achiral nematic host materials. [4] Recently, light-driven chiral molecular switches have been the materials of choice in the fabrication of cholesteric materials due to the fact that such systems provide unique opportunity to take advantage of the special characteristics of light, i.e., remote wireless controllability with high spatial and temporal resolution. [5,6] Accordingly, a variety of light-driven chiral molecular switches have been designed and synthesized that have enabled the development of cholesteric LCs in many applications including wavelength and chirality tunable color reflectors, [7,8] sensors, [9] photodisplays, [10,11] and beam steering. [12] To broaden the scope of the light-driven chiral molecular switches and to develop multifunctional cholesteric LCs for sophisticated and unconventional device applications, we have now turned towards the design and synthesis of photodynamic luminescent chiral molecular switches with photoluminescence capability. In this endeavor, we have chosen α-cyanostilbene scaffold as the functional photoresponsive moiety in the chiral molecular switches since it is well known to exhibit tunable photoluminescence upon lightdriven isomerization. Here we report on the design, synthesis, and the use of new ɑ-cyanostilbene based chiral fluorescent molecular switches capable of exhibiting reversible photoisomerization without thermal relaxation in the development of multifunctional cholesteric LCs and fabrication of monoand dual-mode transparent display devices. It should be noted that the recently reported cyanostilbene based chiral molecular switches were not able to show reversible photoisomerization behavior [9,11] and hence cannot be employed in the fabrication of highly desirable optically rewritable transparent display devices based on cholesteric LCs. Since the cyanostilbene unit provides necessary handles to tune both the helical twisting power (HTP) and fluorescence intensity, we have harnessed this unique combination of promising characteristics to demonstrate high performance optically rewritable transparent cholesteric devices operating in different modes and capable of displaying information in bright and dark ambient conditions. Furthermore, the feasibility of a "remote-writing board" is disclosed in this study.It is well known that images in cholesteric LC displays are vivid even in full bright sunlight without the aid of a polarizer or color filter. [13] Especially, cholesteric LCs can be employed Functional soft materials exhibiting distinct functionalities in response to a specific stimulus are highly desirable towards the fabrication of advanced devices with superior dynamic performances. Herein, two novel light-driven chiral fluorescent molecular switches have been designed and synthesized that are able to exhibit unprecedented reversible Z/E photoisomerization behavior along with tunable fluorescence intensity in both isotropic and anisotropic media. Cholesteric liquid crystals fabricated using these new fluorescent molecular switches as chiral dopan...
