The 2020 Luckhurst-Samulski Prize

The Luckhurst-Samulski Prize was announced by the present Editor, Corrie Imrie [1], in 2009 when he explained that with the Publishers, Taylor & Francis, it had been decided to inaugurate a new Award named for the Founding Editors of the Journal [2]. Since that time the Prize and its Modus Operandi have been rapidly established. It is to be awarded for the best paper published in Liquid Crystals in a given year; the current list of such papers is shown in Table 1. Interestingly ‘best’ is to be decided each year by the Prize Selection Committee which is composed of the Editorial Board and the Editor. The referees of the papers appearing in the Journal are also involved in this process; they are asked to indicate if the paper they have reviewed and recommended for publication might be considered for the Prize. This list together with that suggested by members of the Editorial Board comprises the long list or pool of potential prize winners which is to be considered by the Selection Committee. They are then asked to nominate those papers which will form the short list which is then considered by a revised Selection Committee; in the sense that Board Members who are authors of the papers on the short list have been removed from it. In addition if the Editor has also authored a paper on this list then he will be replaced by one of the two Founding Editors who then chairs the activities of the Prize Selection Committee; not for the first time I now have this honour. I should also say that I have been aided in my task by Nigel Balmforth representing the Publishers.

Table 1. Previous winners of the Luckhurst-Samulski Prize and their authors

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 SE, Vaschenko V.	Molecular complexity and the control of self-organising processes.	[3]
2010	Jakli A.	Electro-mechanical effects in liquid crystals.	[4]
2011	Skarabot M, Lokar Z, Gabrijelcic K, Wilkes D, Musevic I.	Atomic force microscope based method of measuring short cholesteric pitch in liquid crystals.	[5]
2012	Picken SJ, Dingemans TJ, Madsen LA, Frascescangeli O, Samulski ET.	Uniaxial to biaxial nematic phase transition in a bent-core thermotropic liquid crystal by polarising microscopy.	[6]
2013	Pieranski P, Yang B, Burtz LJ, Camu A, Simonetti F.	Generation of umbilics by magnets and flow.	[7]
2014	Takezoe H, Araoka, F.	Polar columnar liquid crystals.	[8]
2015	Alshomrany A, Clark NA.	Fisheye lens conoscopy.	[9]
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.	[10]
2017	Paterson DA, Abberly JP, Harrison WT, Storey JM, Imrie CT.	Cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase.	[11]
2018	Tschierske C.	Mirror symmetry breaking in liquids and liquid crystals.	[12]
2019	Cruickshank E, Salamonczyk M, Pocieha D, Strachan GJ, Storey JMD, Wang C, Feng J, Zhu CH, Gorecka E, Imrie CT.	Sulfur-linked cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase.	[13]

After very careful consideration by this Committee I am particularly pleased to announce that from the short list of six quality papers that entitled Molecular structure and the twist-bend nematic phase: the role of the terminal chains [14] authored by J.P. Abberley, R. Walker, J.M.D Storey and C.T. Imrie has been awarded the Luckhurst-Samulski Prize for 2020. As the title of this paper hints, for conventional nematics the length of terminal chains can have a significant influence on the transitional properties of the nematogens. It is to be expected and found that analogous behaviour will and, indeed, has been found for twist-bend nematics. This paper certainly demonstrates this to be the case and the details are well worth reading. Here, a range of liquid crystals have been carefully designed and investigated. For example one such system is 1-(4-methoxybiphenyl-4ʹ-yl)-6-(4-alkylanilinebenzylidene-4ʹ-oxy)hexanes, denoted by MeOB6O.m, where MeO denotes a methoxy group attached to a biphenyl group, B, which is linked via a Schiff’s base group attached to which is an alkyl chain having a length m. For the shortest chain with a single methyl group the dimer has a nematic-isotropic transition and below this there is a transition to a twist-bend nematic. As the alkyl chain grows in length so the alternation in T_NI decreases in contrast that in T_NTBN which increases. The variation in the two nematic transitions with m is intriguing and will certainly stimulate some theoretical interest. For the final three values of m the mesogens form a smectic phase, although great care has been taken to ensure that these phases are not a twist-bend nematic.

I also wish to commend the other five shortlisted papers on the list, see Table 2, and will comment briefly on them here in the order that they occur on the list.

