Leucoemeraldine, poly

When 0 < y < 1 these structures are the poly(p-phenyleneamineimines), in which the oxidation state of the polymer increases with increasing content of the imine form. The fully reduced form (y = 1) is leucoemeraldine , the fully oxidized form (y = 0) is pernigraniline , and the 50% oxidized structure (y = 0.5) is emeraldine . Each structure can exist as die base or as its salt, formed by protonation, so that we can envisage four repeat units in the polymer chain, in amounts which depend on the extent of both oxidation and protonation of the structure (Fig. 5). 

Polymers (CH), PPA Poiy(o-Me3SiPA) PPY DP-PPY PPY PAN PNA EM LM NA PTH PPS PBT PBiT PMeT PHeT PPV PPP P2VP P4VP PVK polyacetylene polyphenylacetylene poly[[o-(trimethylsilyl)phenyl]acetylene] polypyrrole deprotonated (25%) polypyrrole fully reduced polypyrrole polyaniline pernigraniline emeraldine leucoemeraldine nigraniline polythiophene poly(phenylene sulfide) polybenzothiophene poly(2,2 -bithiophene) poly(3-methylthiophene) poly(3-hexylthiophene) poly(phenylene vinylene) poly( p-phenylene) poly(2-vinylpyridine) poly(4-vinylpyridine) poly(A-vinylcarbazole)... 

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). 

Let us estimate the enthalpy of formation of the leucoemeraldine tetramer, which now is written as Poly [—CgLLjNH—]4, by assuming thermoneutrality for the solid phase reaction 11. The result is 367 kJ mol 1. 

PANl can be prepared by the polymerization of aniline in an oxidizing medium, and the resulting polymer is found to be in a partially oxidized state [295]. Its molecular constitution is intermediate between that of poly(para-phenylene amine), which represents the so-called leucoemeraldine form, and that of poly(par o-phenylenc imine), known as the pemi-graniline form (Figure 1.45). Since the polymer is prepared under acidic conditions (HCl), it is also partly... 

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.

No protons were found to he involved in both the first and second redox reactions of poly(N-methylaniline), but two anions each were taken up for two electrons removed from four aniline units for the oxidation of leucoemeraldine to emeraldine and its further oxidation to the second oxidation state. 

We have re-analyzed the available data in comparison with the results of band structure calculation to provide the basis for an understanding of the electronic structure of the four principal forms of poly aniline the fuUy reduced leucoemeraldine, (1 A)n the partially oxidized emeraldine base, [(1 A)(2A)]n the oxidized and fully protonat emeraldine salt, [IS] (A )n and the fully oxidized bipolaron lattice, (-B-NH+=Q=NH+-)n. 

Figure 4-1. Chemical structures of conducting polymers, (a) Frans-polyacetylene (b) cw-polyacetylene (c) poIy(/i-phenylene) (d) polypyrrole (e) polythiophene (f) poly(/>-phenylenevinylene) (g) poly(2,5-thienylenevinylene) (h) polyaniline (leucoemeraldine base form) (i) polyisothianaphthene.

In contrast to ring-sulfonation of polyaniline, Bergeron et al. derivatized the leucoemeraldine form of poly aniline at the N-position with an alkylsulfonate group as shown in Figure 20.46 [38]. The sodium salt was achieved by reacting the leucoemeraldine base with NaH and 1,3-propanesultone. 

FIGURE 10.2 (a) Polyaniline in oxidized state (y= 1 leucoemeraldine y=0.5 emer-aldine y = 0 pemigraniline) (b) polypyrrole (c) polyphenylene vinylene (d) polythi-enopyrrole (e) poly(paraphenylene) (f) polythiophene (g) polyphenylene sulfide (h) polyfuran (i) poly(diphenylamine) (j) polypyridine (k) polyfluorene (1) poly(phenylene vinylene) (m) polyacetylene (n) poly(thienylene vinylene) (o) poly(furylene vinylene) and (p) poly(3,4-ethylenedioxythiophene). 

Polyaniline, one of the most studied conducting polymers (in general as well as for corrosion protection), is usually obtained by protonation of what is called the emeraldine base form, shown in Figure 2. The protonation reaction does not change the number of electrons in the polymer backbone. However, starting at the leucoemeraldine form of polyaniline, one would obtain the emeral e salt (conducting) form of polyaniline by an oxidation reaction. Protonic doping has also been observed in the case of alkoxy substituted poly(para-phenylene vinylene) (PPV) ... 

Fig. 1. (a) Leucoemeraldine base (b) emeraldine base (c) pernigraniline base (d) polyCparaphenylene sulfide) le) emeraldine hydrochloride salt polymer (f) poly(orthotoluidine) (emeraldine base form) (g) sulfonated polyaniline (self-doped salt form). 

Fig. 26 Reversible electrochemical switching between vesicles and its puck-like fragments TAPEG-EB tetraaniline-modified poly(ethylene glycol) with tetraaniline in the emeraldine base form, TAPEG-LEB with tetraanaline in the leucoemeraldine form (reprinted with permissitm fiorn [298]. Copyright 2011 American Chemical Society)...

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