Optical 3D alignment of nanocylinders has been successfully attained for thin films of a block copolymer (see figure) comprising azobenzene‐containing liquid‐crystalline polymers and poly(ethylene oxide) via photoinduced massive migration. The out‐of‐plane and in‐plane alignments are achieved by controlling the film thickness and selection of linear polarization direction upon illumination, respectively.

The orientation of liquid crystal molecules is very sensitive towards contacting surfaces, and this phenomenon is critical during the fabrication of liquid crystal display panels, as well as optical and memory devices. To date, research has focused on designing and modifying solid surfaces. Here we report an approach to control the orientation of liquid crystals from the free (air) surface side: a skin layer at the free surface was prepared using a non-photoresponsive liquid crystalline polymer film by surface segregation or inkjet printing an azobenzene-containing liquid crystalline block copolymer. Both planar-planar and homoeotropic-planar mode patterns were readily generated. This strategy is applicable to various substrate systems, including inorganic substrates and flexible polymer films. These versatile processes require no modification of the substrate surface and are therefore expected to provide new opportunities for the fabrication of optical and mechanical devices based on liquid crystal alignment.

Photoalignment and realignment of nanocylinder domains of a polystyrene-based block copolymer film in both in-plane and out-of-plane modes are successfully attained by irradiating with linear polarized (LPL) or nonpolarized light at 436 nm followed by annealing. This photocontrol allows the on-demand 3D photoalignment and micropatterning of the nanostructures.

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An orientational change from homeotropic to planar of liquid crystal (LC) mesogens and the microphase separation (MPS) domains is attained by the segregated skin layer at the free surface. This allows for an efficient in-plane photoalignment of the cylindrical domains. The surface segregation strategy is very simple and is therefore expected to open up new possibilities for the orientation control of various types of LC materials.