Switching polyaniline

Conducting Polymers Electronically conducting polymers (such as polypyrrole, polythiophene, and polyaniline) have attracted considerable attention due to their ability to switch reversibly between the positively charged conductive state and a neutral, essentially insulating, form and to incorporate and expel anionic species (from and to the surrounding solution), upon oxidation or reduction ... 

Fig. 7. Solid state molecular transistor based on polyaniline bridged microelectrodes. PVA layer of polyvinyl alcohol 1 drain current Vg gate voltage rendering the polyaniline non-conductive Vg gate voltage switching on conductivity of the polyaniline layer (from ref.

Polyaniline (Scheme 3), is not strictly a heteroaromatic monomer, hut has a number of similarities to polypyrrole. There are differences, however, one of which is that are three redox levels each of which may be protonated or deprotonated. Of these, the pH-driven switch between the emeraldine (17) salt and emeraldine base (18) is attracting interest. 

The composition of polyaniline (emeraldine base) is shown in Fig. 12, and consists of alternating reduced and oxidized repeating units. Polyaniline can be switched back and forth from its insulating state to the conducting state by doping with HCl... 

An interesting option in terms of dopants is to incorporate an inherently conducting polymer such as a sulfonated polyaniline (PMAS Figure 2.8) as the molecular dopant. An interesting electrically conducting hydrogel (>90% [w/w] H20) with multiple electrochemical switches is the result.66... 

W.E. Rudzinski, L. Lozano and M. Walker, The effects of pH on the polyaniline switching reaction, J Electrochem. Soc., 1990, 137, 3132 D. Moon, T. Maruyama, K. Osakada and T. Yamamoto, Chemical oxidation of polyaniline by radical generating reagents, 02, H202-FeCl3 catalyst, and dibenzoyl peroxide, Chem. Lett., 1991, 1633. 

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