Emeraldine hydrogenation

According to a general rule, not only dihydric phenols, but also those diamines of the p-series which still contain one hydrogen atom attached to each nitrogen, are dehydrogenated to quinone or quinonediimine with great ease. Hence in the oxidation solution emeraldine is also immediately converted into the doubly quinonoid chain... 

Leucoemeraldine is the formal hydrogenation product of emeraldine. As shown in reaction 12, each tetramer unit contains one reducible quinonediimine moiety. 

There are two related hydrogenation reactions for which there are requisite enthalpy of formation data p-benzoquinone to hydroquinone and p-xylylene to p-xylene. For the former reaction, the enthalpies of hydrogenation are —179 kJmol-1 (s) and —142 kJ moL1 (g). For the latter62, the gas-phase hydrogenation enthalpy is ca —192 kJmol-1. An interpolated gas-phase hydrogenation enthalpy for p-quinonediimine is ca — 167 kJ mol-1. Based on the benzoquinone/hydroquinone example, the solid-phase value presumably would be more negative. The enthalpy of formation of solid emeraldine thus would be at least 534 kJmol-1. 

Fig. 10.19 Normalised (to sample mass) INS spectra of polyanilines [33]. Upper all hydrogenated, lower ring deuterated. (a) Emeraldine base, (b) emeraldine salt.

Both, aniline and anilium hydrochloride were polymerized in direct and in inverse miniemulsion, respectively [140]. The polymerization of anilium hydrochloride, which was initiated by hydrogen peroxide, yielded a highly crystaUine emeraldine polyaniline. In direct miniemulsions, additional stabilizers (e.g., poly(vinyl pyrroU-done) or PVA) were employed to preserve colloidal stability. The polymerization of aniline in direct miniemulsion has also been reported [141] in this case, following polymerization the polymer was first treated with stannous chloride and then doped with p-toluenesulfonic acid. A dramatic increase in conductivity after treatment with stannous chloride was considered due to pernigraniline moiety in the emeraldine base structure having been reduced. Such oxidative polymerization of aniline may be used to add an additional conductive shell to preformed latexes. For example, Li et al. polymerized aniline in the presence of dodecylbenzesulfonic acid on the surface of polyurethane and polyurethane/poly(methyl methacrylate) nanoparticles prepared in miniemulsion [142]. 

Hydrogen-bonding and electronic mobility in emeraldine salts. / Mol Struct 317 261. 

The reduction of emeraldine to leucoemeraldine consumes four atoms of hydrogen. 

Fig. 34. Polyaniline emeraldine base whose iminic nitrogens have been Fig. 32. Emeraldine-base form of polyaniline and the protonation of its p otonated using DBSA and aminic nitrogens hydrogen-bonded to DBSA...

Fig. 33. Schemes of supermolecules consisting of the emeraldine-base form of PANI complexed by (a) a protonating amphiphilic acid, such as DBSA and (b) a protonating amphiphilic acid and plasticizing am-phiphiles, which are strongly bound to the backbone due to hydrogen bonds [100,188] or coordination bonds [113].

Also with UV-vis spectroscopy, the chemical oxidation of leu-coemeraldine to emeraldine by oxygen and hydrogen peroxide catalyzed by copper and iron chloride was studied by Moon et al. 

In a degassed water solution, we also observed the reoxidation of the leucoemeraldine into the emeraldine salt, but, very interestingly, we could see gas formed at the surface of the film, which we suppose was hydrogen. 

Shacklette and Han [15] showed that uncharged emeraldine base has a high propensity for polar and hydrogen bonding interactions and that dopant can influence... 

Spectroscopic analyses As described above, the nature of the guest can be readily identified from its infrared spectrum. Figure 5 shows the infrared spectra of aniline intercalated y-zirco-nium copper phosphate over the region 1200 -1900 cm In this spectrum, the absorption maxima at 1309,1496 and 1576 cm" are characteristic of the emeraldine salt form of polyaniline, (typical frequencies for bulk polyaniline formed by oxidation using H /(NH4>2S20g are 1302,1496, and 1578 cm (12 1,32)). In a-zirco-nium copper hydrogen phosphate intercalate, the band at 1309 cm" is weak, but more intense... 

This chapter investigates hydrogen storage via physisorption in polyaniline (PANI). PANI is a conducting polymer that has been well characterized. Its chemical structure is shown in Fig. 8.1. The emeraldine base form of PANI consists of quinoid and benzenoid rings. This means that the theoretical hydrogen capacity... 

The first form of the emeraldine base polyaniline (PANI) to be investigated was bulk polyaniline. Bulk simply refers to the nanostructure of PANI, indicating that the PANI is used as-synthesized in its non-nanostructured form. This means that the surface morphology was not adjusted into nanofibrous form. After some baseline characterization and hydrogen sorption experiments, filler materials could be added to the PANI. The addition of filler materials to the matrix material could be used to... 

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