Distinct differences in the nanoscale behaviors of the twist-bend liquid crystal phase of a flexible linear trimer and homologous dimer

Michael R Tuchband; Daniel A Paterson; Mirosław Salamończyk; Victoria A Norman; Alyssa N Scarbrough; Ewan Forsyth; Edgardo Garcia; Cheng Wang; John M D Storey; David M Walba; Samuel Sprunt; Antal Jákli; Chenhui Zhu; Corrie T Imrie; Noel A Clark

doi:10.1073/pnas.1821372116

Distinct differences in the nanoscale behaviors of the twist-bend liquid crystal phase of a flexible linear trimer and homologous dimer

Proc Natl Acad Sci U S A. 2019 May 28;116(22):10698-10704. doi: 10.1073/pnas.1821372116. Epub 2019 May 14.

Authors

Michael R Tuchband¹, Daniel A Paterson², Mirosław Salamończyk^{3

4}, Victoria A Norman⁴, Alyssa N Scarbrough^{5

6}, Ewan Forsyth², Edgardo Garcia⁷, Cheng Wang⁴, John M D Storey², David M Walba^{5

6}, Samuel Sprunt³, Antal Jákli³, Chenhui Zhu⁸, Corrie T Imrie², Noel A Clark^{1

6}

Affiliations

¹ Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, CO 80309; michael.tuchband@colorado.edu chenhuizhu@lbl.gov noel.clark@colorado.edu.
² Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, AB24 3UE Aberdeen, United Kingdom.
³ Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH 44242.
⁴ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
⁵ Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, CO 80309.
⁶ Soft Materials Research Center, University of Colorado Boulder, Boulder, CO 80309.
⁷ Laboratório de Química Computacional, Instituto de Química, Universidade de Brasilia, CP 4478 Brasilia, Brasil.
⁸ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; michael.tuchband@colorado.edu chenhuizhu@lbl.gov noel.clark@colorado.edu.

Abstract

We synthesized the liquid crystal dimer and trimer members of a series of flexible linear oligomers and characterized their microscopic and nanoscopic properties using resonant soft X-ray scattering and a number of other experimental techniques. On the microscopic scale, the twist-bend phases of the dimer and trimer appear essentially identical. However, while the liquid crystal dimer exhibits a temperature-dependent variation of its twist-bend helical pitch varying from 100 to 170 Å on heating, the trimer exhibits an essentially temperature-independent pitch of 66 Å, significantly shorter than those reported for other twist-bend forming materials in the literature. We attribute this to a specific combination of intrinsic conformational bend of the trimer molecules and a sterically favorable intercalation of the trimers over a commensurate fraction (two-thirds) of the molecular length. We develop a geometric model of the twist-bend phase for these materials with the molecules arranging into helical chain structures, and we fully determine their respective geometric parameters.

Keywords: RSoXS; heliconical; liquid crystal; trimer; twist–bend nematic.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.