Synthesis of diblock copolymers by combination of organocatalyzed ring‐opening polymerization and atom transfer radical polymerization using trichloroethanol as a bifunctional initiator

This study reports an application of trichloroethanol (TCE) as a bifunctional initiator for the synthesis of block copolymers (BCPs) by organocatalyzed ring‐opening polymerization (OROP) and atom transfer radical polymerization (ATRP). TCE was employed to synthesize a low dispersity poly (valerolactone) macroinitiator, which was subsequently used for the ATRP of tert‐butyl methacrylate. While it is known that TCE can serve as an initiator in ATRP, the ability to induce polymerization under OROP is reported for the first time. The formation of well‐defined BCPs was confirmed by gel permeation chromatography and ¹H NMR. Computational studies were performed to obtain a molecular‐level understanding of the ring‐opening polymerization mechanism involving TCE as initiator. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 563–569     

Characterization and Control of Residual Stress and Curvature in Anodically Bonded Devices and Substrates with Etched Features

While anodic bonding is commonly used in a variety of microelectromechanical systems (MEMS) applications, devices and substrates that incorporate this processing technique are often subjected to significant residual stress and curvature that create post-processing and reliability issues. Here, using an anisothermal anodic bonding procedure, residual stresses and the resulting wafer curvature in these structures are controlled by varying the initial bond temperatures of the silicon and Pyrex wafers independently. Residual stresses are quantified by measuring bulk wafer curvature and, locally, stress concentrations are measured using infrared photoelasticity accompanied by 3-D thermomechanical finite element analysis. Based on the good agreement between numerical predictions and experimental results, this process can be used to determine the bulk post-bond wafer curvature and to reduce the likelihood of structural failure at these sites, by changing the residual stresses from tensile in nature, which may drive initiation and growth of cracks, to compressive, which can suppress such failures.     

Development of a time-resolved white-light interference microscope for optical phase measurements during fs-laser material processing

A modified Mach–Zehnder interferometer set-up combined with microscope objectives has been developed for the measurement of phase changes in the processed material sample, like modification and melting of glass. The white light is generated by focusing ultrafast laser radiation (t _p=80 fs) in a sapphire crystal using a micro-lens array to minimize temporal and spatial fluctuations in the white-light continuum. Lateral and coaxial pump-probe measurements of the phase changes during material processing are performed using two coupled ultrafast laser sources at different repetition rates (f _rep=1 Hz–1 MHz). The optical phase shift and therefore the refractive index of the material are calculated from the interference images using two approaches. The knowledge of the refractive index during the laser processing with a temporal resolution in the ps-range and a spatial resolution of several microns leads to a better understanding of the initial processes for the permanent material modifications.     

Syntheses and structural analysis of 10-monoxy- and -dioxy-5-N-substituted iminothianthrene derivatives and the stereochemical change on their sulfur atom under acidic and thermal conditions

5-(N-p)-Toluenesulfonyl)iminothianthrenes, whose sulfur atoms are oxidized to a sulfoxide or sulfone at the 10-position, were hydrolysed readily in high yield to N-unsubstituted-sulfilimines by using concentrated H2SO4. During hydrolysis, 10-monoxy-5-N-unsubstituted-sulfilimines were obtained as a separable mixture of the cis and trans isomers. The stereochemical interconversion of these compounds was studied under both hydrolytic and thermal conditions and their structures were elucidated by using X-ray crystallography.     

The KAPA system in biochemical analysis. Principles-instrumentation-application

Summary The KAPA technique is a mechanized microanalytical system for biochemical analysis, particularly adapted to enzymatic analysis in research, clinical chemistry and toxicology. Total test volumes are between 5 and 80l. The reagent waste is reduced to about 0.5–5% of that with conventional tests. Fifty assays are carried out in parallel. The efficiency is between 300 assays/hour and 500/day. There are three versions of the technique. (1) Threshold tests requiring a minimum of equipment and delivering semiquantitative results; they are suitable for large scale screening and yes/no decisions. (2) Quantitative paper tests using a relatively simple measuring device and giving an analytical quality acceptable for clinical chemistry. (3) Multicuvette tests using a measuring instrument of higher sophistication, and suitable for kinetic determinations; they open a wide field of application, including colorimetric, polarimetric, nephelometric and fluorimetric evaluation, the last being the preferred evaluation mode for all three versions. The instrumental equipment comprises reaction chambers, a special measuring device, dispenser pipette, fully mechanized 50-fold multipipette and various accessories.

