Chemical polymerization polyaniline

Sample Preparation. Chemically polymerized 2-ethyl polyaniline, with reported molecular weight of 5000, was prepared by the method outlined by Leclerc et al. (15). Treatment of the insoluble product with ammonium hydroxide solution resulted in transforming the salt into the soluble EB form, which exhibited slight solubility in methanol. The soluble EB form of PANi is known to be readily protonated under acidic conditions, producing the highly insoluble ammonium salt form (16.17). In order to maintain the free amine base form in solution, it was necessary to synthesize the silica gel in the presence of a minimal amount of acid catalyst. 

This section discusses the reactivities and biosensor applications of functionalized electrosynthetic polyanilines prepared by (i) electropolymerization and (ii) chemical polymerization of aniline on the surfaces of Au, glassy carbon or Pt disk electrodes. Four such polyaniline or substituted composite polyaniline films developed by our research group are (a) nanofibrillar polyaniline-polyvinyl sulfonate (PANI-PVS), (b) poly(2,5-... 

Gupta and Warhadpande [177] chemically prepared substituted polyaniline by polymerizing m-toluidine, o-toluidine, o-anisidine, acetanilide, diphenylamine and o-naphthylamine. The thermogravimetric studies revealed that the ring-substituted polymers were less stable than the N-substituted polymers as evident from the weight loss at 800°C for poly(m-toluidine) (62.2%), poly(o-toluidine) (61.6%), poly(o-anisidine) (100%), poly(acetanilide) (51.9%), poly(diphenylamine) (29.5%) and poly(o-naphthylamine) (69.72%), which also indicates that the stability of strained-chain polymers is less than that of flat-chain polymers. 

P.-C. Wang, E. C. Venancio, D. M. Sarno, and A. G. MacDiarmid, Simplifying the reaction system for the preparation of polyaniline nanofibers Re-examination of template-free oxidative chemical polymerization of aniline in conventional low-pH acidic aqueous media. React. Funct. Polym., 69, 217-223 (2009). 

Figure 14.7 TEM ofPANI hollow spheres produced by chemical polymerization of aniline on polystyrene particles and removal with tetrahydrofuran, and decorated with gold nanoparticles. (Reprinted with permission from Langmuir, Polyaniline / Au composite hollow spheres Synthesis, characterisation, and application to the detection of dopamine by X. M. Feng, C.J. Mao, C. Yang et al., 22, 9, 4384-4389. Copyright (2006) American Chemical Society)...

Nanofibers in Conventional Polyaniline Morphological Evolution of Polyaniline during Chemical Polymerization Suppressing Secondary Growth to Make Pure Nanofibers Effect of Solvents on the Intrinsic Morphology of Polyaniline Polyaniline Nanofibers Obtained by Solvent Exchange Processing and Characterization of Polyaniline Nanofibers... 

Using functional molecules as structural directors in the chemical polymerization bath can also produce polyaniline nanostructures. Such structural directors include surfactants [16-18], liquid crystals [19], polyelectrolytes (including DNA) [20,21], or complex bulky dopants [22-24]. It is believed that functional molecules can promote the formation of nanostructured soft condensed phase materials (e.g., micelles and emulsions) that can serve as soft templates for aniline polymerization (Figure 7.3). Polyelectrolytes such as polyacrylic acid, polystyrenesulfonic acid, and DNA can bind aniline monomer molecules, which can be polymerized in situ forming polyaniline nanowires along the polyelectrolyte molecules. Compared to templated syntheses, self-assembly routes are more scalable but they rely on the structural director molecules. It is also difficult to make nanostructures with small diameters (e.g., <50 nm). For example, in the dopant induced self-assembly route, very complex dopants with bulky side groups are needed to obtain nanotubes with diameters smaller than 100 nm, such as sulfonated naphthalene derivatives [23-25], fidlerenes [26], or dendrimers [27,28]. 

FIGURE 7.5 TEM images of polyaniline powders made by traditional chemical polymerization using 1.0 M HCl showing a small portion of nanofibers (arrows) in the sample. A magnified view of the nanofibers is shown on the right. (Reproduced Ifom Huang, J.X. and Kaner, R.B., /. Am. Chem. Soc., 126, 851-855, 2004. With permission.)... 

Morphological Evolution of Polyaniline during Chemical Polymerization... 

Liu, J.M., and S.C. Yang. 1991. Novel colloidal polyaniline fibrils made by template guided chemical polymerization. Chem Commun 21 1529-1531. 

Tang, X., Y. Sun, and Y. Wei. 1988. Molecular-weight of chemically polymerized polyaniline. Makromol Chem Rapid 9 (12) 829-834. 

FeSj/polyaniline (PANI) composite as cathode material for LIB was synthesized via in-situ chemical polymerization of aniline in the presence of fine FeS particles in aqueous suspension. The FeS /PANI composite exhibited the capacity of 767.5 mAh/g at a current density of 100 mA/g with weaker polarization and improved reversible capacity, compared with the FeSj particle. The improvement of the electrochemical properties was due to the enhanced electrical conduction and the buffer connection of amorphous polymer between the particles of the composite [56]. 

Hierarchical porous graphene/polyaniline composite film with a superior rate performance for supercapacitors was fabricated by chemical polymerization method. This composite exhibited 385 F/g at a current density of 0.5 A/g, with a capacity retention of 94% as current density was varied from 0.5 to 10 A/g. This superior rate performance was demonstrated to be due to the interconnected porous structure of the film, which allowed electrolyte ions to pass through quickly during the rapid charge-discharge process [62]. 

The amphiphilic polyaniline derivative (degree of polymerization > 20), prepared by the chemical polymerization method with (NH4)2S20s in THF and 2 mol 1" HCl solution was used. More than 200 layers of the polyaniline derivative were prepared by transferring the monolayer on the HCl (0.1 mol 1 ) subphase onto polyester, gold- or ITO-deposited polyester and silated glass substrates at a surface pressure of 20-25 mNm" by the horizontal lifting method. 

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