  Hydrophobically modified polymers are good candidates for the stabilization
of liquid interfaces thanks to the high anchoring energy of the hydrophobic
parts. In this article we probe the interfacial anchoring of a series of
home-made hydrophobically modified polymers of controlled degree of grafting by
studying their behavior upon large area dilations and compressions. By
comparing the measured interfacial tension to the one that we expect in the
case of a constant number of adsorbed monomers, we are able to deduce whether
desorption or adsorption occurs during area variations. We find that the
polymer chains with the longest hydrophobic grafts desorb for larger
compressions than the polymers with the shortest grafts, because of their
larger desorption energy. Furthermore, we observe more desorption for polymers
with the highest grafting densities. We attribute this counter intuitive result
to the fact that for high grafting densities, the length of the polymer loops
is shorter, hence the elastic penalty upon compression is larger for these
layers, leading to a faster desorption. The dilatation experiments reveal that
the number of adsorbed anchors remains constant in the case of chains with low
grafting density while chains with the highest degree of grafting seem to show
some degree of adsorption during the dilatation. Therefore for these highly
grafted chains there may be unadsorbed grafts remaining in the vicinity of the
interface, which may adsorb quickly to the interface upon dilatation.
