Polyanilines, synthesis emeraldine base

Han et al. [64, 66] reported the synthesis of highly conductive and thermally stable self-doped mercaptopropanesulfonic-acid-substituted polyanilines by the concurrent reduction and substitution reaction between polyaniline and a nucleophile. These reactions were carried out on both electrochemically generated and free standing polyaniline films prepared from emeraldine base dissolved in N-methylpyrrolidinone. The electrochemically prepared films were dedoped with 5 % aqueous NaiCOs to convert them the into the emeraldine base form. The sulfonated polyaniline was prepared by reaction of a polyaniline emeraldine base film with 0.1 M 3-mercapto-l-propanesulfonic acid sodium salt in methanol under nitrogen at room temperature for approximately 14h [66]. A catalytic amount (0.01 M) of acetic acid was reported to accelerate the reaction. The resulting sulfonated polyaniline film was thoroughly rinsed with methanol, followed by 5 % aqueous NaiCOs to remove reactants. 

Synthesis Polyaniline emeraldine base (PANI-EB) was prepared via the FeC13 method as described elsewhere (19). 

When we reported the first synthesis of the emeraldine base form of polyaniline 13 years ago (54) by the deprontonation (removal of HCl) from the emeraldine hydrochloride form of polyaniline by aqueous ammonium hydroxide, we were content with elemental C,H and N analyses which added up to -99%. In some cases, we reported the Cl content (as HCl) as <0.4%. Few research groups investigating conducting or non-conducting forms of electronic polymers report elemental analyses and fewer still pay attention to small amount of impurities. It has generally been believed that the properties of interest in such polymers are not particularly sensitive to traces of impurities. However, we have recently found as shown below, that selected properties of interest in the LED field are very sensitive to traces of certain impurities. 

The emeraldine salt of polyaniline which is one of the three different forms of polyaniline—leucoemeraldine (the fully reduced state], emeraldine (the half oxidized state] and pernigraniline (the fully oxidized state] (Fig. 8.1]—is electrically conductive while the others are insulators. Conventional chemical synthesis of polyaniline is based on an oxidative polymerization of aniline by using an oxidant in the presence of a strong acid dopant in the reaction mediunL ... 

ABSTRACT. Detailed experimental procedures are given for the chemical synthesis from aniline of analytically pure emeraldine hydrochloride, a highly conducting polymer derived from the emeraldine oxidation state of polyaniline, which contains equal numbers of oxidized and reduced repeat units, the non-protonated base form of which has the composition,... 

---