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- Pulsed plasma polymerization (2)
- r.f. pulsed plasma (2)
- Adhesion promoting interlayers (1)
- Charcterization of homo- and copolymers (1)
- Chemical conversion of functional groups (1)
- Conducting films (1)
- Copolymers (1)
- Degradation (1)
- Doping with metal atoms (1)
- ESCA/XPS (1)
- Encapsulation of nanoparticles (1)
- Functional groups (1)
- Long-term stability (1)
- Metal-polymer interactions (1)
- Metal-polymer interface (1)
- Metal-polymer systems (1)
- Oxygen low-pressure plasma treatment of polymers (1)
- Peel strength (1)
- Photoelectron spectroscopy (1)
- Plasma modification (1)
- Plasma polymer (1)
- Plasma polymerization (1)
- Plasma polymers with functional groups (1)
- Plasma treatment (1)
- Plasma-initiated copolymerization (1)
- Poly(propylene) (PP) (1)
- Polyethylene (1)
- Polymer-metal composites (1)
- Polypropylene (1)
- Pulsed plasma (1)
- Spacers (1)
- Surface modification (1)
- Surfaces (1)
- X-ray (1)
The chemical and morphological stabilities of polymer segments in the near-surface layer were investigated by spectroscopic methods such as X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. Model studies were undertaken with LangmuirBlodgett films, self-assembled monolayers and oligomer films. For thin polymer layers (30 to 500 nm), the changes in molecular-weight distributions of some polymers were investigated systematically by size exclusion chromatography, matrix-assisted laser desorption/ionizationtime-of-flight mass spectrometry and thermal-field flow fractionation for oxygen- and helium-plasma exposures. The polymer surfaces were found to be relatively stable at exposure to an oxygen low-pressure plasma up to ca. 2 s. This is important information to get maximum adhesion to metals in composites. In correlation to their redox potentials, potassium, aluminium and chromium react with oxygen functional groups at the polymer/metal interface. In a dedicated study, chromium was found to attack aromatic rings and form different reaction products.
Eine neue Generation von alterungsbeständigen Plasmapolymeren mit definierter chemischer Struktur
(2000)
Monotype functionalizations with different types of functional groups (OH, NH2, COOH) on polypropylene and poly(tetrafluoroethylene) surfaces were synthesized using pulsed plasma-initiated homo- or copolymerization of functional group-carrying monomers. The maximum concentrations of functional groups were 31 OH, 18 NH2 or 24 COOH groups per 100 C atoms using allyl alcohol, allylamine or acrylic acid respectively as the monomer. The measured peel strengths of aluminium deposits increased linearly with the concentration of functional groups. Near the maximum concentration of OH (>27 OH/100 C atoms) or at moderate concentrations of COOH groups (>10 COOH/100 C atoms), constant (maximum) peel strengths were measured due to the mechanical collapse of one component in the composite (cohesive failure). Interface failures in Al-PP composites were found with COOH, NH2 and OH groups and cohesive failures were seen when higher concentrations of COOH groups were applied (>10 COOH/100 C atoms).
Several possibilities exist to produce a modified polymer surface with a high density of only one sort of functional group such as: (i) the plasma grafting of unfragmented monomer molecules and their polymerization forms OH, NH2, COOH groups, etc. in concentrations of approximately 25 groups per 100 C atoms; (ii) selective plasma bromination provides 1025 CBr groups; (iii) the plasma oxidation of polymer surfaces in an O2 plasma followed by the chemical reduction of all O-containing groups to OH groups by diborane, vitride (Na complex) or LiAlH4 yields 914 OH groups per 100 carbon atoms; and (iv) the grafting of spacers with different endgroups onto OH or CBr groups produces 710 spacer molecules/100 C. This work was focused on the formation of thin plasma deposited polymer layers with a maximum of (homo)functional groups and with a minimum of chemical irregularities using the pulsed plasma technique. The monomers were allylalcohol, allylamine, acrylonitrile and acrylic acid. The further intent was to study the interactions of functional groups (OH, COOH, NH2) and deposited metals (Cr, Al, Ti). It was expected that more basic (NH2), weakly basic or neutral (OH) or more acidic (COOH) groups would show different interactions and chemical reactions with metal atoms.