Pub Date : 2021-01-02DOI: 10.1080/1358314X.2021.1928969
Yuan Shen
K. Peddireddy, S. Copar, K. V. Le, I. Musevic, C. Bahr and V. S. R. Jampani, PNAS, 118(14) e2011174118, 2021 It is still a challenge to reproduce the shape diversity and controlled re-configurability of closed surfaces and filamentous structures, which are generally found in cellular colonies and living tissues. In this work, liquid crystal (LC) droplets are self-shaped into anisotropic and three-dimensional superstructures, including LC fibres, LC helices, and differently shaped LC vesicles by mixing two surfactants with an LC dispersed phase and an aqueous continuous phase. The authors tune the bulk LC elasticity and interfacial energy through thermal stimuli, thus transforming an emulsion of polydispersed, spherical nematic droplets into a number of uniform-diameter fibres with multiple branches. Furthermore, when the nematic LC is cooled to the smectic-A phase, the nematic fibres are broken into monodispersed microdroplets with a tunable diameter dictated by the cooling rate. The experimental findings are further supported by a theoretical model of equilibrium interface shapes. The shape transformation is induced by negative interfacial energy, which promotes a spontaneous increase of the interfacial area at a fixed LC volume. This method is successfully applied to many different LC materials and phases, demonstrating a universal mechanism for shape transformation in complex fluids.
{"title":"Research news","authors":"Yuan Shen","doi":"10.1080/1358314X.2021.1928969","DOIUrl":"https://doi.org/10.1080/1358314X.2021.1928969","url":null,"abstract":"K. Peddireddy, S. Copar, K. V. Le, I. Musevic, C. Bahr and V. S. R. Jampani, PNAS, 118(14) e2011174118, 2021 It is still a challenge to reproduce the shape diversity and controlled re-configurability of closed surfaces and filamentous structures, which are generally found in cellular colonies and living tissues. In this work, liquid crystal (LC) droplets are self-shaped into anisotropic and three-dimensional superstructures, including LC fibres, LC helices, and differently shaped LC vesicles by mixing two surfactants with an LC dispersed phase and an aqueous continuous phase. The authors tune the bulk LC elasticity and interfacial energy through thermal stimuli, thus transforming an emulsion of polydispersed, spherical nematic droplets into a number of uniform-diameter fibres with multiple branches. Furthermore, when the nematic LC is cooled to the smectic-A phase, the nematic fibres are broken into monodispersed microdroplets with a tunable diameter dictated by the cooling rate. The experimental findings are further supported by a theoretical model of equilibrium interface shapes. The shape transformation is induced by negative interfacial energy, which promotes a spontaneous increase of the interfacial area at a fixed LC volume. This method is successfully applied to many different LC materials and phases, demonstrating a universal mechanism for shape transformation in complex fluids.","PeriodicalId":18110,"journal":{"name":"Liquid Crystals Today","volume":"30 1","pages":"17 - 18"},"PeriodicalIF":3.1,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1358314X.2021.1928969","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49630646","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 : 2021-01-02DOI: 10.1080/1358314X.2021.1928967
I. Dierking
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Pub Date : 2021-01-02DOI: 10.1080/1358314X.2021.1928961
C. F. Dietrich
ABSTRACT There are two classes of liquid crystals (LCs): Thermotropic LCs where the organic molecule represents the anisotropically shaped mesogen and lyotropic LCs, where the mesogens are non-spherical supramolecular assemblies dispersed in a solvent. Various kinds of lyotropic nematic liquid crystals (LLCs) exist, differing in shape and composition of the aggregates: Chromonic, polymeric or micellar LLCs.However, micellar LLCs are the most ubiquitous kind of LLCs, occurring in soaps and biological systems. Although these nematic lyotropics are so different, they exhibit – contrary to thermotropic nematics – spontaneous reflection symmetry breaking under confinement. We discuss spontaneous mirror symmetry breaking under capillary confinement for a standard micellar ND phase and give a detailed director field structure of the twisted polar configuration. Furthermore, we measure for the first time a complete set of viscoelastic properties of a micellar nematic LLC, finding a small twist elastic constant K 22, which is at least one order of magnitude smaller than K 11 and K 33. As demonstrated by the following work, a small K 22 and therefore spontaneous mirror symmetry breaking under confinement is rather the rule than the exception in lyotropic nematics and constitutes a unique difference between lyotropic and typical thermotropic nematics, for which the well-known one-constant approximation holds. Abbreviations: LC: Liquid Crystal; LLC: Lyotropic liquid crystal; TER: twisted escaped radial director configuration; TP: twisted polar director configuration; : director; K 11: splay elastic constant of the nematic phase; K 22: twist elastic constant of the nematic phase; K 33: bend elastic constant of the nematic phase; s: strength of a defect/disclination; ER: escaped radial director configuration; CDEAB: N,N-ethylhexadecylammonium bromide; DOH: decan-1-ol; ND: nematic phase of disk-shaped building blocks; NC: nematic phase of rod-shaped building blocks; H-field: magnetic field; PR: planar radial director configuration; PP: planar polar director configuration; RR: right handed – right handed; LL: left handed – left handed; RL: right handed – left handed; LR: left handed – right handed.
