Thermal annealing-driven surface sealing of polymeric bowl

We investigate surface sealing behavior of polymer hollow particles with an open hole on their surfaces during thermal annealing. A series of processes involving synthesis of polystyrene (PS) solid particles, their swelling with the use of a swelling solvent, and freeze-drying enable us to make hollow particles with a controllable structure including outer/inner diameter and surface hole size. Based on structural change of the hollow particles experimentally observed during thermal annealing above the glass transition temperature of the polymer, we analyze theoretically the sealing behavior of the hollow particles. The experimental and theoretical results conclude that the structure of as-prepared hollow particles determines whether the successful sealing of the particles can be achieved or not.