Measurement of the solubility of metal complexes in supercritical carbon dioxide using a UV–vis spectrometer

A new apparatus based on the circulation method was developed to measure the solubility of metal complexes in supercritical carbon dioxide (scCO₂) at a wide range of temperatures and pressures. A UV–vis spectrometer, which was connected to a small saturation cell through optical fibers, was used to determine solubility. The solubilities of cobalt(III) acetylacetonate (Co(acac)₃) and chromium(III) acetylacetonate (Cr(acac)₃) in scCO₂ were measured to check the validity of both the apparatus and the method and to accumulate new solubility data. The solubility data for Cr(acac)₃ obtained in this study were in good agreement with the data reported in the literature.The measured solubilities of Co(acac)₃ and Cr(acac)₃ were also correlated with the empirical equation including the three adjustable parameters, based on the equation proposed by Chrastil. The parameters were determined by fitting the equation to the experimental data for each metal complex and the calculated results closely replicated the experimental data.     

Preparation and chemical properties of soluble π‐conjugated poly(aryleneethynylene) consisting of azabenzothiadiazole as the electron‐accepting unit

A soluble charge‐transfer type poly(aryleneethynylene), PAE‐AzaBzTdz , consisting of a highly electron‐accepting azabenzothiadiazole unit was prepared in 99% yield by palladium‐catalyzed polycondensation between 4,7‐dibromo‐2,1,3‐azabenzothiadiazole ( Br₂‐AzaBzTdz ) and 1,4‐diethynyl‐2,5‐didodecyloxybenzene. PAE‐AzaBzTdz showed a number‐average molecular weight, M_n, of 6000 in gel‐permeation chromatography analysis and had good thermal stability as measured by TGA. UV–vis spectrum of PAE‐AzaBzTdz exhibited an absorption peak at 529 nm in chloroform, and the absorption peak shifted to a longer wavelength (601 nm) in film. Addition of MeOH to a CHCl₃ solution of PAE‐AzaBzTdz led to aggregation of the polymer to form stable colloidal particles. Results of filtration experiments using 0.2 and 0.02 μm membranes supported aggregation of the polymer. Addition of trifluoroacetic acid (TFA) to a chloroform solution of PAE‐AzaBzTdz led to a red‐shift of the UV–vis peak from 529 to 640 nm. An X‐ray diffraction pattern of powdery PAE‐AzaBzTdz indicated that the polymer assumed a layer‐to‐layer stacked structure with an interlayer distance of 3.4 Å in the solid state. An X‐ray diffraction pattern of cast film of PAE‐AzaBzTdz revealed that the polymer molecules in the cast film were ordered on the surface of Pt plate with the dodecyl side chain oriented toward the surface of the Pt plate. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2975–2982, 2008     

Enhancing the electrochromic characteristics of conjugated polymer with TiO2 nano‐rods

Organic soluble, oleic acid capped TiO₂ nano‐rod was well‐mixed with the electrochromic polymer: Poly‐(4,4‐dioctylcyclopenta[2,1‐b:3,4‐b′]‐dithiophene (PDOCPDT) to form TiO₂/PDOCPDT nanocompsoite. TiO₂/PDOCPDT film showed high electrochemical stability and its coloration efficiency is 1.5 times of that for pure PDOCPDT. The function of TiO₂ nano‐rods can be regarded as a dispersion agent. PDOCPDT chains in TiO₂/PDOCPDT may have a less aggregated structure and more open morphology, therefore has higher coloration efficiency. TiO₂ may also act as electron transport or temporary electron storage centers, electrons can be transferred reversibly between PDOCPDT and TiO₂ nano‐rods. TiO₂/PDOCPDT is well‐soluble in CHCl₃, large area thin films can be fabricated reproducibly simply by spin coating. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1121–1130, 2008     

The electrochemical behaviour of the altenuene mycotoxin and its acidic properties

The electrooxidation of altenuene (ALT), one of the mycotoxins of the Alternaria alternata genus, on a glassy carbon disk electrode is studied for the first time by using cyclic and square wave voltammetry. From the electrochemical responses, a complex reaction mechanism could be inferred. Values of 1.06×10⁻⁵ cm² s⁻¹, 1.116 V and 2 were determined for the diffusion coefficient, the apparent formal potential and the electron number, respectively, for the overall electrode process by convolution analysis of linear scan voltammograms. Square wave voltammetry was used to generate I_p versus c_ALT* calibration curves for this fungal metabolite. A detection limit of 4.0×10⁻⁷ M was determined for a 2:1 signal to noise ratio. The acid dissociation constant for ALT was determined from conventional UV–vis spectrophotometric measurements. Experimental variations of absorbance as a function of pH at a given wavelength were fitted by using the exact equation that describes the system. Good agreement between the experimental absorbance versus pH plots and the curves generated by the fitting process was found.     

High performance polymer field‐effect transistors based on polythiophene derivative with conjugated side chain

Poly(3‐[2‐(5‐hexyl‐2‐thienyl) ethenyl]‐2,2′‐bithiophene) ( P2 , see Scheme 1 ) with conjugated thienylvinyl side chain was synthesized by copolymerization of the thiophene units with and without conjugated side chain with Pd‐catalyzed Stille coupling method. For comparison, P1 with the hexyl side chain instead of conjugated side chain was also synthesized. P2 film shows broad absorption in the visible region with absorption edge at about 700 nm. The solution‐processed polymer field‐effect transistors were fabricated and characterized with bottom gate/top contact geometry. The organic field‐effect transistors (OFET) based on P2 showed an average hole mobility of about 0.034 cm²/Vs (the highest value reached 0.061 cm²/Vs) upon annealing at about 180 °C for 30 min, with a threshold voltage of ?1.15 V and an on/off ratio of 10⁴ with n‐octadecyltrichlorosilane (OTS) modified SiO₂ substrate. In comparison, the OFET based on P1 displayed a hole mobility of 8.9 × 10^–4 cm²/Vs and an on/off ratio of 10⁴ with OTS modified SiO₂ substrate. The results indicate that the polythiophene derivative with conjugated thienylvinyl side chain is a promising polymer for the application in polymer field‐effect transistors. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5304–5312, 2009     

