Nematic cells patterned with square arrays of strength m = ±1 topological defects were examined as a function of cell thickness (3 < h < 7.5 μm), temperature, and applied voltage. Thicker cells tend to exhibit an escape or partial escape of the nematic director as a means of mitigating the elastic energy cost near the defect cores, whereas thinner cells tend to favor splitting of the integer defects into pairs of half-integer strength defects. On heating the sample into the isotropic phase and cooling back into the nematic, some apparently split defects can reappear as unsplit integer defects, or vice versa. This is consistent with the system’s symmetry, which requires a first order transition between the two relaxation mechanisms.
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Azimuthal Anchoring Strength in Photopatterned Alignment of a Nematic
Spatially-varying director fields have become an important part of research and development in liquid crystals. Characterization of the anchoring strength associated with a spatially-varying director is difficult, since the methods developed for a uniform alignment are seldom applicable. Here we characterize the strength of azimuthal surface anchoring produced by the photoalignment technique based on plasmonic metamsaks. The measurements used photopatterned arrays of topological point defects of strength +1 and −1 in thin layers of a nematic liquid crystal. The integer-strength defects split into pairs of half-integer defects with lower elastic energy. The separation distance between the split pair is limited by the azimuthal surface anchoring, which allows one to determine the strength of the latter. The strength of the azimuthal anchoring is proportional to the UV exposure time during the photoalignment of the azobenzene layer.
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- Award ID(s):
- 1663394
- PAR ID:
- 10285071
- Date Published:
- Journal Name:
- Crystals
- Volume:
- 11
- Issue:
- 6
- ISSN:
- 2073-4352
- Page Range / eLocation ID:
- 675
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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