Spectrophotometric and electrochemical quartz crystal microbalance investigations of viologen and poly(viologen) films.

摘要

The electrochemical quartz crystal microbalance (EQCM) technique is used to study the deposition and dissolution mechanisms of thin films of diheptylviologen bromide. Deposition of a uniform, compact film with little incorporation of supporting electrolyte is indicated for potential steps well past the first reduction wave of the viologen. Films with considerable surface roughness are deposited when using potential sweep methods, depending on conditions. Methods are presented which provide the apparent molar mass of the depositing species from appropriate combination of the QCM and electrochemical data. Due to the potentially detrimental influence of non-uniform current density on the QCM measurements, an ancillary study of copper deposition was carried out to demonstrate the uniformity of the current density in the viologen experiments and to verify the use of QCM measurements under such conditions.;The electrochemistry of surface modified poly(xylylviologen) (PXV) and poly(xylylviologen)-poly(strenesulfonate) (PXV-PSS) on gold electrodes are studied using the EQCM. These findings show that anion expulsion takes place in the PXV polymer film during electrochemical reduction to maintain electroneutrality in the film. Some percentage of solvent accompanies this transport. It is further reported that in the PXV-PSS composite film ion transport can be controlled across the polymer/solution interface by changing the ratio of PXV to PSS in the polymer complex. QCM measurements are used to identify the species in transit.;The N = 3 rule is investigated on poly(propylviologen) (PPV), poly(hexylviologen) (PHV), and poly(hexylpropylviologen) (PHPV). Spectroelectrochemical studies are done on these compounds both as polymer films and in solution phase. UV-Visible spectra are collected both before and during redox. These results show the formation of an intramolecular complex by those molecules containing a propyl group (3 methylene units) in the chain. Spectroelectrochemical studies are also reported on 1,1