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Ultrathin polyelectrolyte capsules fabricated by stepwise assembly of poly(styrenesulfonate sodium salt) and poly(diallyldimethylammoniumchloride) are examined by confocal laser scanning microscopy and scanning force microscopy. The capsule surface is composed of grains that are formed by laterally segregated polyelectrolyte complexes and incubation in salt solution induced capsule shrinking and grain aggregation.

The effects of ionic strength and solvent polarity on the equilibrium distribution of fluorescein (FL) and FITC-dextran between the interior of polyelectrolyte multilayer microcapsules filled with negatively charged strong polyelectrolyte and the bulk solution are investigated. The results have shown that the concentration depends on the Donnan equilibrium and less on the wall permeability and the specific interactions between the permeants and the encapsulated polyelectrolytes might play a vital role in the permanent distribution.

Multilayer microcapsules showing unique charge-controlled permeability is successfully fabricated by employing poly(styrene sulfonate) (PSS)-doped CaCo3 particles as templates. It is revealed that by reversing the charge of the probes through pH change, or by suppressing charge repulsion through salt addition, the permeation can be readily switched for proteins such as albumin or small dyes such as fluorescein sodium salt.

Loading and releasing behaviors of compressed polyelectrolyte multilayers composed of poly(styrenesulfonate sodium salt) and poly(diallyldimethylammonium chloride) were investigated using fluorescein and rhodamine 6G as indicators by confocal laser scanning microscopy, fluoroscence spectroscopy, and UV-vis spectroscopy. Utilizing the difference of loading and release rates between the compressed and the uncompressed regions, arrays of dye reservoirs are fabricated on a chemical homogenous but physical heterogenous multilayer film.