EDOT Derivatives

Chemical pol5mierization of allqrlated or alkoxylated EDOT derivatives results in regiorandom PEDOT derivatives soluble in common organic solvents such as chloroform and tetrahydrofiiran (THF). These pol5miers can be characterized by standard methods for example, gel permeation chromatography (GPC) determined values for a PEDOT range from 10,000-25,000 g/mol. 

Alkylation of Thiophene Poly(3,4-Ethylenedioxythiophene) and Sulfur Derivatives Reduced Bandgap Polymers Based on Chalcogen 3,4-Substituted Thiophenes Structural Modifications of EDOT Functionalized EDOT Derivatives... 

Cyanobiphenyl (55) [148] and redox pendant groups such as ferrocene (56) [149], viologen (see Section 13.4.3) [150], and Tetrathiafulvalene [151] (see Section 13.4.1.1) cores have been grafted on hydroxymethyl-EDOT 45. A copolymer containing pendant ferrocene groups has been obtained by copolymeri2ation of 56 and another EDOT derivative [149]. 

Segura, J.L., R. Gomez, E. Reinold, and P. Bauerle. 2005. Synthesis and electropolymerization of a perylenebisimide-functionalized 3,4-ethylenedioxythiophene (EDOT) derivative. Org Lett 7 2345-2348. 

Functionalization at the end, 9-17 Functionalized EDOT derivatives, 13-17-13-19 Functionalized polythiophenes, 13-19-13-55 Functionalized side chains, 9-13-9-22 Fused rings, 20-12-20-13... 

Figure 14.2 Transetherification as a synthetic route to EDOT derivatives...

In addition to chemical polymerization, EDOT is also accessible to electrochemical polymerization [14, 44]. Industrial use of electrochemically prepared PEDOT obviously has not been reported yet, but many scientifically very important results have been obtained. The electrochemistry of EDOT and EDOT derivatives has been reviewed in a comprehensive article [45]. 

To improve performance, many PEDOT derivatives, used either alone or in combination, have been proposed. Whereas the electro-optical properties of WO3 are fixed, the colors and hues of conducting polymers may be altered by modification of the monomers. Reynolds and co-workers have studied the electrochromic properties of a multitude of EDOT derivatives [82], and recently reported an all-polymer electrochromic device based on two different PEDOT derivatives [187]. Depending on their chemical structure, the various PEDOT derivatives may exhibit different colors upon switching from the oxidized to the reduced state. Furthermore, the contrast ratio is also dependent on the stmcture. For example, polytetradecylethylenedioxythiophene (C14-PEDOT) is similar to PEDOT in switching from transparent to blue, but it has an enhanced optical contrast, and for 2,2-dimethyl-ProDOT an improved contrast ratio combined with a different color - purple instead of blue - is observed [82, 187]. 

Mitsunobu reaction for the synthesis of EDOT derivatives. (Adapted from D. Caras-Quintero and P. Bauerle, 2002, Chem Commun 22 2690-2691.)... 

The aforementioned lithiation of EDOT by, for example, butyllithium, is one of the key steps to 2-substituted EDOT derivatives. Some typical subsequent reactions of the 2-Li-EDOT (except the oxidative coupling to BEDOT described earlier) are summarized in Figure 5.20. 

The transformations of 2-Li-EDOT as a key intermediate to various EDOT derivatives comprise (a) formation of EDOT-Grignard compounds (b)... 

Several interesting properties may be a motivation for the use of hypervalent iodine compounds. For example, EDOT derivatives with thioether function like 3,4-ethyleneoxythiathiophene cannot be oxidatively polymerized with peroxides due to the oxidation of the thioether function to a sul-fone group. Use of periodate excludes this reaction and facilitates oxidative polymerization. Nevertheless, achievable conductivities are only very moderate, and so the practical value is limited. 

The oxidative polymerization with the aid of persulfate in water is limited to EDOT and a few derivatives, which are water-soluble to a certain extent (for example, EDOT-CH3, EDOT-CH2OH, sulfonate-modified EDOT or oligo-ethylenglycol-substituted EDOT). In contrast, the in situ polymerization is of far broader range with respect to the EDOT derivatives applicable. The minimum prerequisite is a moderate to good solubility in alcohols like ethanol or n-butanol at slightly elevated or room temperature. Another important aspect is the reactivity of the monomer, which must not be too high with iron-III toluenesulfonates to avoid instantaneous polymerization. 

EDOT derivatives for in situ polymerization (for a detailed explanation of R and R, see Table... 

All films were made with the following simple recipe 14 mmol EDOT derivative, 50 g iron(III)-tosylate as a 41% (wt/wt) solution in n-butanol and 212 g n-butanol were mixed. The solution was coated on glass by a doctor blade with wet film thickness 60 pm at room temperature and then dried at room temperature or slightly enhanced temperature (for example, at 23°C for 20 min or at 40°C for 10 min). After drying, e films were rinsed with deionized water to remove iron salts and toluenesulfonic acid. Surface resistances were measured by a two-point method. 

Several alkyl-EDOT derivatives (synthesis via Williamson ether s)mthe-sis, transetherificahon,28 or Mitsunobu reaction, see Chapter 5) have been... 

Surprising data are obtained from the chiral EDOT derivatives (entry 2 to 4, 7 to 8, and 12 to 13). In all cases the enantiomerically pure compoimds result in higher surface resistances than mixtures of the enantiomers, contrary to expectations. 

EDOT derivatives with mesogenic side chains/general formula. 

Electrochromic layers with PEDOT are either prepared by electrochemical or chemical polymerization of the corresponding monomer. Both the electrochemical and the chemical polymerization can be well controlled and this makes it easy to test a larger number of EDOT derivatives. However, the aqueous dispersion of PEDOT PSS is much easier to process by simple coating and therefore has been a preferred material in technical developments. 

Chemical structures of substituted ethylenedioxythiophene (EDOT-OH, EDOT-S, EDOT-F) and unsaturated EDOT derivatives (Benzo-EDOT, VDOT). 

Bulky mesogenic groups were first introduced without utilizing the specific liquid crystalline (LC) properties of the EDOT derivative. Kumar s group... 

EDOT-CH2CI is a very versatile synthon for functionalized EDOT derivatives. Two advantageous aspects, compared to EDOT-CH2OH, have to be considered. First, the more straightforward reactivity for the synthesis of efhers and amines or amides. Second, the product is free from its ProDOT isomer, which contaminates ED0T-CF120H dependent on synthetic route and method of purification. 

Water Soluble, "Self-Doping" EDOT Derivatives... 

A vast amount of 2-substituted and 2,5-disubstituted EDOT derivatives have been s)mthesized. Several examples like simple derivatives elucidating the typical EDOT chemistry have been mentioned in Chapter 5. The following part of this chapter focuses on derivatives that have been prepared and investigated with the intention to create interesting electro-optical properties. A comprehensive review was published in 2005 by Roncali et al. Due to the great number of publications, only selected summaries will be presented here. 

---