Structure of multiresponsive "intelligent" core-shell microgels

A doubly temperature-sensitive core-shell microgel composed of two temperature-sensitive polymers with different lower critical solution temperatures (LCSTs) in the core and shell has been studied by small-angle neutron scattering (SANS). The application of a novel universal form factor model in the analysis of the SANS data reveals that the radial density profile at temperatures above the LCSTs of both polymers can be well described by a two-box profile with narrow interfaces. At temperatures between the LCSTs, the radial density profile reveals that the core in the core-shell microgel has larger dimensions than the naked core. Thus the swollen shell pulls the core apart. At temperatures below both LCSTs, however, the shell restricts the core swelling, and the core is found to be smaller than in its native state. This clearly demonstrates the mutual influence of core and shell swelling.     

In-situ and ex-situ examination of the early stages of chemical vapor deposition

A cold working steel was coated both with high temperature CVD (TiN) and moderate temperature CVD (Ti[C,N]). AES depth profiles show a significant difference at the interface, where a thin oxide layer remains detectable at deposition temperatures of 750 °C. It could be shown that an impedance signal at a frequency of 13 MHz is well suited to detect the early stages of the growth of a CVD coating. Received: 15 July 1997 / Revised: 5 February 1998 / Accepted: 9 February 1998     

A host-guest optical sensor for aliphatic amines based on lipophilic cyclodextrin

A host-guest optical sensor for the determination of aliphatic amines as exemplified by octylamine is proposed. It is based on the reversible fluorescence enhancement of heptakis(2,6-di-O-isobutyl)-β-cyclodextrin(DOB-β-CD) hosting tetraphenylporphyrin (TPP) immobilized in poly(vinyl chloride) (PVC) membrane by aliphatic amine extracted from aqueous phase into membrane phase. The optimum membrane contained 1.15 wt % TPP, 6.15 wt % DOB-β-CD as sensing reagent and other membrane materials. The fluorescence enhancement of the membrane resulted from the formation of a stable three-component complex among DOB-β-CD, TPP, and aliphatic amines. With the optimum conditions described, the fluorescence response of the sensor to octylamine shows a good correlation with the theoretically derived equation in the range 1.0 × 10^–6 to 8.0 × 10^–4 mol/L. The response characteristics including reversibility, response time, reproducibility and lifetime and selectivity of this optical device are also discussed in detail. This sensor has also been applied for the determination of octylamine in water samples containing interferents with satisfactory recovery. Received: 21 November 1999 / Revised: 10 January 2000 / Accepted: 15 January 2000     

Accretion Product Formation from Self‐ and Cross‐Reactions of RO2 Radicals in the Atmosphere

Hydrocarbons are emitted into the Earth's atmosphere in very large quantities by human and biogenic activities. Their atmospheric oxidation processes almost exclusively yield RO₂ radicals as reactive intermediates whose atmospheric fate is not yet fully unraveled. Herein, we show that gas‐phase reactions of two RO₂ radicals produce accretion products composed of the carbon backbone of both reactants. The rates for accretion product formation are very high for RO₂ radicals bearing functional groups, competing with those of the corresponding reactions with NO and HO₂. This pathway, which has not yet been considered in the modelling of atmospheric processes, can be important, or even dominant, for the fate of RO₂ radicals in all areas of the atmosphere. Moreover, the vapor pressure of the formed accretion products can be remarkably low, characterizing them as an effective source for the secondary organic aerosol.     

Auger depth profiling of BaTiO3 ceramics

We investigated the sputter depth profiling of BaTiO₃ by means of Auger Electron Spectroscopy. A quantitative analysis was done for ceramic and single crystal material. Sputtering yield for 2 and 3 keV Ar⁺ ions was determined. For under UHV conditions fractured specimens no preferential sputtering was found. Mechanically polished or contaminated ceramic specimens show preferential sputtering of Ba or Ti. Using sputtering – heating cycles we succeeded in preparing non-contaminated but ion beam mixed surfaces which are stable upto 150 °C.