NEUTRON REFLECTIVITY AND ELLIPSOMETRY STUDIES OF A POLYMER MOLECULAR LAYER SPREAD ON THE WATER-SURFACE

We have studied poly(dimethylsiloxane) (PDMS) layers spread at the free surface of water by using neutron reflectivity techniques. The results together with previous data from ellipsometry experiments confirmed that PDMS is able to form different kinds of stable molecular layers. The density of the layers is about 0.85 times the bulk polymer density for the first layer and evolves toward the bulk density when the surface concentration C is increased. The thickness evolves via discrete jumps when C increases and remains independent of the molecular weight. Thick layers spread with difficulty and the corresponding kinetics has also been studied.