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 co upled electrochemical quartz crystal microbalance (QCM) and cyclic voltamme try analyses. These data have been compared to the previously published ana lyses for methacrylonitrile (MAN). At the potential E-p1 of the less cathod ic of the two voltammetric peaks observed (peak I), the polymer formed is a nchored 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 s itu by the QCM up to E-p1 and the PAN film thickness measured ex-situ by el lipsometry. 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 lo nger 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 metha crylic chains are not grafted at E-p1. This coexistence of adsorbed and des orbed chains is not observed for the polyacrylic chains in that potential r ange. 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 r eserved.