The 2017 Luckhurst-Samulski Prize

As will become clear, this announcement of the Luckhurst-Samulski Prize winner for 2017 is different from earlier years. Rather than the Editor, Corrie Imrie, this year it is to be made by the Founding Editors of the international journal Liquid Crystals. The Journal first appeared in 1986 following a year of hard work and fun aided by staff from our Publishers, Taylor & Francis. Since then the Journal has established a strong reputation for its support of the liquid crystal community. A further example of such support came in 2008 when the Publishers, with the agreement of the Editor and the Editorial Board, decided to endow an Annual Prize for the best paper published in a given year in the Journal [1]. As Founding Editors we were surprised and honoured when we were asked by the Publishers if they could name the Prize after us; we were delighted to agree to this. Since then, whenever possible, one or other of us has endeavoured to be available to present the Prize to the authors of the winning paper. We have been really impressed by the quality and diversity of the papers which are both high, as can be seen from the list of the eight previous winners given in Table 1.

Table 1. Previous winners of the Luckhurst-Samulski Prize.

Year	Authors	Title	Reference
2009	Goodby JW, Saez IM, Cowling SJ, Gasowska JS, MacDonald RA, Sia S, Watson P, Toyne KJ, Hird M, Lewis RA, Lee S-E, Vaschenko V.	Molecular complexity and the control of self-organising processes.	[2]
2010	Jákli A.	Electro-mechanical effects in liquid crystals.	[3]
2011	Skarabot M, Lokar Z, Gabrijelcic K, Wilkes D, Musevic I.	Atomic force microscope based method of measuring short cholesteric pitch in liquid crystals.	[4]
2012	Picken SJ, Dingemans TJ, Madsen LA, Francescangeli O, Samulski ET.	Uniaxial to biaxial nematic phase transition in a bent-core thermotropic liquid crystal by polarising microscopy.	[5]
2013	Pieranski P, Yang B, Burtz LJ, Camu A, Simonetti F.	Generation of umbilics by magnets and flows.	[6]
2014	Takezoe H, Araoka, F.	Polar columnar liquid crystals	[7]
2015	Alshomrany A, Clark NA.	Fisheye lens conoscopy	[8]
2016	Dawood AA, Grossel MC, Luckhurst GR, Richardson RM, Timimi BA, Wells NJ, Yousif YZ.	On the twist-bend nematic phase formed directly from the isotropic phase	[9]

This year sees the award of the ninth Prize, the winners of which were decided by a well-tried and tested process. It is, however, an increasingly demanding process given the large number of papers published, which in 2017 was 230. The process starts with the referees who already play a major role in maintaining the standards for our Journal. In addition they are asked by the Editor if the paper would merit the award of the Luckhurst-Samulski Prize; this leads to the creation of an initial pool of interesting papers. The next stage comes at the end of the year when the Selection Committee, comprising the Editorial Board and Editor are made aware of the referees’ suggestions. They then add to this list from which a shortlist is constructed. Based on this process it was decided that the 2017 Luckhurst-Samulski Prize should certainly be awarded to Daniel Paterson, Jordan Abberley, William Harrison, John Storey and Corrie Imrie for their innovative paper titled Cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase [10]. For impartiality, the Editor, Corrie Imrie was not involved in the selection process; his role was assigned to the Founding Editors, Geoffrey Luckhurst and Ed Samulski, who were aided by Colin Bulpitt, from the Publishers.

