Pub Date : 2020-01-02DOI: 10.1080/1358314X.2020.1771841
R. Walker
ABSTRACT This article will review some of our recent work concerning the relationships between molecular structure and the observation of the fascinating twist-bend nematic, NTB, phase. From a chemist’s perspective, understanding the molecular features influencing the formation and stabilisation of the NTB phase is of paramount importance, and allows for the design of new materials that have targeted properties. As such, recent work in Aberdeen has had the primary aim of enhancing our current understanding of these relationships in dimeric liquid crystals, through the synthesis and characterisation of a diverse range of materials, including a selection of supramolecular liquid crystals. A second aim has been to explore the intriguing question as to how the NTB phase, having spontaneous structural chirality, would respond at a microscopic level to the presence of intrinsic molecular chirality – the inclusion of chiral fragments in the dimers – and to obtain examples of the ‘chiral’ twist-bend nematic phase (N*TB) for comparative study alongside the conventional NTB phase. We also show that bent achiral molecules form heliconical smectic phases, as predicted by Dozov in his seminal 2001 work.
{"title":"The twist-bend phases: structure–property relationships, chirality and hydrogen-bonding","authors":"R. Walker","doi":"10.1080/1358314X.2020.1771841","DOIUrl":"https://doi.org/10.1080/1358314X.2020.1771841","url":null,"abstract":"ABSTRACT This article will review some of our recent work concerning the relationships between molecular structure and the observation of the fascinating twist-bend nematic, NTB, phase. From a chemist’s perspective, understanding the molecular features influencing the formation and stabilisation of the NTB phase is of paramount importance, and allows for the design of new materials that have targeted properties. As such, recent work in Aberdeen has had the primary aim of enhancing our current understanding of these relationships in dimeric liquid crystals, through the synthesis and characterisation of a diverse range of materials, including a selection of supramolecular liquid crystals. A second aim has been to explore the intriguing question as to how the NTB phase, having spontaneous structural chirality, would respond at a microscopic level to the presence of intrinsic molecular chirality – the inclusion of chiral fragments in the dimers – and to obtain examples of the ‘chiral’ twist-bend nematic phase (N*TB) for comparative study alongside the conventional NTB phase. We also show that bent achiral molecules form heliconical smectic phases, as predicted by Dozov in his seminal 2001 work.","PeriodicalId":18110,"journal":{"name":"Liquid Crystals Today","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1358314X.2020.1771841","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44085269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-02DOI: 10.1080/1358314X.2020.1726065
J. Lydon
ABSTRACT There is a strategic difference between the process of cell division by mitosis in animal cells and that in cells of higher plants. One particularly puzzling feature is the absence of centrioles in plant cells, when they appear to be of central importance in the control of the process in animal cells. It is argued that in both cases the dividing cell uses the versatility of the liquid crystalline state of the mitotic cytoplasm created by the wide-scale assembly of microtubules prior to mitosis. It is not the centrioles per se which are vital – it is the director field of the mesophase which is crucial – and alternative procedures have been developed by plants and animals to create this. In both cases, they can be related to known spontaneous alignment states of liquid crystalline systems.
{"title":"A liquid crystal model for mitotic cell division - and the enigma of centriole involvement in mitosis in animals but not plants","authors":"J. Lydon","doi":"10.1080/1358314X.2020.1726065","DOIUrl":"https://doi.org/10.1080/1358314X.2020.1726065","url":null,"abstract":"ABSTRACT There is a strategic difference between the process of cell division by mitosis in animal cells and that in cells of higher plants. One particularly puzzling feature is the absence of centrioles in plant cells, when they appear to be of central importance in the control of the process in animal cells. It is argued that in both cases the dividing cell uses the versatility of the liquid crystalline state of the mitotic cytoplasm created by the wide-scale assembly of microtubules prior to mitosis. It is not the centrioles per se which are vital – it is the director field of the mesophase which is crucial – and alternative procedures have been developed by plants and animals to create this. In both cases, they can be related to known spontaneous alignment states of liquid crystalline systems.","PeriodicalId":18110,"journal":{"name":"Liquid Crystals Today","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2019-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1358314X.2020.1726065","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42948757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-02DOI: 10.1080/1358314X.2020.1726068
A. Draude
Nematic liquid crystals have complex rheological properties compared to isotropic liquids, and achieving precise flows can be difficult experimentally. In this paper, Čopar et al. demonstrate transitions a discontinuous transition from homeotropic to planar director orientation in a microfluidic channel with homeotropic boundaries as the flow rate is increased. Furthermore, they demonstrate the existence of a topologically protected intermediate state, which is chiral despite the chosen system (5CB) being achiral. The authors go on to show that small amounts of chiral dopant can break the symmetry of the system and only one handedness is observed in the intermediate state. Laser tweezers which give rise to localised heating are also employed to manipulate the flow states. It is proposed that such phenomena could be exploited technology in optical shutters, in which the state is carefully tuned by the flow rate and/or laser heating.
