Poly-anilines: Synthesis, characterization and applications

The purpose of the present study was to determine factors responsible for the conductivity of polyaniline. This objective was approached: (A) by studying selected properties of doped and non-doped polyaniline; (B) by studying oligomers of aniline upon which the properties of polyaniline are believed to be based. Polyaniline. It was found that molecular conformation which was itself dependent on processing conditions had a pronounced effect on the conductivity of doped polyaniline powder: (1) Changes in molecular conformation of polyaniline emeraldine base (EB) and d, l-camphorsulfonic acid (HCSA)-doped polyaniline in the solid state can be induced by mechanical shear forces. These forces “straighten out” the polymer chain from a “coil-like” to “extended coil-like” state resulting in more extensive delocalization of the π system of the polymer chain and increased conductivity of the doped polymer. (2) The highest reported bulk conductivity of HCSA-doped polyaniline powder (40S/cm) was obtained using excess dopant acid. (3) Doped polyaniline powder (0.4S/cm) was obtained by the solid state reaction of EB and HCSA powders. Oligomers of aniline. Because of the potential role of oligomers in determining the properties of polyaniline, the following phenyl/amino end-capped oligomers of aniline (emeraldine oxidation state), having the same terminal groups as polyaniline, have been synthesized: [special characters omitted] (4) The new octaaniline and hexadecaaniline, and the previously known tetraaniline, were synthesized by oxidative coupling of lower oligomers in the leucoemeraldine oxidation state. (5) The exciton absorption of the oligomers increases in wavelength with increase of chain length, indicating the exciton transition of polyaniline is not localized. (6) Agglomeration of the oligomers in the solid state is related to intermolecular hydrogen bonding. (7) The conjugation length of the HCSA-doped oligomers increases with increasing chain length. (8) The bulk conductivity of the HCI-doped oligomers is two to three orders of magnitude lower than that of HCI-doped polyaniline. (9) Sensors for detection of volatile organic compounds made from doped (dodecylbenzenesulfonic acid) octaaniline had excellent sensitivity, reversibility and environmental stability