Polymer blends are of increasing interest in the field of surface technology because they can be used to change or tailor the properties of surfaces for special application. In most cases not only the chemical nature of the components is important for the physical properties of the blend but also the components distribution on the blend surface. This distribution is strongly dependent on the adsorption energy of the polymers onto the substrate. According to the Flory-Huggins theory, the criterion for polymer miscibility in blends is that the average interaction parameter for a binary mixture of polymers, 12, must be less than a critical value cri, which is calculated from weight-average degrees of polymerization of the two polymers [1]. This parameter also describes the difference of the interaction energies between similar and different monomers. During the spin coating process the system tries to reach a state of low energy, indicating that the substrate surface and the vapor phase influence the wetting and dewetting of the substrate by the resulting polymer films. However, one should notice that spin-coated film structure may not correspond to the equilibrium one due to the rapid solvent evaporation during the spin coating process and to solvent effects [2].