# Investigating the Electro-Optic Response of Steroid Doped Liquid Crystal Devices
## 3 Results and Discussion
When the voltage is removed, the system returns to its initial scattering state as the LCs relax back to the focal conic state. The transparent state is only achieved in the presence of an electric field, and is not stable due to the relaxation of the nematic LC EZ when the stimuli is removed. Next, an LC sample exhibiting \"reverse mode\" switching was fabricated using progesterone. To obtain a \"reverse mode\" device, the positive dielectric host EZ was replaced with MLC-2079 which has a negative dielectric anisotropy. LCs with a negative dielectric anisotropy do not reorient when an external stimuli is applied, unlike positive dielectric LCs. In \"reverse mode\" devices, the planar CLC texture is stabilized, and the selective reflection notch is present in the transmittance spectra; generally, it is placed in the infrared to obtain a sample that is transparent in the visible region. Upon the application of sufficiently high electric stimuli, the planar structure is lost, and the focal conic state is formed leading to significant scattering. The focal conic state is stable when the electric field is removed. The planar texture can be regenerated upon the application of sufficiently high electric fields [35]. This sample is considered bistable as the focal conic state and the planar state are stable when the electric field is removed [36]. A \"reverse mode\" CLC containing progesterone is highlighted in Figure 3b. Here, the initial sample is optically transparent  
Figure 2: POM images of (**a**) androsterone, (**b**) cholic acid, (**c**) epiandrosterone, (**d**) hydrocortisone, (**e**) prednisone, (**f**) stigmasterol, (**g**) \(\beta\)-estradiol, (**h**) cholesterol, and (**i**) progesterone at 5 wt. % in EZ7. with high transmittance from 400 to 800 nm, with the selective reflection placed in the near-infrared region at 950 nm. The application of DC voltage triggered the switching of the sample to the focal conic scattering state which was retained when the voltage was removed. The planar texture was recovered by applying 40 V of AC and was stable once the electric field was removed. To further demonstrate the applicability of progesterone in LC devices, reactive monomers were added to the formulations to generate PSCLCs. The reactive monomers are mesogenic and adopt the orientation of the director; in CLCs, the monomers are distributed throughout the helical superstructure. As the system is exposed to UV light, the polymerization occurs and the resulting polymer network behaves as a template for the LC mesogens, acting as an interwoven anchoring layer [37; 38]. The anchoring of the LCs to the polymer network enables unique responsive behavior that is not observed in most LC systems. The unique behavior is attributed to the deformation of the polymer network as ions trapped within the polymer are pulled towards the electrode when a voltage is applied. The ions in the solutions come from the added photoinitiator and ionic impurities in the nematic liquid crystals themselves. The deformation of the polymer network results in a change in the helical pitch and a shifting of the selective reflection. If the pitch distortion is uniform, broadening of the selective reflection can occur; if distortion of the pitch is non-uniform, tuning of the selective reflection is observed [39; 40]. PSCLC formulations exhibiting both red and blue tuning behavior containing progesterone as the primary chiral dopant were fabricated. The formulations for both RT1 and BT1 are listed in Table S2. The structures of the chemicals used to fabricate the PSCLCs are shown in Figure S4. The LC monomer RM82 was chosen to form the polymer stabilizing network as the six carbon chain extender affords greater notch tuning ability [15]. MLC-2079 was chosen as the nematic LC host due to the negative dielectric anisotropy, which enables the distortion of the polymer network [39].