Cationic polymer-induced ultralight electrospun fiber aerogels for dual-functional photothermal heating and insulation.

The fabrication of fiber aerogels via electrospinning typically requires either high-humidity environments or intricate post-treatment protocols, both of which compromise process simplicity and impede industrial scalability. Direct ambient-condition construction of mechanically stable three-dimensional fibrous networks thus remains a pivotal challenge in this field. To overcome this limitation, we report a one-step electrospinning strategy that leverages the in-situ protonation of the cationic polymer polyethyleneimine (PEI) under ambient conditions. Protonation triggers intermolecular electrostatic repulsion, enabling spontaneous self-assembly of electrospun fibers into a well-defined three-dimensional porous architecture. By precisely tuning the polystyrene/PEI (PS/PEI) mass ratio, aerogels with densities as low as 8.53 mg cm-3, porosities reaching 99.21%, and thermal conductivities of 51.09 mW m-1 K-1 were obtained. Building upon this platform, a Janus-structured fiber aerogel was fabricated through microfluidic-assisted co-electrospinning, integrating a PS/carbon black (CB) photothermal layer with a PS/PEI insulating layer. Under simulated solar irradiation at 1 kW m-2, this bifunctional aerogel generated an intralayer temperature rise of 81.5 °C. This work establishes a robust, ambient-condition methodology for engineering competitive thermal insulation fiber aerogels and offers tangible pathways toward applications in personal thermal regulation and building energy efficiency.