Conducting polymers dedoping conductivity change

For a polyanUine film, the light absorption measurements were conducted after the film was exposed to HCl and NH3 vapors, respectively, as shown in Fig. 14 [19]. The difference in the spectra indicated that HCl and NH3 vapors induced a different band structure and conformation of the polymer. Therefore, the optical property of the film changed when the film switched from one state (doped by HCl) to another (dedoped by NH3). The refractive index measurement by ellipsometry showed that the refractive index changed from 2.43 (doped by HCl) to 1.95 (dedoped by NH3). 

It has been established that when polyelectrolytes are incorporated as dopants in PAn, the switch from conducting to nonconducting material is shifted to very-high-pH solutions, enabling electrochemistry to be carried out on PAn in neutral solutions.37 Poly(methoxyanilines) have been used as the basis of electromechanical actuating changes in dimensions in the thickness direction of more than 20% were reported as the polymers are doped and dedoped.38-39 Similar effects are observed if some level of self-doping is introduced into the PAn backbone.40... 

Additional annealing of doped polymers also accelerates the process of dedoping. Li and Wan (1999) have shown that temporal change in film conductivity of doped poly aniline at room temperature is increased strongly after thermal treatment of doped polymer at 7=150 °C. Results of this research are shown in Fig. 19.6. We need to recognize that the indicated effect limits the application of any thermal treatments during gas sensor fabrication. It was noted that the conductivity of PANICS A and PANI-p-TSA are the most stable below 200 °C, while the stability of PANI films doped with H SO and H PO are much better than the PANI-HCIO and PANI-HCl after thermal treatment at a high temperature (200 °C) (Li and Wan 1999). 

The oxidized (doped) form of PBT can be reduced (dedoped) reversibly by controlling the potential of the polymer coated electrode. The redox process is accompanied by a drastic change in the properties of the polymer (e.g. PBT), such as electrical conductivity (cf. Sect. 3.2.3, BU4NCIO4), stability (cf. Sect. 4.3, the doping/dedopping degree), color (cf. Sect. 3.4.3), optical properties (cf. Sect. 3.5) and wettability (see Sect. 3.11) [217,261-263]. The reversible redox behavior of PT depends on the monomer concentration [264,265]. PT films electrochemically formed in solutions of 0.4 M thiophene have reversible redox behavior, in contrast to PT films formed in 0.01 M solutions of thiophene. This is explained by overoxidation due to the limited transport of the monomer by... 

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