Evidence for a new spreading regime between partial and total wetting

We present an investigation of the macroscopic spreading behavior of polydimethylsiloxane droplets on solid surfaces of adjustable spreading power. This is obtained through chemical grafting of mixed self-assembled monolayers on silicon wafers. Between partial wetting and high-energy-type total wetting, we identify for the first time a new regime in which the whole spreading kinetics is highly sensitive to the layer polarizability. This new regime can be interpreted in terms of oscillating van der Waals interactions, and identified with the pseudo partial wetting recently predicted.