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].