Layer‐by‐layer engineered polyelectrolyte microcapsules studied by ToF‐SIMS and related analytical techniques

Engineered polyelectrolyte multilayer (PEM) films of polyallylamine hydrochloride (PAH) and polystyrene sulfonate (PSS) assembled on polyethylene terephthalate (PET) substrate as well as PEM microcapsules of PAH and PSS templated onto polystyrene latex were fabricated through a layer-by-layer assembly and characterized by various analytical techniques. The characteristic ion intensities from the respective outermost layer obtained by ToF-SIMS accorded well with the layer composition. The S and C8H7SO3 ion intensities were higher in PSS layers; whereas Cl ion intensity was higher in PAH layers. The SEM image displayed morphology which involved electrostatic interactions during the formation of the multilayer. AFM measurement showed the shell thickness of PEM microcapsules as 1.21 nm. ToF-SIMS total ion, S ion, and Cl ion images were useful to delineate the PEM microcapsules location and to indicate successful assembly. The results demonstrated for the first time the feasibility of label-free ToF-SIMS imaging of PEM microcapsules. Copyright © 2010 John Wiley & Sons, Ltd.