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A Unified Model to Explain the Large Chiroptical Effects in Polymer Systems Through Natural Optical Activity

preprint
submitted on 10.05.2020 and posted on 12.05.2020 by Jess Wade, James Hilfiker, Jochen R. Brandt, Letizia Liirò-Peluso, Li Wan, Xingyuan Shi, Francesco Salerno, Seán Ryan, Stefan Schöche, Oriol Arteaga, Tamás Jávorfi, Giuliano Siligardi, Cheng Wang, David B. Amabilino, Peter Beton, Alasdair Campbell, Matthew Fuchter

Polymer thin films that emit and absorb circularly polarised light have been demonstrated with the promise of achieving important technological advances; from efficient, high-performance displays, to 3D imaging and all-organic spintronic devices. However, the origin of the large chiroptical effects in such films has, until now, remained elusive. We investigate the emergence of such phenomena in achiral polymers blended with a chiral small-molecule additive (1-aza[6]helicene) and intrinsically chiral-sidechain polymers using a combination of spectroscopic methods and structural probes. We show that – under conditions relevant for device fabrication – the large chiroptical effects are caused by coupling of electric and magnetic transition dipole moments (natural optical activity), not structural chirality as previously assumed, and may occur because of local order in a cylinder blue phase-type organisation. This disruptive mechanistic insight into chiral polymer thin films will offer new approaches towards chiroptical materials development after almost three decades of research in this area.

History

Email Address of Submitting Author

m.fuchter@imperial.ac.uk

Institution

Imperial College London

Country

UK

ORCID For Submitting Author

0000-0002-1767-7072

Declaration of Conflict of Interest

A. Campbell and M. Fuchter are inventors on a patent concerning chiral blend materials (WO2014016611).

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