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.

The B23 Circular Dichroism beamline at Diamond Light Source has been operational since 2009 and has seen visits from more than 200 user groups, who have generated large amounts of data. Based on the experience of overseeing the users' progress at B23, four key areas requiring the most assistance are identified: planning of experiments and note-keeping; designing titration experiments; processing and analysis of the collected data; and production of experimental reports. To streamline these processes an integrated software package has been developed and made available for the users. The subsequent article summarizes the main features of the software.

We highlight the power of electronic circular dichroism imaging (CDi), a technique developed at Diamond Light Source B23 beamline for synchrotron radiation circular dichroism (SRCD) to detect local domains endowed with a chiral supramolecular order in thin films of chiral oligomers and polymers. The highly brilliant and collimated beam light of B23 enabled CDi at a spatial resolution of 0.1 mm, unattainable with benchtop electronic circular dichroism (ECD) spectropolarimeters. CDi is bridging the gap between standard ECD spectroscopy and conventional microscopy. Presently, we apply CDi to reveal the local polymorphism of chiral oligothiophene-based molecules. By extensive use of a post-acquisition data-analysis tool called similarity factor, we quantified the polymorphs revealing a manifold of aggregation pathways whose relative weight was a function of the sample preparation protocol. This work uncovers the parameters that need to be optimised in order to obtain reproducible and controllable supramolecular structures in thin films, which is of paramount importance for materials with optoelectronic properties. It is noteworthy that this analysis is based on CDi measurements at high spatial resolutions of thin films of organic chiral semiconductors at the ultimate stage of preparation as the active layer of an optoelectronic device.