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A ferroelectric liquid crystal confined in cylindrical nanopores : reversible smectic layer buckling, enhanced light rotation and extremely fast electro-optically active Goldstone excitations
Citation Link: https://doi.org/10.15480/882.1614
Publikationstyp
Journal Article
Date Issued
2017-11-27
Sprache
English
TORE-DOI
TORE-URI
Journal
Volume
9
Issue
48
Start Page
19086
End Page
19099
Citation
Nanoscale 9, (2017) 48 : pp. 19086-19099
Publisher DOI
Scopus ID
ArXiv ID
Publisher
Royal Society of Chemistry (RSC)
The orientational and translational order of a thermotropic ferroelectric liquid crystal (2MBOCBC) imbibed in self-organized, parallel, cylindrical pores with radii of 10, 15, or 20 nm in anodic aluminium oxide monoliths (AAO) are explored by high-resolution linear and circular optical birefringence as well as neutron diffraction texture analysis. The results are compared to experiments on the bulk system. The native oxidic pore walls do not provide a stable smectogen wall anchoring. By contrast, a polymeric wall grafting enforcing planar molecular anchoring results in a thermal-history independent formation of smectic C* helices and a reversible chevron-like layer buckling. An enhancement of the optical rotatory power by up to one order of magnitude of the confined compared to the bulk liquid crystal is traced to the pretransitional formation of helical structures at the smectic-A*-to-smectic-C* transformation. A linear electro-optical birefringence effect evidences collective fluctuations in the molecular tilt vector direction along the confined helical superstructures, i.e. the Goldstone phason excitations typical of the para-to-ferroelectric transition. Their relaxation frequencies increase with the square of the inverse pore radii as characteristic of plane-wave excitations and are two orders of magnitude larger than in the bulk, evidencing an exceptionally fast electro-optical functionality of the liquid-crystalline-AAO nanohybrids.
Subjects
Physics - Soft Condensed Matter
Physics - Soft Condensed Matter
Physics - Mesoscopic Systems and Quantum Hall Effect
Physics - Materials Science
Physics - Chemical Physics
Physics - Optics
DDC Class
530: Physik
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