In his Editorial for the 2016 Prize Corrie Imrie noted that the twist-bend nematic phase, (N_TB), was one of the hottest topics in liquid crystal science of recent years [11]. This novel phase had been associated with the theoretical predictions by Bob Meyer in 1976 [12] and Ivan Dozov in 2001[13]. Recent developments have maintained interest in this topic with simulations and experiments involving this unusual nematic phase formed from achiral, odd liquid crystal dimers. The winning paper describes a particularly important aspect namely the relationship between the formation of the currently accepted N_TB phase and the molecular structure and interactions. In their significant contribution to this major problem the Authors have enhanced the list of key liquid crystal dimers which have a common structure; that is the cyanobiphenyl group, linked through the spacer together with different groups, two methylene (CBnCB), one methylene and one ether (CBnOCB) and two ether (CBOnOCB). Armed with these coherent and related groups it proved possible to generate a wealth of data, in particular how the transitional properties of the odd dimers vary with the spacer length and the different links. There are some especially intriguing results that really demand attention not only from theoreticians but also experimentalists. For example, the significant difference in T_NI between say CBnCB and CBnOCB while the difference in the T_NTBN for these are quite similar. Their paper also demonstrates in a transparent manner the question of the role of molecular curvature in determining the bend elastic constant and associated with this the transition temperature T_NTBN and the way in which the molecules pack in the heliconical structure; as the Authors have noted the steric interactions are connected with this as indicated by the local intercalated structure of the phase. To gauge the important molecular curvature, use is made of quantum mechanical density functional theory to give the ground states of the dimers. This is of special interest not least because for the odd dimer, CB4OCB, the all-trans conformer has a less-curved shape compared with that of the ground state which contains a gauche link and so has a greater curvature (see Figure 1). The Authors have made an important contribution to the structure-property problem; they also understand that the challenge for theoreticians now is to recognise the roles of different conformers in calculations of the average molecular shapes and the transitional properties.

Figure 1. Representations for CB4OCB of (a) the all-trans structure and (b) the ground-state conformation with its gauche link (reproduced with permission from [10]).

The shortlist of papers considered for the 2017 Luckhurst-Samulski Prize also included three highly rated papers which we wish to note here; they are given in chronological order. The first of these is by Patrick Oswald and his colleagues with the title Lehmann rotation of twisted bipolar cholesteric droplets: role of Leslie, Akopyan and Zel’dovich thermomechanical coupling terms of nematodynamics [14].Their story starts in 1900 with the observation by Lehmann that when a thermal gradient is applied to cholesteric droplets their internal structure rotates. This has been associated with a thermomechanical effect related to a variety of models starting with Leslie, and a texture dependent torque by Akopyan and Zel’dovich which was modified by Pleiner and Brand. The new experiments involved a biphasic system of droplets dispersed in an isotropic phase; these have been found to rotate rapidly which suggests that the thermomechanical terms cannot explain the Lehmann rotation. Clearly more experiments with other systems are needed to help resolve this intriguing behaviour.

The second of the highly rated list is by John Goodby and has the enigmatic title Free volume, molecular grains, self-organisation, and anisotropic entropy [15]. The contents of this article are just as intriguing as its title since they are related to a diverse range of topics concerned with the twist-bend phase. It is understood that the transition temperature between the N and N_TB phases is related to the molecular curvature as reflected by the bend angle. Results for a large number of odd liquid crystal dimers support this result and show that to form an N_TB phase the bend angle should cover the narrow range from 110º to 130º. It is also reported that for such dimers T_NTBN is linear in T_NI which suggests that the chemical structure of the dimers is insignificant in the formation of the twist-bend phase. Another observation was that the director fluctuations in the N phase are quenched on entering the N_TB phase. This is indicative of the high viscosity of the phase and accounts for the lack of response to external electric fields. Clearly this paper merits careful attention

The final paper of this shortlist is by Jan Lagerwall and his colleagues; its title is Elucidating the fine details of cholesteric liquid crystal reflection patterns [16]. It describes an ingenious study, both experimental and theoretical, describing the creation of shells in which a cholesteric phase is surrounded by two inaccessible isotropic phases. These contain a drop at the centre of a cholesteric droplet which itself is surrounded by another isotropic aqueous fluid. Such shells can form close-packed systems which, when illuminated, produce a rich pattern of reflection spots having striking optical textures. These and their communication have been convincingly analysed with the aid of computer simulation. The Authors suggest that these systems of cholesteric shells have the exciting potential for applications in photonics, sensing and security-pattern generation.

As the Founding Editors of Liquid Crystals we wish to take this unique opportunity to thank all of those Authors who have supported the Journal so well since its foundation. We also want to recognise our Editorial Successors and the members of the Editorial Board for their continuing endeavours in improving the quality of the Journal as reflected by, amongst other things, its Impact Factor. Finally we must thank the Selection Committee for undertaking the challenging activity of selecting the winner of the 2017 Luckhurst-Samulski Prize; their next task will begin shortly.