Thermal degradation and flame retardance in copolymers of methyl methacrylate with diethyl(methacryloyloxymethyl)phosphonate

Methyl methacrylate (MMA) has been free radically copolymerized, both in bulk and in solution, with diethyl(methacryloyloxymethyl)phosphonate (DEMMP), to give polymers which are significantly flame retarded when compared with PMMA, as indicated by the results of limiting oxygen index (LOI) measurements, UL 94 tests, and the results of cone calorimetric experiments. The physical and mechanical properties of the copolymers are similar to those of PMMA, except that the bulk copolymers are slightly crosslinked, and are better than those of PMMA flame retarded to a similar extent by some phosphate and phosphonate additives. Examination of the some of the gaseous products of pyrolysis and combustion, and of chars produced on burning, show that flame retardation occurs in the copolymers by both a condensed-phase and a vapour-phase mechanism. The condensed-phase mechanism is shown to involve generation of phosphorus acid species followed by reaction of these with MMA units giving rise to methacrylic acid units. The methacrylic acid units subsequently form anhydride links, which probably impede depolymerization of the remaining MMA sequences, resulting in evolution of less MMA (the major fuel when MMA-based polymers burn). By undergoing decarboxylation, leading to interchain cyclisation and, eventually, to aromaticisation, the anhydride units are probably also the principal precursors to char.     

Cosmic-muon results from the NUSEX experiment

Summary Muon underground data collected in the NUSEX experiment at Mont Blanc have been analysed concerning the following topics: I) vertical muon intensity, II) prompt muon flux, III) muons from the direction of Cygnus X-3. Preliminary results from the analysis of more than 20 000 muons are presented and discussed.

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Riassunto Gli eventi di muoni rivelati sottoterra nell'esperimento NUSEX al Monte Bianco sono stati analizzati per studiare I) l'intensità verticale dei muoni, II) il flusso di muoni pronti, III) l'eccesso di muoni dalla direzione di Cygnus X-3. In questo lavoro sono presentati c discussi i risultati preliminari ottenuti dal'lanalisi di piú di 20.000 eventi.

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Резюме Был проведен анализ данных, собранных в экспеимемнте NUSEX на Мон Блане. Анализировались следующие вопросы: 1) интенсивность вертикальных мюонов, 2) поток мгновенных (быстрых) мюонов, 3) мюоны, движущиеся в направлении от Лебедь X-3. Приводятся и обсуждаются предварительные результаты анализа для более, чем 20 000 муонов.

     

Electron impact ion fragmentation pathways of peracetylated C‐glycoside ketones derived from cyclic 1,3‐diketones

Monosaccharide C‐glycoside ketones have been synthesized by aqueous‐based Knoevenagel condensation of isotopically labeled and unlabeled aldoses with cyclic diketones, 5,5‐dimethyl‐1,3‐cyclohexanedione (dimedone) and 1,3‐cyclohexanedione (1,3‐CHD). The reaction products and their corresponding acetylated analogs produce characteristic molecular adduct ions by matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐TOF MS). Analysis of the peracetylated C‐glycosides by electron ionization (EI) gas chromatography/mass spectrometry (GC/MS) revealed diagnostic fragment ions that have been used to deduce the EI fragmentation pathways and the structure of each C‐glycoside ketone. Characteristic gluco‐ and ribo‐specific ions were observed at m/z 350 and 278, respectively. Ions common to both carbohydrate fragmentation pathways were observed at m/z 193 and 169 for the dimedone‐C‐glycosides, and m/z 165 and 141 for the 1,3‐CHD‐C‐glycosides. Ions with m/z 169 and 141 retain the anomeric carbon (carbon‐1) of the original sugar, while m/z 193 and 165 are shown to retain carbons‐1, 2, and 3. Published in 2009 by John Wiley & Sons, Ltd.     

Convexity control and approximation properties of interpolating curves

A constrained rational cubic spline with linear denominator was constructed in [1]. In the present paper, the sufficient condition for convex interpolation and some properties in error estimation are given.     

Copper(II) complexes with a flexible oxamato ligand

We report on a convenient synthesis of the ligand precursor, diethylethylene-1,2-bis(oxamate), (Et₂H₂oeo, 1), and show how a partial and preferential hydrolysis of the ester group can give rise to the dianionic ligand, (H₂oeo)²⁻. Reaction of this ligand with Cu(II) affords the neutral dimeric species, [Cu₂(H₂oeo)₂], which has a low aqueous solubility. We describe the crystal structure of the hydrate Cu₂(H₂oeo)₂(H₂O)₄ (2) and report magnetic studies that show a weak exchange interaction in the solid. Under more basic conditions and in the presence of Cu(II) ions, we are able to avoid amide cleavage and yet deprotonate the amide group, resulting in the formation of the highly soluble [Cu(Hoeo)₂]⁴⁻ complex anion. The structure of (NBu₄)₄[Cu(Hoeo)₂](H₂O)₄ (3) is described and compared with the recently reported anhydrous phase.     

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Fortschritte in der analytischen Chemie seltener Metalle

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