greater than 98% were achieved. The permeate flux for experiments conducted with various dyestuffs was increased with increasing operating pressure and solution temperature. The permeability was increased and the rejection of dyestuffs was slightly decreased with increasing cross-flow velocity of solution. The effect of solution pH on the rejection of dyestuff was elucidated by the electrostatic characteristics between the species of dyestuff and the membrane surface. Maximum permeability was obtained for experiments operated in aqueous solution of pH 5, which was close to the isoelectric point of the membrane.     

Signal-Induced Release of Guests from a Photolatent Metal–Phenolic Supramolecular Cage and Its Hybrid Assemblies

The coordination chemistry of plant polyphenols and metal ions can be used for coating various substrates and for creating modular superstructures. We herein explored this chemistry for the controlled release of guests from mesoporous silica nanoparticles (MSNs). The selective adsorption of tannic acids (TAs) on MSN silica walls opens the MSN mesoporous channels without disturbing mass transport. The channel may be closed by the coordination of TA with Cu^II ions. Upon exposure to light, photolysis of Trojan horse guests (photoacid generators, PAGs) leads to acid generation, which enables the release of payloads by decomposing the outer coordination shell consisting of TA and Cu^II. We also fabricated a modular assembly of MSNs on glass substrates. The photoresponsive release characteristics of the resulting film are similar to those of the individual MSNs. This method is a fast and facile strategy for producing photoresponsive nanocontainers by non-covalent engineering of MSN surfaces that should be suitable for various applications in materials science.     

Determination of vanadium in titanate-based ferroelectrics by INAA with discriminating gamma-ray spectrometry

Instrumental neutron activation analysis was used for determination of vanadium mass fraction in crystals of incipient ferroelectric strontium titanate and ferroelectric barium titanate. In order to improve vanadium limit of detection, discriminating gamma-ray spectrometry was used by inserting an absorption filter between the samples and an HPGe detector. The use of the absorption lead filter 6-mm thick yielded improvement of the vanadium limit of detection by a factor of two. The vanadium mass fraction determined in a quality control sample, which was NIST standard reference material SRM 1648 Urban Particulate Matter, was in close agreement with the certified value.

     

An Analysis of Low Frequency Discharge in a CH3SiCl3-Ar-H2 Mixture by Optical Emission Spectroscopy and Actinometry

Low frequency (100 kHz) discharge in Ar-H₂ and CH₃SiCl₃-Ar-H₂ mixtures was studied to obtain information on the processes involved in plasma deposition of Si_xC_y:H films from CH₃SiCl₃-Ar-H₂ plasma once the properties of Ar-H₂ plasma are known. The plasmas were studied using optical emission spectroscopy. The addition of small amounts of nitrogen to the plasma mixtures also permitted the use of an actinometry technique. First, plasma parameters (electron density and temperature) and actinometric concentrations of atomic hydrogen in an argon–hydrogen plasma were investigated as a function of the hydrogen content in the feed. Second, the emission intensities of Si, Si⁺, CH, H, Ar and Ar⁺ species produced in the CH₃SiCl₃-Ar-H₂ discharge were analysed as a function of time following the introduction of CH₃SiCl₃ (methyltrichlorosilane, MTCS) to the argon–hydrogen plasmas with various proportions of the feed gasses. The results reveal a rapid decay of the Si-excited state number density versus time, while those of Si⁺ and CH fell off more slowly. The emission of atomic silicon was believed to be a result of electron impact dissociative and excitation processes occurring in the bulk of the discharge, whereas the Si⁺ and CH seemed to originate mainly from products of sputtering of the growing film surface. The fragmentation of the MTCS associated with HCl formation and enhanced atomic hydrogen production as a result of HCl dissociation are proposed. Variations in the radical densities of H and CH₃ were determined using an actinometry technique. The results indicate a significant role for H₂ in gas-phase reactions occurring in the CH₃SiCl₃-Ar-H₂ plasma, as well as in gas-surface interactions, leading to competition between deposition and chemical sputtering of already deposited material.     

FT-IR study of gamma-radiation induced degradation of polyvinyl alcohol (PVA) and PVA/humic acids blends

Samples of pure polyvinyl alcohol (PVA) and PVA doped with humic acids were exposed to gamma radiation. Gamma rays induced the degradation of the pure polymer. Degradation changes were observed using ATR FT-IR equipment. Dehydration, double bond creation, and their subsequent oxidation (surrounding atmosphere was air) were found out. Also, other degradation reactions (e.g. chain scission, cyclization) occur simultaneously. Formation of C=C and C=O bonds is apparent from FT-IR spectra. In contrast the presence of humic acids in the PVA sample showed stabilizing effect on PVA structure within the concentration range 0.5–10%.     

Tunable THz metamaterials based on an array of paraelectric SrTiO<Subscript>3</Subscript> rods

This work presents theoretical and experimental investigations of a tunable metamaterial which exhibits negative permeability in the THz frequency range. The tunability is obtained by temperature changes, and the sample consists of an array of high-permittivity SrTiO₃ (STO) rods micromachined by a femtosecond laser. Structures exhibiting a negative permeability on multiple frequency bands are also investigated and a proper choice of the dimensions of the pattern allows us to achieve a substantial broadening of the frequency band with negative μ.     

Review of fluorescence anisotropy decay analysis by frequency-domain fluorescence spectroscopy

This didactic paper summarizes the mathematical expressions needed for analysis of fluorescence anisotropy decays from polarized frequency-domain fluorescence data. The observed values are the phase angle difference between the polarized components of the emission and the modulated anisotropy, which is the ratio of the polarized and amplitude-modulated components of the emission. This procedure requires a separate measurement of the intensity decay of the total emission. The expressions are suitable for any number of exponential components in both the intensity decay and the anisotropy decay. The formalism is generalized for global analysis of anisotropy decays measured at different excitation wavelengths and for different intensity decay times as the result of quenching. Additionally, we describe the expressions required for associated anisotropy decays, that is, anisotropy decays where each correlation time is associated with a decay time present in the anisotropy decay. And finally, we present expressions appropriate for distributions of correlation times. This article should serve as a reference for researchers using frequency-domain fluorometry.