Electrografting of poly (carbazole-co-acrylamide) onto highly oriented pyrolytic graphite. A cyclovoltammetric, atomic force microscopic and ellipsometric study

The electrocopolymerization of carbazole and acrylamide on highly oriented pyrolytic graphite (HOPG) from ACN solutions via cyclovoltammetry (CV) was studied in order to evaluate the possibility to deposit uniform and thin bu t pinhole-free and still reactive coatings onto graphite-like substrates. T he morphology of the coatings was investigated using atomic force microscop y and the coating thicknesses and optical parameters were measured using el lipsometry. It was found that under the chosen conditions thin (coating thi ckness h(f) > 180 nm) and relatively smooth (root mean square surface rough ness RMS < 150 nm) P(Cz-co-AAm)-coatings exhibiting a uniform globuoidal mo rphology can be deposited onto graphite. From a certain coating thickness ( h(f) > 50 nm) no pinholes could be detected. It was found that the thicknes s of the deposited coatings increases almost linearly with increasing numbe r of CV-cycles while keeping all other experimental parameters (scan rate a nd comonomer concentration ratio) constant. No influence of the comonomer c oncentration ratio on the film thickness and coating appearance could be ob served, however, at quite low initial concentrations. However, the CV-scann ing rate has quite a significant influence on the thickness of the deposite d coatings. Higher scan rates (100 mV/s) result in thin (h(f) approximate t o 22 nm) coatings whereas at lower scan rates (< 50 mV/s) coatings with thi cknesses of approximately 50 nm were obtained. The optical coating paramete rs (the refractive index n and extinction coefficient k) seem to be indepen dent of the deposition parameters and therefore averaged values of (n) over bar = 1.54 +/- 0.03 and (k) over bar = 0.08 +/- 0.03 were obtained. (C) 20 01 Elsevier Science B.V. All rights reserved.