Aromatic Xanthates and Dithiocarbamates for the Polymerization of Ethylene through Reversible Addition–Fragmentation Chain Transfer (RAFT)

Aromatic xanthates and dithiocarbamates were used as chain‐transfer agents (CTAs) in reversible addition–fragmentation chain‐transfer (RAFT) polymerizations of ethylene under milder conditions (≤80 °C, ≤200 bar). While detrimental side fragmentation of the intermediate radical leading to loss of living chain‐ends was observed before with alkyl xanthate CTAs, this was absent for the aromatic CTAs. The loss of living chain‐ends was nevertheless detected for the aromatic xanthates via a different mechanism based on cross‐termination. Narrow molar‐mass distributions with dispersities between 1.2 and 1.3 were still obtained up to number average molar masses M_n of 1000 g mol^?1. The loss of chain‐ends was minor for dithiocarbamates, yielding polyethylene up to M_n=3000 g mol^?1 with dispersities between 1.4 and 1.8. While systems investigated showed significant rate retardation, the dithiocarbamates are the first CTAs giving polyethylene with a high livingness via RAFT polymerization.     

Crude Oil Model Emulsion Characterised by means of Near Infrared Spectroscopy and Multivariate Techniques

Water-in-oil emulsions are investigated by means of multivariate analysis of near infrared (NIR) spectroscopic profiles in the range 1100 — 2250 nm. The oil phase is a paraffin-diluted crude oil from the Norwegian Continental Shelf. The influence of water absorption and light scattering of the water droplets are shown to be strong. Despite the strong influence of the water phase, the NIR technique is still capable of predicting the composition of the investigated oil phase.     

Study on capillaries covalently bound with phospholipid vesicles for open‐tubular CEC and application to on‐line open‐tubular CEC‐MS

Phospholipid vesicles were covalently attached to iminoaldehyde‐coated fused silica capillaries and applied to the separation of model steroids by open‐tubular CEC (OT‐CEC). The effects of reducing the formed Schiff's base with sodium borohydride and of the liposome composition on the stability of the coating were investigated. In addition, the studies were focused on the optimization of running conditions (pH values and composition of BGE solution) when CEC, using capillaries covalently bound with liposome dispersions, was coupled to MS. The effect of cholesterol in the liposome dispersion on the binding of model analytes was studied, using liposome dispersions comprising 80:20 mol% zwitterionic 1‐palmitoyl‐2‐oleyl‐sn‐glycero‐3‐phosphocholine (POPC) and the negatively charged phospholipid 1 ‐ palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phospho‐l ‐serine (POPS) and 40:40:20 mol% POPC/POPS/cholesterol. Cholesterol in liposomes (greatly) enhanced the stability of the capillaries by making the coatings more rigid, resulting in lower retention factors for all the studied model steroids. Although most of the studies were carried out by open tubular CEC‐UV Vis, the applicability of the capillaries to on‐line CEC‐MS was demonstrated as well. On‐line CEC‐MS studies on model steroids proved the suitability of coated capillaries for analyte–lipid membrane interaction studies, and especially for such analytes that are difficult to detect by conventional on‐line UV Vis.     

Adsorption and adhesion studies of PdSn‐nanoparticles on protonated amine and carboxylic acid‐terminated surfaces

Electroless plating of acrylonitrile‐butadiene‐styrene‐terpolymers (ABS‐plastics) is used for decorative applications and relies on the immobilization of catalytic palladium‐tin nanoparticles. We used chemical force microscopy to measure the adhesion force of palladium‐tin nanoparticles on a patterned amine and carboxyl‐terminated surface prepared by micro‐contact printing. The kinetics of the adsorption process and the population density of the nanoparticles on amine and carboxyl‐terminated surfaces were monitored by quartz crystal microbalance with dissipation analysis. The surface chemistry was investigated by means of polarization‐modulated infrared reflection absorption spectroscopy and X‐ray photoelectron spectroscopy. Enhanced adhesion and population density of PdSn nanoparticles on protonated amine‐terminated surfaces compared with carboxyl‐terminated surfaces is observed. Copyright © 2016 John Wiley & Sons, Ltd.     

Mathematisches Denken in der Linearen Algebra

How can first years students learn to think and act mathematically by learning Linear Algebra? We want to present an approach that considers reflection of mathematical acting and its connections to general thinking to be an important part of learning. By understanding mathematics as a specific conventionalization of general thinking, patterns of general thinking can become the starting point for learning mathematics. This points out the specific contribution that mathematics can give to describe reality. By example of Linear Algebra, we discuss the common ground and differences between thinking in mathematics and in non-mathematical subjects. Based on this discussion, we analyse why and how these reflections can be objects of learning.