Fall, W.S. orcid.org/0000-0001-6778-1348, Yen, M.-H., Zeng, X. orcid.org/0000-0003-4896-8080 et al. (4 more authors) (2019) Molecular ejection transition in liquid crystal columns self-assembled from wedge-shaped minidendrons. Soft Matter, 15 (1). pp. 22-29. ISSN 1744-683X
Abstract
Fan-shaped molecules with aromatic head-groups and two or more flexible pendant chains often self-assemble into columns that form columnar liquid crystals by packing on a 2d lattice. Such dendrons or minidendrons are essential building blocks in a large number of synthetic self-assembled systems and organic device materials. Here we report a new type of phase transition that occurs between two hexagonal columnar phases, Colh1 and Colh2, of Na-salt of 3,4,5-tris-dodecyloxy benzoic acid. Interestingly, the transition does not change the symmetry, which is p6mm in both phases, but on heating it involves a quantised drop in the number of molecules n in the cross-section of a column. The drop is from 4 to 3.5, with a further continuous decrease toward n = 3 as temperature increases further above Tc. The finding is based on evidence from X-ray diffraction. Using a transfer matrix formulation for the interactions within a column, with small additional mean field terms, we describe quantitatively the observed changes in terms of intermolecular forces responsible for the formation of supramolecular columns. The driving force behind temperature-induced molecular ejection from the columns is the increase in conformational disorder and the consequent lateral expansion of the alkyl chains. The asymmetry of the transition is due to the local order between 4-molecule discs giving extra stability to purely n = 4 columns.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © The Royal Society of Chemistry 2018. This is an author produced version of a paper subsequently published in Soft Matter. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Materials Science and Engineering (Sheffield) The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield) |
Funding Information: | Funder Grant number LEVERHULME TRUST (THE) RPG-2012-804 ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL (EPSRC) EP/K034308/1 ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL (EPSRC) EP/P002250/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 29 Nov 2018 12:25 |
Last Modified: | 02 Nov 2021 14:32 |
Status: | Published |
Publisher: | Royal Society of Chemistry |
Refereed: | Yes |
Identification Number: | 10.1039/c8sm01851k |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:139364 |