(Per)nigraniline is prepared by oxidation of the emeraldine base with a peracid: : CS1 maint: uses authors parameter ( link) The polymer precipitates as an unstable dispersion with micrometer-scale particulates. The formation of leucoemeraldine can be described as follows, where is a generic oxidant: n C 6H 5NH 2 + → n + H 2OĪ common oxidant is ammonium persulfate in 1 M hydrochloric acid (other acids can be used). The same material can be prepared by oxidation of leucoemeraldine.Īlthough the synthetic methods to produce polyaniline are quite simple, the mechanism of polymerization is probably complex. Undoped polyaniline has a conductivity of 6.28 ×10 −9 S/m, whereas conductivities of 4.60 ×10 −5 S/m can be achieved by doping to 4% HBr. Treatment of emeraldine with acids increases the electrical conductivity by up to ten orders of magnitude. Polyaniline sensors typically exploit changes in electrical conductivity between the different oxidation states or doping levels. The colour change associated with polyaniline in different oxidation states can be used in sensors and electrochromic devices. Leucoemeraldine and pernigraniline are poor conductors, even when doped with an acid. Emeraldine base is regarded as the most useful form of polyaniline due to its high stability at room temperature and the fact that, upon doping with acid, the resulting emeraldine salt form of polyaniline is highly electrically conducting. Protonation helps to delocalize the otherwise trapped diiminoquinone-diaminobenzene state. The emeraldine (n = m = 0.5) form of polyaniline, often referred to as emeraldine base (EB), is neutral, if doped (protonated) it is called emeraldine salt (ES), with the imine nitrogens protonated by an acid. Studies have shown that most forms of polyaniline are one of the three states or physical mixtures of these components.

Pernigraniline is the fully oxidized state (n = 0, m = 1) with imine links instead of amine links. Leucoemeraldine with n = 1, m = 0 is the fully reduced state. In the figure, x equals half the degree of polymerization (DP).

(per)nigraniline – blue/violet (C 6H 4N) n.

emeraldine – green for the emeraldine salt, blue for the emeraldine base ( 2 2) n.

leucoemeraldine – white/clear & colorless (C 6H 4NH) n.

Polymerized from the inexpensive aniline, polyaniline can be found in one of three idealized oxidation states:

Structures of polyaniline (n+m = 1, x = half degree of polymerization).

Subnautica polyaniline