%0 Journal Article
%T A Twist-Bend Chiral Helix of 8nm Pitch in a Nematic Liquid Crystal of Achiral Molecular Dimers
%A Dong Chen
%A Jan H. Porada
%A Justin B. Hooper
%A Arthur Klittnick
%A Yongqiang Shen
%A Eva Korblova
%A Dmitry Bedrov
%A David M. Walba
%A Matthew A. Glaser
%A Joseph E. Maclennan
%A Noel A. Clark
%J Physics
%D 2013
%I arXiv
%R 10.1073/pnas.1314654110
%X Freeze Fracture Transmission Electron Microscopy (FFTEM) study of the nanoscale structure of the so-called "twist-bend" nematic (NX) phase of the cyanobiphenyl (CB) dimer molecule CB(CH2)7CB reveals a stripe texture of fluid layers periodically arrayed with a bulk spacing of d ~ 8.3 nm. Fluidity and a rigorously maintained spacing produce long-range-ordered fluid layered focal conic domains. Absence of a lamellar x-ray reflection at wavevector q ~ 2{\pi}/8 nm-1 or its harmonics in synchrotron-based scattering experiments indicates that this periodic structure is achieved with no detectable associated modulation of the electron density, and thus has nematic molecular ordering. A search for periodic ordering with d ~ 8nm in CB(CH2)7CB using atomistic molecular dynamic computer simulation yielded equilibration of a conical twist-bend helixed nematic ground state, of the sort first proposed by Meyer, and envisioned in systems of bent molecules by Dozov and Memmer, We identify {\theta} ~ 33 degree as the cone angle, and p ~ 8nm as the full pitch of the helix, the shortest ever found in a nematic fluid.
%U http://arxiv.org/abs/1306.5504v1