The surface of multilayered opal crystals resulted in homeotropic alignment of liquid crystal (LC), originated from the surface topography of opal crystals rather than a chemical nature of the nanoparticles. The polar anchoring energy (5.51 × 10 J/m) of the crystal surface for nematic LC molecules was in a similar range to the conventional polyimide alignment layer (2.11 × 10 J/m) used for commercial applications. The critical length scale for anchoring transition was approximately Lw = ~1 μm. If a diameter of particle d << 1 μm for opal crystals, LC molecules preferred to anchor vertically to the surface to minimize elastic free energy of bulk LCs. The LC favored a planar anchoring if d >> 1 μm. The results provide crucial insights to understand the homeotropic alignment of LCs on solid surfaces and therefore offer opportunities to develop novel materials for a vertical alignment of LCs.

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A unique and versatile method for forming optically (that is, orientationally) and spatially patterned polymer architectures was developed based on the photopolymerization of reactive mesogens (RMs) in a periodically deformed liquid crystal (LC). Without using lithographic or holographic implements, various polymer patterns were produced by employing nematic LCs as reaction solvents and spatially nonuniform electric fields. The nematic mixture, containing 5.0 wt.% RMs and sandwiched between patterned electrodes, was exposed to spatially uniform reaction-initiating radiation. The spatially nonuniform electric field induced periodic optical patterns in the reaction template with spatially varying elastic deformations. The resulting polymerized RM networks were both spatially and optically patterned, with good fidelity with respect to the electrode pattern and subsequent periodic director profiles. The spatial distribution of dense RM networks coincided precisely with the profile of highly deformed regions in the reaction medium. The optical birefringence of the polymer network was templated by the local director of the reaction template. Numerical calculations of director configuration and the associated elastic energy of the reaction template precisely matched the spatial and orientational order of polymerized RM networks. The proposed method provides ease and flexibility in forming organized polymer architectures for functional materials that require both positional and orientational order for their applications. NPG Asia Materials (2017) 9, e429; doi:10.1038/am.2017.151; published online 25 August 2017 INTRODUCTIONProcessing soft matter with various functionalities is critical for organic electronic and photonic applications. Soft materials provide conformational, processing and design advantages in effectively exploiting the desired properties of small molecules on longer length scales. 1,2 However, making functional materials is only the first step. To realize and optimize the performance of practical devices, patterning in one or more dimensions is frequently required to achieve both spatial distribution and orientational order in their collective assembly. [3][4][5][6][7][8] The materials' functionality and potential for application are severely compromised if they cannot be effectively processed using straightforward techniques.In this context, liquid crystals (LCs) have attracted great attention as a typical example of self-assembling soft materials with electronic and photonic functionalities. 7-10 Because of their mesomorphic behaviors, particularly their electrical and optical anisotropies with respect to dynamic fluidity, LCs have been intensively studied for several decades. LC-polymer composites in particular have been broadly investigated for electro-optical applications. 11-13 Polymerization of reactive mesogens (RMs) in LC phases has been widely explored for the stabilization of particular optical states, for the modification of electro-optical properties and for templating the orientational orde...

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