Table 2. Papers shortlisted for the 2020 Luckhurst-Samulski Prize and their authors selected from volume 47 of Liquid Crystals

Authors	Title	Pages
Kołacz J, Gotjen HG, Bekele RY, Myers JD, Frantz JA, Ziemkiewicz M, and Spillmann CM.	Propagating transverse electric and transverse magnetic modes in liquid crystal-clad planar waveguides.	531-539
Lehmann M, and Dechant M.	Click procedure of phthalocyanine star-shaped mesogens – the effect of size and spacer length.	1214-1222.
Pišljar J, Posnjak G, Pajk S, Godec A, Podlipec R, Kokot B, and Muševič I.	Comparison of STED, confocal and optical microscopy of ultra-short pitch cholesterics.	1303-1311.
Hiraoka K, Taira S, Hoshino Y, Ishihara T, Yamada K, and Oshima M.	Electric-field-induced deformation caused by electroclinic and flexoelectric effects in liquid crystalline elastomer with wedge-shaped mesogens derived from cholesterol.	1535-1545.
Dvinskikh SV.	Nuclear magnetic resonance studies of translational diffusion in thermotropic ionic liquid crystals.	1975-1985.

The first is entitled Propagating transverse electric and transverse magnetic modes in liquid crystal-clad planar waveguides, it is by J. Kołacz, H.G. Gotjen, R.Y. Bekele, J.D. Myers, J.A. Frantz, M. Ziemkiewicz and C.M. Spillmann. This is an intriguing paper describing the application of liquid crystals in a range of beam steering devices thus avoiding mechanical techniques. Here the approach employs a multicomponent nematic with T_NI of 87^°C and a birefringence, ∆n, of 0.234 and having the liquid crystal to clad a passive waveguide. The analysis of the steering magnitude of the waveguide was performed with a range of techniques. It was found that the effect of mode confinement involved the thickness of the waveguide. It seems that TE mode steering used the liquid crystal more efficiently because of the singular component of the electric field. However, the higher restriction of the mode results in reduced steering compared with the magnetic mode.

The next paper has the title Click procedure of phthalocyanine star-shaped mesogens – the effect of size and spacer length. by M. Lehmann and M. Dechant. This provides impressive syntheses of some complex molecules; one is based on a star-shape centred on a phthalocyanine core with four arms (1b). This molecule has significant space between its arms which is then filled with fullerenes attached to the star centre with alkyl chains (2b). However, the equimolar mixture of these two species is amorphous. In contrast and intriguingly the mixture of (1b) with the star (2a), prepared previously having a shorter spacer to the fullerenes, was found to form a columnar hexagonal phase via a click process.

The third paper is entitled Comparison of STED, confocal and optical microscopy of ultra-short pitch cholesterics; it is by J. Pišljar, G. Posnjak, S. Pajk, A. Godec, R. Podlipec, B. Kokot and I. Muševič. In general the use of standard optical polarisation microscopy in the investigation of liquid crystals to determine transition temperatures and the nature of the phase is well understood. In this paper we are introduced to a novel technique based on the introduction of synthetic fluorescent dyes into the sample with a STED (Stimulated Emission Depletion) microscope. It would seem that for a relatively thin sample (say 158nm) of a chiral nematic phase doped with fluorescent dye molecules the technique would be able to probe the structure of the phase.

The following paper is Electric-field deformation caused by electroclinic and flexoelectric effects in liquid crystalline elastomer with wedge-shaped mesogens derived from cholesterol. by K. Hiraoka, S. Taira, Y. Hoshino, T. Ishihara, K. Yamada and M. Oshima. The uniaxial version of the elastomer film has been studied in detail and with some interesting and curious results. As an example when an electric field is applied to the film the bending deformation induced resembles the motion of the flukes of a dolphin. Another intriguing feature is that as the sample temperature is increased the major orientational order parameter, S, decreases rapidly but not quite to zero suggesting that a pseudo-isotropic phase is formed.

The final paper on the short list is entitled Nuclear magnetic resonance studies of translation in thermotropic ionic liquid crystals and it is by S.V. Dvinskikh. The nuclear magnetic resonance technique has played and continues to play an important role in studying the orientational order of liquid crystal phases. Such applications continue to grow and include the translational diffusion tensor measured on the basis of the pulse field gradient methodology described in the paper. Some of this methodology as well as the wide range of applications are described here and include, in particular, thermotropic ionic liquid crystals where the director is aligned with the magnetic field of the spectrometer.

In conclusion I should like to thank the referees who helped by indicating those papers that might be considered for the Prize. I also wish to thank all members of the Prize Selection Committee for constructing the short list and then selecting the paper to receive the Luckhurst-Samulski Prize for 2020. For various reasons we have reached the selection of the paper to receive the Prize rather late in the year; indeed soon it will be necessary to start the hunt for the paper to be awarded the Luckhurst-Samulski Prize for the year 2021.We trust that you and your family will enjoy good health in the coming New Year.