Aniline polymerization

Z. Guang-Ming, T. Lin, S. Guo-Li, H. Guo-He and N. Cheng-Gang, Determination of trace chromium (VI) by an inhibition-based enzyme biosensor incorporating an electro polymerized aniline membrane and... 

PAn composites have been formed by polymerizing aniline in the presence of a latex.50 The latexes were chlorinated copolymers (Haloflex EP 252), which were film-forming latexes. Interestingly, the thermal stability of the resultant composite was better than either of the individual components. Polyaniline-polyacrylamide51 composites have been prepared by carrying out a chemical oxidation of aniline in the presence of polyacrylamide. Films that could be cast were stable up to 250°C. However, conductivities were low (approximately 5 x 10-2 S cm-1). 

Both Buchwald and Hartwig have explored the use of palladium-catalyzed amination for the synthesis of dendrimers and polyanilines. Dendrimers, such as 48, can be easily assembled through sequential aiylation of aminoanilines.89 These dendrimers are useful in creating metal-organic frameworks and often can exhibit interesting electronic effects, such as diradicals, and as optical materials. Polymeric anilines 49 are of intense interest due to their unique electrical conducting properties. Using the... 

Although no quantitative description has been made after Zotti el al. s work [93], other investigators have described similar observations. Kuramoto el al. [95] reported that the growth rate and structure of electro-polymerized aniline were modified by using sodium polyvinyl sulphonate. Similar observations were made by Hyodo el al. [98], Dhawan and Trivedi [100], and Cordova el al., who used a variety of organic and inorganic electrolyte anions. 

The comparative XPS studies was done on the thermal stability of polyaniline salts doped in three different ways such as (i) heavily protonated by HCIO4 or metanilic acid (ii) self-doped by sulphonation of emeraldine base and (iii) co-polymerizing aniline with metanilic acid to give a self-doped material which was fitrther protonated by HCIO4 or metanilic acid. Polyaniline protonated with HCIO4 underwent de-protonation on thermal or water treatment easily whereas the polyaniline with SO," groups attached by covalent bonds showed the lowest stability [169]. 

SWNTs Chemical polymerization Aniline, acide (HCl, H2SO4), KjCraOy PANI doped with small CNT fragments, closed-shell Ceo... 

MWNTs Electrochemical polymerization Aniline-E HCl Coaxial wire of PANI and MWNTs... 

NFs acted as an oxidant to oxidatively polymerize aniline. Consequently, Mn O was completely consumed while PANl/TiO -NFs were formed. Composite fiber film having a PANI nanowire-on-TiO nano/microfiber hierarchical nano/microstructure was fabricated by electrospinning, calcinations and in situ polymerization [121], The photocatalytic electrodeposition of PANI in nanotubular TiO host matrice was recently reported by Janaky ef a/. [ 108]. TiO films were initially electrosynthesized on titanium foil by anodization at different voltages in fluoride-containing aqueous media, and then the PANI was electrografted onto the entire surface of... 

Both, aniline and anilium hydrochloride were polymerized in direct and in inverse miniemulsion, respectively [140]. The polymerization of anilium hydrochloride, which was initiated by hydrogen peroxide, yielded a highly crystaUine emeraldine polyaniline. In direct miniemulsions, additional stabilizers (e.g., poly(vinyl pyrroU-done) or PVA) were employed to preserve colloidal stability. The polymerization of aniline in direct miniemulsion has also been reported [141] in this case, following polymerization the polymer was first treated with stannous chloride and then doped with p-toluenesulfonic acid. A dramatic increase in conductivity after treatment with stannous chloride was considered due to pernigraniline moiety in the emeraldine base structure having been reduced. Such oxidative polymerization of aniline may be used to add an additional conductive shell to preformed latexes. For example, Li et al. polymerized aniline in the presence of dodecylbenzesulfonic acid on the surface of polyurethane and polyurethane/poly(methyl methacrylate) nanoparticles prepared in miniemulsion [142]. 

The preponderance of patent or sdentific literature regarding polyaniline synthesis in aqueous media reports synthetic conditions whereby the concentration of the acid is measurable on the pH scale and the acid most frequently reported is HCl. The activity and concentration of the hydronium ion are obtained by measurements of pH by ion-selective electrodes or pH paper-containing indicators. However, such pH measurements are valid only in single-solvent systems, typically water, for very dilute concentrations of an acid. However for very concentrated add solutions, such as those used to polymerize aniline at subzero temperatures, the preferred measure of the ability of an acid to dissociate a proton from an indicator, according to HB+ H+4-B, is the Hammett acidity function, Hq given by... 

A different method of S3mthesizing polyanUine was reported [77]. It uses an enzyme, horseradish peroxidase, in the presence of hydrogen peroxide to polymerize aniline. To prevent reactions at the ortho positions of the phenyl rings that yield insoluble branched materials, a polyelectrolyte template, like sulfonated polystyrene, was used. The polyelectrolyte aligns the monomers, dopes the polyaniline to the conducting form, and forms an irreversible complex with the polyaniline to keep it water-soluble [77]. The conductivity of the complex increases with increasing polyaniline to sulfonated polystyrene molar ratios. Conductivities of0.005 S/cm are obtained with the pure complex and increase to 0.15 S/cm after additimial doping by exposure to HCl vapor [77]. 

H. Tang, A. Kitani, T. Yamashita, S. Ito, Highly sulfonated polyaniline electrochemically synthesized by polymerizing aniline-2,5-disulfonic acid and copolymerizing it with aniline, Synthetic Metals 1998, 96, 43. 

In 1994 Mattoso et al. [53] reported a method of polymerizing aniline at — 40°C in the presence of LiCl and HCl to yield a high molecular-weight... 

Gospodinova et al. have reported [160] the preparation of colloidal polyaniline by polymerizing aniline in a 10% polyvinyl alcohol solution. However, this in-situ polymerization of aniline in hosts matrix requires a post-synthesis work-up is required to remove impurities. 

Chen and Fang [161] have reported the preparation of polyvinyl alcohol and polyaniline by polymerizing aniline on polyvinyl alcohol-coated electrodes by chemical and electrochemical methods. Their report indicates that the electrochemical method yields a better composite. Various morphological aspects show that electrochemical polymerization of aniline on PVA surfaces leads to the formation of a composite having different gradients of polyaniline content. 

The substrate behavior and the influence of the substituent groups on the properties of the polymerized aniline derivatives were investigated by comparing the effects of the Hammett constants of the substituents. The Hammett equation (Hammett relation) is given as ... 

Recently, interesting results have been obtained in this field by combining the plasma polymerization and sputtering methods. For instance, the synthesis of composite thin films made of platinum nanoclusters (3-7 nm) embedded in a porous hydrocarbon matrix was carried out by simultaneous PECVD of pp-ethylene and sputtering of a platinum target. The metal content in the films could be controlled over a wide range of atomic percentages (5-80%) (Dilonardo et al., 2011). Aniline mixed with functionalized platinum nanoparticles as a precursor of PECVD was, in turn, used to prepare a typical 3D-catalyst. The plasma deposition was performed under atmospheric pressure conditions. Plasma polymerized aniline (pp-aniline), which is characterized by both electronic and ionic conductivity, associated with the Pt catalyst in a 3D porous network, without doubt lead to the development of the three-phase boundary (Michel et al., 2010). 

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