Polypyrroles PPy and polythiophenes PTh

The pyrrole units carry a partial positive charge, which is balanced by one BF4 ion to every four pyrrole rings [39]. 

PPy has also been produced with CIO4 and CH3C6H4SO3 as the counter-ions in place of fluoroborate (BFJ). With PPy toluenesulphonate (PPTS), significant improvements in tensile strength and Young s modulus have been reported, and this has prompted its thorough investigation [40]. 

Derivatives of PPy have also been investigated and some copolymers made. Films of poly-N-methylpyrrole have conductivities much lower than PPy, while film produced from mixtures of pyrrole and N-methylpyrrole have conductivities that vary with composition over five orders of magnitude. The size of any substituent group plays a part in determining the ultimate conductivity of the films, and may even inhibit film formation. For example, poly-N-phenylpyrrole and poly-N-butylpyrrole have reduced conductivities in the range of 0.1-1 S m , while with bulky substituents such as t-butyl and cyclohexyl, brown-black powdery products are obtained instead of films. As with other materials, graft copolymers of PPy have been made by the electrochemical oxidation of pyrrole in the presence of a chain that had been initially modified with a pendant pyrrole unit [43]. 

Many other aromatic systems can be similarly electropolymerized, including thiophene, furan, carbazole, azulene, indole, aniline, phenol and thiophenol among others. 

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Figure 28.3. Structural formulas of several electron-conducting polymers (a) frans-poly(acetylene), (b) cw-poly(acetylene), (c) poly(p-phenylene), (d) polyanUine (PAni), (e) poly(n-methylaniline) (PNMA), (f) polypyrrole (PPy), (g) polythiophene (PTh), (i) poly(3,4-ethylenedioxythiophene) (PEDOT), (j) poly(3-(4-fluorophenyl)thiophene) (PFPT), (k) poly(cyclopenta[2,l-b 3,4-dithiophen-4-one]) (PcDT), and (m) Mg polyporphine.

Conductive polymers such as polypyrrole (PPy), polyaniline (PAni), and polythiophen (PTh) have been the subject of much research owing to their wide applications in biosensors, electrochemistry, and electrocatalysis [191, 192]. Recently, conductive polymers have been also investigated as ORR electrocatalysis in three different ways (1) utilizing conductive polymers as ORR electrocatalysts on their own, (2) incorporating non-precious metal complexes into the conductive polymer matrix, and (3) employing conductive polymers as a nitrogen/carbon precursor material for pyrolyzed M-N c/C catalysts [105]. 

The largest aetuation strains in ICPs have been obtained from polypyrroles (PPy) and these polymers are the most studied. Both polyaniline (PANi) and polythiophene (PTh) ICPs have also been investigated and the solution-processability of these polymers offers some advantages in fabricating actuators. For example, continuous fibres of doped PANi that can be readily bundled to give large force actuators have been prepared [22] (Figure 10.4). 

In all the cases of poly acetylene, polythiophene, and polypyrrole coating, the amount of plasma-film deposition was different, caused by the difference in the structure of the three different monomers and their reactivity during the plasma process. PPy- and PTh-silica are more hydrophobic than PA-silica, probably due to the presence of different chemical moieties in the complex film structure deposited onto the silica surface. 

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. 

We recently succeded in forming intrazeolite polyaniline (PANI), polypyrrole (PPy), polythiophene (PTh) and poly(3-methylthiophene) (P3MTh)l by oxidative polymerization inside the cavities of different zeolites, as demonstrated by vibrational, ESR, and electronic absorption data. It was observed that the dimensionality and pore size of the host determine the polymerization rates and intrazeolite products. This communication compares the above zeolite/polymer systems and discusses evidence for polymerization inside the host channel structures. 

The typical conjugated polymers (CPs] with conjugated chain structures include polyacetylene, polypyrrole (PPy], polythiophene (PTh], polyaniline (PANl] and their derivatives.The conjugated structures exhibit strong UV-Vis absorptions in visible... 

Conjugated polymers have been the subject of great interest, both theoretically and experimentally, since the discovery of conductivity in doped polyacetylene in the seventies [1]. Many works have been devoted to their synthesis, characterizations and properties [2]. They have found many apphcations, particularly in the field of optoelectronics, as light-emitting diodes (LEDs), field-effect transistors (FETs), solar cells, etc., due to the semi-conducting behavior of the conjugated backbone [3]. Among them, polythiophenes (PTh) and polypyrroles (PPy) have been extensively studied because of their synthesis versatility and environmental stability [4-6]. Their functionalization permits the combination of their... 

Various conjugated polymers, such as poly( >-phenylene) (PPP), polythiophene (PTh) and polypyrrole (PPy), have aromatic ring units in the conjugated backbone as illustrated in Figure 7.1. The aromatic rings usually enlarge the bandgap relative to PA. The increase in the gap of e.g. PTh relative to PA can be rationalized in two alternative ways ... 

Thanks to the presence of a r-electron conjugated system, a few organic polymers, such as polypyrrole (PPy), polyaniline (PANI), polythiophene (PTh), and relevant derivatives, are classified as semiconductors that become well conductive by partial oxidation or reduction [1-10]. For this peculiar characteristic, similar materials are called intrinsically conducting polymers (ICPs). The structures of the most meaningful ICPs are displayed in Fig. 2.1. 

The years that followed saw the synthesis of a bewildering number of conjugated polymers and copolymers from a wide variety of aromatic, heteroaromatic, and acetylene monomers with and without substituents, that were converted into their respective conductive forms with the aid of equally numerous oxidizing agents or Br0nsted acids. These highly conductive polymers include the polyacetylenes (PAc), polypyrroles (PPy), polythiophenes (PTh), polyphenylenes (PPP), and polyanilines (PAni). The conductivities achieved range from = 10" S/cm (intrinsic semiconductors) to =10 S/cm. 

Other conducting polymers that have paying attention in composite preparation due to their remarkable physical and chemical properties are polypyrrole (PPy), polyvinylcarbazole (PNVCz), polythiophene (PTh), and their derivatives. 

CPs, polyaniline (PANI), polythiophene (PTH), polypyrrole (PPy) have been found to be suitable electrode materials similar to other energy storage devices (fuel cells, photoelectrochemical, and batteries) [19-21], Table 1 shows the theoretical and experimental capacitance data of few selected conducting polymers. With the nano-engineered techniques, 3-D stmctures of CPs gain many interests toward... 

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