In Situ Morphology of Cationic Flocculants Adsorbed on Surfaces and Their Interaction Forces Investigated by Atomic Force Microscopy

Images of typical cationic flocculants of high molecular weight, poly[2-(acryloyloxy)ethyl(trimethyl)ammonium chloride] (PATC), adsorbed on mica surface in situ in water were observed by tapping-mode atomic force microscopy (AFM) under various conditions. The corresponding interaction forces between surfaces were measured using force-mode AFM, in order to know how the microstructure of polymers adsorbed on the surfaces affects the interaction and adhesive forces between surfaces. It was found that it takes a long time for cationic polymers of high molecular weight to relax completely in water, even though the dissolving process is enhanced by mixing. It seems that polymers relaxed in solutions are fundamentally spherical in shape but their structure becomes fragile as the size increases, so that highly swollen high polymers are easily extended by external disturbances to form various structures at their adsorption on surfaces. It was found that these characteristics of polymers adsorbed on surfaces are correlated well with the features of the interaction and adhesive forces between surfaces in the cases of both pure water and NaCl solutions.