Leucoemeraldine base

For example, the investigations of the current-generating mechanism for the polyaniline (PANI) electrode have shown that at least within the main range of potential AEn the "capacitor" model of ion electrosorption/ desorption in well conducting emeraldine salt phase is more preferable. Nevertheless, the possibilities of redox processes at the limits and beyond this range of potentials AEn should be taken into account. At the same time, these processes can lead to the fast formation of thin insulation passive layers of new poorly conducting phases (leucoemeraldine salt, leucoemeraldine base, etc.) near the current collector (Figure 7). The formation of such phases even in small amounts rapidly inhibits and discontinues the electrochemical process. 

Figure 2 Illustration of the oxidative doping (p-doping) of leucoemeraldine base and protonic acid doping of emeraldine base, leading to the same final product,...

FIGURE 1.2. Molecular structure of widely used it-conjugated and other polymers (a) poly(para-phenylene vinylene) (PPV) (b) a (solid line along backbone) and it ( clouds above and below the a line) electron probability densities in PPV (c) poly(2-methoxy-5-(2 -ethyl)-hexoxy-l,4-phenylene vinylene) (MEH-PPV) (d) polyaniline (PANI) (d.l) leucoemeraldine base (LEB), (d.2) emeraldine base (EB), (d.3) pernigraniline base (PNB) (e) poly(3,4-ethylene dioxy-2,4-thiophene)-polystyrene sulfonate (PEDOT-PSS) (f) poly(IV-vinyl carbazole) (PVK) (g) poly(methyl methacrylate) (PMMA) (h) methyl-bridged ladder-type poly(jf-phenylene) (m-LPPP) (i) poly(3-alkyl thiophenes) (P3ATs) (j) polyfluorenes (PFOs) (k) diphenyl-substituted frares -polyacetylenes (f-(CH)x) or poly (diphenyl acetylene) (PDPA). 

Espe and coworkers108 109 have conducted a detailed structural characterization of annealed PANI powder samples by solid state 13C and 15N NMR and FT-IR. Comparing annealed PANI with PANI that has been chemically reduced to Leucoemeraldine Base (LB) 40 form, the solid state 13C and 15N NMR data clearly show the conversion of the quinoid rings to benzenoid rings upon heating at 473 K in vacuum. The structures... 

Figure 1,45. Various forms of PANl (a) leucoemeraldine base (LEB, poly(paro-phenylene amine)) (b) pemigraniline base (PNB, poly(poro-phenylene imine)) (c) emeraldine base (EB) (d) emeraldine salt (ES), bipolaron form (e) emeraldine sail, polaron form.

Figure 3. Raman spectra of a) diphenylamine (DPA). b) NJf-d henyl-1,4-phenylenediamine (PCD) and c) leucoemeraldine base T = 300K, Xl = 4S7.9 nm.

Leucoemeraldine base, the completely reduced form of polyaniline base, can be controllably oxidatively doped to the highly conducting regime/analogously to (CH)x,viz.,... 

Leucoemeraldine base powder can be oxidized, for example, as a suspension in a solution of chlorine in CCl or by solutions of (NO) (PFg) , FeCl3 or SnCl4 in organic solvent, and by oxygen,or H202/as a suspension in aqueous acid media. 25, 26, 27 The analogy between oxidative doping of (CH)x and leucoemeraldine can be seen from equations 5 and 6... 

The doping level and/or oxidation state of the resulting polymer can be controlled/ within limits according to the stoichiometric ratio of leucoemeraldine base and oxidant employed. ... 

Fig. 4. Approximate energy per site versus ring twist angle W for leucoemeraldine base, assuming equal near-neighbor angles. 

Fig. 5 Calculated band structure for a leucoemeraldine base within the extended zone scheme.

Photoinduced infrared absorption studies show that the photoinduced infixired modes are much weaker in intensity, than the photoinduced electronic transition [23], in contrast to the behavior of polyacetylene [51,52] and polythiophene [6]. Analysis, within the amplitude mode formalism [53], indicates that the polarons are massive, > or -60 m, while use of bond order [54] or Holstein [55] polaron formalisms leads to an even larger estimate of the mass of the polarons. Photoexcitation, into either the exciton peak or the 7C-to-7t peak of emeraldine base, produces essentially identical long-lived photoinduced infrared modes [29]. The long-lived photoinduced spectra of the leucoemeraldine base are much weaker. Similarly, the photoinduced infrared absorptions in the pemigraniline base are much weaker, than the photoinduced electronic transitions, again indicating massive photoinduced defects [30]. 

A model for the effects of electron-lattice coupling via ring rotation on the electronic structure of leucoemeraldine base has been developed [15]. The charge defect states in leucoemeraldine and other phenyl ring-containing polymers, particularly hole polarons, are... 

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