Acid-base property of double-strand polyaniline and the preparation of inorganic/organic composite by physical adsorption.

摘要

This dissertation consists of two manuscripts. The first manuscript concerns the question of why the pKa for the conductor-to-insulator transition of polyaniline is shifted significantly when it forms a non-covalent complex with a polymeric anion. The second manuscript concerns the physical adsorption process to form inorganic particles coated with the conducting polymer, the double-strand polyaniline. The experimental data in both manuscripts show that the electrostatic interaction is the underlying driving force for these two apparently different phenomena.; In the first manuscript we studied the reason for the large pKa shift of double-strand polyaniline complex. The amount of the pKa shift is dependent on the choice of the polyelectrolyte and the synthesis temperature. The comparison of pKa shift for double-strand polyaniline/PVP complex (pKa = 6) and double-strand polyaniline/poly(styrene sulfonic acid) complex (pKa = 9) shows the importance of the negative charges on the template polymer. And the different pKa shift of two polyaniline/poly(acrylic acid) complexes of the same composition but synthesized under different temperatures indicates that the 2nd strand of the complex electrostatically stabilizes the conductive state of polyaniline. The experimental observations are consistent with the hypothesis that the large pKa shift is induced by electrostatic interaction.; In the second manuscript, we studied the physical adsorption of double-strand polyaniline on inorganic metal oxide. It is desirable to have efficient adsorption process in which almost all the dispersed conducting polymer is transferred to the surface of the inorganic particles by directly mixing the particles and the double-strand polyaniline together, such as CeO2, SrHPO 4, ZrO2, and BaSO4 particles. But there is a group of inorganic particles that does not adsorb the conducting polymer complex directly, such as Zr(HPO4)2, WO3, and MoO 3 particles. These particles need to be surface-modified using poly(diallyl dimethyl ammonium chloride) which is a kind of polycation to make the physical adsorption happen. The literature values of isoelectric point show that CeO 2, SrHPO4, ZrO2, and BaSO4 particles have positively charged surface and Zr(HPO4)2, WO 3, and MoO3 particles have negatively charged surface, which indicate the attraction force for the physical adsorption to be electrostatic interaction.