Characterization of the brush regime for grafted polymer layers at the solid-liquid interface

Using small-angle neutron-scattering techniques, the scaling laws between the thickness of a grafted polymer layer h, its graft density \ensuremath{\sigma}, and the molecular weight of the grafted chains M have been determined for polydimethylsiloxane chains end grafted on porous silica. The observed laws h\ensuremath{\approxeq}M\ensuremath{\sigma} in bad solvent and h\ensuremath{\approxeq}M${\mathrm{\ensuremath{\sigma}}}^{1/3}$ in good solvent provide the first experimental evidence of the ``brush'' regime, where the grafted chains, confined by their neighbors, are stretched normal to the surface.