Characterization of Solution and Solid State Properties of Undoped and Doped Polyanilines Processed from Hexafluoro-2-propanol

Abstract

We have investigated the changes in the molecular conformation, morphology, and conductivity of polyaniline as it transforms from the insulating emeraldine base (PANI-EB) to the conducting emeraldine salt (PANI-ES) in solutions of hexafluoro-2-propanol (HFIP) and in films processed from the same solvent. Since both PANI-EB and PANI-ES dissolve in this single solvent, we are able to observe for the first time conformational changes as a function of the molar doping level, y. HFIP both solvates and complexes PANI-EB (i.e., y = 0) which promotes a disruption in secondary interactions between chains and allows individual polyaniline chains to adopt a more expanded molecular conformation. As PANI-EB is fully doped to PANI-ES (i.e., y = 0.50), a decrease in the GPC retention time and an increase in [η] argues in favor of an expanded chain conformation in HFIP. When the solvent is removed (under very mild conditions) from PANI-ES, the expanded molecular conformation is retained in the solid state, based on the strong absorption of the UV−vis/near-IR free carrier tail at 2500 nm and good room temperature conductivity. The results in this study indicate that the HFIP solvent can be used to process PANI-EB and PANI-ES with diversified dopant counteranions; in some cases, enhanced optical, conductivity, and morphology properties result from the use of this solvent.

Protonation of Polyaniline in Hexafluoro-2-propanol. Spectroscopic Investigation

“…10 The spectra of EB in HFIP are strongly time dependent ( Figure 2). The protonation of EB by acidic solvents such as m-cresol has been reported.…”

“…Exploiting this research pathway, Hopkins et al 10 have discovered that fluorinated alcohols, which are even more acidic than phenols, also dissolve PANI in the basic (unprotonated) and salt (protonated) form. Exploiting this research pathway, Hopkins et al 10 have discovered that fluorinated alcohols, which are even more acidic than phenols, also dissolve PANI in the basic (unprotonated) and salt (protonated) form.…”

Synthesis of a water‐soluble diblock copolymer of polysulfonic diphenyl aniline and poly(ethylene oxide)

“…For the HCl‐doped PSDA I solution below pH = 2 (spectrum a in Fig. 3), in addition to the π‐π* transition band of the benzenoid ring at 320 nm of the PANI backbone,28 there were also absorption bands at 600, 490, and 900 nm because of the exciton transitions in the quinoid diimino units, bipolaron, and polaron, respectively 29. The aforementioned bands characterized the external‐doping‐induced coplanarity or electron delocalization.…”

Surface segregation of fluorinated moieties on poly(methyl methacrylate-ran-2-perfluorooctylethyl methacrylate) films during film formation: Entropic or enthalpic influences

“…It was reported that the chain shapes or the conformations of polymers in solutions could affect the structures and properties of the polymers in bulk [22,23]. The influence of the preparation methods on the surface properties of fluorinated polymers has been reported in several publications [21,[24][25][26][27][28][29] and it was found that various surface structures can be obtained by controlling film-formation conditions such as the solvent species and preparation methods.…”