Formation of uniform polyaniline thin shells and hollow capsules using polyelectrolyte-coated microspheres as templates

Multilayers of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate) precoated onto melamine formaldehyde (MF) particles via the layer-by-layer (LbL) self-assembly procedure were used as templates for the subsequent deposition of polyaniline (PANI). Transmission electron microscopic (TEM) and scanning electron microscopic (SEM) images reveal that the as-prepared PANI-containing polyelectrolyte (PE)-MF core-shell particles are narrowly dispersed and possess uniform surface morphology. Intact hollow PANI/PE capsules can also be produced by extracting the MF cores in an acidic solution. FTIR spectra of the hollow capsules indicate that PANI and PE are both present and suggest that the PANI exists in the emeraldine form. The incorporation of PANI in the shells was found to enhance the rigidity of these composite materials, and the PANI/PE-coated MF core-shell particles have comparable conductivities with other PANI-coated colloidal particles. The amount of PANI incorporation was also found to increase with the PE layer number, suggesting that the LbL procedure for forming PE multilayers is a convenient method for modifying the colloidal particle surfaces for a favorable PANI film growth and for controlling the PANI thin shell thickness. The method developed is simple, versatile, and colloidal particle general.