Morphology Control of Perpendicularly Oriented Lamellar Films from Azobenzene-Containing Block Copolymers with Different Spacer Lengths

Block copolymer (BCP) films with vertically aligned lamellar structures hold great application potential in multiple fields. Nevertheless, systematic control of the lamellar morphology in BCP films has rarely been reported so far, including connectivity, etch selectivity, and orientation. Here, we report an effective approach to construct perpendicularly oriented lamellar domains by incorporating the azobenzene groups into the side chains of polystyrene-block-polymethacrylate (PS-b-PMMA) with different flexible spacers (x), namely, PS-b-PMA(xC)Az (x = 0, 6, or 11). Two- and three-dimensional vertical lamellae, such as thick high-connectivity lamellae, thin defect-free lamellae, and mixture lamellae, can be fabricated by manipulating x. Simultaneously, the perpendicular lamellae with different morphologies can be obtained on various substrates, such as hard silicon wafers, flexible aluminum sheets, and transparent polyethylene terephthalate (PET) films. Herein, a plausible mechanism is demonstrated. The present strategy might open an avenue to engineer the morphology of perpendicularly aligned lamellar films for applications that either require high-connectivity percolating transport or defect-free lithography templates.