In-Situ TEM Visualization of Pressure-Induced Ordering of Nanostructured Block Copolymer Thin Films

Here, we aim to suggest a facile and effective method for controlled orientation of block copolymer (BCP) thin films driven by pressure-induced ordering during thermal annealing. A novel chip with a built-up metal wire-based micro heater was fabricated utilizing microelectromechanical system (MEMS) technique to in-situ investigate the morphological evolution of free-standing polystyrene-block-polydimethylsiloxane (PS-PDMS) star-block copolymer thin films for demonstration of the suggested pressure-induced ordering. Owing to the high vacuum (~10^-4 Pa) environment, the low pressure could transfer the extremely selective surface to weakly selective surface for the PDMS and PS, giving the neutral air surface for the formation of span-thru perpendicular cylinders with high-degree lateral ordering, as directly visualized by TEM. We believe that this finding will bring the new opportunities for the designs of polymeric materials in practical applications.