Design and development of tunable polypyrrole nanofibrous aerogels for multifunctional applications

Aerogels are highly porous, lightweight materials with large specific surface areas, but their limited mechanical strength restricts broader application. Nanofibrous aerogels (NFAs), featuring three-dimensional interconnected structures, address this limitation and expand usability in sorption, filtration, water treatment, thermal insulation, and energy storage. NFAs are prepared by electrospinning a polymeric solution to form nanofibers, followed by homogenization with a non-solvent and freeze-drying. In this study, polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) are used to fabricate the aerogel framework. This thesis focuses on functionalizing PAN/PVP aerogels with polypyrrole (PPy) via oxidative polymerization. PPy forms a conductive coating on the nanofibers and inter-fiber space, creating continuous conductive pathways across the 3D structure. The effects of polymerization time and oxidant-to-monomer ratio on coating and conductivity are systematically studied. The resulting PPy-coated aerogels function as piezoresistive sensors, with sensitivity up to 2 kPa⁻¹ and a gauge factor of 0.27 in the low compression range (0–5%), showing excellent stress and strain sensitivity owing to their porosity and PPy loading. They also retain compressibility up to 70%, showing good mechanical performance. Beyond sensing, PPy potential is explored for environmental use in adsorbing per- and polyfluoroalkyl substances (PFAS). PPy powder with a porous morphology achieves up to 99.4% removal of Nafion-byproduct 4 (NFB4) at pH 5. Further functionalization is performed by quaternizing nitrogen in PPy with maleic anhydride and methyl iodide to introduce a permanent positive charge, aiming to improve adsorption across a wider pH range. Future work will focus on incorporating these types of PPy into the NFAs and exploring their functional attributes.