Azobenzene/Triptycene-Based Cholesteric Liquid Crystal Dopants

The noncovalent interactions in cholesteric liquid crystals (CLCs) can be modulated using switchable chiral dopants resulting in the phototuning of the reflected structural color. The nature of the interactions between the CLC and dopant, and how the latter can effectively transfer chiral information to the former is still somewhat of a black box. To gain insights into the nature of these interactions, we conducted structure-property analysis of five photoswitchable chiral dopants comprised of triptycene as the chiral core and azobenzene as the switchable unit. Our findings show that this combination results in high (e.g., 127 µm^-1) helical twisting power (β ) values (i.e., extent of chiral information transfer between dopant and host), with dispersion interactions and/or electron deficient aromatic units playing a crucial role in determining the value. The large change in β values upon E/Z photoswitching enabled us to devise multicolor, high contrast LC films that reflect across the UV to infrared light range.