Influence of Interfacial Constraints on the Morphology of Asymmetric Crystalline-Amorphous Diblock Copolymer Films

Through control of the temperature, T, and film thickness, h, the relative influence of forces associated with crystallization, long-range van der Waals forces, and block-copolymer ordering were manipulated to control the structure of films of asymmetric polyethylene-b-poly(styrene-r-ethylene-r-butene) (E-b-SEB) diblock copolymers. The bulk equilibrium structure of this copolymer consists of spheres of the crystallizable E block embedded in the amorphous SEB matrix. In thin films, the E component resides at the free surface and the SEB block resides in contact with the substrate. Within the temperature range T > Tm, where Tm is the melting temperature, yet below the order−disorder transition (ODT) temperature, TODT, all films of thickness h > 12 nm were ordered throughout. The thickness of the brush layer L0, in contact with the substrate, of these films was 12 nm; this thickness is about one-half of the intersphere spacing of the bulk copolymer. Films equal to or thinner than 12 nm dewet, forming droplet...