Strongly Phase-Segregating Block Copolymers with Sub-20 nm Features

The modular synthesis and lithographic potential of diblock copolymers based on polystyrene-<i>block</i>-poly(2-ethyl-2-oxazoline) (PS-<i>b</i>-PEtOx) are highlighted herein. Controlled radical and living cationic polymerization techniques were utilized to synthesize hydrophobic PS and hydrophilic PEtOx building block of varying molar mass. Subsequently, "click" chemistry was used to couple the blocks and obtain a family of PS-<i>b</i>-PEtOx polymers. The influence of molar mass, composition, and thin-film thickness on the microphase-segregated morphology and orientation were investigated with atomic force microscopy (AFM) and grazing incidence small-angle X-ray scattering (GISAXS). Dense hexagonal arrays of cylindrical nanodomains normal to the substrate, having a periodicity of less than 20 nm were obtained.