Switchable adhesion and friction by stimulus responsive polymer brushes

Controlling friction and adhesion is relevant in nature and in our daily life. Such control can be achieved using stimulus responsive end-anchored polymers forming a brush. These brushes can adapt their physicochemical properties upon changing the surrounding environments, such as temperature, light, pH, electrical and magnetic fields. In this Thesis, we primarily use atomic force microscopy (AFM) to study the relation between the degree of solvation of the macromolecules in the brush and the friction and adhesion. In general, it is accepted that collapsed brushes promote high friction/adhesion and swollen brushes exhibit low friction/adhesion. However, our results show that brush swelling and adhesion/friction is not necessarily related. We show that the relation between swelling of a brush and its tribomechanical properties is rather complex, and that it can depend on the specific interactions in the contact: chemically identical/different brush-brush or brush-solid counter surface. Switchable adhesion and friction we observed by stimulus-responsive polymer brushes have potential applications in pick up-release system, robots and in biomedical systems.