1 IMFUFA, Department of Science and Environment, Roskilde University2 The Department of Science, Systems and Models, Roskilde University3 Technische Universität München4 Cornell University5 Deutsches Elektronen-Synchrotron
The nanostructures of thin films spin-coated from binary blends of compositionally symmetric polystyrene-b-polybutadiene (PS-b-PB) diblock copolymer having different molar masses are investigated by means of atomic force microscopy (AFM) and grazing-incidence small-angle X-ray scattering (GISAXS) after spin-coating and after subsequent solvent vapor annealing (SVA). In thin films of the pure diblock copolymers having high or low molar mass, the lamellae are perpendicular or parallel to the substrate, respectively. The as-prepared binary blend thin films feature mainly perpendicular lamellae in a one-phase state, indicating that the higher molar mass diblock copolymer dominates the lamellar orientation. The lamellar thickness decreases linearly with increasing volume fraction of the low molar mass diblock copolymer. After SVA, well-defined macrophase-separated nanostructures appear, which feature parallel lamellae near the film surface and perpendicular ones in the bulk.
Macromolecular Rapid Communications, 2014, Vol 35, Issue 18, p. 1622-1629