Resonant Carbon K-Edge Soft X-Ray Scattering from Lattice-Free Heliconical Molecular Ordering: Soft Dilative Elasticity of the Twist-Bend Liquid Crystal Phase.
Resonant x-ray scattering shows that the bulk structure of the twist-bend liquid crystal phase, recently discovered in bent molecular dimers, has spatial periodicity without electron density modulation, indicating a lattice-free heliconical nematic precession of orientation that has helical glide symmetry. In situ study of the bulk helix texture of the dimer CB7CB shows an elastically confined temperature-dependent minimum helix pitch, but a remarkable elastic softness of pitch in response to dilative stresses. Scattering from the helix is not detectable in the higher temperature nematic phase.
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Chenhui
C
Zhu
Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0390, USA.
Michael R
MR
Tuchband
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Anthony
A
Young
Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0390, USA.
Min
M
Shuai
Department of Chemistry and Biochemistry and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0215, USA.
Alyssa
A
Scarbrough
Department of Chemistry and Biochemistry and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0215, USA.
David M
DM
Walba
Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0390, USA.
Joseph E
JE
Maclennan
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Cheng
C
Wang
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Alexander
A
Hexemer
Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0390, USA.
Noel A
NA
Clark