The mechanism of coating formation by electropolymerization of poly(2-vinylpyridine) has
been studied on a copper electrode by surface-enhanced Raman scattering spectroscopy and cyclic
voltammetry. The experimental results are consistent with a mechanism in which 2-vinylpyridine
molecules become protonated in acidic aqueous solutions and are selectively adsorbed on cathodic surfaces.
The adsorbed 2-vinylpyridinium ions then undergo electrochemical reduction to free radicals, which initiate
polymerization by combining with neutral 2-vinylpyridine molecules also present in solution. The pH of
the electrolyte has been found to be critical for this process. On the basis of the voltammetric experiments,
an additional mechanism for polymer growth on the cathodic surface at more negative potentials is
proposed. This involves protonation of nitrogen sites along the newly formed poly(2-vinylpyridine) chains,
followed by their reduction to form polymeric radicals that can initiate chain branching. In this way,
inactive polymer chains can be reactivated and highly branched and cross-linked poly(2-vinylpyridine)
coatings can be formed, leading to the relatively low solubility of these coatings in typical organic solvents.
ABSTRACT:A new nondestructive technique, confocal scanning laser microscopy (CSLM), is described that is used to characterize the topography and morphology of polymer coatings. The topography of the coating can be determined even when the coating is completely opaque. When the coating is not completely opaque, CSLM has the distinct advantage of also being able to distinguish between the coating surface and the substrate, thus enabling coating thickness to be determined over a wide range of areas. In this study CSLM was successfully applied to poly(2-vinylpyridine) coatings formed on mild steel substrates by in situ electropolymerization. Satisfactory morphological details were obtained for areas ranging from 200 1 200 mm to 4 1 4 mm. Quantitative measurements of the coating thickness and the surface roughness distribution were also carried out. Although several other nondestructive techniques for coating morphological analyses are available, CSLM has unique advantages in being able to provide simultaneous qualitative and quantitative information on coating surfaces as well as measurements over a wide range of surface areas. A comparison of CSLM with other popularly used methods is provided and the characteristics and limitations of the various techniques are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.