Department of Physics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.
Centre for Processable Electronics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.
Nat Commun. 2020 Dec 1;11(1):6137. doi: 10.1038/s41467-020-19951-y.
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 magneto-electric coupling (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.
聚合物薄膜可以发射和吸收圆偏振光，这一特性有望实现重要的技术进步；从高效、高性能显示器，到 3D 成像和全有机自旋电子器件。然而，到目前为止，这种薄膜中巨大的手性光学效应的起源仍然难以捉摸。我们使用光谱方法和结构探针研究了在与手性小分子添加剂（1-氮杂[6]轮烯）混合的非手性聚合物以及本征手性侧链聚合物中出现这种现象的情况。我们表明，在与器件制造相关的条件下，大的手性光学效应是由磁电耦合（自然旋光性）引起的，而不是以前假设的结构手性，并且可能是由于圆柱蓝相组织中的局部有序性引起的。这一对手性聚合物薄膜的机制的突破性见解将为近三十年来该领域的手性材料开发提供新的途径。
