Towards the control of surface properties via nanostructured polymeric materials

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The research program focuses on the investigation of dynamic surface forces (friction, adhesion, time- and distance-dependence of the surface forces) of end-grafted charged polymers in aqueous media. The surface properties will be directly measured using a Surface Forces Apparatus (SFA), being one of the most reliable instruments for the direct measurement of molecular forces acting between surfaces. Although several studies using SFA have been carried out in the past for different classes of polymer-bearing surfaces, the lubrication and adhesion mechanisms are not clearly elucidated. The lack of systematic studies examining the influence of polymer properties and environmental conditions on the surface interactions is in part a result of the difficulty in controlling the polymer grafting density and the stability of grafted layers on mica, which is the most reliable substrate for SFA measurements. We have recently developed different approaches allowing direct covalent attachment of polymers onto plasma activated mica surfaces with a control in the grafting density. We propose to use diblock copolymers (hydrophobic/ionizable block) covalently attached to mica substrates with an innermost hydrophobic layer directly bond to mica and the ionizable polymers as the outermost layer dangling in aqueous media. The hydropbobic block will act as a protective layer against hydrolysis reactions at the polymer/mica interface, a likely location for polymer cleavage or slip. With these approaches, we aim to establish reliable correlations between physical and chemical properties of the end-grafted polymer layers (thickness, grafting density, degree of ionization, elasticity, surface roughness, chemical functionality), environmental conditions (ionic strength, pH, temperature, solvent condition, compression, shear) and surface interactions (friction, adhesion and distance-dependence of the forces) between polymer-bearing surfaces.