| Summary: | 博士 === 國立清華大學 === 化學系 === 94 === We can synthesize Pan-MEA via concurrent reduction and substitution reaction (CRS). After the instrumental analyses, we can confirm that 2-mecaptoehanol (MEA) is truly introduced into the polymer backbone, but the residue in the polymer. Moreover its substitution degree is nearly 25 % as the CRS reaction mechanism originally proposed. And with the solubility test, we find the introduction of MEA substituting group truly changes its dissolved parameter, and it could be dissolved in the organic solvent which polyaniline is unable to dissolve originally, like THF, 2-methoxyethanol and di(ethylene glycol) and so on. It also could have good conductivity about 1.4~5 S/cm (the substitution degree is 24~38 %). Compared to the other literature reports, the conductivity of Pan-MEA is at least higher than the poly(alkoxyaniline)s about three orders. Therefore the CRS reaction is proved as a better method compared to the traditional oxidative polymerization.
Using the temperature-changed technique and adding D2O, we define the -NH and -OH group position of Pan-MEA. From the 1H NMR results, we can calculate its substitution degree is about 22~25 % and the same as the ESCA results. In addition, according to the literature and the 1H NMR result of Pan-MEA and Pan-SBu (Pan-SC4H9), we discover that the influence of sulfoxide and hydrogen bonding can cause splits from its main signal peak toward the downfield position. Finally according to the temperature-changed and trimer-SBu 1H NMR results, we could conclude the ortho、meta and para hydrogen position when benzene ring has the substituted group.
Using the method of air bubbling and adding I2, we can oxidize Pan (LB form) to Pan (PB form) in short time (1 hour) with catalytic amount of CuCl2 in the DMF solvent system. Moreover using the solubility difference in DMF, we can obtain high oxidation state polyaniline (almost PB form) powder. When we introduce 1-butabethiol to the polyaniline via the CRS reaction, the substitution degree is 43% (1~3% error), and no crosslinking phenomenon occurs.
If the carbon chain number of thiol is below three, the substitution degree of polyaniline copolymer is 24~25 %, just as the CRS theory predicts. But when above three, for example 1-butanethiol, the substitution degree of Pan-SBu measured with ESCA will be over 25 %. The more the carbon chain number is, the more the substitution degree. This is possibly because the polyaniline copolymer has disulfide side product in the polymer backbone. When the carbon chain number increases, the van der Waals force will also become stronger; therefore it will cause disulfide surrounded in the polymer is hard to removed. But when Pan-SBu is dissolved in NMP, the substitution degree of dissolved and non-dissolved Pan-SBu is 25 % because of the remove of disulfide. In addition, with the second time CRS reaction, we can introduce different types of thiol into the polyaniline chain, and increase its application.
Pan-MEA has many kinds of application, for example, it can be used in the production of TiO2 antase form nano-particle (25 nm); it also may be used as dye on the solar cell; in addition it can form the so-called micelle structure (size 116 nm) as the pattern plate of the production of nano-particles.
Finally we use Pan-SBu as cathode/electrolyte in the tantalum semiconductor capacitor, and indeed obtain very good capacity (99% of the maximum theory capacity), although the DF and ESR value still cannot achieve the commercialized goal. But we have known where the question is, and in the future we will choose the suitable clean step and select a better doping method to reduce its DF and ESR value, and will make great strides toward the commercialized direction.
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