New silicon-based polycationic microspheres, which consist of alternating 3,3-dimethyl-3-silapentamethylene and N,N'-diethylethylenediamine, were prepared. The deswelling of the poly(silamine) microspheres by means of pH-jump experiments revealed the formation of an extremely stable skin layer. The layer could be kept at the interface between particle core and U and shows a significantly different chemical layer. This may be explained by a limited osmotic-pressure wave due to the high activation energy associated with the conformational changes.