EQUILIBRIUM ORIENTATION OF CONFINED DIBLOCK COPOLYMER FILMS

Using a two-dimensional Scheutjens and Fleer self-consistent field cal culation, we determine the equilibrium morphology of thin films of sym metric AB diblock copolymers confined between hard, smooth plates. A l amellar phase is established with the stripes either perpendicular or parallel to the walls. With neutral walls, the perpendicular orientati on is stabilized by the nematic ordering of the monomers, which arises from the orientational constraint imposed by the walls. When the subs trates are composed of pure A monomer (thus repulsive to B), there are transitions from strained parallel conformations, which wet the subst rates with A polymer, to distorted perpendicular configurations as the film thickness is varied. It is possible that the removal of one of t he walls (the usual experimental scenario of thin films spun cast onto a substrate) can still lead to spontaneous and robust pattern formati on on the scale of tens of nanometers.