Azobenzene Sulphonic Dye Photoalignment as a Means to Fabricate Liquid Crystalline Conjugated Polymer Chain-Orientation-Based Optical Structures

Haoran Zhang, Lingling Ma, Qian Zhang, Yuping Shi, Yueting Fang, Ruidong Xia, Wei Hu, Donal Bradley

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

The use of a noncontact photoalignment method to fabricate in-plane optical structures, defined by the local uniaxial ordering of liquid crystalline conjugated polymer chains, is reported. Molecular orientation is demonstrated for both green-light-emitting fluorene-benzothiadiazole alternating copolymer F8BT and F8BT/red light emitting complex copolymer Red-F binary blend films deposited on a well-known azobenzene sulphonic dye photoalignment material SD1. Absorption anisotropy ratios of up to 9.7 are readily achieved for 150 nm thickness F8BT films. Spatial pattern definition, afforded by masking the UV polarized light exposure of the photoalignment layer, allows the fabrication of optical structures with a resolution down to the micron scale. The alignment process is further extended to enable the serial, independent orientation of films deposited on top of each other and to permit the molecular orientation to follow curvilinear patterns. In the former case, this allows F8BT bilayer structures to be fabricated that show even higher absorption anisotropy ratios, up to ≈12, close to the theoretical limit for the previously deduced ≈22° optical transition dipole moment angle relative to the chain axis.
Original languageEnglish (US)
Pages (from-to)1901958
JournalAdvanced Optical Materials
DOIs
StatePublished - Feb 17 2020

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: H.Z., L.M., and Q.Z. contributed equally to this work. The authors thank Takeshi Yamada and the Sumitomo Chemical Company for providing the Red-F polymer. The authors further thank Mariano Campoy-Quiles for assistance with refractive index measurements. R.X. acknowledges funding from the National Natural Science Foundation of China (Grants 61874058, 51861145301, and 61376023), a Chinese 973 project (grant 2015CB932203), and the Priority Academic Program Development Fund of Jiangsu Higher Education Institutions (PAPD-YX030003). D.D.C.B. acknowledges the University of Oxford and the Jiangsu Province Double Creation Team Award for funding support. Y.S. thanks the Hong Kong Jockey Club for a DPhil Graduate Scholarship.

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