The initial growth of ultra-thin films fabricated by a weak polyelectrolyte layer-by-layer adsorption process

A weak polyelectrolyte layer-by-layer self-assembled multilayer has several morphologies depending on solution pH, including the morphology of poly(allylamine hydrochloride) (PAH) pH 7.5/poly(acrylic acid) (PAA) pH 3.5, which is called texture structure. We confirmed the initial growth of a weak polyelectrolyte layer-by-layer (LBL) multilayer in a stepwise adsorption process. The growth states of bilayers from 0.5 to 4.0 and over 4.5 were different when measured by quartz crystal microbalance (QCM), scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and contact angle measurements. The texture structure appeared in 1.0 bilayer, after PAA adsorption. The initial growth was changed around 4.0 bilayers. In this phenomenon, the LBL layer of PAH pH 7.5/PAA pH 3.5 had two zones at least, similar to a strong polyelectrolyte LBL layer.