Interfacial Interaction Effects on Phase Transition Behavior of Block Copolymer Thin Films

Confined in a film geometry, the preferential interaction of the polymer/air and polymer/substrate interfaces generates cylindrical and lamellar microdomains oriented parallel to the substrate. We presented the thickness dependent phase diagram of BCP films using ex-situ grazing incidence small-angle x-ray scattering (GISAXS) and transmission electron microscopy (TEM). With decreasing film thickness (t) when t < t_o, where t_o is an onset thickness above which the ODT temperatures (T_ODTs) of the films are independent of film thickness, the T_ODTs of cylinder- and lamella-forming polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) films supported on preferential substrates remarkably increase. Consistent between cylinder- and lamella-forming PS-b-P2VP films, this effect is so intense in very thin BCP films.