Synthesis and characterization of polyaniline and its derivatives

This study is an investigation into (a) the process by which one obtains the conductive polymer, polyaniline, from aniline, and (b) the effect of ring alkyl- and alkoxy-derivatization on the electrical and electronic properties of polyaniline, and (c) the determination of absolute molecular weight of chemically synthesized polyaniline. (1) A new potential-time profiling technique was developed to monitor chemical oxidative polymerization of aniline and its derivatives. (2) The above technique was instrumental in the successful detection and isolation of polyaniline in the pernigraniline oxidation state during the conventional chemical synthesis of emeraldine.HCl. (3) Periodic regeneration of polyaniline in the pernigraniline oxidation state by sequential addition of oxidant ($\rm NH\sb4)\sb2S\sb2O\sb8,$ resulted in a controlled increase in molecular weight by GPC (M$\sb{\rm w}$) to values as high as $\sim$90,000. (4) Synthesis of polyaniline at $\sim-50\sp\circ$ C (by carrying out the reaction in the presence of LiCl) resulted in molecular weights by GPC (M$\sb{\rm w}$) as high as 439,000. (5) Ring alkyl- and alkoxy-substituted polyanilines exhibit enhanced processibility from solvents such as CHCl$\sb3$ and CH$\sb2$Cl$\sb2$. Poly-2-ethoxyaniline base fibers ($\sigma\sim10\sp{-3}$ S/cm upon HCl doping) can be thermally stretch-oriented to 1/1$\sb{\rm o}$ values as high as $\sim$7.7 ($\sigma\sim4.5 - 25$ S/cm upon HCl doping). (6) The absolute weight average (M$\sb{\rm w}$) and number average (M$\sb{\rm n}$) molecular weight of polyaniline (conventional synthesis) in the leucoemeraldine oxidation state as obtained by light scattering measurements were found to be $\sim$25,500 and $\sim$11,500 respectively, resulting in a degree of polymerization of $\sim$128