Surfactant-mediated formation of alginate layers at the water-air interface

The self-organization process of polysaccharide alginate with different cationic surfactants at the water-air interface was investigated over a wide concentration regime. The changes of surface properties determined by surface tension measurements, surface rheology, and X-ray reflectivity are correlated with changes of bulk properties measured by turbidity, light scattering, and zeta potential measurements. We demonstrate that the interactions between the alginate and cationic surfactants result in significant changes of bulk and interfacial properties. The results of surface shear experiments point to the existence of highly viscoelastic interfacial films. In combination with X-ray reflectivity, we demonstrate that these rheological features are related to polymer-surfactant associations at the interface. In the regime of high surfactant concentrations, we observed the existence of multilayer structures.     

A STUDY ON THE ADDITIVITY OF SUBSTITUENT EFFECTS IN THE TRIPHENYLPHOSPHONIUM SYSTEM

Abstract

Aromaticity has been claimed for phosphorins, arsorins, phospholes and arsoles, but the facts brought forward to support this view are easily rationalized without recourse to this concept.     

Die Hamiltonsche partielle Differentialgleichung als Ausgangspunkt für die Umkehrung des Variationsproblems und ihre damit zusammenhängende Bedeutung für die Integration der allgemeinen partiellen Differentialgleichungen erster Ordnung

Ohne Zusammenfassung     

Pflanzenchemie

Ohne Zusammenfassung     

The Crystal Structure of α-F2: Solving a 50 Year Old Puzzle Computationally

The cohesive energy of α-fluorine, with C2/c space group symmetry, was calculated at benchmark quality by applying the method of increments. The known experimental X-ray structure data needed to be refined, since the reported intramolecular bond length was unrealistically large. At the CCSD(T) level, including corrections for zero-point energy, the basis set superposition error, and extrapolated to the complete basis set limit, a cohesive energy of −8.72 kJ mol⁻¹ was calculated, which agrees well with the 0 K-extrapolated experimental value of −8.35 kJ mol⁻¹. 1 Comparison of the C2/c structure with a Cmca structure, isotypic to that of chlorine, bromine, and iodine reveals that the origin of the different structure of solid fluorine, compared to the heavier halogens, is the lack of significantly stabilizing σ-hole interactions. In addition, the wave numbers of the stretching mode in solid fluorine were calculated at coupled cluster level and compared to newly recorded Raman spectra of condensed fluorine. Both experiment and calculation indicate a slight up-shift for the stretching mode by 2 or 5 cm⁻¹, respectively, with respect to a free F₂ molecule in the gas phase.     

Preparation,characterisation and modification of carbon‐based monolithic rods for chromatographic applications

A range of porous carbon‐based monolithic (PCM) rods with flow‐through pore sizes of 1, 2, 5 and 10 μm, were produced using a silica particle template method. The rods were characterised using SEM and energy‐dispersive X‐ray spectroscopy, BET surface area and porous structure analysis, dilatometry and thermal gravimetry. SEM evaluation of the carbon monolithic structures revealed an interconnected rigid bimodal porous structure and energy‐dispersive X‐ray spectroscopy analysis verified the quantitative removal of the embedded silica beads. The specific surface areas of the 1, 2, 5 and 10 μm rods were 178, 154, 84 and 125 m²/g after pyrolysis and silica removal, respectively. Shrinkage of the monolithic rods during pyrolysis is proportional to the particle size of the silica used and ranged from 9 to 12%. Mercury porosimetry showed a narrow distribution of pore sizes, with an average of ～700 nm for the 1 μm carbon monolith. The suitability of bare and surface oxidised PCM rods for the use as a stationary phase for reversed and normal phase LC was explored. The additional modification of PCM rods with gold micro‐particles followed by 6‐mercaptohexanoic acid was performed and ion‐exchange properties were evaluated.     

Thermal Properties of Oligo(2-ethyl-2-oxazoline) Containing Comb and Graft Copolymers and their Aqueous Solutions

Summary: The cationic ring opening polymerization of 2-ethyl-2-oxazoline (EtOx) was applied for the synthesis of methacrylate end-functionalized well-defined macromonomers that could be polymerized in a controlled manner using reversible addition-fragmentation chain transfer polymerization. The obtained comb polymers revealed lower critical solution temperature behavior in aqueous solution. The cloud points of these solutions could be tuned in a range from 35 °C to 85 °C by the incorporation of hydrophobic methyl methacrylate comonomer in varying amounts into the graft copolymers whereas copolymerization with methacrylic acid rendered temperature and pH sensitive copolymers. Thermo-gravimetric analysis showed a two-step decomposition of the graft copolymers and differential scanning calorimetry revealed glass transition temperatures that are significantly lowered in comparison to linear PEtOx.