'Structurally Neutral' Densely Packed Homopolymer-Adsorbed Chains for Directed Self-Assembly of Block Copolymer Thin Films

We here report that adsorbed chains composed of one of the constituent blocks can be used as a new surface modification approach to induce perpendicularly oriented lamellar microdomains in block copolymer thin films. A nearly symmetric polystyrene-block-poly(methyl methacrylate) (PS-block-PMMA) diblock copolymer was used as a model. Densely packed PS- or PMMA-adsorbed chains of about 2–3 nm in thickness (“polymer nanocoatings”) were deposited on silicon (Si) substrates using a solvent-rinsing approach. Spin-cast films of 40 or 60 nm-thick PS-block-PMMA (equivalent to two or three interdomain spacings) were subsequently deposited onto the PS or PMMA nanocoatings. Grazing incidence small-angle X-ray scattering experiments revealed the formation of perpendicularly oriented lamellar microdomains within the entire films at 200 °C, where balanced interfacial interactions at the polymer–air interface were achieved. Additionally, X-ray photon correlation spectroscopy studies demonstrated the dynamics of the fully...