In Situ, Real-Time Observations of the Adsorption and Self-Assembly of Macromolecules from Aqueous Solution onto an Untreated, Natural Surface

Susan L. S. Stipp Geological Institute, Copenhagen's Univ., Øster Voldgade 10, DK-1350 Copenhagen K, Denmark

and Environmental Surface Analysis Collaboration (DP-IGS, DGR-IATE-P, DMX-LMCH at

Ecole Polytechnique Fédéral and Sci Terre at the University) Lausanne, Switzerland

Scanning force microscopy (SFM) was used to observe the attachment and arrangement of polyacrylic acid (PAA) from a monodispersed solution to the surface of freshly cleaved muscovite. The purpose was to use model materials to investigate some of the dynamic processes that occur in natural aqueous environments in situ and in real-time. The method was effective, but the susceptibility of the adsorbed polymer layers to nanometer scale "scratching" allowed imaging only under a carefully selected range of instrument parameters. Nanometer scale observations under solution showed stages of roughening and flattening as sequential polymer layers adsorbed and became attached to the surface and to other polymer molecules. More concentrated solutions produced rougher surfaces, faster. Measurements of adhesion forces between the tip and sample showed that the polymer layer became "stickier" with increased solution concentration and with time.