Poly PEDOTPSS

The separated metallic S WCNTs were also found to enhance transparent conductive performance in composite films with conductive polymers, particularly the poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOTPSS) blend as it is optically transparent in the visible spectral region (Figure 16.20). In such composites, the conductive polymer blend served the function of dispersion agents, so no surfactants were necessary in the film fabrication. In the work by Wang et al, suspensions of nanotubes (enriched metallic or nonseparated S WCNTs) in DMSO were mixed with aqueous PEDOTPSS in various compositions, and the resulting mixtures were sprayed outo au optically transparent substrate. The sheet resistance results demonstrated that the composite films with enriched metallic SWCNTs were consistently and substantially better in performance than those with nonseparated SWCNTs (and both better than films with neat PEDOTPSS). Aqueous PEDOTPSS is not as effective as commonly used surfactants in the dispersion of SWCNTs, which... 

Wet spinning methods are also being explored by fiber scientists to develop conducting polymer fibers. Continuous poly(3,4-ethylenedioxythiophene) p oly(styrenesulfonate) (PEDOTPSS) fibers were produced by using a simplified wet spinning process. Optimum wet spinning conditions were shown to produce fibers with good mechanical and electrical properties. The fiber... 

This chapter intends to give an overview about all known chemical methods yielding the PEDOT, or poly(3,4-ethylenedioxythiophene), structure. Details for relevant methods for in situ polymerization and the synthesis of PEDOTPSS, or poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), are presented in Chapters 8 and 9, respectively. Electrochemical synthesis is described in Chapter 14. 

In situ poly(3,4-ethylenedioxythiophene) (PEDOT) was the first example for PEDOT as synthesized under film-forming conditions. Up to now in situ PEDOT is the polythiophene with the highest achievable electric conductivity, although PEDOTPSS (poly(styrenesulfonate)) is catching up. That is why in situ PEDOT is of great practical and commercial value. These industrial aspects are described in Chapters 10 and 11. 

One of the reasons why poly(3,4-ethylenedioxythiophene) (FEDOT) has become a successful conductive polymer is the availability as a polymer dispersion. In combination with poly(styrenesulfonic acid) (PSS) as a counterion, a polyelectrolyte complex (PEC) can be prepared that forms a stable dispersion, which is producible on an industrial scale and can be used in many deposition techniques. To understand the function of PSS and the requirements for the formation of a stable PEC, this chapter will start with a general view on polyelectrolyte complexes. This is followed by a section on the synthesis and properties of PEDOT PSS dispersions, the properties of PEDOTPSS films, and the function of conductivity enhancement agents. 

The density of holes in PEDOTPSS can simply be calculated using a geometrical consideration. For highly conductive PEDOTPSS, the ratio of PEDOT to PSS is 1 2.5 by weight. The density of solid films is approximately 1 g/cm. Owing to the molecular weight of the monomeric units of PEDOT and poly(styrenesulfonic acid) with 140 and 182 g/mol respectively, the density of EDOT monomer can be estimated to be approximately I ICF cm 3. From electrochemical measurement, the level of oxidation per monomer unit is known to be approximately 1 charge per 3 EDOT units as outlined in Section 9.1. Consequently tire density of holes in PEDOTPSS films can be estimated to be ftp = 3-10 cm 3. 

The continuous improvement of PEDOTrPSS, or poly(3,4-ethylenedioxythio-phene) poly(styrenesulfonate), pol5uner dispersions over the last decade has made the application of these dispersions for polymer capacitors feasible. Waterborne PEDOT PSS dispersions were developed for the formation of the outer polymer layer first. The requirement on conductivity is much lower for this application than for the inner solid electrolyte because the electrical current passes perpendicular to the 5 to 50 microns thick outer polymer layer. Filmforming properties, adhesion to the anode body and edge, and comer coverage, which are critical to guarantee good barrier layer properties, are adjusted by appropriate formulations of PEDOTPSS. In Figure 10.10 a dense outer layer made of a PEDOTPSS dispersion on a tantalum capacitor is shown. 

This deposition method allows the assembly of materials of different functionalities into a single film without phase separation issues. Layer-by-layer assembly works well with PEDOT-S sodium salt as the polyanion combined polyallylamine hydrochloride (PAI)278-28o well as PEDOTiPSS as the polyanion combined with linear poly(ethyleneimine) (LPEI), polyaniline and viologen polymers as polycations. In layer-by-layer assemblies of PEDOTPSS with a viologen polymer it was clearly shown that both redox steps, the redox step from the PEDOT main chain and the redox step from the viologen, occur successively and not simultaneously. 

The text covers all relevant aspects of PEDOT beginning with a historical view on conducting polymers and polythiophenes, in particular. The story continues by describing the invenhon of PEDOT based on the development of the suitable monomer EDOT and subsequent important polymerization routes to the conducting polymer. The properties of PEDOT depend on counterions, which led to the development of PEDOTPSS, or poly(3,4-ethyl-enedioxythiophene) poly(styrenesulfonate), dispersions, which is the basic form of the commercial product. In the second part of the book, important applications in electronics and organic electronics concomitant with technical and commercial aspects are extensively described. 

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