Aniline interfacial polymerization

The chemical polymerization of aniline at the interface between two immiscible solvents provides an attractive alternative route to PAn s. Such interfacial polymerization was first demonstrated in 1994 by Michaelson and McEvoy,82 who produced a freestanding PAn film at the interface between a solution of aniline/sodium dodecylsulfate in carbon tetrachloride and an aqueous oxidant solution containing ammonium persulfate/HCl. The analogous interfacial polymerization of a range of /V-alkylanilincs and o-alkylanilines using hexane and water phases for chemical oxidation with ammonium persulfate has also been briefly described.83... 

Interfacial polymerization of aniline in a water-toluene stirred mixture containing pTS acid dopant... 

Figure 2.8 Snapshots showing interfacial polymerization of aniline in a water/chloroform system. From (a) to (e), the reaction times are 0, 1.5, 2.5, 4, and 10 min, respectively. The top layer is an aqueous solution of 1.0 M HCIO4 and APS the bottom layer is aniline dissolved in chloroform. (Reprinted with permission from Journal of the American Chemical Society, A General Chemical Route to Polyaniline Nanofibers by J. Huang and R. B. Kaner, 126, 3, 851-855. Copyright (2004) American Chemical Society)...

Solid-State Mechanochemical Synthesis Facile template-free solid-state mechano-chemical synthesis of highly branched PANI-NFs with coralloid tree-like superstrueture, via the oxidative polymerization of aniline hydrochloride with FeCl3 6H2O, has been demonstrated [194]. The synthetic yield ( 8%) was comparable to that of the solution interfacial polymerization method. Solid-phase mechanochemical synthesis of branched PANI-NFs was also achieved by using anhydrous FeCl3 as the oxidant [195]. 

Interfacial Polymerization Thin PANI-NTs with an average outer diameter of 28 nm have been synthesized by interfacial polymerization in a calcium carbonate-stabilized oil/ water emulsion [161]. PANI-NTs were synthesized by simply tuning the concentration of APS in a two-phase (toluene solution of aniline/acetic acid aqueous solution of APS) medium [392], or by tuning the concentration of oL-tartaric acid in a two-phase (toluene solution of aniline/DL-tartaric acid aqueous solution of APS) medium [393]. The difference in the PANI morphologies was attributed to the difference in the relative rates of interfacial nucleation to aqueous nucleation. 

Interfacial polymerization is performed in an aqueous-organic hiphasic system (Figure 7.7) with aniline dissolved in an organic solvent and the oxidant, ammonium peroxydisulfate, dissolved in an aqueous acid solution. A great variety of organic solvents can be used, including benzene, hexane, toluene, carhon tetrachloride, chloroform, methylene chloride, diethyl ether, carbon disulfide, or o-dichlorobenzene. 

FIGURE 7.7 Snapshots showing the interfacial polymerization route to polyaniline nanofibers. The reaction times are (a) 0, (b) 60, (c) 120, and (d) 180 s. The top layer is an aqueous solution of acid and oxidant, the bottom layer is aniline dissolved in an organic solvent, (e) A typical electron microscopy image of the nanofiber products. 

Till date, liquid-crystalline phases [51], colloidal particles [52], and structure-directing molecules [53[ as the soft-template have been employed to synthesize PANI nanostructures. Based on the traditional synthesis method of PANI, in particular, some simple approaches such as interfacial polymerization [54], mixed reactions [55], dilute polymerization [56] and ultrasonic irradiation [57] have also been employed to synthesize PANI. The interfacial polymerization method only allows the oxidative polymerization of aniline to take place at the interface of the organic/water phases and the product directly enters into the water phase, which could facilitate environmentally friendly processing. 

Several synthetic methods for preparing PEDOT nanoparticles have been reported including seed polymerization, emulsion polymerization and dispersion polymerization. There have been several reports related to PEDOT-coated particles and PEDOT hollow particles [43, 44], Dispersion polymerization has been applied for PEDOT-coated Polystyrene (PS) particle fabrication. lOOnm PS nanoparticles were used as the core material [44]. Poly aniline (PANi) nanofibers have been synthesized using interfacial polymerization without templates or functional dopants [45,46]. Scanning electron microscopy (SEM) images of PANi nanofibers are shown in Figure 14.3. 

Figure 3.21 Temporal sequence of photographs of a vial during the interfacial polymerization of aniline. Times (a) 0 s, (b) 60 s, (c) 90 s, (d) 120 s, (e) 180 s. The aqueous solution of the acid and the oxidant agent fills the volume above the interface. Reproduced with permission from Ref. 269, Chem. Eur. J., 2004, 10, 1314-1319. Doi 10.1002/chem.200305211. Copyright 2004, Wiley-VCH Verlag GmbH Co. KGaA.

At room temperature, polyaniline nanofibres are synthesised using interfacial polymerisation between 1 M HCl in water (25 ml) containing ammonium persulfate and xylene (25 ml) containing aniline. The molar ratio of aniline to ammonium persulfate is kept at 4 1. Upon polymerization, xylene containing unreacted aniline is removed from the top and replaced with an equal volume of xylene. 

Coatings of fabrics is important as it provides flexibility and mechanical strength to the otherwise powdery, unprocessable poly aniline. Undoubtedly, the in-situ grafting of conducting polyaniline onto substrates can be compared with coating of the electrode during polymerization as both these are solid-liquid interfacial reactions, and therefore the mechanism for the formation of polyaniline cannot differ drastically [302-5]. The polymerization reactions mechanism can be written as... 

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