Comparative Gas-Sensing Studies of EPAA with Aniline Tetramer in the Main/Side Chain and Corresponding Densely/Porous Electro-Spun Films

Rapid low-ppm detection of toxic and corrosive hydrogen sulfide (H2S) is essential to protect workers and the public. This research presents the synthesis and gas-sensing application of two electroactive poly(amic acid)s (EPAAs): a linear-type (L-EPAA) and a branched-type (B-EPAA). Synthesized via condensation polymerization using electroactive diamine monomers composed of linear and pendant side-chain double-terminal aniline tetramers, their chemical structures, molecular weight, electroactivity, and conductivity were verified using ATR-FTIR, GPC, cyclic voltammetry, and four-point probe testing. To significantly increase the specific surface area, electrospinning technology was employed to fabricate a porous fiber film (B-EPAA-ES). All samples were deposited onto interdigitated electrodes to evaluate their H2S gas sensing properties. Among the tested results, the electrospun B-EPAA-ES film demonstrated the most outstanding performance, exhibiting a 47.4% response to 10 ppm of H2S with a rapid response time of 53.1 s. Moreover, the sensor displayed remarkable reproducibility (CV of 0.2% over three cycles) and the H2S response is unaffected by other gases. Ultimately, the B-EPAA-ES film combines high processability of poly(amic acid), reversible redox properties of side-chain aniline tetramers, and a large specific surface area. This synergistic combination enables highly repeatable H2S detection and the response is unaffected by other gases.