Synthesis and characterization of thermally crosslinkable hole‐transporting polymers for PLEDs

Two new thermally crosslinkable hole‐transporting polymers, X‐PTPA and X‐PCz, were synthesized via Yamamoto coupling reactions. The number‐averaged molecular weights (M_n) of X‐PTPA and X‐PCz were found to be 45,000 and 48,000, respectively, and therewith, polydispersity indices were of 1.8 and 1.7, respectively. Thermally crosslinked X‐PTPA and X‐PCz exhibit excellent solvent resistance and stable optoelectronic properties. The UV–visible maximum absorption peaks of X‐PTPA and X‐PCz in the thin film state are at 389 and 322 nm, respectively. The HOMO levels of X‐PTPA and X‐PCz are estimated to be ?5.27 and ?5.39 eV, respectively. Multilayered devices (ITO/crosslinked X‐PTPA or X‐PCz/SY‐PPV/LiF/Al) were fabricated with SY (SuperYellow) as the emitting layer. The maximum efficiency of the multilayered device with a crosslinked X‐PTPA layer is approximately three times higher than that of the device without a crosslinked X‐PTPA layer and much higher than that of the crosslinked X‐PCz device. This result can be explained by the observations that crosslinked X‐PTPA produces increased electron accumulation within the emitter, SY, and also efficient exciton formation due to improved charge balance. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5111–5117     

Curing temperature- and concentration-dependent dielectric properties of cross-linked poly-4-vinylphenol (PVP)

In this paper, dielectric properties of various thick PVP films cured at temperatures between 125° C and 200 °C are investigated. The thicknesses of PVP films are adjusted by varying their concentration in PGMEA solvent from 10 wt% to 2.5 wt%. Through FT-IR, C–V, SEM, and AFM analyses, the optimum curing process temperatures (150 °C for 10 wt% and 7.5 wt% samples, and 175 °C for 5 wt% samples) where PET substrates can be thermally endured are proposed in terms of their low hysteresis voltage in the C–V curve (1–2 V in 10 wt% samples, below 1 V in 7.5 wt% samples, and 0.5 V in 5 wt% samples).     

Rational approaches for combining redundant,independent measurements to minimize combined experimental uncertainty

General methods for combining multiple, independent measurements for minimized uncertainty are presented. Although the methods are general, the presentation is motivated by the reduction of heat exchanger performance data. It is demonstrated that the prevalent practice of using the arithmetic mean of two measured heat transfer rates for the evaluation of heat exchanger performance, which is widely adopted in the literature and used in engineering standards, does not always lead to reduced experimental uncertainty and very rarely—if ever—leads to a minimized experimental uncertainty. For the case of averaging two redundant measurements, simple criteria are developed to determine whether using the arithmetic mean or a single measurement yields a smaller absolute or relative uncertainty. Then, more general methods are proposed in the form of weighted-linear averages, in which the weight factors are determined to minimize the combined uncertainty. The methods are generally applicable to averaging any number of redundant measurements with varying uncertainties.     

Amino-acid-mediated epoxidation of α,β-unsaturated ketones by hydrogen peroxide in aqueous media

Amino acids, such as arginine and lysine, can be used as an efficient catalyst in the epoxidation of α,β-unsaturated ketones with aqueous hydrogen peroxide. Up to >99% conversion was obtained in the reaction toward 11 α,β-unsaturated ketones.     

Simultaneous Separation and Determination of Isosorbide Dinitrate and Isosorbide 5-Mononitrate in Human Plasma by LC–MS–MS

A sensitive, selective, and simple liquid chromatography-tandem mass spectrometry method has been developed for the simultaneous separation and determination of isosorbide dinitrate and its active metabolite, isosorbide 5-mononitrate, in human plasma. Topiramate was used as the internal standard. Sample preparation consisted of a simple one-step liquid–liquid extraction with ethylacetate without pH adjustment. The method was fully validated with respect to linearity, sensitivity, specificity, recovery, accuracy, and precision. Isosorbide dinitrate and isosorbide 5-mononitrate were stable in standard solution and in plasma samples under storage and processing conditions. The assay was successfully applied to the pharmacokinetic study of isosorbide dinitrate and isosorbide 5-mononitrate in human plasma.     

Mechanical properties of titania nanofiber mats fabricated by electrospinning of sol–gel precursor

Flexible mats of titania fibers are prepared by calcination of electrospun polyvinylpyrrolidone fibers containing titanium isopropoxide precursor. Structural investigation of the calcinated nanofibers by X-ray diffraction (XRD) and electron diffraction (ED) combined with the morphologies by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show the titania fibers, with an average diameter of 180 nm, were comprised of anatase and rutile crystals. The mechanical, chemical and thermal properties of the titania fiber mats are further investigated by the techniques of Instron mechanical tester, thermogravimetric analyzer (TGA), and Fourier transform infrared spectroscopy (FT-IR). The titania fiber mat prepared in this method exhibited a significant flexibility with 461 MPa Young’s modulus.