Metastable room-temperature twist-bend nematic phases via photopolymerization

The heliconical twist-bend nematic (NTB) phase is a promising candidate for novel electro-optic and photonic applications. However, the phase generally exists at elevated temperatures and across a narrow temperature interval, limiting its implementation in device fabrication, which would ideally require the liquid crystal phase to be stable at room temperature. Here we report the formation of room-temperature NTB phases by in situ photopolymerization. A complete phase diagram of the liquid crystal and monomer mixtures is presented and the nature of the polymerized samples is discussed in detail. In contrast to samples before polymerization–where the NTB phases exist at elevated temperatures and across temperature intervals of width <10 °C–all photopolymerized NTB samples are found to be stable at room temperature and exist over a temperature interval of up to 80 °C. Scanning electron microscopy of the polymerized NTB phase shows that the polymer strands assemble at an angle with respect to the direction of the helical axis. This suggests that photopolymerized NTB phases could be used to facilitate the tilt angle measurements in the twist-bend nematic phase.