Photocontrolled microphase separation in a nematic liquid-crystalline diblock copolymer

Using a bromo-terminated poly(ethylene oxide) as a macroinitiator, an amphiphilic liquid-crystalline (LC) diblock copolymer with an azobenzene moiety as a nematic mesogen was prepared by an atom transfer radical polymerization process. In thin films of the well-defined diblock copolymer with the mesogenic block as a continuous phase upon microphase separation, the influence of supramolecular cooperative motion on the microphase-separated nanocylinders was systematically studied. Although the major phase of the hydrophobic nematic LC block showed only one-dimensional order, it could endow the separated minor phase of the hydrophilic PEO nanocylinders with three-dimensionally ordered structures. Both out-of-plane perpendicular and in-plane parallel patternings of the regularly ordered nanocylinder arrays were successfully fabricated on macroscopic scales by thermal annealing and photoalignment, respectively. The microphase-separated nanostructures with high regularity showed excellent reproducibility and mass production, which might guarantee nanotemplated fabrication processes and would lead to novel industrial applications in macromolecular engineering.