Neutron reflectivity of grafted polymer brushes under shear

The behavior of tethered polymer brushes under shear was studied using neutron reflectivity experiments. Polystyrene (PS) with a trichloro-silane end group was used to graft the PS brush chemically to a single crystal Si surface. Both toluene and cyclohexane were used as the solvent media. The dry brush height was measured by X-ray reflectivity to be 17.5 nm. Without shear, the brush extends to 31 nm and 75 nm in cyclohexane and toluene. Up to shear rates of 30000/s, no effect of shear was observed. The neutron reflectivity profiles at zero and 30000/s shear look identical indicating less than 2-3% change in the brush density profile.