Abstract
The twist-bend nematic liquid crystal phase is a three-dimensional fluid in which achiral bent molecules spontaneously form an orientationally ordered, macroscopically chiral, heliconical winding of a ten nanometer-scale pitch in the absence of positional ordering. Here, the structure of the twist-bend phase of the bent dimer CB7CB and its mixtures with 5CB is characterized, revealing a hidden invariance of the self-assembly of the twist-bend structure of CB7CB, such that over a wide range of concentrations and temperatures, the helix pitch and cone angle change as if the ground state for a pitch of the TB helix is an inextensible heliconical ribbon along the contour formed by following the local molecular long axis (the director). Remarkably, the distance along the length for a single turn of this helix is given by 2πRmol, where Rmol is the radius of bend curvature of a single all-trans CB7CB molecule. This relationship emerges from frustrated steric packing due to the bent molecular shape: space in the fluid that is hard to fill attracts the most flexible molecular subcomponents, a theme of nanosegregation that generates self-assembled, oligomer-like correlations of interlocking bent molecules in the form of a brickwork-like tiling of pairs of molecular strands into duplex double-helical chains. At higher temperatures in the twist-bend phase, the cone angle is small, the director contour is nearly along the helix axis z, and the duplex chains are sequences of biaxial elements formed by overlapping half-molecule pairs, with an approximately 45° rotation of the biaxis between each such element along the chain.
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MDPI and ACS Style
Tuchband, M.R.; Shuai, M.; Graber, K.A.; Chen, D.; Zhu, C.; Radzihovsky, L.; Klittnick, A.; Foley, L.; Scarbrough, A.; Porada, J.H.;
et al. Double-Helical Tiled Chain Structure of the Twist-Bend Liquid Crystal Phase in CB7CB. Crystals 2024, 14, 583.
https://0-doi-org.brum.beds.ac.uk/10.3390/cryst14070583
AMA Style
Tuchband MR, Shuai M, Graber KA, Chen D, Zhu C, Radzihovsky L, Klittnick A, Foley L, Scarbrough A, Porada JH,
et al. Double-Helical Tiled Chain Structure of the Twist-Bend Liquid Crystal Phase in CB7CB. Crystals. 2024; 14(7):583.
https://0-doi-org.brum.beds.ac.uk/10.3390/cryst14070583
Chicago/Turabian Style
Tuchband, Michael R., Min Shuai, Keri A. Graber, Dong Chen, Chenhui Zhu, Leo Radzihovsky, Arthur Klittnick, Lee Foley, Alyssa Scarbrough, Jan H. Porada,
and et al. 2024. "Double-Helical Tiled Chain Structure of the Twist-Bend Liquid Crystal Phase in CB7CB" Crystals 14, no. 7: 583.
https://0-doi-org.brum.beds.ac.uk/10.3390/cryst14070583
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