Chirality switching is intriguing for the dynamic control of the electronic and optical properties in nanoscale materials. The ability to photochemically switch the chirality in liquid crystals (LCs) is especially attractive given their potential applications in electro-optic displays, optical data storage, and the asymmetric synthesis of organic molecules and polymers. Here, we present a dynamic photoswitching of the helical inversion in chiral nematic LCs (N*-LCs) that contain photoresponsive axially chiral dopants. Novel photoresponsive chiral dithienylethene derivatives bearing two axially chiral binaphthyl moieties are synthesized. The dihedral angle of the binaphthyl rings changes via the photoisomerization between the open and closed forms of the dithienylethene moiety. The N*-LCs induced by the dithienylethene derivatives that are used as chiral dopants exhibit reversible photoswitching behaviors, including a helical inversion in the N*-LC and a phase transition between the N*-LC and the nematic LC. The present compounds are the first chiral dopants that induce a helical inversion in N*-LC via the photoisomerization between open and closed forms of the dithienylethene moiety.

Novel multifunctional conjugated polymers, [poly(p‐phenylene)s and poly(bithienylene‐phenylene)s with (R)‐ and (S)‐configurations], which have fluorescence, chirality, and photoresponsive properties, have been designed and synthesized. The polymers are composed of π‐conjugated main chains, where poly(p‐phenylene) and poly(bithienylene‐phenylene) are fluorescence moieties, and the side chains of the photochromic dithienylethene moiety are linked with chiral alkyl groups. The polymer films exhibit right‐ or left‐handed circularly polarized fluorescence (CPF) and also show reversible quenching and emitting behaviors as a result of photochemical isomerization of the dithienylethene moiety upon irradiation with ultraviolet and visible light. This is the first report realizing the reversible switching of CPF using chirality and photoresponsive properties.

wileyonlinelibrary.comand aggregation-enhanced emission (AEE) characteristics were reported in selected ACPs. [14][15][16] Therefore, it is of great interest to investigate ACPs in the aggregated state that are quite different from those the isolated chain state.The polymer nanosphere solution can be treated as an intermediate state between a solution state and a solid fi lm state because the polymer nanoparticles uniformly disperse in a solvent, similar to their behavior in solution, whereas the polymer chains aggregate with each other, similarly to their behavior in a solid fi lm. In other words, the polymer nanosphere solution can be regarded as a dispersed nano-ordered crystalline polymer system. This bilateral character of the nanosphere solution causes the polymer to exhibit high processability and fl uidity as well as aggregation effects. In addition, the polymer nanosphere solution enables quantitative analysis of the aggregated state of polymers from the spectroscopic point of view. Hence, the polymer nanosphere solution is useful for understanding the aggregation effect on ACPs as compared with the solution and solid fi lm states.Dynamic control of the fl uorescence of ACPs using an external light stimulus is of particular interest because such photoresponsive polymers are essential for next-generation optoelectronic materials. Dithienylethene (DE) derivatives [17][18][19][20] are one class of the most attractive photoresponsive materials because of their outstanding fatigue resistance, thermal stability, and ability to undergo conformational changes between open and closed forms via photoisomerization, and therefore they are regarded as promising materials for the fabrication of photodynamically controllable luminescent devices [ 21,22 ] as well as photodynamically color-tunable systems. [23][24][25][26][27] The DE derivatives are also known to display luminescent color changes via photoisomerization. [ 20,[28][29][30][31][32][33][34][35][36][37] Similarly, conjugated polymers that contain DE moieties in the polymer backbones exhibit photochromism. [ 20,[38][39][40][41] The chromism in both absorption and luminescence of the conjugated polymers is attributed to structural changes in the conjugated backbones resulting from the DE photoisomerization. Hence, it is necessary to properly design the molecular structure to realize the desired switching behavior and fl uorescent colors.It is well known that in ACP nanoparticles doped with luminescent dopants, the ACP fl uorescence is almost completely quenched and the fl uorescence of the dopant is mainly