Study of a zinc chloride in poly(ethylene glycol) layer on an aluminium oxide surface by inelastic electron tunneling spectroscopy

Abstract

AbstractInelastic electron tunneling spectroscopy is used to compare the adsorption onto aluminium oxide of poly(ethylene glycol) of relative molar mass 400 (PEG400) with poly(ethylene glycol) that has been coordinated 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 aluminium oxide surface. The zinc bonds both to atmospheric water and to the ether oxygens in the polymer, which restricts the conformational freedom of the polymer. This restriction causes the attachment of the polymer to the aluminium oxide substrate to be primarily by hydrogen bonding, which reveals itself through the appearance of an extra peak in the inelastic electron tunneling spectrum at ∼440 meV. The implication is that when monolayer coatings of PEG400/ZnCl2 are adsorbed on aluminium oxide, the coordination of the zinc with the polymer imposes a structure upon the latter.