Self-doped conducting polymers doping mechanism

Y. Ikenoue, N. Uotani, A. O. Patil, F. Wudl, A. J. Heeger, Electrochemical studies of self-doped conducting polymers - verification of the cation-popping doping mechanism, Synthetic Metals 1989, 30, 305. 

Other 3-substituted thiophenes that have been polymerized include 3-methoxy [309-311], other 3-alkoxy [312], 3-phenyl [313,314], 3-(4-methoxyphenyl) [314], 3-(4-trifluoromethylphenyl) [314], 3-bromo [315], 3-alkylsulfonatethiophene [316-318], and others [319-323]. Poly-3-alkylsulfonate thiophenes are particularly interesting due to a striking property. Sodium poly-3-thiophene-j8-ethanesulfonate and sodium poly-3-thiophene-6-butanesulfonate and their conjugate acids are water soluble in both the doped and undoped states [317,318]. Ikenoue et al. [318] examined the conduction mechanism for this self-doped conducting polymer. 

The mechanism for the SPAN layer changing the emission properties of the PPy VPV polymer is attributed to the formation of new emissive species due to protonation of the pyridyl units by SPAN. These species was identified by both absorption and PL experiments. Figure 9.15 shows the absorbance spectra of a PPy VPV layer, a SPAN layer, and a bilayer of PPy VPV/SPAN. SPAN is a self-doped, water-soluble conducting polymer with a room-temperature conductivity of 10-2 S/cm.18 It has a wide optical window from green to near infrared PPy VPV... 

Recently, Fabre et al. [31] and Freund et al. [7, 8] used electro-chemically deposited, self-doped, boronic-acid-substituted, conducting polymers for saccharide and fluoride detection. Freund et al. prepared a potentiometric sensor for saccharides using self-doped PABA [7, 8]. The transduction mechanism in that system is reportedly the change in pKa of polyaniline that accompanies complexation, and the resulting change in the electrochemical potential. Sensors produced with this approach exhibit reversible responses with selectivity to various saccharides and 1,2-diols (Figure 3.22) that reflect their binding constants with phenylboronic acid observed in bulk solutions. The sensitivity... 

The self-encapsulation effect is successful in interpreting the stability of FET. However, this effect is not suitable to reveal the mechanism of enhanced conductivity of SP/IP composite as compared with corresponding pure semiconducting polymer, because for the conductivity, doping is necessary. 

As discussed by Han et al [76], protonic acids are not suitable dopants for PTs or P3ATs, although the optical and mechanical properties of P3ATs, mixed with protonic acids, to some extent resemble those of doped PTs. The reason is the protonation of the thiophene rings, which prevents the conduction of the electric current, in analogy with the case of the self-doped polymers. 

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