Composition Effects in Polymer Blends Spin-Cast on Patterned Substrates

Blends of poly(2-vinylpyridine), polystyrene, and poly(methyl methacrylate) of four different compositions (2:3:0, 3:2:0, 1:1:0, and 2:2:1 w:w:w) were spin-cast onto periodically (λ = 4 μm) patterned substrate (with two alternating stripes: Au attracting PVP and neutral self-assembled monolayer), and resulting film morphologies (with inherent domain scale 0.2 λ ≤ R < 1.8 λ) were recorded with scanning force microscopy and examined with Fourier transform analysis and the integral geometry approach. The morphologies depend on not only spatial ( R /λ) but also compositional commensuration between blends and symmetric pattern: λ/2-substructures are present, in addition to λ-structures, for isolated (2:3:0) but not for continuous (3:2:0) PVP domains. This explains also the data for 1:1:0 blends which present a transition from isolated to continuous PVP domains (for larger R values). In turn, interfacial compatibilizer (PMMA in 2:2:1) results in the well-ordered λ/2-substructures for both morphology types.