STUDY OF A ZINC-CHLORIDE IN POLY(ETHYLENE GLYCOL) LAYER ON AN ALUMINUM-OXIDE SURFACE BY INELASTIC ELECTRON-TUNNELING SPECTROSCOPY

Inelastic electron tunneling spectroscopy is used to compare the adsor ption onto aluminium oxide of poly(ethylene glycol) of relative molar mass 400 (PEG(400)) with poly(ethylene glycol) that has been coordinat ed with zinc chloride. This work carried out on a low-molecular-weight analogue of a polymer electrolyte reveals that the steric hinderance brought about by the coordination of zinc chloride with poly(ethylene glycol) changes the mechanism by which the polymer bonds to an alumini um oxide surface. The zinc bonds both to atmospheric water and to the ether oxygens in the polymer, which restricts the conformational freed om of the polymer. This restriction causes the attachment of the polym er to the aluminium oxide substrate to be primarily by hydrogen bondin g, which reveals itself through the appearance of an extra peak in the inelastic electron tunneling spectrum at similar to 440 meV. The impl ication is that when monolayer coatings of PEG(400)/ZnCl2 are adsorbed oo aluminium oxide, the coordination of the zinc with the polymer imp oses a structure upon the latter.