3 years ago

Periodic Planar-Homeotropic Anchoring Realized by Photoalignment for Stabilization of Chiral Superstructures

Periodic Planar-Homeotropic Anchoring Realized by Photoalignment for Stabilization of Chiral Superstructures
Jeroen Beeckman, Kristiaan Neyts, Inge Nys, Ke Chen
Self-organization of chiral superstructures in liquid crystal (LC) materials is a powerful tool in developing functional devices based on soft matter. The control and manipulation of the helical axis orientation in chiral nematic liquid crystals are currently attracting significant attention, but are hindered by limited control over the anchoring at the interfaces. The development of new alignment techniques with local control over polar and azimuthal anchoring can open up a wide range of possibilities. Here a new photoalignment process based on a mixture of photosensitive azo compounds and homeotropic alignment materials is developed and demonstrated. The alignment of the LC director near the surface depends on both intensity and polarization of the UV illumination. By two-beam interference UV illumination, periodic stripes of planar and homeotropic anchoring are realized. In addition it is demonstrated that the stripes of planar and homeotropic anchoring stabilize and align cholesteric fingers in cells with thickness smaller than the pitch. The 2D director configuration in the cholesteric fingers is identified by matching the experimental observations with numerical simulations based on finite element Q-tensor calculations. A novel mask-less photoalignment technique with spatial control over polar and azimuthal anchoring is presented. A single layer of two-component alignment material is illuminated with two-beam UV interference to create periodic stripes with planar and homeotropic anchoring. This anchoring pattern helps to stabilize and align new chiral liquid crystal superstructures in confined geometries.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/adom.201701163

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