Induced Interaction between Polypyrrole and SO$_{2}$ via Molecular Sieve 13X

Electrical conductivity sensitivity and interaction mechanisms between polypyrrole(Ppy)/molecular sieve 13X composites and CO$_{2}$, CO, and SO$_{2}$ were investigated. Polypyrrole was synthesized and composites were fabricated from dry mixing and dispersing zeolite particles into the Ppy matrix particles, and followed by compressing into a pellet form. Effects of zeolite concentration, cation type, and cation concentration were investigated. The electrical conductivity in air of Ppy doped with naphthalene-2-sulfonic acid($\beta )$ sodium salt increased monotonically with the doping level. There were negligible negative electrical conductivity responses of Ppy and its composites when exposed to CO$_{2}$, and CO in contrast to definite positive responses towards SO$_{2}$ in which the interaction was irreversible. Undoped Ppy and doped Ppy composites at 10{\%} v/v of zeolite13X content possessed the highest sensitivity to SO$_{2}$; beyond this volume fraction the sensitivity was reduced with increasing molecular sieve 13X content. The composites of unmodified 13X, with Na$^{+ }$ fully present within its cavity, gave the greatest electrical conductivity sensitivity towards SO$_{2}$. The sensitivity of Ppy/13X composite to SO$_{2}$ diminished when the cation Na$^{+}$ was exchanged to other alkali cations in this decreasing order: Cs$^{+}$, K$^{+}$, and Li$^{+}$.