Novel pH-sensitive poly(silamine) hydrogel microsphere possessing a stable skin layer

New silicon-based polycationic microspheres, which consist of alternating 3,3-dimethyl-3-sila-pentamethylene 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 skin layer and shows a significantly different chemical potential. This may be explained by a limited osmotic-pressure wave due to the high activation energy associated with the conformational changes.