EQCM Study of the Adsorption/Desorption Processes of Polyethyleneglycol with Molecular Weight 20,000 on Pt in Perchloric Acid Solution

The adsorption of polyethyleneglycol with molecular weight 20,000 (PEG20000) on a Pt-QCM electrode was investigated using an electrochemical quartz crystal microbalance (EQCM). A study of the adsorption of PEG20000 on the surface of the Pt-QCM at the open circuit potential showed that the mass adsorbed reached a stationary value with time. In addition, the adsorption of PEG20000 did not interfere with the oxidation of the Pt surface to form a PtO film. Analysis of simultaneously recorded voltammograms and massograms disclosed that during the potential scan in the negative direction, three processes occur involving the partial desorption from the Pt surface of different species formed by the degradation of PEG20000. During the positive potential scan, an oxidation/adsorption process was observed in the potential range 0.10 to 0.60 V. This process involves the oxidation of products from the reduction of PEG20000, and corresponds to the oxidation of an alcohol CHCHO)CH(CH-O-H 32822 −−− − ) to form the corresponding adsorbed carboxylic acid ( ads22262223 COOH)CHO-CH-()CHCHO(CHCH −−−−−−− − CHO)