Emergent Ferroelectric Nematic and Heliconical Ferroelectric Nematic States in an Achiral “Straight” Polar Rod Mesogen

Ferroelectric nematic liquid crystals (N_FLCs) are distinguished by their remarkable polarization characteristics and diverse physical phenomena, sparking significant interest and excitement within the scientific community. To date, over 150 N_FLC molecules are developed; however, there are no reports regarding straight linear polar molecules with a parallel alignment of the permanent dipole moment and the molecular axis. The straight polar mesogen nBOE exhibits an enantiotropic N_F phase with a wide temperature window (up to 100 K) despite having a longer alkyl chain (up to n = 6) than the critical alkyl chain length of conventional models. Interestingly, nBOE with a medium-length alkyl chain displays an exotic phase sequence of N_F-^HCN_F-SmX_F during the elimination of positional displacement among adjacent molecules. Furthermore, the reflective color modulation of the ^HCN_FLC over the entire VIS-NIR spectral regime by ultralow E-field (up to 0.14 V µm^-1) is demonstrated.