Click chemistry‐assisted triazole‐substituted azobenzene and fulgimide units in the pendant‐based copoly(decyloxymethacrylate)s for dual‐mode optical switches

Copolymer containing new thermally reversible click chemistry‐assisted triazole‐substituted azobenzene and fulgimide units in the pendant F‐co‐A was prepared by free‐radical solution addition polymerization technique. The F and A were also prepared for comparison. The DSC analysis of F indicates that the polymer possessing the C‐form of fulgimide unit exhibited higher T_m than that of E‐form of the same polymer and revealed that the C‐form of fulgimide unit in F is highly ordered. The cis‐trans back isomerization behavior of the click chemistry‐assisted triazole‐substituted azobenzene unit in film A has thermal irreversibility, while in F‐co‐A it exhibited thermal reversibility. The UV‐exposed film of F‐co‐A heated around T_g leads to cis‐trans back isomerization of azobenzene unit and thermally stable C‐form of fulgimide which retains its conjugated structure where both the photochromic units are converted into planar conformations and exhibit high fluorescence properties. The fluorescence maxima of C‐form in F‐co‐A red shifted compared with F , because the substituted triazole ring in the azobenzene unit stabilized the C‐form of fulgimide unit. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7843–7860, 2008     

Offline combination of pressurized fluid extraction and electron paramagnetic resonance spectroscopy for antioxidant activity of grape skin extracts assessment

A comprehensive characterization of grape skin methanolic and ethanolic extracts prepared by pressurized fluid extraction (PFE) at various temperatures within 40 to 120 °C from two wine grape varieties, St. Laurent and Alibernet was performed. For the first time, an offline combination of PFE and electron paramagnetic resonance (EPR) spectroscopy together with other experimental methods was employed to assess the effect of extraction conditions on numerous extract characteristics including antioxidant or radical-scavenging ability, HPLC profile of anthocyanins, total phenolic compounds content (TPC), tristimulus color values (CIE Lab), and pH values. The properties of extracts depend on the solvent used, the mass of grape skins as well as on the extraction conditions among which the temperature plays a crucial role. In spite of wide interval of extraction temperatures, all extracts still retain their antioxidant and/or radical-scavenging properties, indicating that the extracts prepared by PFE can serve as potential source of functional food supplements or color enhancers.     

Coloring–decoloring behavior of fluoroalkyl end‐capped 2‐acrylamido‐2‐methylpropanesulfonic acid oligomer/acetone composite in methanol

A reddish‐brown fluoroalkyl end‐capped 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) oligomer/acetone composite was prepared by heating the white oligomer powder with acetone at 80 °C for 3 h. The color was not observed in the corresponding non‐fluorinated AMPS oligomer/acetone composite, which was prepared under similar conditions. The coloring was probably caused by the formation of acetone polyaldol condensation products in the fluorinated oligomeric gel network cores. The colored R_F‐(AMPS)_n‐R_F/acetone composite powders were stable and did not exhibit any color change after 2 years in natural light at room temperature. The colored composite powders dissolved in methanol to give a reddish‐brown solution at room temperature. However, the retro‐polyaldol condensation decolored the solution after 1 day at room temperature. This is the first example of the retro‐aldol polycondensation of acetone under mild conditions. The decoloration increased by between 38‐ and 70‐fold under UV irradiation, compared with that in dark conditions. The coloring–decoloring behavior was consistent and repeatable; therefore our fluorinated oligomer/acetone composites are promising candidates for new fluorinated coloring materials. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2555–2564     

Blue‐light‐emitting polyfluorene functionalized with triphenylamine and cyanophenylfluorene bipolar side chains

A new bipolar conjugated polyfluorene copolymer with triphenylamine and cyanophenylfluorene as side chains, poly{[9,9‐di(triphenylamine)fluorene]‐[9,9‐dihexyl‐fluorene]‐[2,7‐bis(4′‐cyanophenyl)‐9,9′‐spirobifluorene]} ( PTHCF ), was synthesized for studying the polymer backbone emission. Its absolute weight‐average molecular weight was determined as 4.85 × 10⁴ by using gel permeation chromatography with a multiangle light scattering detector. In contrast to the electronic absorption spectrum in dilute solution, the absorbance of PTHCF in thin film was slightly blue shifted. By comparison of the solution and thin‐film photoluminescence (PL) spectra, a red shift of Δλ = 8–9 nm was observed in the thin‐film PL spectrum. The HOMO and LUMO energy levels of the resulting polymer were electrochemically estimated as ?5.68 and ?2.80 eV, respectively. Under the electric‐field intensity of 4.8 × 10⁵ V cm^?1, the obtained hole and electron mobilities were 2.41 × 10^?4 and 1.40 × 10^?4 cm² V^?1 s^?1, respectively. An electroluminescence device with configuration of ITO/PEDOT:PSS/ PTHCF _70%+PBD_30%/CsF/Ca/Al exhibited a deep‐blue emission as a result of excitons formed by the charges migrating along the full‐fluorene main chain. The incorporation of the bipolar side chains into the polymer structure prevented the intermolecular interaction of the fluorene moieties, balance charge injection/transport, and thereby improve the polymer backbone emission. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010