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 phot oelectron spectroscopy and near-edge X-ray absorption fine structure spectr oscopy. Model studies were undertaken with Langmuir-Blodgett films, self-as sembled monolayers and oligomer films. For thin polymer layers (30 to 500 n m), the changes in molecular-weight distributions of some polymers were inv estigated systematically by size exclusion chromatography, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry and thermal-he ld flow fractionation for oxygen- and helium-plasma exposures. The polymer surfaces were found to be relatively stable at exposure to an oxygen low-pr essure plasma up to ca. 2 s. This is important information to get maximum a dhesion to metals in composites. Ln correlation to their redox potentials, potassium, aluminium and chromium react with oxygen functional groups at th e polymer;metal interface. in a dedicated study, chromium was found to atta ck aromatic rings and form different reaction products. (C) 1999 Elsevier S cience S.A. All rights reserved.