Electrostatic Adsorption of Polystyrene Nanospheres onto the Surface of an Ultrathin Polymer Film Prepared by Using an Alternate Adsorption Technique

We studied the adsorption of polystyrene nanospheres that have anionic charges on their surfaces from their aqueous dispersions onto the surfaces of cationic ultrathin polymer films quantitatively and kinetically by using a quartz crystal microbalance (QCM) and scanning electron microscopy (SEM). The polymer films were successively prepared by the alternate adsorption of poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS) in the absence or presence of suitable NaCl concentrations onto the QCM substrate so that we could observe their formation process by its frequency shifts. We observed the specific adsorption of the nanospheres by means of electrostatic interaction onto the outermost PAH surface by QCM as well. The dependence of their adsorption amounts against the NaCl concentration in polymer precursor film preparation was a sigmoid curve, indicating that there is a critical charge on/in the film for their adsorption. SEM observations showed monolayer adsorption without three...