ARGON PLASMA-INDUCED MODIFICATIONS AT THE SURFACE OF POLYCARBONATE THIN-FILMS

The chemical modification of the surfaces of polycarbonate films by mi crowave-induced argon plasma treatment has been followed by X-ray abso rption spectroscopy (XAFS) and core level photoemission spectroscopy ( XPS). Measurements have been made on thin films of both ex-situ spin-c oated bis-phenol-A polycarbonate with phenol endgroups and the model c ompound bis-phenol-A polycarbonate (n = 1) with tert-butyl phenyl endg roups evaporated in-situ in UHV on single crystal surfaces. A preferen tial orientation of a monolayer of the model compound on a Ag{111} sur face was determined from the angular dependence of the XAFS spectra. S pectral features were assigned to contributing transitions within diff erent moieties. Relatively mild microwave Ar plasma activation of the surfaces of both types of films led to a decrease in intensity of carb onyl features in both XAFS and XPS. Combined with the observation of n ew spectral features in XPS the data can be interpreted in terms of a formation of ester and ether groups in the near-surface region with po ssible cross-linking after desorption of CO or CO2. (C) 1998 Elsevier Science B.V.