Polyethylene films Responsive surfaces

Friedrich et al. also used XPS to investigate the mechanisms responsible for adhesion between evaporated metal films and polymer substrates [28]. They suggested that the products formed at the metal/polymer interface were determined by redox reactions occurring between the metal and polymer. In particular, it was shown that carbonyl groups in polymers could react with chromium. Thus, a layer of chromium that was 0.4 nm in thickness decreased the carbonyl content on the surface of polyethylene terephthalate (PET) or polymethylmethacrylate (PMMA) by about 8% but decreased the carbonyl content on the surface of polycarbonate (PC) by 77%. The C(ls) and 0(ls) spectra of PC before and after evaporation of chromium onto the surface are shown in Fig. 22. Before evaporation of chromium, the C(ls) spectra consisted of two components near 284.6 eV that were assigned to carbon atoms in the benzene rings and in the methyl groups. Two additional... 

These films have also been used to improve the charge transfer efficiency of photovoltaic cells employing solid state electrolyte Polypyrrole was used to modify the interface between n-Si and polyethylene oxide-KI/I solid electrolyte in a thin film photoelectrochemical cell (see Fig. 11). This cell has an open circuit potential of 320 mV when irradiated with 100 mW/cm tungsten-halogen light. The photocurrent response and the stability of the cell was improved by an order of magnitude when the n-Si surface was precoated with 1--2 nm of platinum. 

As indicated above, the surface treatment process may be responsible for the removal of such material and exposing the bulk of the polymer underneath the segregated layer. Such a situation can be illustrated by the XPS spectra of Fig. 10.4 fi om PVC in its extruded form and after flame treatment. The extrudate is protected by a thin film of low density polyethylene (LDPE), and upon removal of this film the spectrum (O Fig. 10.4a) is dominated by carbon and oxygen with significant contributions from PVC-spedfic elements such as chlorine, lead, and zinc. On flame treatment (O Fig. 10.4b), the carbon level is reduced to a certain extent... 

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