Hydrophobic Polyaniline Homopolymers and Copolymers for the Detection of Perfluorobutanoic Acid and Trifluoroacetic Acid Vapors

Abstract Per- and polyfluoroalkyl substances (PFAS) have garnered increasing attention as a result of their detrimental impact on public and environmental health. PFAS have infiltrated the environment through industrial manufacturing, military sites, and airports; hence, emerging methods for the detection of PFAS emissions are imperative. We have targeted covalently functionalized poly(aniline) (PANI-X) materials to produce oleophobic and/or hydrophobic interactions to selectively detect PFAS acid vapors. PANI-X sensors are fabricated via drop-casting, and changes in the electrical resistance are used as a sensing signal. The PANI-X materials are initially in a highly resistive free-base (undoped) form, and acidification protonates the backbone, thereby doping the materials with a concurrent decrease in resistance. We demonstrate real-time monitoring of the PANI resistance with increasing concentrations of PFBA and TFA acids. Alternating PANI copolymers containing fluorinated and non-fluorinated groups (PANI-F13-Co) produced sensors with limits of detection for TFA at 585 ppm and PFBA at 209 ppm, and responses of up to 104- and 103-fold conductance increases for each analyte, respectively, with a data acquisition setup unit containing a multimeter. Improved limits of detection of 3.1 ppm for TFA are achieved through high-resistance measurements of PANI-F13 sensors with an electrometer. Our PANI-X materials and sensing PFAS acid vapor detection methods enable the further development of selective and low-cost PFAS acid vapor sensors.