Conducting polymers ellipsometry

Some works have been recently published on several monomers using various techniques especially EQCM [152], AFM [153], and ellipsometry [154] have been used in parallel to electrochemistry [155-157] to analyze the growth of the polymer, but always without focusing on the first steps. In another approach, polymeric additives have been used in the polymerization feed to act as templates for the formation of the conducting polymer. A remarkable recent work shows that PPy nanotubes can be directly prepared from a polymer blend solution, without an external porous membrane (or clay) as formerly classically prepared [158]. 

The application of combined electrochemical and nonelectrochemical techniques, such as piezoelectric microgravimetry atEQCM [10,40,73,74,132,134,139-144], radiotracing [27,145], various spectroscopies [16,44,72,100,116,117,146] and microscopies [19,29,46,79,97,114,127,147,148], ellipsometry [15,21,26,86], conductivity [80], and probe beam deflection [149], has allowed irs to gain very detailed insights into the nature of electropolymerization and deposition processes, and so the production of conducting polymers, polymeric films, and composites with desired properties is now a well-established area of the electrochemical and material sciences. 

In the previous section it was shown that detailed information about electrochemical processes and the kinetics of follow-up chemical reaction steps can be investigated by UV/Vis/NIR spectroelectrochemical experiments in transmission mode in the diffusion layer at optically transparent or microstructured non-transparent electrodes. Many metal electrodes show a high reflectivity and therefore optical spectra may also be recorded under in situ conditions in reflection mode [70, 71]. This approach is essential for the study of adsorbed species, the formation of solid layers at the electrode surface, reactions of solids [72-74], and the redox behaviour of conducting polymer layers [75-77]. Furthermore, in reflection mode, the angle of incidence may be modified and polarised light maybe used in ellipsometry studies [78]. 

Finally, application of other methods of analysis can be recommended. Many of the previous electrochemical studies devoted to conducting polymers were carried out in combination with radiotracer technique, AC electrogravimetry, quartz-crystal microbalance, surface plasmon resonance, and even ellipsometry, and atomic-force microscopy. In this context application of emerging experimental techniques such as local EIS and nonlinear impedance analysis may also be recommended. 

For a polyanUine film, the light absorption measurements were conducted after the film was exposed to HCl and NH3 vapors, respectively, as shown in Fig. 14 [19]. The difference in the spectra indicated that HCl and NH3 vapors induced a different band structure and conformation of the polymer. Therefore, the optical property of the film changed when the film switched from one state (doped by HCl) to another (dedoped by NH3). The refractive index measurement by ellipsometry showed that the refractive index changed from 2.43 (doped by HCl) to 1.95 (dedoped by NH3). 

An initial dissolution study was conducted with spin cast films containing different concentrations of PAC dispersed uniformly throughout the polymer matrix. Solutions containing S wt% solids in 2-etho ethanol were spun at 2000 rpm for 40 seconds yielding films that were approximately 1000 A. Thicknesses were determined by ellipsometry after the films were baked at 90 C for 30 minutes on an aluminum block in a convection oven to remove residual casting solvent. Samples with PAC concentrations varying from 0-50% by weight of polymer were prepared for study. 

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