Electrochemical growth of polypyrrole

H.J. Lee and S.M. Park, Electrochemistry of conductive polymers 37. Nanoscale monitoring of electrical properties during electrochemical growth of polypyrrole and its aging. J. Phys. Chem. B, 109, 13247 (2005). 

Rodriguez, I., Marcos, M. L., and Gonzalez Velasco, J., Mechanism of electrochemical growth of polypyrrole on a glass electrode doped with SnOj (ITO) from aqueous solution, Electrochim. Acta, 32, 1181-1185 (1987). 

Figure 37. Lateral section of a polymeric film during the nucleation and growth of the conducting zones after a potential step. (Reprinted from T. F. Otero, H.-J. Grande, and J. Rodriguez, A new model for electrochemical oxidation of polypyrrole under conformational relaxation control. /. Electroanal. Chem. 394, 211, 1995, Figs. 2-5. Copyright 1995. Reprinted with permission from Elsevier Science.)...

However, while the evidence for the existence of polarons was extremely convincing, that for bipolarons was rather more problematical in that it was largely effectively negative in nature the absence of an absorption peak in the optical spectrum, the absence of a signal in epr studies on the decline of the observed signal. In essence, bipolarons had not been actually observed. This fact was remedied by the work of Christensen and Hamnett (1991) who employed ellipsometry and FTIR to study the growth and electrochemical cycling of polypyrrole in situ in aqueous solution. 

Fig. 11.8. Current density as a function of rotation rate during growth of electrodeposited polypyrrole film at 0.550 ( ), 0.600 ( ), 0.650 (T), and 0.700 ( ) V. (Reprinted with permission from D. J. Fermin, M. Mostany, and B. Scharifker, Electronically Conducting Polymers Synthesis and Electrochemical Properties of Polypyrrole, Curr. Topics Electrochem. 2 132-136, 1993.)...

EQCM may be combined with spectroscopy (see Chapter 2.7 in this volume). Usually, the crystal is used in transmission mode [202, 217, 218]. Various plots, such as absorbance versus frequency, have been presented to help understand the complex electrochemical response of polypyrrole [219.] The growth of poly(l-naphthylamine) was monitored using a fiber-optic bundle in front of the crystal [220]. 

Otero, T. F., and Larreta-Azelain, E., Electrochemical control of the morphology, adherence, appearance and growth of polypyrrole films, Synth. Metals, 26, 79-88 (1988). 

Electrochemical properties of polypyrrole films grown in LiC104 acetonitrile solution (2% water) at gold electrodes modified with thiolated /3-cyclodextrin self-assembled monolayers have been investigated. Scanning electron microscopic results show that thiolated /3-cyclodextrin acts as a molecular template to restrict the growth sites within the /3-cyclodextrin cavities (50). 

In addition, we have recently described a procedure for controlling the morphologies of electronically conductive polymers (32). This procedure involves the electrochemical growth of the conductive polymer at an electrode surface which has been masked with a microporous polymer membrane. The pores in this membrane act as templates for the nascent electronically conductive polymer. Because the template membrane contains linear cylindrical pores, cylindrical conductive polymer fibrils are obtained (32). We will show in this manuscript that microfibrillar polypyrrole films prepared via this approach can support higher rates of charge-transport than conventional polypyrrole. 

Warren MR, Madden JDW (2006a) A structural, electronic and electrochemical study of polypyrrole as a function of oxidation state. Synth Met 156(9-10) 724—730 Warren MR, Madden JDW (2006b) Electrochemical switching of conducting polymers a variable resistance transmission line model. J Electroanal Chem 590(1) 76-81 Wing Yu Lam J (2011) Influences of growth conditions and porosity on polypyrrole for supercapacitor electrode performance. UBC, Vancouver, BC, Canada Wu Y et al (2007) Soft mechanical sensors through reverse actuation in polypyrrole. Adv Funct Mater 17(16) 3216-3222... 

Although a variety of synthetic techniques have been exploited to prepare composite superconductor systems [9], electrochemical growth of polymers such as polypyrrole onto the surface of YBa2Cu307- is by far the most common method [22,23]. Electrochemical procedures provide convenient and versatile methods for forming such polymers. Moreover, pyrrole can be elec-trochemically polymerized at relatively low potentials (l.O V vs. SCE), and polypyrrole is relatively stable in its conductive form. Thus, pyrrole is an ideal candidate for the direct polymerization onto the surface of cuprate superconductors. 

Figure 3.80 Values of n, k and thickness L obtained t ia three parameter fits to the A, T and intensity data obtained during the growth of a polypyrrole film on a sputtered Pt electrode in N2-saturated I M NaCIO4/0,l M pyrrole. The potential was stepped from OV to 0.8 V vs, SCE for 15 s, and readings taken every 20 ms. Reprinted from tkarochimica Acia, 36. P,A. Christensen and A. Hamnett, In situ Spectroscopic Investigations of the Growth, Electrochemical Cycling and Overoxidation of Polypyrrolc in Aqueous Solution, pp. 1263-1286 (1991), with kind permission from Pergamon Press Ltd., Headington Hill Hall. Oxford 0X3 OBW, UK.

The him morphology of electrochemically prepared polythiophene has been shown in numerous studies to be almost identical to that commonly observed for polypyrrole (described in Chapter 2). A nodular surface is observed for both unsubstituted and 3-alkyl substituted thiophenes.92 As with PPy, the electrochemical preparation of PTh at higher current densities produced rougher surface morphologies. The similarity in morphologies suggest a similar growth mechanism for electrochemically polymerized PPy and PTh. 

The growth and the surface properties of polypyrrole on single crystal graphite electrodes as studied by in-situ electrochemical scanning probe microscopy... 

Atomic force microscopy (AFM) and electrochemical atomic force microscopy (ECAFM) have proven usefiil for the study of nucleation and growth of electrodeposited CP films on A1 alloy [59]. AFM was used to study adhesion between polypyrrole and mild steel [60], whereas electric force microscopy (EFM) has been used to study local variations in the surface potential (work function) of CP films [61]. AFM with a conductive tip permits a nanoscale AC impedance measurement of polymer and electrolyte interfaces, permitting differentiation between highly conductive amorphous regions and less-conductive crystalline regions of the CP film [62]. 

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