Nanoconfined heliconical structure of twist-bend nematic liquid crystal phase

ABSTRACT

We produced controlled heliconical structures of a twist-bend nematic (N_TB) liquid-crystal (LC) phase in nanoconfinement in a porous anodic aluminium oxide (AAO) film. The structural parameters of the N_TB phase such as conical angle and helical pitch can be modulated by varying the surface energy of the inner surface of the porous AAO film, done by using different self-assembled monolayers (SAMs). The LC molecules tend to be more freely packed, thus forming a larger conical angle, when placed on the tri-deca-fluoro-1,1,2,2-tetrahydrooctyl-trichlorosilane (FOTS)-treated substrate, which has a relatively low surface energy. In contrast, the molecules form a more tightly packed structure, and thus a smaller conical angle, when placed on the 2-(methoxy(polyethyleneoxy)-propyl)trimethoxysilane (PEG 6/9)-treated substrate, which has higher surface energy. This work improves our collective understanding of self-assembled heliconical structures in the N_TB phase.

Graphical Abstract

KEYWORDS:

• Twist bend nematic phase
• nano-structure control
• nanoconfinement
• surface treatment

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by a grant from the National Research Foundation (NRF) and funded by MSIT, Korea (2017R1E1A1A01072798 and 2017M3C1A3013923). Experiments at the PLS-II were supported in part by MSIT and POSTECH, Korea. It was also supported by the Materials Research Science and Engineering Center (MRSEC) program funded by NSF DMR-1420736, US.