Compliance measurements of confined polystyrene solutions by atomic force microscopy

The use of the atomic force microscope (AFM) as a local probe for elastohydrodynamic lubrication is discussed. Compliances are measured with a modified AFM that allows application of ac and dc force-displacement curves on end-grafted poly(styrene) chains in good (toluene) and poor (water) solvents. In toluene, the chains form a stretched brush whose elastic modulus is an order of magnitude larger than that of the collapsed layer in water. The dc force-displacement curves are compared to those previously obtained on similar systems with the surface forces apparatus.