Filtern
Erscheinungsjahr
Dokumenttyp
- Vortrag (38)
- Beitrag zu einem Tagungsband (16)
- Posterpräsentation (13)
- Zeitschriftenartikel (10)
- Beitrag zu einem Sammelband (9)
- Buchkapitel (2)
Referierte Publikation
- nein (88) (entfernen)
Schlagworte
- MALDI-TOF MS (7)
- MALDI (5)
- Mass spectrometry (4)
- Polylactide (4)
- Ionization (2)
- MALDI TOF MS (2)
- Pollen (2)
- Polymers (2)
- Ring-opening polymerization (2)
- Transesterification (2)
- Abbauverhalten (1)
- Adhesion promoting interlayers (1)
- Bewitterung (1)
- Biobased (1)
- Biobased polymers (1)
- Carbon capture (1)
- Catalyst (1)
- Catalysts (1)
- Chemical conversion of functional groups (1)
- Chromatography (1)
- Climate change (1)
- Conductive carbon tape (1)
- Copolymers (1)
- Coupling techniques (1)
- Crystalinity (1)
- Cyclic (1)
- Depollution (1)
- Desorption (1)
- ESI (1)
- ESI-TOF MS (1)
- Electrospray ionization (1)
- Equilibration (1)
- Feuchte (1)
- Field flow fractionation (1)
- HPLC (1)
- Hyperbranched polyesters (1)
- ICP-MS (1)
- Imaging techniques (1)
- Isotope dilution analysis (1)
- Klassifizierung (1)
- Linear (1)
- Liquid adsorption chromatography (1)
- Lubricant (1)
- MALDI Imaging (1)
- MALDI-TOF Mass Spectrometry (1)
- MALDI-TOF Massenspektrometrie (1)
- MALDI-ToF MS (1)
- Matrix-assisted laser desorption/ionization (1)
- Metal-polymer interactions (1)
- Metal-polymer systems (1)
- Micro manufacturing (1)
- Multiphysics simulations (1)
- Multivariate Analyse (1)
- Multivariate statistics (1)
- Nanoparticles separation asymetrical flow field flow fractionation (1)
- Nässe (1)
- Oxygen low-pressure plasma treatment of polymers (1)
- Peel strength (1)
- Plasma modification (1)
- Plasma polymers with functional groups (1)
- Pollenkörner (1)
- Poly(lactide) (1)
- Polyethylene (1)
- Polyglycolide (1)
- Polylactides (1)
- Polylaktid (1)
- Polylaktide (1)
- Polymer (1)
- Polymer chromatography (1)
- Polymer mass spectrometry (1)
- Polymere (1)
- Polymerisation (1)
- Polypropylene (1)
- Polyurethan (1)
- Polyurethane (1)
- Principal component analysis (1)
- Ring-expansion polymerization (1)
- Sample pretreatment (1)
- Silver nanoparticles (1)
- Spacers (1)
- Surface analysis (1)
- TPU (1)
- Tandem MS (1)
- Time of flight (1)
- Tin acetates (1)
- Toxicology (1)
- UV (1)
- WMRIF (1)
- Zyklen (1)
- r.f. pulsed plasma (1)
Organisationseinheit der BAM
- 6 Materialchemie (12)
- 6.3 Strukturanalytik (12)
Eingeladener Vortrag
- nein (38)
The catalytic potential of tin(II)acetate, tin(IV)acetate, dibutyltin-bis-acetate and dioctyl tin-bis-acetate was compared based on polymerizations of L-lactide conducted in bulk at 160 or 130°C. With SnAc2 low-Lac/Cat ratios (15/1–50/1) were studied and linear chains having one acetate and one carboxyl end group almost free of cyclics were obtained. Higher monomer/catalyst ratios and lower temperatures favored formation of cycles that reached weight average molecular weights (Mw's) between 100,000 and 2,500,000. SnAc4 yielded mixtures of cycles and linear species under all reaction conditions. Dibutyltin- and dioctyl tin bis-acetate yielded cyclic polylactides under most reaction conditions with Mw's in the range of 20,000–80,000. Ring-opening polymerizations performed with ε-caprolactone showed similar trends, but the formation of COOH-terminated linear chains was significantly more favored compared to analogous experiments with lactide. The reactivity of the acetate catalysts decreased in the following order: SnAc2> SnAc4>Bu2SnAc2~Oct2SnAc2
Einfluss von Feuchte und Nässe auf die Witterungs-induzierte Alterung am Beispiel eines Polyurethans
(2017)
In diesem Beitrag soll der relative Einfluss des Wassers als Feuchte und Nässe unter den Beanspruchungsfaktoren untersucht werden. Die Unterscheidung von Luftfeuchte und Nässe bezüglich ihrer Wirkung ist dabei notwendig, weil die stehende Nässe zusätzliche Extraktionswirkung besitzt und auch die verfügbare Sauerstoffmenge beeinflusst.
