Phase Transfer Catalysis Preparation of Acyl Isothiocyanates

The use of phase transfer catalysis, PTC, for nucleophillic substitution reactions is well documented.^1,2 Included among these reactions is the preparation of both alkyl³ and aryl⁴ thiocyanates. However, PTC reactions at an acyl carbon are much less common. Brándstróm⁵ has reported the preparation of acyl azides and Weber⁶ has used PTC to prepare benzoyl cyanide. Recently Illi⁷ has used PTC to acylate sterically crowded phenols.     

Role of radicals in UV‐initiated postplasma grafting of poly‐ε‐caprolactone: An electron paramagnetic resonance study

Electron paramagnetic resonance (EPR) measurements were performed on poly‐ε‐caprolactone (PCL) films at different stages of the postplasma‐grafting process. PCL films prepared by solvent casting (SC) or electrospinning (ESP) yield very similar EPR spectra after Ar‐plasma treatment and subsequent exposure to air, but the EPR signal is much stronger in the PCL‐ESP films. The free radicals appear to be mainly, and possibly exclusively, oxygen centered. The radicals generated by UV irradiation in PCL‐ESP films were studied in situ with EPR, using a UV‐LED (λ = (285 ± 5) nm). Their EPR spectrum is distinctly different from the plasma‐induced signal, indicative of carbon‐centered radicals, and appears to be independent of the plasma pretreatment. UV‐induced homolytic splitting of (hydro)peroxide bonds was not observed. Both the plasma‐ and UV‐induced radicals decay at room temperature (RT), even in an inert atmosphere. This study demonstrates the potential of electrospun films and UV‐LEDs for the study of plasma‐ and UV‐generated free radicals with EPR in polyesters, and raises questions with respect to the validity of some generally accepted molecular mechanisms underpinning the postplasma grafting technique for polyesters. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Mathematical Modeling of Tidal Effects in Groundwater

This paper presents a special use of the linear poroelasticity theory to describe tidally induced groundwater oscillations. Two models of oscillation inducing mechanism make use of this theory to predict groundwater level fluctuations. The numerical solutions of both models are presented and compared with well water level measurement obtained in Police Basin, north-east Bohemia.     

Overcoming the Inhibition Effects of Citrate: Precipitation of Ferromagnetic Magnetite Nanoparticles with Tunable Morphology,Magnetic Properties,and Surface Charge via Ferrous Citrate Oxidation

This study demonstrates how the method of thermally assisted oxidative precipitation in water can be opened for—the so far neglected—metal organic iron(II) complexes (herein: citrate) in order to obtain, in one step, ferromagnetic magnetite nanoparticles, possessing essential ligand properties. Based on a dedicated analysis of the specific precursor in combination with the consideration of known properties of the ligand, it is possible to identify existing inhibition-attributes of the iron organyl such that these can be overcome. Moreover, they can be exploited in a targeted manner; thus, simply by changing concentrations, a variety of magnetite nanoparticle morphologies with distinct properties can be obtained. In the case of the herein investigated ferrous citrate, three major inhibition effects are identified. While two of them efficiently prevent the formation of magnetite and need to be addressed to be overcome, the third can be exploited to selectively synthesize, for example, relatively stable carboxyl group-bearing nuclei clusters, exhibiting the properties of magnetically responsive photonic crystals, or relatively large mesocrystals, whose intraparticular magnetic interactions are apparently disturbed.     

Optical microscopy at high pressure : P-T phase behaviour of 80cb and CBOOA and their mixtures

By direct texture observations under pressure in a diamond anvil cell, the phase behaviour of 80CB and CB00A and their mixtures have been investigated. The maximum pressure (p_M) of ocurrence of the smectic A phase (smA) runs through a maximum value as a function of mole fraction, the highest p_M being observed at about 2.2 kbar for x(CBOOA)-0.284.