Abstract
Interactions between polymers and inorganic surfaces are present in a series of phenomena involving processes such as coagulation and deffloculation of ceramic powder and adsorption of organic macromolecules on the surface of implants, among others. In this work, Atomic Force Microscopy (AFM) was modified to allow the evaluation of interactions between polymeric chains and inorganic surfaces (silica) with different structures. Polymers (sulfonated polysulfone) were grafted onto AFM cantilevers. AFM force-distance curves were obtained for this modified tip against a series of substrates produced by depositing silica films on silicon wafers. The structure of the silica layer was modified by employing heat treatments at different temperatures. The results showed that the interactions between polymer and surfaces are dependent on the structure of the surfaces. Penetration of the polymeric chains can occur through a soft gel layer (substrates treated at low temperature, 110 °C). For surfaces with dense silica layers, the results showed that not only the concentration of hydroxy groups but also their spatial distribution along the surfaces are important in defining the magnitude of interactions between polymers and surfaces. A model involving a molecular recognition process, in which interactions are maximized for inorganic surfaces with structures that can match the chemical architecture of the polymer, was then used to explain the obtained results.
Highlights
Interactions involving polymeric chains and inorganic surfaces are present in a large number of processes, including: coagulation and deffloculation of colloidal suspensions; interfacial phenomena in polymer composites; interactions between biological moieties and the surface of implants; catalytic processes induced by inorganic surfaces; and many others
The results of force-distance curves obtained by Atomic Force Microscopy (AFM) in aqueous solution are shown in Fig. 8 for a glass sphere treated with sulfonated polysulfone (SPSF) in contact with silica substrates
Interactions between polymeric entities and the surface of inorganic materials were monitored by using an Atomic Force Microscope (AFM)
Summary
Interactions between sharp AFM tips and samples can be monitored and the information obtained can be associated with physical-chemical and chemical processes, such as adhesion, van der Waals forces, electrostatic forces and even primary forces. The results showed the capability of the technique to reveal individual unbinding events[11,12,13,14] Another advantage of AFM in comparison with other analytical techniques is its ability to be used in many different types of environments, ranging from ultra-vacuum to fluids. This fact is very important for characterizing processes occurring at surfaces, since the surrounding environment at the analytical chamber can be made to mimic the real ambient conditions that define the process
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