Mechanistic studies of electrochemically deposited poly(o-anisidine) films

Abstract

Electrochemically deposited poly(o-anisidine) films exhibit a transition from insulating pernigraniline to conducting emeraldine salt phase by decreasing the pH of solution from 4.13 to -0.21 as observed from the optical spectra. A further decrease in pH does not affect the polymerization process. The sheet resistance of the substrate also has a remarkable influence in terms of rate and selectivity in the deposition of a particular phase. Morphological investigations indicate a change from a granular to a fibrillar type pattern with decrease in pH from 4.13 to -0.55. The substrate resistance and pH of solution are responsible for the voltammetric features. The polymerization mechanism mainly involves -NH,+ cationic coupling through preceeding chemical reactions. Thermograms exhibit a three-step decomposition pattern with large differences in the weight loss of individual steps. The final decomposition temperature of polymer varies with the pH of electrolyte solution, indicating the formation of different types of species during deposition.

Poly(m-chloroaniline): Electrochemical Synthesis and Characterization

“…16 However, the present results show that the conversion of these two species does not take place even at pH of 0.47 indicating that these higher acidic conditions are required for complete protonation of poly(m-chloroaniline). The exact reason behind this is still not clear and further studies are necessary to confirm this possibility.…”

“…24 The absence of peak around 0.13 Vat -1.66 pH demonstrates the short term stability of radical cations in highly acidic solution, which is in agreement with our previous results on poly(a-anisidine). 16 Increase in pH to -0.22 does not disturb the generalized pattern of cyclic voltammogram as observed at pH -1.66 except a new peak corresponding to the radical cation emerges around 0. I 3 V. Thus it can be stated that the concentration of protons at this pH is quite sufficient for making radical cation stable.…”

“…This loss seems equal to that for poly(a-anisidine) deposited electrochemically under identical condition. 16 Therefore, it is concluded that the loss of benzenic Cl -at pH -0.22 takes place in the beginning of the third stage, which is accompanied by destruction of the backbone completely. In contrast to this, at higher pH loss in the initial stage of second step can be attributed to the low molecular weight fragments along with a meagre amount of chlorine that could be coming from the fraction of pernigraniline salt.…”

Effect of protonation media on chemically and electrochemically synthesized polyaniline

“…Polyaniline and some of its derivatives have been extensively studied because of their ease of preparation by chemical and electrochemical methods, good environmental stability, and also because their electrical properties can be modified by both the oxidation state of the main chain and by protonation 1–4. These materials are found to be useful for a wide range of applications ranging from lightweight batteries to corrosion inhibitors 5–7.…”

Microspheres of Conducting Poly(N-methylaniline)

“…[1][2][3] The derivatives of PANI have also attracted considerable attention especially due to their higher solubility in common solvents than PANI. [4][5][6] Although several reports are available on ring alkyl substituted 7,8 and ring alkoxy substituted PANI, 6,9,10 N-alkyl substituted aniline still remains less attentive inspite of the fact that they are useful in certain applications. Barbero et al have used chemically produced poly(N-methylaniline) (PNMA) as a substrate for diazonium ion coupling in order to ensure preferential attack on the ring and to protect the amine nitrogen from possible exposure.…”