A theoretical study of the behavior in liquid chromatography of star polymers of two different kinds of arms is presented, including the special cases of diblock copolymers and regular star polymers. The two different kinds of interactions between the substrate and the monomeric units which can be repulsive attractive or neutral combine in these heteroarm stars. They can act cooperatively or antagonistically determining, in connection with the effects of the architecture and the sizes of the branches, the mode of retention of the macromolecules. The compensation point, where no surface effects remain when the surface−monomer interactions are negligible, can also be reached by cancellation of the opposite but not negligible interactions of the two different kinds of arms with the substrate.

We study the quantitative behavior of a two-component polymer blend in the presence of an impenetrable interacting surface. A solution of the problem for ring chains is given, which can also describe the behavior of linear chains. While first-order perturbation theory is used for the interactions between the different monomers, the interactions between the monomers and the surface are taken into account to all orders. The monomer concentrations on the surface are found to be linear functions of the bulk concentrations only in the absence of interactions between the two components. The deviation from linearity between the surface and the bulk concentrations increases on increasing both the intensities of all three different interactions and the molecular weights of the polymers. Surface enrichment of one of the components is enhanced when the difference between the two surface interactions increases and reaches its largest value near the coexistence curve of the corresponding phase diagram of the blend. The theoretical predictions compare well with experimental results found by means of scattering and other spectroscopic techniques.

We use the Gaussian chain model in half-space, to study surface interacting binary polymer blends for a system that is not laterally incompressible. We derive the partition function of the system to all orders of the surface interaction parameters and find the spinodal limits. Surface-spinodal lines are shifted from those of the bulk on changing the thickness of the film or surface interactions, due to the change of the average number of heterocontacts between the units of different kind. These heterocontacts generally decrease for opposite surface interactions of the two species and contribute to the stability of the blend while they increase for surface interactions of the same kind, leading to destabilization. We thus explain quantitatively the experimental observations of both positive and negative shifts of the spinodals of polymeric films. For large confinements, an increase of the stability of a film is seen. This agrees with what is found in polymer blends and mixtures of smaller molecules between two symmetrical surfaces by Monte Carlo techniques and mean and self-consistent field theories.