Electrical conductivity responses and interactions of poly(3-thiopheneacetic acid)/zeolites L, mordenite, beta and H2

Poly(3-thiopheneacetic acid), P3TAA, was chemically synthesized via an oxidation polymerization and doped with perchloric acid. Composites were fabricated from P3TAA and zeolites, zeolites L (L), mordenite (MOR), and beta (BEA) through random dry mixing. The electrical conductivity response toward H2 was investigated for the effects of zeolite contents, zeolite type, cation type, and cation concentration. Negative electrical conductivity response and sensitivity generally occur when exposed to H2 relative to N2. A weaker interaction is suggested to occur between H2 and the polaron or the bipolaron species relative to the interaction between N2 and active sites of the doped P3TAA. For the effect of zeolite content, the composite with 20% (v/v) MOR has the highest electrical conductivity sensitivity value. The reduction of sensitivity values occurs with increasing MOR zeolite concentration from 20 to 50% (v/v); this arises from the diminishing active sites available for the interaction between H2 and the polaron or the bipolaron species. For the composites with 20% (v/v) L, MOR and BEA, the electrical conductivity sensitivity increases with decreasing Al content because of a lesser interaction between H2 and the zeolite, and consequently a greater interaction between H2 and the active sites on the polymer chain. The higher electronegativity and smaller ionic radius of Li+ loaded into the MOR zeolite framework causes the lowering of electrical conductivity sensitivity than the composites loaded with Na+ and K+. For composites with zeolite L loaded with Na+ at 0, 15, 20, 30 and 50 mole%, the electrical conductivity sensitivity increases with increasing Na+ content up to 30 mole% and decreases beyond that.