Conducting polymers poly-bithiophene

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).

Finally, the oxidative coupling with CuCla has also been used for the chemical synthesis of various polythiophenes. Thus the reaction of the bifunctional Li—Tj—Li 26, obtained in 92% yield by deprotonation of H-Tj-H 2, with two equivalents of n-BuLi, with cuprous chloride in anisole lead to poly(bithiophene) P2, an insoluble brown precipitate [Eq. (10)]. After extraction, the polymer was obtained in yields ranging from 25 to 50%. Its doping with AsFs afforded a polymer with a conductivity of 5 Scm which is somewhat lower than that determined for films grown electrooxidatively [53]. 

A laminate combination useful for an imaging process working with seamless polymeric belts comprise a laminate of a host polymer layer and a laminate of an electrically conductive polymer layer [PT, poly(bithiophene)] [159],... 

In order to co-polymerize the IC unit, Suzuki and Stille polymerizations have been used. First, Blouin et al. [94] were able to obtain polyindolo[3,2-fr]-carbazole derivatives with bithiophene or biEDOT as co-monomers. Unfortunately, these studies demonstrated a relatively low oxidation potential for these polymers (especially for P35 and P37), limiting their applications in OFETs and PCs. However, for doped state applications, these polymers may exhibit interesting properties [35]. For instance, when copolymerized with bithiophene, the resulting copolymer shows a good electrical conductivity (as high as 0.7 Scm 1) but a low Seebeck coefficient of 4.3 iV K 1 [35]. Finally, the UV-Vis absorption maxima are similar for poly(2,8-indolocarbazole-a/f-bithiophene) and poly(2,8-indolocarbazole-a/f-bis(3,4-ethylenedioxythiophene)). A broad absorption band is centered at 430 nm whereas, for the 3- and 9-substituted copolymers, the broad band is centered around 490-500 nm [94],... 

As reported by Heinze et al. poly(4,4 -dimethoxy-2,2 -bithiophene) oxidizes at 0.20 V vs. Ag/AgCl, combines moderate bandgap (1.60 eV) and high stability in the conducting state [66]. Based on its transparency in the oxidized state, this polymer has been proposed for hole injection in OLEDs [67]. 

The poly(4-carboxy-2,2 -bithiophene) can be prepared by direct chemical or electrochemical polymerization of 4-carboxy-2,2 -bithiophene (Figure 4.34) [51]. Hutchison et al. have suggested that this approach reduces undesirable side reactions and allows facile incorporation of strong electron-withdrawing side chains. Chemical synthesis was carried out using anhydrous ferric chloride in chloroform. The electrochemical polymerization was carried out in propylene-carbonate-containing tetra-butyl ammonium hexafluorophosphate. The conductivity of a pressed pellet of chemically synthesized polymer was approximately 10 " S/cm and the polymer was water soluble in its neutral form. 

Regiochemically defined poly(alkylthiophene)s have also been prepared by electrooxidation of 3,3 - or 4,4 -dialkyl-2,2 -bithiophenes (5), (6) [189,193]. Although the polymers obtained are considerably less conjugated than poly (alky lthiophene)s deriving from alkylthiophenes, because of the large proportion of HH linkages, this steric effect is not detrimental to their conductivity. 

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