Synthesis of polyaniline

Polyaniline is less tolerant of preparation conditions than polypyrrole, and the list of anion dopants used in the preparation is more limited. However, subsequent replacement of the anion used in preparation by a dodecylben-zene sulfonate makes polyaniline become soluble in solvents such as Af-methyl pyrrolidone (NMP), or zn-cresol, and it can be spin-coated or otherwise solution-processed. In a similar way derivatives of aniline, such as 

2-methoxyamline when oxidized in a similar fashion to that given in Protocol 9 below give a conducting polymer that is soluble in solvents such as chloroform, dichloromethane, and acetonitrile. 

Caution Carry out all procedures in a well-ventilated fume-cupboard, wear appropriate disposable gloves, a lab-coat, and safety glasses. 

Preparation. Aniline is distilled from calcium hydride under reduced pressure prior to use and stored under nitrogen in the fridge at 4°C. 

A volumetric flask (100 ml) is charged with aniline (0.93 g, 10 mmol) and made up to the mark with hydrochloric acid (1 M). The solution is then purged with nitrogen for approximately an hour prior to use. 

The different steps involved in the formation of PANI are as follows  

Para coupHng of the radical cations is preferred over ortho coupling, as it does not lead to disrupted polymer. The use of an ortho-substituted monomer can enhance para coupling. The properties of the end products are greatly influenced by the polymerization conditions such as temperature and pH. 

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Recently developed catalyst systems make it possible to construct carbon (.v/>2 )-catbon (sp3) bonds and carbon-nitrogen bonds under mild conditions (Scheme 9.14).19,20 These new developments have also been incorporated into step-growth polymerization. Kanbara et al. reported the synthesis of polyanilines and related polymers in 1996 (Scheme 9.15).21 Wang and Wu reported the synthesis of polyketones in 1999 (Scheme 9.16).22... 

Ganesan R, Shanmugam S, Gedanken A (2008) Pulsed sonoelectrochemical synthesis of polyaniline nanoparticles and their capacitance properties. Synt Met 158 848-853... 

The synthesis of polyaniline and copolymers of aniline with o-nitroaniline is aimed at obtaining an electroactive material. This material can be used, for example, as an electrode in conjunction with the magnesium electrode to construct chemical power sources. The polymers were prepared by oxidation of aniline or its mixture with nitroaniline ammonium persulfate in aqueous hydrochloric... 

Xu P, Singh A, Kaplan DL (2006) Enzymatic catalysis in the synthesis of polyanilines and derivatives of polyanilines. Enzyme Catal Synth Polym 194 69-94... 

Alvarez S, Manolache S, Denes F (2003) Synthesis of polyaniline using horseradish peroxidase immobilized on plasma-functionalized polyethylene surfaces as initiator. J Appl Polym Sci 88(2) 369-379... 

The inter-relationship between colloid and polymer chemistries is completed by colloidal polymer particles. The formation of 50-nm-diameter, 100- to 200-nm-long polyaniline fibrils in a poly(acrylic acid)-template-guided polymerization, similar in many ways to those produced from polymerized SUVs (see above), provides a recent example of polymer colloids [449], The use of poly(styenesulfonic acid) as a template yielded globular polyaniline particles which were found to be quite different morphologically from those observed in the regular chemical synthesis of polyaniline [449]. 

Osteryoung and coworkers have also investigated the use of chloroaluminate ionic liquids for the synthesis of polyaniline [62, 63]. Unlike pyrrole and thiophene, aniline was successfully polymerized in acidic, neutral and basic chloroaluminate melts, although the best results were obtained using the neutral composition. 

The HRP-catalyzed polymerizations were preferentially ortho and para directing, resulting in branched polymeric materials, which were intractable and had poor electrical properties. However, SBP-mediated synthesis of polyaniline at 1°C in either aqueous or partially organic solvents resulted in low branching and ortho-coupled polyaniline at pH higher than 3.0. SBP actually outperforms HRP in terms of stability and is now used in numerous biotechnological applications [51]. 

Scheme 1. (Left) Synthesis of Polyaniline by Electropolymerization in the Presence of an Optically Active Acid and (Right) Structure of Oxazoline-Containing Polythiophene 29...

The combinatorial synthesis based on the combination of microfluidics and electropolymerization was realized with a microchip consisting of two areas microfluidic channels for generation of gradient of two substances and a parallel electrochemical reactor with platinum electrodes (Fig. 13.3). The system was tested for synthesis of polyaniline in the presence of polysulfonic acid. The reagent ratio providing the best efficiency of the polymer synthesis was evaluated. 

Such ILCE showed remarkably high enantioselectivity for transesterification reaction of several secondary alcohols in the presence of vinyl acetate in toluene, and there was no significant deterioration in activity even after multiple (five times) use. Horseradish peroxidase (HRP) is another example to be coated with both hydrophobic and hydrophilic ILs such as [BMIMJITf N] and [BMIM][PEg] toward enzymatic synthesis of polyaniline [23]. An attractive point of the ILCE-based immobilization method is easy recovery of enzyme/IL phase by liquid-liquid phase separation and effective reusability of the enzyme (Eigs. 10.8, 10.9) [23, 59]. 

Enzymatic Synthesis of Polyaniline and Other Electrically Conductive Polymers... 

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