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showing 10 items of 2669 documents
Solvent Determines Nature of Effective Interactions between Nanoparticles in Polymer Brushes
2015
We study the effective interaction between two parallel rod-like nanoparticles in swollen and collapsed polymer brushes as a function of penetration depth by 2D self-consistent field calculations. In vertical direction, the interaction is always attractive. In lateral direction, the behavior under good and poor solvent conditions is qualitatively different. In swollen brushes (good solvent), nanoparticles always repel each other. In collapsed brushes (poor solvent), we identify two different regimes: an immersed regime, where the nanoparticles are fully surrounded by the brush, and an interfacial regime, where they are located in the interface between brush and solvent. In the immersed regi…
Proton Conducting Membrane Prepared by Cross-Linking Highly Sulfonated Peek for PEMFC Application
2009
The proton conducting membrane was prepared by cross-linking highly sulfonated and sulfinated poly(etheretherketone) (SsPEEK). The cross-linked membrane is low cost due to its use of non-expensive chemical and simple production procedure. The membrane exhibited high proton conductivity (0.04 S/cm at 60 °C), extremely reduced water uptake, enhanced strength and stability compared with that of non-cross-linked membrane. These results suggested that the cross-linked PEEK membrane is a suitable candidate of proton conducting membranes for polymer electrolyte membrane fuel cell (PEMFC) applications, particularly promising to be used in direct methanol fuel cell (DMFC) due to its lower methanol c…
Direct monitoring of spin state in dinuclear iron(II) coordination compounds
2001
So far there has been no direct method to determine the spin state of molecules in dinuclear iron(II) compounds. The molecular fractions of high-spin (HS) and low-spin (LS) species have been deduced from magnetic susceptibility and zero-field Mossbauer spectroscopy data irrespective of whether they belong to LS–LS, LS–HS and HS–HS pairs. However, the distinction of pairs becomes possible if Mossbauer measurements are carried out in an external magnetic field. The proposed method opens new possibilities in the study of spin crossover phenomena in dinuclear compounds.
1986
When Chlorides are the Most Reactive: A Simple Route towards Diverse Mono- and Dicationic Dimethyl Phosphate Ionic Liquids
2014
Structurally diverse aromatic and aliphatic ionic liquids have been prepared via anion metathesis utilizing alkylammonium chlorides and trimethyl phosphate. Excellent oxygen-containing functional-group tolerance in preparation of potentially greener dimethyl phosphate ionic liquids has been demonstrated. For the first time, this method has been employed in the synthesis of dicationic imidazolium-based ionic liquids possessing a dimethyl phosphate counterion, providing a simple, direct route towards structurally novel products of high purity.
A Covalently Cross-linked Polyetheretherketone Proton Exchange Membrane for DMFC
2009
The proton exchange membrane was prepared by covalent cross-linking sulfonated-sulfinated polyetheretherketone. The cross-linked membrane showed high proton conductivity (0.04 S/cm) with suitable water uptake, low methanol permeability (2.21 × 10-7 cm2/s) and good electrochemical stability. The results suggested that cross-linked polyetheretherketone membrane is particularly promising to be used as proton exchange membrane for the direct methanol fuel cell application.
1981
In order to investigate the influences of different end-groups on oligomer miscibility with other substances, oligo(propylene glycol)s bearing OH groups (OPG-OH) studied in the previous paper2, were acetylated at both ends (OPG-AC). The limits of miscibility of OPG-AC with oligo(dimethylsiloxane) (ODMS) were measured turbidimetrically. A simple and reliable method for the determination of the critical points from turbidity data is presented. The observed upper critical temperatures (Tc) increase with degree of oligomerization of ODMS (ranging from 1 to 5), whereas Tc shows a minimum when the degree of oligomerization of the OPG-AC is raised (from 1 to 57,5). For lower mol. wt. oligoglycols,…
Terrylene in p-terphenyl: single-molecule experiments at room temperature
1999
Abstract This paper reports on fluorescence microscopy and spectroscopy of single terrylene molecules embedded in p -terphenyl at room temperature. The basic photophysical parameters of this crystalline host/guest system such as photostability, single-molecule emission rates and the properties of dispersed fluorescence spectra are reported. The stability of the single-molecule signals allowed the direct observation of singlet–triplet quantum jumps at room temperature, by means of which the underlying intersystem crossing rates can be investigated. The results of earlier investigations at liquid-helium temperatures are reviewed briefly where appropriate. The properties of terrylene in p -ter…
A Versatile Palladium/Triphosphane System for Direct Arylation of Heteroarenes with Chloroarenes at Low Catalyst Loading
2010
International audience; Put a ring on it: The use of an air-stable, robust palladium/tridentate phosphane catalyst in direct C[BOND]H and C[BOND]Cl activation reactions is reported (see scheme; DMAc=N,N-dimethylacetamide, TBAB=tetra-n-butylammonium bromide). Electron-rich, electron-poor, and polysubstituted furans (X=O), thiophenes (X=S), pyrroles (X=NR5), and thiazoles were arylated with chloroarenes in the presence of the catalyst.