End-adsorbed telechelic polymer chains at surfaces: Bridging and elasticity

We have studied the interaction of telechelic polymer chain (hydrophobic end-capped poly(ethylene oxide)) layers with hydrophobic polystyrene surfaces in water using the atomic force microscope. There are polymer bridges between the surfaces. The bridging creates an attractive force between surfaces at distances larger than the equilibrium thickness of the layer and a repulsive force at short distances. The attraction is attributed to polymer bridges in which the two end groups of a single triblock chain simultaneously adsorb onto opposing surfaces. The attractive forces depend strongly on the number of the approach-and-retract cycles. The comparison between theoretical and experimental profiles allows an estimation of the adsorption energy of the end groups of the triblock chains on the polystyrene surface.