Insights into the origins of inverted circular dichroism in thin films of a chiral side chain polyfluorene

Abstract

We synthesized a fluorene‐bithiophene co‐polymer with chiral side chains (cPFT2) and investigated its chiroptical properties via synchotronradiation circular dichroism. We observed that thin films of the polymer display an intense circular dichroism (CD) upon annealing, which is of opposite handedness to the CD reported for similar polyfluorenes bearing the same enantiomeric chiral side chain. We then contrast the properties of this polymer with chiral side chain fluorene homopolymer (cPF) and observe large differences in their thin film morphology. Using photoluminescence spectroscopy, we uncover evidence of polymer chain bending in cPFT2, which is further supported by theoretical calculations, and propose an explanation for the observed inverted optical activity.

Ultrafast electron dynamics in excited states of conjugated thiophene–fluorene organic polymer (pF8T2) thin films

“…27 Recently, this material has been employed by Fuchter and co-workers for the generation of circularly polarized light based on an injection of electrons with orbital angular momentum (OAM) which yields opposite helicity of the light emitted in opposite direction. [28][29][30] In reverse, polymer solar cells can benefit from the large absorption in the blue spectral region and, together with a potential acceptor, cover a wide part of the solar spectrum. 31 A current density of 0.23 mA cm À2 has been measured for pF8T2-based polymer solar cells.…”

“…27 Recently, this material has been employed by Fuchter and co-workers for the generation of circularly polarized light based on an injection of electrons with orbital angular momentum (OAM) which yields opposite helicity of the light emitted in opposite direction. 28–30…”

Annealing temperature-dependent induced supramolecular chiroptical response of copolymer thin films studied by pump-modulated transient circular dichroism spectroscopy

“…These properties make them attractive for a range of applications in organic optoelectronics, such as photodetectors 3,4 or organic light-emitting diodes (OLEDs) that produce circularly polarised luminescence [5][6][7] . Several research groups have successfully synthesised and investigated such supramolecular structures by using intrinsically chiral copolymers [8][9][10][11][12][13][14][15][16][17][18] . Another way to achieve a supramolecular chiroptical response is by embedding a chiral inducer into an achiral copolymer.…”

Negative Nonlinear CD–ee Dependence in Polycrystalline BINOL Thin Films

“…However, any g -value versus ee relationships will still be referred to as CD–ee dependence to be compatible with previous literature. The CD–ee dependence in polycrystalline BINOL films at 310 nm, close to the 1 L b transition, presented in Figure a, is extracted from g -value curves of the samples after considering and removal of all known nontrue-CD contributions ,− (see SI). The data clearly show a nonlinear CD–ee dependence with a zero-crossing around 80% ee.…”