Dazu wurde ein Polymer, das im Rahmen des BAM-internen Projektes PolyComp untersucht wird, künstlich bewittert. Hierzu wurde ein Fluoreszenzlampengerät mit UV-A 340 nm Leuchtstoffröhren verwendet, in dessen Probenraum durch zusätzliche Kammern die gleichzeitige Bewitterung unter drei unterschiedlichen Feuchte-Varianten realisiert wurde (bei konstanter Temperatur):
- UV und trocken
- UV und hohe Luftfeuchte
- UV und stehende Nässe
Das gleichzeitige Einwirken der einzelnen Einflussfaktoren kann dabei konkurrierende oder aufeinander folgende chemische Reaktionen und physikalische Prozesse und somit ein anderes Ergebnis bewirken, als wenn sie isoliert nacheinander auf eine Probe eingewirkt hätten.
Über die erwähnten Varianten hinaus kann auch noch der spezifische Einfluss der UV-Strahlung mit untersucht werden, weil die Proben im Bereich ihrer Befestigung verdeckt sind.
Die Methodik und erste Ergebnisse dieser Untersuchung werden präsentiert.
The performance of a miniaturized channel for the separation of polymer and metal nanoparticles (NP) using Asymmetrical Flow Field-Flow Fractionation (AF4) was investigated and compared with a conventional AF4 system. To develop standard separation methods, experimental parameters like cross flow, gradient profile and injection time were varied and optimized.
Corresponding chromatographic parameters were calculated and compared. Our results indicate that the chromatographic resolution in the miniaturized channel is lower, whereas significantly shorter analyses time and less solvent consumption were obtained. Moreover, the limit of detection (LOD) and limit of quantification (LOQ) obtained from hyphenation with a UV-detector are obviously lower than in a conventional channel, which makes the miniaturized channel interesting for trace analysis.
Poly(l-lactide)s are synthesized and annealed at 120 °C and changes of the molecular weight distribution (MWD) are monitored by matrix-assited laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. For example, benzyl alcohol+SnOct2 causes equilibration of odd- and even-numbered chains and the final goal of the transesterification is the most probable distribution. The underlying intermolecular transesterification is even observed at 100 and 80 °C in the solid state. However, cyclic tin mercaptide catalysts transform the initial most probable distribution into a MWD with maxima, which display a conspicuous fine structure due to a preferential crystallization of certain ring sizes. The optimum ring sizes for the crystallization are provided by ring-ring equilibration. The gradual formation of a special morphology shifts the melting temperature to values up to 187 °C. Annealing of commercial poly(l-lactide) with a cyclic tin catalyst also yields a distribution of mass peaks with a maximum showing the characteristic fine structure.
Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) is a well-implemented analytical technique for the investigation of complex biological samples. In MS, the sample preparation strategy is decisive for the success of the measurements. Here, sample preparation processes and target materials for the investigation of different pollen grains are compared. A reduced and optimized sample preparation process prior to MALDI-TOF measurement is presented using conductive carbon tape as target. The application of conductive tape yields in enhanced absolute signal intensities and mass spectral pattern information, which leads to a clear separation in subsequent pattern analysis. The results will be used to improve the taxonomic differentiation and identification, and might be useful for the development of a simple routine method to identify pollen based on mass spectrometry.
Ring-expansion polymerizations (REPs) catalyzed by two cyclic tin catalysts (2-stanna-1.3-dioxa-4,5,6,7-dibenzazepine [SnBiph] and
2,2-dibutyl-2-stanna-1,3-dithiolane [DSTL]) are performed at 140 °C in bulk.
Small amounts (4 vol%) of chlorobenzene or other solvents are added to
facilitate transesterification reactions (ring–ring equilibration) in the solid poly(l-lactide)s. In the mass range up to m/z 13 000 crystalline PLAs displaying a so-called saw-tooth pattern in the MALDI-TOF mass spectra are obtained indicating the formation of extended-ring crystals. The characteristics of extended-ring crystallites and folded-ring crystallites are discussed. Furthermore, extremely high melting temperatures (Tm’s up to 201.2 °C) and melting enthalpies (𝚫Hm’s up to 106 J g−1)) are found confirming that 𝚫Hm max, the 𝚫Hm of a perfect crystal, is around or above 115 J g−1 in contrast to literature data.
Glycolide was polymerized in bulk by means of four different ROPPOC catalysts: tin(II) 2-ethylhexanoate (SnOct2), dibutyltin bis(pentafluoro-phenoxide) (BuSnOPF),zinc biscaproate (ZnCap), and zinc bis(pentafluoro-phenyl sulfide) (ZnSPF). The temperature was varied between 110 and 180°C and the time between 3 h and 7 days. For the few polyglycolides (PGAs) that were soluble extremely high molecular masses were obtained. The MALDI TOF mass spectra had all a low signal-to-noise ration and displayed the peaks of cyclic PGAs with a“saw-tooth pattern ”indicating formation of extended-ring crystallites in the mass range below m/z 2500. The shape of DSC curves varied considerably with catalyst and reaction conditions, whereas the long-distance values measured by SAXS were small and varied little with the polymeriza-tion conditions.