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Das KAPA-System in der biochemischen Analyse

Zusammenfassung Die KAPA-Technik ist ein mikroanalytisches System für die biochemische und insbesondere enzymatische Analyse in Forschung, klinischer Chemie und Toxikologie. Es werden Testvolumina zwischen 5 und 80l benutzt. Der Reagenzienverbrauch ist auf 0,5–5% gegenüber herkömmlichen Techniken gesenkt. 50 Tests werden parallel ausgeführt. Der Probendurchsatz liegt zwischen 300/Stunde und 500/Tag.Drei Versionen der Technik stehen zur Verfügung: 1. Schwellentests erfordern ein Minimum an Ausrüstung und liefern semiquantitative Ergebnisse. Sie sind den Bedingungen großer Reihenuntersuchungen und ja/nein-Entscheidungen angepaßt. 2. Für quantitative Papiertests kann ein relativ einfaches Meßgerät benutzt werden. Die analytische Qualität entspricht üblichen Empfehlungen für die klinische Chemie. 3. Multiküvettentests werden in einem Meßgerät größerer technischer Komplexität durchgeführt.Sie ermöglichen kinetische Bestimmungen und sind in weitem Rahmen für die Lösung vielfältiger analytischer Aufgaben mit kolorimetrischer, polarimetrischer, nephelometrischer und fluorimetrischer Auswertung einsetzbar. Diese wird in allen drei Versionen bevorzugt.Die Geräteausrüstung umfaßt Reaktionskammern, ein spezielles Meßgerät, Hohlkolbenpipette, vollmechanisierte 50fach-Multipipette und verschiedene Zusatzgeräte.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Einfluß der Verarbeitungsbedingungen auf die Kristallinität und Gefügestruktur teilkristalliner Spritzgußteile

Zusammenfassung Es wurden Mikrotomschnitte von teilkristallinen Spritzgußteilen (PE, PP, POM) aus verschiedenen Querschnittstiefen entnommen und mit dem Polarisationsmikroskop, der DTA/DSC-Analyse sowie durch Dichtemessungen untersucht. Die Kristallinität und Gefügestruktur sind entsprechend den unterschiedlichen Abkühl- und Fließbedingungen über dem Querschnitt stark inhomogen. Bei linearem Polyäthylen liegt die Zone höchster Kristallinität dicht unterhalb der Formteiloberfläche. Bei der Differential-thermoanalyse tritt bei Proben aus diesem Bereich ein typischer Doppelschmelzpeak auf. Im Zugversuch weisen diese Zonen eine geringe Bruchdehnung auf, während sich die Rand- und Kernschichten duktil verhalten.

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Summary Microtome cuts of partially crystalline injection mouldings (PE, PP, POM) were taken out of different cross-section layers and analysed with the polarization microscope, the DTA/DSC-analysis and by density measurements. The crystallinity and morphological structure are strongly inhomogeneous according to the different cooling and flow conditions across the cross-section. With linear polyethylene the zone of the highest crystallinity lies closely under the moulding's surface. In differential thermal analysis a typical double melting peak appears with samples of this range. In the tensile test these zones show a small elongation at fracture, whereas the marginal and core layers behave ductily.

     

Effects of neutrino degeneracy on the transport properties of presupernovae

Degeneracy of neutrinos undergoing coherent scattering by atomic nuclei inhibits their diffusion and enhances their thermal conduction and viscosity. For great degeneracy diffusion vanishes, while viscosity becomes independent of the temperature; the heat conductivity becomes independent of the neutrino chemical potential after attaining a maximum in the regime of intermediate degeneracy.     

Silicon in organic synthesis. 14. Five ring annulation processes based upon thermal rearrangement of (1-trimethylsilylcyclopropyl)ethylenes

Pyrolysis of (1-trimethylsilylcyclopropyl)ethylenes affords silyl substituted cyclopentenes in high yield. Subsequent reaction of these products with varied electrophiles forms the basis of a new and versatile five-ring annulation sequence.