Chemical reactions at polymer surfaces interacting with a gas plasma or with metal atoms -: their relevance to adhesion

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 Langmuir-Blodgett 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/ionization-time-of-flight mass spectrometry and thermal-held 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. Ln 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. (C) 1999 Elsevier Science S.A. All rights reserved.