Morphological Investigations of Electrochemically Deposited Polyaniline Films

Abstract

ABSTRACT:The effect of rate of mass transfer on the surface morphology of electrochemically deposited polyaniline films was studied using scanning electron microscopy (SEM). The rate of mass transfer was controlled by varying the sheet resistance of electrode and the monomer concentration. Both these parameters are found to affect the deposition process and the surface morphology to a considerable extent. The polyaniline film deposited using 0.1 M monomer concentration on electrode with 50 0/0 sheet resistance shows a granular structure joined together with fine fibrils. Increase in the monomer concentration and decrease in the sheet resistance of the electrode lead to the enhancement in the growth of the polymer film as revealed from the current time transient measurements. The formation of fibres with different shapes such as rope-like, curved, cyclone-like, petal-like, wavy, wing-like, and criss-cross linking depends on the growth conditions of films. The sheet resistance of electrode mainly determines the number density of these fibres, whereas, the patterning is governed by the monomer concentration.KEY WORDS Polyaniline / Electrochemical Deposition / Morphology / Scanning Electron Microscopy (SEM) / Polyaniline has turned out to be a very promising electroconductive polymeric material because of its ease in preparation as well as good environmental stability. Attempts are being made to prepare thin films of this material having good thermal, mechanical and electrical properties so as to use these films for various applications as in electrochromic devices, batteries, smart windows etc. 1 • 2 For such kind of applications it is important that the surface of the film be quite smooth. Therefore, it becomes necessary to study the morphological properties of films deposited under various experimental conditions. This would help in establishing the optimum conditions for obtaining good quality films. Limited work in this regard have been published. 3 -5 deposition of poly(o-anisidine) films, while the monomer concentration determines the extent of formation of variable oxidation states of polymer. 6 The present study was undertaken to examine the effect of rate of mass transfer on the morphological properties by varying sheet resistance of electrode and monomer concentration on the electrochemically deposited polyaniline films using SEM technique.We have already reported that the sheet resistance of the electrode con trolls the rate of EXPERIMENT ALAll the chemicals used were of analytical reagent grade. The aqueous solutions were prepared using double distilled water. Transparent Sn0 2 : F thin films having coated on corning 7059 glass substrates were used as electrodes. Electrodes with three different sheet resistances* 1 as 50, 20 and 100/D (referred * 1 The sheet resistance, p,(0/0) is defined asp, =p/t where pis the reciprocal of conductivity (0cm) and tis the thickness of, film (cm) (cf,

Electrochemical polymerization of poly(o-anisidine) thin films: effect of synthesis temperature studied by cyclic voltammetry

“…All the spectra indicate a major peak at about 800 nm and a shoulder at about 440 nm. The peak at 800 nm corresponds to the emeraldine salt (ES) form of POA, while the latter may be attributed to the formation of radical cations.22,23 The general features of these spectra resemble closely those reported by Bedekar et al 19 However, in our case, a shift in the peak positions towards the lower wavelength side is observed, which may be attributed to the e †ect of the supporting electrolyte…”

“…This concept has been successfully applied to polyaniline.17,18 Considerable work is still needed to understand basic issues related to the synthesis of substituted polyanilines and to explore the possibility of utilizing them as alternatives to polyanilines in technological applications. Recently, Bedekar et al 19 have studied the synthesis of poly(o-anisidine) Ðlms under galvanostatic conditions in aqueous solutions of HCl and have investigated the e †ects of monomer concentration, surface resistance of substrate and current strength on the optical, morphological and thermal properties. However, the inÑuence of temperature on the electrochemical synthesis of poly(o-anisidine) Ðlms has not yet been investigated.…”

Poly(m-chloroaniline): Electrochemical Synthesis and Characterization

“…Further increase in pH to 2.18 and 3.3 yields films that are thicker and posses better quality in terms of smoothness and adherence in comparison with the films obtained at highly acidic pH as supported by the increase ,\ The above spectral features can be interpreted in the light of the mechanism of polymerization proposed earlier. 14 The crucial step which hinders the polymerization process in the present case is the head to tail attack of the two radical cations leading to the formation of a dimer (RC-RC coupling). From our previous investigations on poly(o-anisidine), 14 it is established that the formation of dimer via head to tail coupling is the most favoured process since -OCH 3 is an electron donating group ( -I or + I) and is a strong activator ( + R and -R) due to which electron is easily available for bonding.…”

“…14 The crucial step which hinders the polymerization process in the present case is the head to tail attack of the two radical cations leading to the formation of a dimer (RC-RC coupling). From our previous investigations on poly(o-anisidine), 14 it is established that the formation of dimer via head to tail coupling is the most favoured process since -OCH 3 is an electron donating group ( -I or + I) and is a strong activator ( + R and -R) due to which electron is easily available for bonding. 15 Contrary to this, Cl -situated at meta position, in m-chloroaniline is strongly electron withdrawing, and access of electrons for bonding is presumably difficult as a result of which, the head to tail coupling of radical cations does not take place effficiently as in the case ofpoly(o-anisidine).…”

Microspheres of Conducting Poly(N-methylaniline)

“…In this regard, several reports on morphological features of PANI and its ring substituted derivatives are available in the literature. [15][16][17][18] All of them have reported either fibrillar or granular morphology, depending upon various deposition parameters. Here, we report that PNMA possesses interesting property to form microspheres.…”