J. Tanguy et al., CATHODIC ELECTROPOLYMERIZATION OF METHACRYLONITRILE STUDIED IN-SITU BY QUARTZ-CRYSTAL MICROBALANCE, CYCLIC VOLTAMMETRY, AND IMPEDANCE SPECTROSCOPY, Journal of electroanalytical chemistry [1992], 417(1-2), 1996, pp. 175-184
The cathodic electropolymerization of methacrylonitrile was followed w
ith an electrochemical quartz crystal microbalance used in combination
with other classical techniques such as cyclic voltammetry, chronoamp
erometry and impedance spectroscopy. The quartz microbalance has revea
led a large adsorption-desorption process of the growing electropolyme
r on the cathode during repeated cycling. However, a polymer layer str
ongly bound to the electrode was obtained after several scans, though
it is normally soluble in the electrolytic solution. A visible delay b
etween the monomer reduction current and the quartz frequency response
was measured during successive sweeps and was found to be dependent o
n the scan rate. This delay was attributed to the time needed to form
a critical polymer concentration in the solution before adsorption. A
progressive change in the polymer conformation on the electrode was fo
und during repeated scans. This reorganization process of the electrop
olymer on the cathode was found to be comparable with the spontaneous
adsorption of special polymer chains bearing reactive groups capable o
f forming chemical bonds with some substrates. These grafted polymers
present well-identified structures, called pancake, mushroom and brush
. Finally, the behaviour of a polymethacrylonitrile layer swollen by s
olvent as well as in the dry state suggests a plausible evolution from
a mushroom type conformation to a definitive brush conformation durin
g the growth of the electropolymer on conducting electrodes.