Reversible functionalization and exfoliation of graphite by a Diels–Alder reaction with furfuryl amine

Furfuryl amine-functionalized few-layered graphene was prepared via a mechanochemical process by a [4 + 2] cycloaddition under solvent-free conditions. By employing ball milling, active sites are merged mostly at the edge of the graphene sheets which makes them prone to Diels–Alder click reactions (D–A) in the presence of a diene precursor. Consequently, one-pot grafting with furfuryl amine onto the graphene sheets, exfoliates pristine graphite resulting in functionalized few-layered graphene which is soluble in organic solvents. Thereafter, the cleavage of the bonds in the adduct can occur by exposure to an external stimulus like temperature, to initiate a retro-Diels–Alder reaction. The success of the thermoreversible functionalization of the few-layered graphene was confirmed by Raman spectroscopy, TGA, XPS, EDX, contact angle and XRD analysis. The morphology of the samples was investigated by scanning electron microscopy and AFM. The latter was utilized to estimate graphene thickness. The results showed that functionalization proceeded under nitrogen with dry ball milling and mild temperatures efficiently

Certification of a Reference Material with Eschericia Coli O157 (NCTC 12900) at a level of 4 Colony forming Unit per Material Sphere, IRMM-351

This report describes the certification of a reference material (IRMM-351) of Escherichia coli O157. Certified Reference Materials (CRMs) for microbiological analysis are indispensable tools for development and validation of detection methods and for the implementation and support of internal and external quality control in the area of microbiological analysis. Each vial contains one material sphere of E. coli O157. The homogeneity and stability (at 4 °C, -20 °C and -70 °C) of the batch was assessed by monitoring colony forming units (cfu) on nutrient agr (NA) and eterohemolysin agar (EhlyA) of selected vials by colony counting. The material is not stable at 4 °C but no instability was detected when stored at -20 °C for up to 12 months and at -70 °C for up to 54 months. The batch was characterised by six laboratories to determine a certified value of cfu per vial on NA and EhlyA. The certified value is 4 cfu on both agars with an expanded uncertainty of 2 using a coverage factor k = 2, corresponding to a level of confidence of about 95 %. DNA sequence analysis of the coding region for the fliC gene identified the material as E. coli O157.JRC.D.2-Reference material

Certification of a Reference Material with Salmonella Enteritidis (NCTC 12694) at a Level of 5 Colony Forming Units on Nutrient Agar and 4 Colony Forming Units on Xylose Lysine Deoxycholate Agar, IRMM-352

This report describes the certification of a reference material (IRMM-352) of Salmonella Enteritidis. Certified Reference Materials (CRMs) for microbiological analysis are indispensable tools for development and validation of detection methods and for the implementation and support of internal and external quality control in the area of microbiological analysis. Each vial contains one material sphere of S. enteritidis. The homogeneity and stability (at 4 °C, -20 °C and -70 °C) of the batch was assessed by monitoring colony forming units (cfu) on nutrient agar (NA) and xylose lysine deoxycholate (XLD) agar of selected vials by colony counting. The material is not stable at 4 °C byt no instability was detected when stored at -20 °C for up to 12 months and at -70 °C for up to 54 months. The batch was characterised by six laboratories to determine a certified value of cfu per vial on NA and XLD agar. A quite considerable performance difference of both agars was observed. The certified value is 5 cfu on NA with an expanded uncertainty of 2 and 4 cfy on XLD agar with an expanded incertainty of 2 using a coverage factor k = 2, corresponding to a level of confidence of about 95 %. DNA sequence analysis of the coding region for the sefA gene identified the material as S. enteritidis.JRC.D.2-Reference material

The nuclear magnetic resonance spectrum and aromatic character of 1,6;8,13-propano-[14]annulene

To corroborate the postulated aromaticity of [14]annulenes (2) we have analysed the pmr spectra of the recently synthesized 1,6; 8, 13-propano-[14] annulene (3) (I) and its 2-nitro derivative (II)

Nuclear Magnetic Resonance. Intermolecular Exchange of Methyl Groups in Methylcadmium Compounds

We wish to report nmr measurements of intermolecular exchange rates of methyl groups in dimethylcadmium. Our interest in this kind of problem has continued for some years, and it seems important to clarify the matter of exchange or nonexchange as the case may be

Korrosionsschutz und Struktur von Polymerblends aus wasserbasierten Polymerdispersionen

Organische Beschichtungen spielen eine große und wichtige Rolle für den Korrosionsschutz von Stahl. Die treibenden Kräfte für die Entwicklung und und Anwendung von Beschichtungen auf Wasserbasis auch für den Korrosionsschutz sind die Herausforderungen der steigenden Umweltanforderungen und die Einhaltung der gesetzlichen Vorschriften. Lösemittelbasierte Systeme werden durch wasserbasierte ersetzt, wobei zum Teil neue wässrige Harze entwickelt werden. Da sich dies aber aufgrund der Vielzahl, der bereits vorhandenen Polymerstrukturen sehr schwierig gestaltet, wird oft mit Hilfe der Blend-Technologie versucht, positive Eigenschaften bekannter Polymere miteinander zu verbinden. Wasserbasierte Polymerdispersionen auf Basis von Acrylaten und Acrylat-Copolymere besitzen einen Vorteil in Bezug auf Umwelt- und Arbeitsschutz, zeigen aber deutliche Schwächen im Korrosionsschutz von Stahl. Dies fällt besonders im Vergleich zu wasserbasierten Beschichtungen auf Basis von Zweikomponenten-Epoxy-Bindemitteln ins Auge. Daher wurden nun beide Bindemittelklassen systematisch gemischt (Blends erstellt) und mit korrosionsrelevanten Prüfungen untersucht. Um allgemeingültige Zusammenhänge abzuleiten, wurden die erhaltenen Resultate aus den Korrosionsprüfungen mit der Phasenstruktur der physikalisch gebildeten Polymerblends korreliert

A Reinvestigation of Nitrogen-15 Chemical Shifts of para-Substituted Nitrobenzenes

Recently several research groups have determined ^(14)N chemical shifts for para-substituted nitrobenzenes, which deviate both in magnitude and sign from ^(15)N shifts for corresponding compounds reported 3 years ago

Nuclear Magnetic Resonance Spectroscopy. Barriers to Internal Rotation in Some Halogenated Methylbutanes

Barriers to internal rotation about the C(2)-C(3) bonds have been determined for ten closely related halogenated methylbutanes by detailed line-shape analysis of their nuclear magnetic resonance spectra. The experimental barriers range from 9 to 16 kcal/mol. In addition, for some of the compounds investigated, free energy differences were obtained for rotational isomers under conditions of slow conformational exchange. The results are discussed in terms of possible contributing nonbonded interactions

Analytical characterization of polyamide 11 used in the context of selective laser sintering: Physico-chemical correlations

Polyamide 11 is an attractive material for additive manufacturing, however, in the selective laser sintering process it is subject to significant thermally induced stress. Suitable analytical methods are necessary to indicate any changes in the material properties. In this work, thermally stressed powder samples and printed tensile bars were analyzed by size exclusion chromatography-multi angle laser light scattering and differential scanning calorimetry. Based on the molecular weight distribution, crystallization and melting temperatures, ageing states of the investigated powders can be defined and transferred to the particles of the printed components. As a result, thermal stress led to an increase in molar mass and polydispersity. Moreover, calorimetric measurements indicated a delayed nucleation process as well as a decrease in polymorphism. Additionally, polymeric material with lower polydispersity values across the tensile bars could lead to decreasing elongation at break (epsilon(B)) values. For the crystallization onset temperature the opposite effect on epsilon(B) was observed