Concentration profiles of end-grafted, diblock and triblock polymers in the melt: Near-wall structure and effects of segment-wall interaction.

We report a neutron reflectivity and secondary-ion mass spectrometry study of segment-density profiles of grafted polymers in a homopolymer matrix. The effect of monomer-wall interactions was investigated by grafting to «neutral» or «attractive» interfaces. The low-density grafting regime was studied where bulk-like screening of the excluded-volume interactions for grafted chains is expected to be effective. Experiments confirm this picture of screened interactions. Current many-chain calculations do not appear to predict the ideal chain statistics observed for the neutral-wall case, nor reproduce the experimentally observed variation of the profiles with wall interaction strength.