{"title":"Research news","authors":"A. Draude","doi":"10.1080/1358314X.2020.1726068","DOIUrl":"https://doi.org/10.1080/1358314X.2020.1726068","url":null,"abstract":"Nematic liquid crystals have complex rheological properties compared to isotropic liquids, and achieving precise flows can be difficult experimentally. In this paper, Čopar et al. demonstrate transitions a discontinuous transition from homeotropic to planar director orientation in a microfluidic channel with homeotropic boundaries as the flow rate is increased. Furthermore, they demonstrate the existence of a topologically protected intermediate state, which is chiral despite the chosen system (5CB) being achiral. The authors go on to show that small amounts of chiral dopant can break the symmetry of the system and only one handedness is observed in the intermediate state. Laser tweezers which give rise to localised heating are also employed to manipulate the flow states. It is proposed that such phenomena could be exploited technology in optical shutters, in which the state is carefully tuned by the flow rate and/or laser heating.","PeriodicalId":18110,"journal":{"name":"Liquid Crystals Today","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2019-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1358314X.2020.1726068","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44480030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-03DOI: 10.1080/1358314X.2019.1681113
Thomas Machon
ABSTRACT We review some our results concerning the topology of knotted and linked defects in nematic liquid crystals. We discuss the global topological classification of nematic textures with defects, showing how knotted and linked defect lines have a finite number of ‘internal states’, counted by the Alexander polynomial of the knot or link. We then give interpretations of these states in terms of umbilic lines, which we also introduce, as well as planar textures. We show how Milnor polynomials can be used to give explicit constructions of these textures. Finally, we discuss some open problems raised by this work.
{"title":"The topology of knots and links in nematics","authors":"Thomas Machon","doi":"10.1080/1358314X.2019.1681113","DOIUrl":"https://doi.org/10.1080/1358314X.2019.1681113","url":null,"abstract":"ABSTRACT We review some our results concerning the topology of knotted and linked defects in nematic liquid crystals. We discuss the global topological classification of nematic textures with defects, showing how knotted and linked defect lines have a finite number of ‘internal states’, counted by the Alexander polynomial of the knot or link. We then give interpretations of these states in terms of umbilic lines, which we also introduce, as well as planar textures. We show how Milnor polynomials can be used to give explicit constructions of these textures. Finally, we discuss some open problems raised by this work.","PeriodicalId":18110,"journal":{"name":"Liquid Crystals Today","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2019-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1358314X.2019.1681113","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43211407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-03DOI: 10.1080/1358314X.2019.1693094
A. Eremin
The 15th European Conference on Liquid Crystals took place in a lovely town of Wrocław from June 30 till 5 July 2019 (Figure 1). This traditional Conference dates back to 1991 and serves as a forum for the dissemination of ideas in the interdisciplinary field of liquid crystals and soft anisotropic materials. This year, the Conference was chaired by Professor Marzena Tykarska from the Military University of Technology with professor Wiktor Piecek and professor Przemysław Kula as co-chairmen. It was a very successful Meeting, indeed. More than two hundred participants from 31 countries attended and contributed to the program with their presentations, lectures and posters (Figure 2). With five plenary talks and fifteen invited talks, the program was most engaging. It covered a broad spectrum of interdisciplinary areas from the synthesis of liquid crystals to optical and photonic properties and applications in industry, biology, and medicine. The first day followed by the Opening ceremony, Małgosia Kaczmarek from the University of Southampton started the first session delivering a talk on smart, hybrid liquid crystal devices. A very inspiring report explored emerging device technologies for nanoelectromechanical systems with liquid crystals. Application of semiconductors and photo-switchable liquid crystals opens the door to great opportunities to design multifunctional hybrid devices such as self-activated modulators as demonstrated in the presentation. The first session continued on physical properties, including elasto-caloric effect in LC elastomers, complex dynamics in the electro-convection in Hall 1. In the lecture Hall 2, the optical properties of liquid crystals were discussed. In particular, starting with the report on novel optical properties of LC/polymer films (Timothy Bunning), the session continued with the reports on the photo-induced anchoring transitions in cholesteric microdroplets (Sergey Shvetsov). The second session started with an inspiring talk by Victor Reshetnyak on tuning Tamm plasmons using cholesteric liquid crystals electro-optical and flexoelectricoptical effects, fast-response electro-plasmonics and complex re-orientation of the LC during photoalignment. Among the highlights of the evening session, were the presentations by Evaggelia Zavvou on the dielectric properties relationships in the nematic phases of cyano-biphenyl dimers, a talk by Nándor Éber on light-tunable gratings based on flexoelectric effect and a presentation by Alessandro Pianelli ‘Visualization and characterisation of the switching process in dye-doped dual-frequency nematic mixtures’. In the evening many participants attended two interesting tutorial lectures delivered by experienced scientists. The first tutorial presented by Mikhail Osipov was devoted to the molecular theory of liquid crystal ordering in rod-coil diblock copolymers. The next tutorial presented by Slobodan Žumer was about the topological soft matter, which leads from confined and c
