Structure of polymer layers adsorbed from concentrated solutions

Loïc Auvray , Philippe Auroy , Margarida Cruz

We study by neutron scattering the interfacial strucuture of poly(dimethylsiloxane) layers irreversibly adsorbed from concentrated solutions or melts. We first measure the thickness h of the layers swollen by a good solvent as a function of the chain polymerisation index N and of the polymer volume fraction in the initial solution Φ. The relation h ≈N0.8Φ0.3, recently predicted from an analogy between irreversibly adsorbed layers and grafted polymer brushes, describes well our results. We can therefore deduce that there is at least one large loop of about N monomers per adsorbed chain. We also study the shape of the polymer concentration profile in the layers by measuring on two samples the polymer-solid partial structure factor, that is proportional to the Fourier transform of the profile. The model of pseudobrushes predicts a concentration decay varying with the distance of the wall z as z-2/5. This power law profile accounts quantitatively for the angular variation of the polymer-solid cross structure factor but it is difficult to distinguish it without anbiguity from less singular profiles. It implies that the adsorption of PDMS onto silica is sufficiently strong and fast to quench completely the loop distribution in the initial layer.

Domaines: Articles anciens

Loïc Auvray, Philippe Auroy, Margarida Cruz. Structure of polymer layers adsorbed from concentrated solutions. Journal de Physique I, 1992, 2 (6), pp.943-954. ⟨10.1051/jp1:1992106⟩. ⟨jpa-00246613⟩