Uploading and Temperature-Controlled Release of Polymeric Colloids via Hydrophilic Emulsion-Templated Porous Polymers

Porous cross-linked poly(N-isopropylacrylamide) (PNIPAM) was prepared using high internal phase emulsions as templates. The materials could absorb a large volume of water and swell largely at room temperature. When the aqueous phase was heated above the lower critical solution temperature (LCST) of PNIPAM, the swollen structure could contract and squeeze some of the absorbed liquids out. This capability was utilized in the uploading at room temperature and then release of polystyrene colloids by increasing the temperature above the LCST. The thermoresponsive porous PNIPAM acted like a pump to load and then release the polymer colloids. The multicycles of loading and release were demonstrated to show its efficiency. Importantly, it showed that most of the PS colloids from the second upload onward could be released during the heating cycle.