Polythiophene, PTH

Fig. 1 Building units of conducting polymers, (1) polyacetylene (PA) (2) polypyrrole (PPy), polythiophene (PTh), polyfurane (PFu) (3) polyphenylene (PP) (4) polyaniline (PANI) 5 polyindole (PIND) (6) polycarbazole (PCaz) (7) polyazulene (Paz) (8) polynaphthalene (PNa) (9) polyanthracene (PAnth) (10) polypyrene (PPyr) (11) polyfluorene (PFiu) (12) poly(isothionaphthalene) (PITN) (13) poly(dithienothiophene) (14) poly(thienopyrrole) (15) poly(dithienylbenzene) (1G) poly(3-alkylthiophene) (17) poly(phenylene vinylene) (18) poly(bipyrrole) (PBPy), poly(bithiophene) (PBT) (19) poly(phenylenesulfide) (20) 4-poly(thienothiophene) (21) poly(thienyl vinylene), poly(furane vinylene) (22) poly(ethylenedioxythiophene) (PEDOT).

Thiophene polymers, in particular, alkyl-substituted polythiophenes (PTH), are some of the conducting polymers being most actively investigated at present. This fact is attributable to their high degree of processability, environmental stability [49, 50] and, in some cases, ability to exhibit reversible electrochrom-ism [51] and thermochromism [52]. Another important family of sulfur-... 

The structure described above for PA is in fact typical of most nonsubstituted undoped CPs studied to date. Among the more extensively studied CPs, polyparaphenylene (PPP), polythiophene (PTh), and polyphenyl-... 

From the late 1970s onwards, efforts to synthesise conjugated polymers rapidly expanded and numerous new materials were prepared. Many of these still proved to be intractable substances that were difficult if not impossible to purify and characterise. The maximum levels of conductivity achieved on doping often fell well short of the metallic range. Such properties meant that the majority of these materials attracted little attention beyond the initial reports, and certainly no commercial interest. An example of the few polymers produced at this time that have been extensively studied subsequently is polythiophene (PTh), Fig. 9.2(h). Although this polymer was also reported in the nineteenth century (Meyer, 1883), the first reliable synthesis appeared in 1980, see McCullough (1998). Another example is polyfluorene, Fig. 9.2(i), which was prepared chemically and electrochemically in 1985, see Rault-Berthelot and Simonet (1986). Much subsequent synthesis has been directed to the inclusion of pendent groups to either enhance solubility,... 

Similarly, a chain structure with predominantly a, a -coupling between the monomer units is postulated for polythiophene (PTh) on the basis of spectroscopic findings and mechanistic studies. IR measurements of uncharged, chemically produced examples in... 

Polythiophenes (PTh s) (1 shown subsequently) have much in common with polypyrroles. They are formed from a cyclepenta-diene molecule, but which has an S heteroatom. Thiophene is oxidized to form a conducting electroactive polymer (CEP), with the greatest conductivity obtained from a-a linkages. There are some important differences between polythiophenes and polypyrroles, and these are discussed here. 

As in the cases of pyrrole and aniline polymers, both chemical and electrochemical procedures have been employed in the synthesis of polythiophene (PTH) and its derivatives. The thiophene polymers exhibit remarkable stability in air and water [119], The alkyl-substituted derivatives also exhibit a high degree of processability [120,121]. PTH has also been synthesized from bithiophane (the dimer) or terthiophene (the trimer). The resulting poly(2,2 -bithiophene) (PbTH) and polyterthiophene (PtTH) are more ordered than PTH and appear to have the same basic structure as the starting monomer [117,122],... 

Polythiophene (PTh) and its derivatives are unique in that they can be prepared both anodically and cathodically. Anodic preparation of PTh was first mentioned by Diaz et al [21b] during their oxidation experiments of aromatic oligomers and monomers, which was followed by Tourillon and Gamier s work in 1982 [24], The cathodic preparation of PTh is not as straightforward and requires the reduction of an organometallic complex, such as (2-bromo-5-thienyl)-tri-phenylnickel dibromide [25]. 

Figure 13.16. Top view of the proposed structure of polythiophene (PTh) saturately doped with iodine (l5 chains). Reproduced from ref. 6.1 by kind permission of the American Chemical Society.

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.

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