报告内容摘要

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Liquid crystal dimers consist of molecules containing two mesogenic units linked by a flexible spacer and have been a rich source for the discovery of new types of mesophases.[1] Most recently, a nematic-nematic transition has been reported for odd-members of the α,ω-bis-4-(4’-cyanobiphenyl)alkanes.[2,3] Cestari et al. assigned the lower temperature nematic as a twist-bend nematic phase, Ntb.[2] This was later confirmed in studies based on freeze fracture transmission electron microscopy.[4,5] In the Ntb phase, the achiral molecules form a helix and the director is titled with respect to the helical axis. The induced twist may be either left or right handed and equal amounts of both types of helix are expected. The Ntb phase had previously been predicted to exist for bent molecules by Dozov [6] who suggested that in a nematic phase the director may bend around bent molecules To stabilize such a bend, either splay or twist must be introduced, resulting in two new nematics with nonuniform director distributions, splay-bend or twist-bend.

To date, the Ntb phase has been observed for just a handful of liquid crystal dimers (see, for example [2, 3, 7-12) and for one bent core mesogen [13]. Given this very limited data set, the development of the empirical relationships linking molecular structure to the observation of this exciting new phase is very much at an embryonic stage. Here we present a range of new liquid crystal dimers, including hydrogen bonded examples [14], which exhibit the Ntb phase and discuss structure-property relationships in materials exhibiting this fascinating new phase.

 

报告人简介

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Higher Education

1981-84         B.Sc.( Honours), class 1, in Chemistry, University of Southampton.

1984-88      Ph.D. (The Role of Molecular Flexibility in the Design of Low Molar Mass Liquid Crystals), University of Southampton

Work Experience

1987-89  Fellow of the Royal Commission for the Exhibition of 1851, University of Southampton

1989-91 AFOSR Research Fellow, Department of Polymer Science and Engineering, University of Massachusetts, Amherst, U.S.A. with Professor FE Karasz

1991-92  AFOSR Research Fellow, University of Southampton

1992-    have been at the University of Aberdeen where I am now a Professor of Chemistry. I served two terms as Head of School (2002-2010).

Professional Status

Currently Editor of the journal Liquid Crystals (2000-to date).

Elected Vice-Chair (2006/07), Chair (2007/09) and Vice-Chair (2009/10) of the British Liquid Crystal Society

Member of the Board of the International Liquid Crystal Society (2006-2012).

Serves on Editorial Boards for Liquid Crystal Reviews, Liquid Crystals Today.

Prizes

1993    British Liquid Crystal Society Young Scientist Prize (awarded for "outstanding contributions to liquid crystal science")

2011    British Liquid Crystal Society Cyril Hilsum Medal (awarded for “independent contributions to liquid crystal science and technology”)

2012    International Liquid Crystal Society LG Display Award (awarded for “for his outstanding and influential work in liquid crystal chemistry”)

Publications

136 publications on Web of Science, 4034 citations and an h-index of 37

 

Department of Chemistry, School of Natural and Computing Sciences,

University of Aberdeen, Aberdeen AB24 3UE, Scotland, UK

 

 

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