Fabrication of micro reaction cages with tailored properties

Hollow polyelectrolyte capsules in micro- and submicrometer size were prepa red. Their interior was functionalized by a "ship in bottle" synthesis of c opolymers. While the monomers permeated the capsule wall easily, the formed polymers remained in the capsule cage. The physicochemical properties of t he capsule interior such as ion strength, pH, light absorption, and fluores cence could be controlled independently from the surrounding solvent by mea ns of the chemical nature of the captured polymer. In case of polyelectroly tes the osmotic pressure of the counterions led to a swelling of the capsul es which can be important for micromechanics. The functionalization with li ght-sensitive materials allowed selective photoreactions inside the capsule s. Synthesis of polyelectrolytes at high concentration resulted in an inter twining of the capsule wall with the polymer. The modified walls behaved li ke ion exchange membranes and showed selectivity toward adsorption and perm eation of organic ions. The modified capsules offer many possibilities for novel applications as containers for controlled precipitation, as nanoreact ors for catalyzed reactions, or as sensors.