Abstract:The use of organic chemistry reactions to introduce additional functional groups on polyanilines is described. Among the reactions discussed are: electrophilic aromatic substitution, nucleophilic addition to the aromatic rings, nucleophilic substitution on the amine groups and reactions on pendant groups. The use of combinatorial chemistry techniques, by coupling of combinatorially synthesised diazonium salts with polyaniline, to produce a functionalized polyanilines library is also reviewed. The modification of polyaniline introduces or alters different properties of the materials: solubility, self-doping and redox coupled ion exchange. The tailoring of those properties to technical applications is therefore examined.
Large areas of polypyrrole (PPy) thin films deposited onto inert polymeric substrates are structured by direct laser interference patterning (DLIP). Several square millimeter areas could be produced with one single (10 ns) pulse, at room temperature and atmospheric pressure. Nanometric arrays of lines (>600 nm) or grids of PPy deposited on dielectric polymers polypropilene or polypirrol (PP or PE) are fabricated by DLIP at 355 nm. The period of the lines structures, measured by white light interferometry (WLI), is 3.5 µm. Regular structures are analyzed using scanning electron microscope (SEM) and a focus ion beam (FIB) tomography. It is shown that only the PPy film is structured while the PP or PE substrate remains unaltered. Fourier transform infrared spectroscopy (FTIR) and UV‐vis spectroscopy, permit to ensure that PPy chemical structure remains unaltered after the structuration process. The width of PPy lines can be tailored by controlling the fluence of the laser beam. Contact angle measurement shows that the wettability is affected by the structuring, making the surface more hydrophobic. The structuring technique seems to be suitable for the fabrication of PPy regular structures over various substrates.
Organic chemical reactions have been used to functionalize preformed conducting polymers (CPs). The extensive work performed on polyaniline (PANI), polypyrrole (PPy), and polythiophene (PT) is described together with the more limited work on other CPs. Two approaches have been taken for the functionalization: (i) direct reactions on the CP chains and (ii) reaction with substituted CPs bearing reactive groups (e.g., ester). Electrophilic aromatic substitution, SEAr, is directly made on the non-conductive (reduced form) of the CPs. In PANI and PPy, the N-H can be electrophilically substituted. The nitrogen nucleophile could produce nucleophilic substitutions (SN) on alkyl or acyl groups. Another direct reaction is the nucleophilic conjugate addition on the oxidized form of the polymer (PANI, PPy or PT). In the case of PT, the main functionalization method was indirect, and the linking of functional groups via attachment to reactive groups was already present in the monomer. The same is the case for most other conducting polymers, such as poly(fluorene). The target properties which are improved by the functionalization of the different polymers is also discussed.
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