Polyanilines alkyl

By analogy with modern routes for the preparation of well-defined polyanilines (D ), palladium-catalysed cross coupling of 1,4-diiodobenzene and primary aryl- and alkyl-phosphines affords the comparatively short chain polymers (66a-c) (Mn= 1000-4000) (Scheme 20), that can be oxidised either by atmospheric... 

Polypyrrole/poly(ethylene-co-vinyl acetate) conducting composites with improved mechanical properties were prepared by a similar method [167], In addition, polyaniline/polystyrene [168] and polyaniline/poly(alkyl methacrylate) [169] composites have been synthesised. A solution of persulphate in aqueous HC1 was added to an o/w HIPE of polymer and aniline in an organic solvent, dispersed in aqueous SDS solution, causing aniline polymerisation. Films were processed by hot- or cold-pressing. 

The next group of materials comprises conducting polymers (ICP). Systems with identical polymers have often been reported for polyacetylene. It is known that this ICP forms insertion compounds of the A and D types (see Section 6.4, and No. 5 in Table 12). Cells of this Idnd were successfully cycled [277, 281-283]. However, the current efficiency was only 35% heavy losses were observed due to an overoxidation of the PA [284]. In other cases as for polypyrrole (PPy), the formation of D-PPy was anticipated but did not occur [557, 558]. Entry (6) in Table 12 represents some kind of ideal model. A PPy/PPy cell with alkyl or aryl sulfates or sulfonates rather than perchlorates is claimed in [559]. Similar results were obtained with symmetric polyaniline (PANI) cells [560, 561]. Symmetric PPy and RANI cells yield about 60% current efficiency, much more than with PA. An undoped PPy/A-doped PPy combination yields an anion-concentration cell [562, 563], in analogy to graphite [47], (cf. No. 7). The same principle can be applied with the PPy/PT combination [562, 563] (cf. No. 8). Kaneto et al. [564] have reported in an early paper the combination of two pol54hiophene (PT) thin layers (< 1 pm), but the chargeability was relatively poor (Fig. 40, and No. 9 in Table 12). A pronounced improvement was due to Gottesfeld et al. [342, 343, 562, 563], who employed poly[3-(4-fluoro-phenyl)thiophene], P-3-FPT, in combination with a stable salt electrolyte (but in acetonitrile cf. Fig. 40 and No. 10 in Table 12). In all practical cases, however, Es.th was below 100 Wh/kg. 

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). 

Polythiophene randomly grafted with alkyl and aniline tetramer groups (157) was synthesized. The tetramer was chosen because it is the minimum oligomer size that mimics the electrochemical behavior of polyaniline, which shows semiconduction and conduction behavior depending on its state of oxidation and the pH. Transition from one structure to the other is illustrated in equation 23, where the electron mobility of quinonoid states (158) rearranging to isolated free radicals (159) is precluded after reduction to 160. A correlation was found between the electrochemical behavior and the UVV-NIR spectra of the 157 polymers255. 

As with polyanilines, polythiophenes can either be prepared directly by electropolymerization, or by casting from solutions (for alkyl-substituted thiophenes). Most interest has focused on the latter because of their improved mechanical properties compared with those of electrochemically prepared films. The factors influencing the mechanical properties of PTh s are reviewed in this section. 

In addition to catalysis of small molecule transformations and biocatalysis, non-functionalized LLC phases used as reaction media have also been found to accelerate polymerization reactions as well. For example, the L and Hi phases of the sodium dodecylsulfate/n-pentanol/sulfuric acid system have been found to lower the electric potential needed to electropolymerize aniline to form the conducting polymer, polyaniline [110]. In this system, it was also found that the catalytic efficiency of the L phase was superior to that of the Hi phase. In addition to this work, the Ii, Hi, Qi, and L phases of non-charged Brij surfactants (i.e., oligo(ethylene oxide)-alkyl ether surfactants) have been observed to accelerate the rate of photo-initiated radical polymerization of acrylate monomers dissolved in the hydrophobic domains [111, 112]. The extent of polymerization rate acceleration was found to depend on the geometry of the LLC phase in these systems. Collectively, this body of work on catalysis with non-functionalized LLC phases indicates that LLC phase geometry and system composition have a large influence on reaction rate. 

