Structure of Adsorbed Polyelectrolyte Monolayers Investigated by Combining Optical Reflectometry and Piezoelectric Techniques

摘要

Polyelectrolyte monolayers on solid substrates arenstudied with optical reflectivity and the quartz crystal microbalancen(QCM). In particular, we investigate the adsorption of anionicnpoly(styrene sulfonate) (PSS) on amino-functionalized silica asnwell as cationic poly(allylamine hydrochloride) (PAH) and poly-Llysinen(PLL) on bare silica. By comparing the dry and wet massesnmeasured on identical substrates with these two techniques, wenobtain information on the layer thickness and water content ofnthese layers. Monolayers typically feature an adsorbed dry mass ofnabout 0.1−2 mg/m2, a layer thickness of 0.5−2 nm, and a waterncontent of 20−50%. One finds that the layer thickness increases with increasing concentrations of monovalent salts andnpolyelectrolytes.