Published online by Cambridge University Press: 10 February 2011
We have measured the growth with time t of a wetting layer (of thickness l(t)) at the surface of a thin film of a binary liquid (polymer) mixture. Over a wide range of experimental parameters, our data is well described by a model of diffusion limited wetting which takes into account the finite film thickness. In this model, l(t) is a function of time which sensitively depends on the nature of the interfacial potential: a detailed comparison shows that long range van-der-Waals forces provide the main driving force for the build-up of the wetting layer.