Investigation of the cathodic electro polymerization of acrylonitrile, ethylarrylate and methylmethacrylate by coupled quartz crystal microbalance analysis and cyclic voltammetry

The cathodic electropolymerization of acrylonitrile (AN), ethylacrylate (EA) and methylmethacrylate (MMA), has been monitored for the first time by coupled electrochemical quartz crystal microbalance (QCM) and cyclic voltammetry analyses. These data have been compared to the previously published analyses for methacrylonitrile (MAN). At the potential E-p1 of the less cathodic of the two voltammetric peaks observed (peak I), the polymer formed is anchored firmly to the cathode even in a good solvent for it, and it remains adsorbed when the voltammetric scan is repeated up to E-p1. In parallel, a linear relationship is observed between the frequency change recorded in situ by the QCM up to E-p1 and the PAN film thickness measured ex-situ by ellipsometry. However, when potentials more negative than peak I are scanned, the: polymer desorption (degrafting) occurs as assessed by solubilization in a good solvent. Polymerization is also resumed but in solution and no longer as grafted chains. The major difference between the acrylic monomers (AN and EA) and the methacrylic ones (MMA and MAN) is that part of the methacrylic chains are not grafted at E-p1. This coexistence of adsorbed and desorbed chains is not observed for the polyacrylic chains in that potential range. The mass of PAN deposited onto the cathode has been approximated from the film thickness and the Sauerbrey equation, so allowing the M-n of the grafted chains to be estimated. (C) 1999 Elsevier Science S.A. All rights reserved.