{"title":"15th European liquid crystal conference 2019 in Wrocław","authors":"A. Eremin","doi":"10.1080/1358314X.2019.1693094","DOIUrl":"https://doi.org/10.1080/1358314X.2019.1693094","url":null,"abstract":"The 15th European Conference on Liquid Crystals took place in a lovely town of Wrocław from June 30 till 5 July 2019 (Figure 1). This traditional Conference dates back to 1991 and serves as a forum for the dissemination of ideas in the interdisciplinary field of liquid crystals and soft anisotropic materials. This year, the Conference was chaired by Professor Marzena Tykarska from the Military University of Technology with professor Wiktor Piecek and professor Przemysław Kula as co-chairmen. It was a very successful Meeting, indeed. More than two hundred participants from 31 countries attended and contributed to the program with their presentations, lectures and posters (Figure 2). With five plenary talks and fifteen invited talks, the program was most engaging. It covered a broad spectrum of interdisciplinary areas from the synthesis of liquid crystals to optical and photonic properties and applications in industry, biology, and medicine. The first day followed by the Opening ceremony, Małgosia Kaczmarek from the University of Southampton started the first session delivering a talk on smart, hybrid liquid crystal devices. A very inspiring report explored emerging device technologies for nanoelectromechanical systems with liquid crystals. Application of semiconductors and photo-switchable liquid crystals opens the door to great opportunities to design multifunctional hybrid devices such as self-activated modulators as demonstrated in the presentation. The first session continued on physical properties, including elasto-caloric effect in LC elastomers, complex dynamics in the electro-convection in Hall 1. In the lecture Hall 2, the optical properties of liquid crystals were discussed. In particular, starting with the report on novel optical properties of LC/polymer films (Timothy Bunning), the session continued with the reports on the photo-induced anchoring transitions in cholesteric microdroplets (Sergey Shvetsov). The second session started with an inspiring talk by Victor Reshetnyak on tuning Tamm plasmons using cholesteric liquid crystals electro-optical and flexoelectricoptical effects, fast-response electro-plasmonics and complex re-orientation of the LC during photoalignment. Among the highlights of the evening session, were the presentations by Evaggelia Zavvou on the dielectric properties relationships in the nematic phases of cyano-biphenyl dimers, a talk by Nándor Éber on light-tunable gratings based on flexoelectric effect and a presentation by Alessandro Pianelli ‘Visualization and characterisation of the switching process in dye-doped dual-frequency nematic mixtures’. In the evening many participants attended two interesting tutorial lectures delivered by experienced scientists. The first tutorial presented by Mikhail Osipov was devoted to the molecular theory of liquid crystal ordering in rod-coil diblock copolymers. The next tutorial presented by Slobodan Žumer was about the topological soft matter, which leads from confined and c","PeriodicalId":18110,"journal":{"name":"Liquid Crystals Today","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2019-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1358314X.2019.1693094","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43097739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-03DOI: 10.1080/1358314X.2019.1693104
M. Nagaraj
Pattern formation in out-of-equilibrium systems is diverse. Examining the nature of hydrodynamic patterns in active nematics has been a topic of interest for the past couple of years. Sokolov et al. investigate the dynamics of circularly aligned swimming bacteria. They show that in an active matter system the interplay of activity, elasticity and geometry leads to a wellcontrolled pattern formation and finer control of dynamic structures and transport phenomena. They report the emergence of bend stripes, an activityinduced undulations of the liquid crystal director field, in areas of high local curvature. Parameters such as velocity, relaxation rate and vorticity are compared for two experimental geometries; a pendant drop attached to a glass slide and in a thin free-standing film suspended between filaments. Hydrodynamic simulations are used to explain the origin of bend stripes. The effect of adding an extensile active stress on the hydrodynamic flows and its implications on the time evolution of the director field and the local curvature are compared. The instability patterns are seen to introduce a strong anisotropy to the angular distribution of emerging topological defects.
{"title":"Research news","authors":"M. Nagaraj","doi":"10.1080/1358314X.2019.1693104","DOIUrl":"https://doi.org/10.1080/1358314X.2019.1693104","url":null,"abstract":"Pattern formation in out-of-equilibrium systems is diverse. Examining the nature of hydrodynamic patterns in active nematics has been a topic of interest for the past couple of years. Sokolov et al. investigate the dynamics of circularly aligned swimming bacteria. They show that in an active matter system the interplay of activity, elasticity and geometry leads to a wellcontrolled pattern formation and finer control of dynamic structures and transport phenomena. They report the emergence of bend stripes, an activityinduced undulations of the liquid crystal director field, in areas of high local curvature. Parameters such as velocity, relaxation rate and vorticity are compared for two experimental geometries; a pendant drop attached to a glass slide and in a thin free-standing film suspended between filaments. Hydrodynamic simulations are used to explain the origin of bend stripes. The effect of adding an extensile active stress on the hydrodynamic flows and its implications on the time evolution of the director field and the local curvature are compared. The instability patterns are seen to introduce a strong anisotropy to the angular distribution of emerging topological defects.","PeriodicalId":18110,"journal":{"name":"Liquid Crystals Today","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2019-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1358314X.2019.1693104","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47222707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：