Poly(ethyleneimine) microcapsules:: glutaraldehyde-mediated assembly and the influence of molecular weight on their properties

Poly(ethyleneimine) (PEI) microcapsules were prepared via the method of glutaraldehyde (GA)-mediated covalent layer-by-layer (LbL) assembly, which utilized GA to cross-link the adsorbed PEI layer and to introduce free aldehyde group on the surface for the next PEI adsorption on MnCO3 microparticles, followed by core removal. Evidenced by ellipsometry, the PEI multilayers grew nearly linearly along with the layer number and their thickness was controlled at the nanometer scale. The hollow structure, morphology, and wall thickness were characterized by scanning electron microscopy (SEM), scanning force microscopy (SFM), and confocal laser scanning microscopy (CLSM), revealing that the capsule structure as well as the cut-off molecular weight of the capsule wall could be tuned by the molecular weight of PEI. This offers a general and novel pathway to fabricate single component capsules with pre-designed structure (size, shape, and wall thickness) and properties. Copyright (C) 2007 John Wiley & Sons, Ltd.