Controlled release using a polymer stereocomplex capsule through the selective extraction and incorporation of one capsule shell component.

Isotactic poly(methyl methacrylate) (it-PMMA)/syndiotactic poly(methacrylic acid) (st-PMAA) stereocomplex hollow capsules were fabricated by the deposition of stereocomplex films of it-PMMA and st-PMAA on silica particles by alternate layer-by-layer assembly and the subsequent removal of the silica particles with aqueous HF. The selective extraction of st-PMAA from the it-PMMA/st-PMAA stereocomplex capsule shells was successfully carried out by immersion in a pH 6-9 aqueous solution. The incorporation of st-PMAA into the resulting porous capsule shells was performed by immersion in an acetonitrile/water (1/1) solution of st-PMAA. The controlled release of an encapsulated dye from the it-PMMA/st-PMAA hollow capsules was achieved by combining the selective extraction of st-PMAA from the capsule shells and the incorporation of st-PMAA into the resulting porous shells.