Warren et al. [240] have explored some twenty ditferent sulphonates, mostly aromatic, in the preparation of films of polypyrrole as well as poly(3-methylthiophene), from aqueous solution and from acetonitrile solution. Only PPy-/ TS films from an aqueous medium show the splitting of diffraction peaks this is not interpreted further. Rather, the degree of order is estimated from the intensity of the diffraction peak. Benzenesulphonate ranks first in this respect. Dodecylbenzenesulphonate is also effective, and additionally shows a small-angle peak. This suggests that especially alkyl chains are effective in arranging themselves in a domain of hydrophobic character. (Dodecylbenzenesulphonic acid has been found to be an excellent surfactant for polyaniline and to facilitate its processing see Section 6.4.1.) Some of the films give spot patterns in electron diffraction. Warren et al. [240] state, however, that cell data cannot be derived from these. 

It is also possible to improve the ion-exchange properties of polypyrrole by its functionalization with alkyl ammonium. In the polymer obtained, it is then easy to incorporate, simply by ion exchange, species such as metallic porphyrins [91,92] or heteropolyanions [93]. Heteropolyanions can also be incorporated into polyaniline [86], polybutyl-thiophene layer [94], or polyamino-naphtol [95]. 

Polyanilines contain a number of amine and/or imine functionalities that can enter the reaction of alkylation with alkyl halides [260]. A scheme below shows the microwave-assisted crossfinking of emeraldine base polyaniline, dissolved in dimethylformamide, with diiodomethane. 

H. Qiu and M. Wan, Synthesis, characterization, and electrical properties of nanostructural polyaniline doped with novel sulfonic acids (4- n-[4-(4-nitrophenylazo)phenyloxy]alkyl] aminobenzene sulfonic acid), J. Polym. Sci. Part A Potyrrc Chem., 39, 3485-3497 (2001). 

Figure 6.11 XRD of (a) PMA/VOPO4 and (b) VOPO4.2H2O. (Reprinted with permission from Solid State Sciences, Novel alkyl substituted polyanilines/VOP04 nanocomposites by R. Bissessur and j. MacDonald, 8, 5, 531-536. Copyright (2006) Elsevier Ltd)...

A. G. Yavuz, E. Dincturk-Atalay, A. Uygun, E Code, E. Aslan, A comparison study of adsorption of Cr(VI) from aqueous solutions onto alkyl-substituted polyaniline/chitosan composites. Desalination 2011,279 (1-3), 325-331. 

Zheng, W.Y., K. Levon, J. Laakso, and J.E. Osterholm. 1994. Characterization and solid-state properties of processable n-alkylated polyanilines in the neutral state. Macromolecules 27 7755. 

Soluble conducting polymers can be solvent cast to form coatings. The addition of appropriate substituents to the polymer backbone or to the dopant ion can impart the necessary solubility to the polymer. For example, alkyl or alkoxy groups appended to the polymer backbone yield polypyrroles [117,118], polythiophenes [118], polyanilines [119,120], and poly(p-phenylenevinylenes) [97] that are soluble in common organic solvents. Alternatively, the attachment of ionizable functionalities (such as alkyl sulfonates or carboxylates) to the polymer backbone can impart water solubility to the polymer, and this approach has been used to form water-soluble polypyrroles [121], polythiophenes [122], and polyanilines [123]. These latter polymers are often referred to as self-doped polymers as the anionic dopant is covalently attached to the polymer backbone [9]. For use as a corrosion control coating, these water-soluble polymers must be cross-linked [124] or otherwise rendered insoluble. 

The XRD pattern and TEM of the cross-section of the LB multilayers reveal the ordered layered structure of the multilayers. The d spacing (37 A) is close to the expected X- or Z-type structure. However, it is expected that this LB multilayer has an X-type structure because hydrophobic substrates were used. The d.c. conductivities of the protonated resulting LB film (208 layers) in the parallel direction a n) and the perpendicular direction (cr ) are 10" Scm" and 10" Scm S respectively. This shows that the insulator-conductor transition on protonation, which is a specific property of ordinary polyaniline (PAn), does not occur in this material. An increase in a is observed after treatment of the LB multilayers with iodine vapour. Exposure to iodine vapour in air at room temperature leads to a change in colour of the film from greenish-blue to brown and an increase in d// of about 10 S cm"L In contrast, the increase in is 10-10 S cm"L The conductive anisotropy due to the alternating layered structure of conducting PAn layers and insulating alkyl chain layers has a value of 10 -10 (ct//= 10"" S cm" (7 = 10-iO-10" Scm" ) [21]. 

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