Reversible thermo-responsive transitions between aerogel-based porous liquids and solid–liquid–vapor triple-state gels

Porous liquids (PLs), porous materials with flowable states, show promising applications in some emerging fields. However, creating porous materials with on-demand flowability is still significantly challenging. Herein, aerogel-based stimulus-responsive porous liquids have been proposed and fabricated via dispersing superhydrophobic silica aerogel microparticles in a polymer aqueous solution with either lower or upper critical solution temperature (LCST or UCST), respectively. The resulting aerogel-based intelligent porous liquids possess quite low density (0.56 g cm−3), high porosity (up to 48.57%), low thermal conductivity (0.239 W m−1 K−1) and appropriate viscosity (4.1–220.6 Pa s). Most importantly, the resulting porous liquids show reversible thermal responsiveness. Thus, a new condensed state, i.e., solid–liquid–vapor triple-state gels, might be obtained via on-demand thermal triggering of these aerogel-based porous liquids. Cut triple-state gels show interesting self-healing behaviors via either thermal treatment or replenishment of a small extra amount of porous liquids. To our surprise, the reversible transition between aerogel-based flowable porous liquids and solid–liquid–vapor triple-state non-flowable gels has endowed these materials with plastic-like processing capability upon demand. These porous liquids, together with those triple-state gels, might find broad applications in some emerging fields, and the work reported here might inspire scientists to fabricate more aerogel-based porous liquids and triple-state gels.