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Schlagworte
- Plasma polymerization (5)
- Surface functionalization (4)
- Fluorescence spectroscopy (3)
- Surface modification (3)
- Aerosol-assisted DBD (2)
- Allyl alcohol (2)
- Aluminium (2)
- Dielectric properties (2)
- Dielectric relaxation (2)
- Peel strength (2)
Polypropylen (PP) ist als Niedrigenergie-Polymer ohne nass- und plasmachemische Vorbehandlung weder haftfest zu beschichten noch verbundfest zu kleben. Typische Haft- bzw. Klebfestigkeiten liegen für die unbehandelte Polymeroberfläche bei maximal 0,5 MPa. Hinzu kommt, dass bei der Bestimmung von Haft- und Klebfestigkeiten der unmodifizierten Oberfläche mit großen Streuungen zu rechnen ist, die bezogen auf die Spannweite durchaus einem Faktor 5 entsprechen können. Generell besteht bei Prüfung der Haftfestigkeit mittels Stirnabzugsversuch und bei der Prüfung der Klebfestigkeit die Notwendigkeit eines statistisch validierten Herangehens. Hierzu sind zeitaufwändige Ein-Proben-Klebungen und -Prüfungen nur eingeschränkt geeignet. Zudem ist, insbesondere für geringe Haft- bzw. Klebfestigkeiten, ein querkraftfreies Prüfen Grundvoraussetzung. Im vorliegenden Beitrag werden verschiedenartige plasmagestützte Oberflächenfunktionalisierungen von PP sowie das Mehr-Proben-Konzept zur Klebung/Prüfung von bis zu acht Proben vorgestellt. Dazu werden ein BAM-Funktionsmuster einer Mehr-Proben-Kleb-Vorrichtung und eine kommerzielle analytische Zentrifuge zum Prüfen verwendet.
Communication: Fire retardant coatings are deposited on polyamide-66 using plasma polymerisation. Chemical composition and thickness of deposits are adjusted varying the plasma treatment based on hexamethydisiloxane mixed with oxygen. The fire retardancy performances are evaluated using a cone calorimeter. The correlation between fire retardancy and thickness as well as chemical composition is discussed.
Immobilization of silanized DNA on glass: influence of the silane tether on the DNA hybridization
(2010)
Two trifunctional (trimethoxy and triethoxy) and one difunctional (methyldimethoxy) 3-mercaptopropyl-alkoxysilanes were covalently tethered to thiolated DNA oligonucleotides in solution. After deposition as microarrays onto glass, the immobilized DNA probes were tested for hybridization ability by a florescence-based method. The results demonstrate a large enhancement in the fluorescence signal when the functionality of the silane tether is reduced from three to two. An XPS analyses revealed that this is not due to a higher DNA surface density. FTIR spectra of the spin-coated silanes showed that the trifunctional silanes form branched and cyclic siloxane moieties, whereas the difunctional silane generates predominantly short straight siloxane chains. Therefore, the propensity of trifunctional silanes to form more complex networks leads to conformations of the bound DNA which are less favorable for the specific interaction with the complementary strand. The data implicate that further significant improvements in the DNA hybridization ability are possible by adroit choice of the silane system.
Bulk samples and thin films of polyamides (PA6 and PA12) were exposed to fluorine (1 - 10 vol.-% F2 in N2) and analysed with photoelectron (XPS) and infrared spectroscopy. Fluorination affects both, the amide and the hydrocarbon parts of the polymers. However, only the carbon atom next to the carbonyl is readily fluorinated. Chemical modification of the amide group is apparent in a large binding energy shift (+5 eV) of the N1s level and the appearance of a CO band at 1734 cm-1. It is concluded that the amide C-N bond is cleaved in the fluorination process and that COOH and NF2 end groups are formed. This conclusion is corroborated by the appearance of ester oxygen in the XPS and by the 19F NMR spectra of the volatile products that show fluorine signals chemically shifted about 200 ppm towards lower field as compared with the CHF environment.