Supramolecular organization of liquid-crystal dimers-bis-cyanobiphenyl alkanes on HOPG by scanning tunneling microscopy

Krzyzewska, Klaudyna; Jaroch, Tomasz; Maranda-Niedba?a, Agnieszka; Pociecha, Damian; Górecka, Ewa; Ahmed, Ziauddin; Welch, Chris; Mehl, Georg H.; Pro?, Adam; Nowakowski, Robert

Abstract

2D supramolecular organization of a series of six cyanobiphenyl bimesogens deposited on highly oriented pyrolytic graphite (HOPG) is studied by scanning tunneling microscopy (STM). The adsorbates
are 1,ω-bis(4-cyanobiphenyl-4’-yl)alkanes (CBnCB) with different length of their flexible alkyl spacer (containing 7 to 12 methylene groups). Microscopic investigations at the molecular resolution allow fordetailed analysis of the effect of the alkyl spacer length on the type and the extent of the resulting 2D
organization. It has been demonstrated that bimesogens with shorter spacers (7 and 8 methylene units)
organize in a similar manner characterized by the formation of two types of differently ordered monolayers: dense packed, wherein the molecules are oriented in one direction and ordered into parallel rows
(layer structure), or less densely packed wherein they are organized into a chiral windmill-like structure. For derivatives with longer spacers (ranging from 9 to 12 methylene units) additional effect of parity of carbon atoms in the spacer (even versus odd) is observed. In this range of the spacer length even membered bimesogens are still organized in a typical layer structure. However, odd-membered dimers exhibit a much complex 2D supramolecular organization with a larger unit cell and a helical arrangement of the molecules. Careful comparison of this structure with the 3D structural data derived from the X-ray diffraction investigations of single crystals indicates that for these bimesogens a clear correlation exists between the observed complex 2D supramolecular organization in the monolayer and the organization in one of the crystallographic planes of the 3D nematic twist-bent phase

Citation

Krzyzewska, K., Jaroch, T., Maranda-Niedbała, A., Pociecha, D., Górecka, E., Ahmed, Z., …Nowakowski, R. (2018). Supramolecular organization of liquid-crystal dimers-bis-cyanobiphenyl alkanes on HOPG by scanning tunneling microscopy. Nanoscale, 10(34), 16201-16210. https://doi.org/10.1039/c8nr02069h

• Journal Article Type: Article
• Acceptance Date: Aug 11, 2018
• Online Publication Date: Aug 13, 2018
• Publication Date: Sep 14, 2018
• Deposit Date: Sep 5, 2018
• Publicly Available Date: Aug 14, 2019
• Journal: Nanoscale
• Print ISSN: 2040-3364
• Electronic ISSN: 2040-3372
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 10
• Issue: 34
• Pages: 16201-16210
• DOI: https://doi.org/10.1039/c8nr02069h
• Keywords: General Materials Science; Liquid crystal; Nematic; Twist bend nematic; STM
• Public URL: https://hull-repository.worktribe.com/output/982391
• Publisher URL: http://pubs.rsc.org/en/Content/ArticleLanding/2018/NR/C8NR02069H
• Additional Information: : This document is Similarity Check deposited; : Supplementary Information; : Single-blind; : Received 12 March 2018; Accepted 11 August 2018; Accepted Manuscript published 13 August 2018