Synthesis of polythiophene

Caution Carry out all procedures in a well-ventilated fume-cupboard, wear appropriate disposable gloves, a lab-coat, and safety glasses. 

Volumetric flask Vacuum desiccator Source of dry nitrogen 

Preparation. Nitrobenzene is dried over calcium chloride and then distilled from barium oxide, 3-hexylthiophene is distilled under reduced pressure. 

A volumetric flask (100 ml) is charged with 3-hexylthiophene (1.68 g 10 mmol) and tetraethylammonium hexafluorophosphate (0.69 g, 2.5 mmol) and made up to the mark with nitrobenzene. The solution is then purged with nitrogen for approximately an hour prior to use. 

With the potentiostat on standby, the electrodes are connected up to the correct outputs. Dry nitrogen gas is then slowly bubbled through the electrolyte. 

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SCHEME 2.59 Synthesis of polythiophene via metal-catalyzed couplings. 

SCHEME 2.60 Synthesis of polythiophene via chemical oxidation polymerization. 

P. Enzel and T. Bein, Intrazeolite Synthesis of Polythiophene Chains. J. Chem. Soc., Chem. Commun., 1989, 1326-1327. 

Scheme 4.4 Synthesis of polythiophene/nickel(II) phthalocyanine hybrid materials.

Ferrocene is an attractive and convenient organometallic species to incorporate into conjugated polymers—it is stable, easy to functionalize, has reversible electrochemistry, and its derivatives (both monomeric and polymeric) can be easily characterized [e.g., by nuclear magnetic resonance (NMR) spectroscopy]. Ferrocene has been incorporated into the backbone and side chains of polythiophene 45 In 1999, both Higgins and Wolf independently reported the synthesis of polythiophenes with ferrocene in the backbone.46,47 Electropolymerization of ferrocene substituted... 

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],... 

The synthesis of polythiophenes with alkyl and perfluoroalkyl substituents is also based on the ability of fluorine-containing thiophenes with a-hydrogen to react with organometallic compounds. 

Oxidative dimerization by treating thienyllithium with copper(II) chloride was reported in CHEC-I. This method has found application in the synthesis of polythiophenes attached to crown ethers these compounds exhibit selective response to alkali-metal ions and can therefore function as sensors. An example of the synthesis is given in Equation (57) <93JA12214>. The monomer (589) was converted to the 5,5 -dilithiated derivative and then polymerized either by direct reaction with Fe(acac)3 or by conversion to the tin derivative followed by Pd-catalyzed cross-coupling (see Section 2.10.4.7.3). 

H. Goto, X. Dai, H. Narihiro, K. Akagi, Synthesis of polythiophene derivatives bearing ferroelectric liquid crystalline substituents. Macromolecules 37, 2353-2362 (2004)... 

Pilston, R.L. 2001. Synthesis and characterization of novel regioregular polythiophenes, random copolymers of thiophene and studies of the GRIM polymerization method for the synthesis of polythiophenes. Carnegie Mellon University. 

Tierney, S., M. Heeney, and I. McCulloch. 2005. Microwave-assisted synthesis of polythiophenes via the Stille coupling. Synth Met 148 195-198. 

Synthesis of polythiophene is possible by electrochemical and chemical polymerization techniques. The technique used in electrochemical synthesis is similar to that used for polypyrrole. As the starting materials, dimer [60-62], trimer [61, 63] and tetramer [61] can be used. 

Electrochemical synthetic methods were also attempted around this time, yet this approach was limited due to solubility issues of the polymer. Electrochemical synthesis of polythiophene was typically performed on metal substrates, the most common being platinum, silver, iron and copper electrodes... 

Electrochemical synthesis of polythiophene was first reported in 1981 [73,74] with material which displayed a conductivity in the range 10 to 10 S cm . Other workers [75-77] polymerized thiophene with a variety of supporting electrolytes to produce thin films from acetonitrile solutions. Similar results were achieved by Kaneto et al. [78-80] using anhydrous solvents (acetonitrile and benzonitrile). 

Since the first studies rqjorting in 1982 the electrochemical synthesis of polythiophene [116], much research has been devoted to the optimization of this oxidative polymerization. Aldiough a-a coupling of... 

Fig. 9.36 The synthesis of polythiophenes with chiral side chains.

Fig. 9.37 The synthesis of polythiophenes with thioether side chains.

Finally, the third and current era of ohgothiophenes was initiated in 1982 with the first synthesis of polythiophene PI as an electrically conductive polymer [8]. Somewhat later, a-bithiophene 2 and a-terthiophene 3 were used as monomers, instead of thiophene 1 itself, as substrates for electropolymerization in order to control the structure of the polymer [Eq. (3)] [28]. Owing to their lower oxidation potential. 

Scheme 57 Synthesis of polythiophene having naphthalene diimide moiety...

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