Poly-3-methylthiophene

Figure 30. In situ measurements of the time evolution of the Cu K-edge when a platinum electrode coated with a polymeric film of poly (methylthiophene) is cathodically polarized in an aqueous solution containing 50 mM CuCl2. (From Ref. 105, with permission.)... 

As stated earlier, the presence of alkyl functional groups on the monomer118 can be used to advantage in preventing overoxidation of the polythiophenes during synthesis. Conductivities as high as 7500 S cm-1 have been obtained for poly(methylthiophene).119... 

In general, the conductivity of materials produced using the chemical oxidation process is lower. Higher conductivities can be obtained by chemical production of copolymers for example, using poly(methylthiophene) and polyurethane,127 conductivities as high as 26 S cm-1 have been reported. 

Polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, and poly-methylthiophene may exhibit a mixed electronic and ionic conductivity, similar to inorganic intercalation, or insertion compounds [43]. In the conductive form these polymers are partly oxidized and these positive charges are equilibrated by inorganic anions, which can diffuse through the polymer net. Alternatively, the conductive polymers can be partly reduced, with cations as counter ions. The eleetronic conductivity originates Irom partial oxidation of conjugated jt-bonds. The positive charge... 

FIGURE 46.33. Optical conductivity versus frequency for poly-(methylthiophene) (PMT) doped with PFe as a function of doping level (from Ref. [190]). The spectra are for different doping levels [with (1) being highest and (3) the lowest doping level]. 

Electrochemical transistors have been manufactured in which the gate is constituted by a poly-methylthiophene [398] or polypyrrole [397] film deposited between the source and the drain, the drain current being driven by the electrochemically controlled conductivity of the polymer film. 

A number of different characterization methods have been performed on poly(thiophene) and poly(alkylderivative)s. NMR of electropolymerized poly(thiophene) films has been studied by Hotta et al. and Osterholm et al. An infrared study about vibrational key band on poly(thiophene) films and FT-IR spectra were also published. Resonance Raman scattering on poly(methylthiophene) and x-ray scattering on poly(thiophene) were performed x-ray photoelectron spectroscopy has been reported on FeCls-doped poly(hexylthiophene) and electrochemically obtained poly(thiophene) [20]. Time resolved fluorescence studies on thiophene oligomers are given by Chosrovian et al. [79]. For studies on oligothiophene films see [80,81]. 

A number of approaches are available to improve the morphology and homogeneity of electrochemically deposited conducting polymer films. Priming of the electrode surface with a monolayer of adsorbed or covalently bonded monomer leads to more compact deposits of polyaniline,87,88 poly thiophene,80 and polypyrrole.89,90 Electrode rotation has been shown to inhibit the deposition of powdery overlayers during poly(3-methylthiophene) deposition.81... 

Figure 7. Cyclic voltammograms of poly(3-methylthiophene) in acetonitrile + 0.1 M E NCICV The solid line represents three identical voltammograms to +1.0 V. while the dashed line is for two subsequent scans to +2.0 V.1 (Reprinted with permission from Anal Chem. 65,696-703.1993. Copyright 1993, American Chemical Society.)...

Reactions with other nucleophiles follow a similar mechanism. For the reaction of Cl with poly(3-methylthiophene) in acetonitrile, the reaction stops at structure 5 (Scheme 2).128 A fully conjugated, Cl-substi-tuted product 6 can subsequently be obtained by electrochemical or chemical dehydrogenation.128 With Br and alcohols, the overoxidation... 

In the dual-electrode techniques, the potential of each electrode is controlled with a bipotentiostat so that a small constant potential difference is maintained across the polymer film as its potential is slowly scanned, relative to a reference electrode. Figure 10 shows the results of this type of experiment for poly(3-methylthiophene) in SO20).37... 

Figure 10. Cyclic voltammetry (top) and in situ electronic resistance (bottom) of poly(3-methylthiophene) from parallel-band electrode [Fig. 9(A)] experiments in S02(1) containing 0.1 M Bu4NPF6.37 (Reprinted with permission from J. Am. Chem. Soc. 112, 7869-7879, 1990. Copyright 1990, American Chemical Society.)...

Figure 11. Cyclic votammetry (top) and in situ electronic conductivity from rotating-disk voltammetry [ , Fig. 9(C)] and sandwich electrode voltammetry [ , Fig. 9(B)] for poly(3-methylthiophene) in acetonitrile containing 0.1 M BU4CIO4.60 (Reprinted from J. Ochmanska and P. G. Pickup, In situ conductivity of poly-(3-methylthiophene) and (3-methylthiophene)x,-[Ru(2,2 -bipyridine)2 (3- pyrrol-l-ylmethyl pyridine)2]2+ copolymers, J. Electroanal. Chem. 297, 211-224, 1991, with kind permission from Elsevier Sciences S.A.)...

Polypyrrole shows catalytic activity for the oxidation of ascorbic acid,221,222 catechols,221 and the quinone-hydroquinone couple 223 Polyaniline is active for the quinone-hydroquinone and Fe3+/Fe2+ couples,224,225 oxidation of hydrazine226 and formic acid,227 and reduction of nitric acid228 Poly(p-phenylene) is active for the oxidation of reduced nicotinamide adenine dinucleotide (NADH), catechol, ascorbic acid, acetaminophen, and p-aminophenol.229 Poly(3-methylthiophene) catalyzes the electrochemistry of a large number of neurotransmitters.230... 

Cyclic voltammetric studies involving polymers, 558 and the nature of charge carriers, 561 and the nucleation loop, 557 of poly (3-methylthiophene), 564 and parallel-band electrodes, 570 Cyclic voltammograms as a function of scan rate, 559 involving polymerization, 559 with polyanaline, 566 of polypyrrole film, 581... 

These authors have also employed this technique for the study of other metallic inclusions into poly(3-methylthiophene) films, including Ir, Au, and Pt. Thus, this type of arrangement could open up new exciting possibilities in terms of kinetic studies. 

Fig. 3 Regioregular poly [3-(2-methyl-1 -butoxy)-4-methylthiophene] (PMBMT) synthesized via oxidative electropolymerization...

Research is also focused on non-precious metal catalysts synthesized with conjugated heterocyclic conducting polymers such as Ppy, Pani and poly (3-methylthiophene (P3MT)) [166, 219-223]. 

Thus, many polymers with different conductivity were synthesized. To cite a few, these are polythiophene [158], 3-methylthiophene [159], polymers of 3-thiophene-acetic acid and methyl 3-thiophene-acetate [160], poly(2,5-thienylenevinylene) [161], poly(benzo[h]-thiophene) [162], poly(naphto[2,3-c]thio-phene) [163], poly(dithieno[3,2-h 2, 3 -fii]-thiophene) [164], poly(3- -hexylthiophene)... 

Fig. 13 Memory effect in cyclic voltammetry poly(3-methylthiophene) in CHsCN/O.l M TBAPFe,...

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