Synthesis and electrical properties of functionalized polyanilines
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Abstract
New synthetic methods for the polymerization were investigated via biocatalysis. Horseradish peroxidase (HRP) was used to synthesize the functionalized polyanilines. The biocatalytic route has significant importance because the chemical and electrochemical methods sometimes do not allow the monomers polymerized. In the second chapter, the enzymatic synthesis of the aniline which has a carboxylic acid (CA) group was investigated with polycationic templates at moderately acidic pH (pH 4-- 6). The optimum pH conditions of polymerization were higher than the pKa value of an amine and that of carboxylic acid. One positive charge in a template, could on average, template up to three monomers. In the third chapter, the unusual doping behavior of PCA/template complex at pH 13 was discussed. It was assumed that the conductivity at pH 13 was due to the generation of n-type polaron. UV-Vis spectra showed that the template plays a critical function during the n-doping process. In the fourth chapter, the synthesis of self-doped sulfonated polyaniline (PSA) with cationic surfactants was fully discussed. Although pure PSA showed olive color, the PSA/micelle complex showed dark green color with high conductivity, which might be due to the different conformations between the homopolymer and the polymer/surfactant complex. In the fifth chapter, the synthesis of polyaniline without templates was discussed. The synthesized PANIs were soluble in water and can be functionalized simply by incorporating functional groups in the ortho or meta position. Peroxyacetic acid proved to serve as a promising mild oxidant under certain reaction conditions and demonstrate a novel way to optimize enzymatic polymerizations. In the final chapter, the synthesis of Poly(aniline-co-anilinebenzeneboronic acid [aniline-co-ABA]) with sulfonated polystyrene at mild pH condition was discussed. The optimum polymerization condition depended on the solubility of anilineboronic acid. The UV-Vis spectra and the result of conductivity measurement showed that a large amount of the weak dopant, B(OH)2 actually impede the doping process of a polyaniline backbone. The poly(aniline-co-ABA)/SPS complex showed larger change of absorption than the copolymer synthesized by ammonium peroxodisulfate.