Photovoltaic properties of the polymer solar cells comprising crosslinked maleimide polymers and fullerene‐derivative PCBM

A series of crosslinkable maleimide conjugated polymers with different vinyl group contents as side‐chain crosslinking sites have been synthesized by the Suzuki coupling reaction. Polymer solar cells (PSCs) were fabricated based on an interpenetrating network of the crosslinkable maleimide polymers as the electron donor, and a fullerene derivative, (6,6)‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM), as the electron acceptor. The crosslinkable maleimide polymers underwent crosslinking reaction at the side‐chain vinyl groups upon the thermal treatment with or without the addition of initiator, azobisisobutyronitrile (AIBN). Better photovoltaic (PV) performances were obtained for the PSCs based on the polymer crosslinking without using initiator, whereas poorer PV performances were observed for the PSCs based on the polymer crosslinking with the AIBN initiator. In addition, higher operational stability was observed for the crosslinked polymer based solar cell as compared to the solar cell based on the un‐crosslinked polymer. The photo‐physical and PV properties of the cross‐linked maleimide polymers/PCBM based PSCs are discussed in detail as the morphology and crosslinking density of the polymers are taken into account. Copyright © 2010 John Wiley & Sons, Ltd.     

Imaging cytoplasmic cAMP in mouse brainstem neurons

Background  

cAMP is an ubiquitous second messenger mediating various neuronal functions, often as a consequence of increased intracellular Ca²⁺ levels. While imaging of calcium is commonly used in neuroscience applications, probing for cAMP levels has not yet been performed in living vertebrate neuronal tissue before.     

Tandem three-component reaction of aldehyde, alkyl acrylate, and amide using ethyl diphenylphosphine as organocatalyst

It is the first time that a chemoselective EtPPh₂-catalyzed three-component reaction of aromatic aldehyde, alkyl acrylate, and phthalimide or methyl toluenesulfonamide has been achieved. A variety of highly functional adducts can be generated efficiently in one step within 1-72 h in 38-93% yields. The reaction mechanism is proposed to undergo Morita-Baylis-Hillman reactions of aryl-substituted aldehydes and alkyl acrylates followed by Michael additions of amides. Our studies indicated that, in combination of EtPPh₂, alkyl acrylate also catalyzed this process.     

Immobilization of chitosan in sol–gel phases for chiral open-tubular capillary electrochromatography

Three different approaches for immobilizing cross-linked chitosan molecules (CS-s) in sol–gel phases to form chiral OT-CEC capillaries were comparatively investigated in this study. To synthesize column I, a bare capillary was first silanized with triethoxysilane (TEOS) and then reacted with the reaction product of 3-glycidyloxypropyltrimethoxysilane (GTS) and CS-s. Column II was prepared by the silanization of a bare capillary with a mixture of TEOS and GTS silanes followed by reaction with CS-s. To obtain column III, all the reagents, including TEOS, GTS, and CS-s were reacted together in a bare capillary. The SEM images showed that the column I phase consisted of two distinct layers, GTS and TEOS sol–gel films, while column II and III phases were homogeneous phases. By elemental analysis, the chitosan contents of the columns were found to decrease in the order column I > II > III, which corresponded to the order of the electroosmotic mobility values obtained from the measurements of the electroosmotic flow in the columns. The retention factor and the selectivity for the chiral separation of phenylglycine enantiomers in the optimized Tris running buffer (100 mM, pH 7.5) also followed this decreasing order. Besides the strength of the interaction with the immobilized functional chitosan, the hydrophobicity of the column affected the resolution of enantiomeric samples. The hydrophilic alanine sample could only be resolved by column III, but the hydrophobic tryptophan and catechin enantiomers were better separated by columns I and II. A reverse-phase mechanism has been found in the separations. Furthermore, the resolution and analysis time of column I and II phases were superior to the phase simply bonded with molecular chitosan.     

Cu-promoted [2 + 2] cycloaddition of 1,4-bisallenes

The thermal reaction of 1,4-bisallenes with the aid of Cu salt/amine significantly suppressed the formal [3,3] sigmatropic rearrangement resulting in the highly selective formation of the bicyclo[4.2.0]octadiene framework. This reaction could be applied to the one-pot synthesis of bicyclo[4.2.0]octadienes from 1,5-hexadiynes via the Crabbé homologation.     

Tensor products and Minkowski sums of Mirkovi?–Vilonen polytopes

The purpose of this paper is to prove that the Mirković–Vilonen (MV) polytope corresponding to the tensor product of two arbitrary MV polytopes is contained, as a set, in the Minkowski sum of these two MV polytopes. This result generalizes the one in our previous paper, which was obtained under the assumption that the first tensor factor is an extremal MV polytope.     

Determining a 'safe' high-mass limit in matrix-assisted laser desorption/ionisation time-of-flight mass spectra of coal derived materials with reference to instrument noise

Three methods for determining a 'safe' estimate for high-mass limits of MALDI spectra of coal derived liquids were explored, using a sample of coal-tar pitch and its pyridine-insoluble fraction. Co-addition of increasing numbers of single-shot spectra (10, 30, 50 and 100 pulses) showed visually observable reductions in noise levels, consistent with robust and statistically meaningful signals. Three separate types of post-acquisition calculation were used to identify high-mass limits of the spectra. (i) A literature method indicated high-mass limits similar to those observed visually-as a shift from baseline at the highest masses, nearly 350 000 u for the coal tar pitch and about 390 000 u for its pyridine insoluble fraction. (ii) Comparing instrument signal with pre-selected multiples of the standard deviation, upper mass estimates of between 40-60 000 u for the coal-tar pitch and about 95 000 u for its pyridine-insoluble fraction were found. (iii) Calculation of the slope was used to identify 'lift-off' of the spectrum from baseline. The angle between the smoothed spectrum and the baseline was matched to a pre-selected value (e.g. 0.5 degrees and 1 degrees ). However, the arbitrary specification of the key parameter did not establish this last method on a firm basis. The choice of a criterion for estimating high-mass limits of MALDI spectra remains a semi-quantitative procedure; a reasonably conservative high-mass limit may be estimated by comparison of signal with five times the standard deviation. However, evaluation of size exclusion chromatograms of the present samples using polystyrene standards suggests that molecular mass distributions of pitch samples arrived at by MALDI mass spectrometry are, at least partly, determined by the limitations of available instruments. Copyright 1999 John Wiley & Sons, Ltd.