Investigating confined complex fluids with neutron reflectivity

Abstract Polymer molecules at solid or fluid interfaces have an enormous spectrum of applications in a wide variety of technologies, including lubrication, adhesion, and protective surface coatings. Over the past decade, neutron reflectivity has become a powerful tool for measuring the properties of ultrathin polymer layers at interfaces. We describe how the penetrating power of neutrons can be harnessed to probe the structure of ultra-thin polymer coatings trapped between two surfaces as a function of confinement. Figure 1 schematically depicts the fundamental question we are trying to answer-that is, what happens when two surfaces come into contact. In the case of two polymer “brush” layers in solution (Figure I), two possible scenarios are shown: the polymer layers compress but remain separate from each other or the polymer layers interpenetrate. Depending on the outcome, the adhesion, lubrication, or shear behavior of the surfaces can be greatly altered. Our goal is to understand what happens when pol...