液晶有两类:热致液晶，其中有机分子代表各向异性形状的介元;溶致液晶，其中介元是分散在溶剂中的非球形超分子组合。目前存在着各种向列相液晶(LLCs)，其聚集体的形状和组成各不相同:共色液晶、聚合液晶或胶束液晶。然而，胶束llc是最普遍的llc类型，出现在肥皂和生物系统中。虽然这些向列溶热带是如此不同，但它们在约束下表现出——与热向列相反——自发反射对称破缺。讨论了标准胶束ND相在毛细约束下的自发镜像对称性破断，给出了扭曲极性构型的详细指示场结构。此外，我们首次测量了胶束向列LLC的一整套粘弹性特性，发现了一个小的扭转弹性常数k22，它比k11和k33至少小一个数量级。正如下面的工作所证明的那样，在约束下，一个小的k22和自发的镜像对称破缺在溶向向线中是规律而不是例外，并且构成了溶向线和典型的热向线之间的独特区别，众所周知的一常数近似适用于此。缩写词:LC:液晶;LLC:溶致液晶;TER:扭曲逃逸径向导向器构型;TP:双极性定向器配置;:导演;k11:向列相的伸展弹性常数;k22:向列相扭转弹性常数;k33:向列相弯曲弹性常数;S:缺陷/缺陷的强度;ER:逃逸径向导向器构型;CDEAB: N,N-乙基十六烷基溴化铵;嗨:decan-1-ol;ND:盘状积木的向列相;NC:棒状积木的向列相;h场:磁场;PR:平面径向定向器构型;PP:平面极向仪配置;RR: right handed—右手的;今天李华学了两个常用语:left handed——左手的;RL:右手-左手;左右手-右右手。
{"title":"Lyotropic nematic liquid crystals: interplay between a small twist elastic constant and chirality effects under confined geometries","authors":"C. F. Dietrich","doi":"10.1080/1358314X.2021.1928961","DOIUrl":"https://doi.org/10.1080/1358314X.2021.1928961","url":null,"abstract":"ABSTRACT There are two classes of liquid crystals (LCs): Thermotropic LCs where the organic molecule represents the anisotropically shaped mesogen and lyotropic LCs, where the mesogens are non-spherical supramolecular assemblies dispersed in a solvent. Various kinds of lyotropic nematic liquid crystals (LLCs) exist, differing in shape and composition of the aggregates: Chromonic, polymeric or micellar LLCs.However, micellar LLCs are the most ubiquitous kind of LLCs, occurring in soaps and biological systems. Although these nematic lyotropics are so different, they exhibit – contrary to thermotropic nematics – spontaneous reflection symmetry breaking under confinement. We discuss spontaneous mirror symmetry breaking under capillary confinement for a standard micellar ND phase and give a detailed director field structure of the twisted polar configuration. Furthermore, we measure for the first time a complete set of viscoelastic properties of a micellar nematic LLC, finding a small twist elastic constant K 22, which is at least one order of magnitude smaller than K 11 and K 33. As demonstrated by the following work, a small K 22 and therefore spontaneous mirror symmetry breaking under confinement is rather the rule than the exception in lyotropic nematics and constitutes a unique difference between lyotropic and typical thermotropic nematics, for which the well-known one-constant approximation holds. Abbreviations: LC: Liquid Crystal; LLC: Lyotropic liquid crystal; TER: twisted escaped radial director configuration; TP: twisted polar director configuration; : director; K 11: splay elastic constant of the nematic phase; K 22: twist elastic constant of the nematic phase; K 33: bend elastic constant of the nematic phase; s: strength of a defect/disclination; ER: escaped radial director configuration; CDEAB: N,N-ethylhexadecylammonium bromide; DOH: decan-1-ol; ND: nematic phase of disk-shaped building blocks; NC: nematic phase of rod-shaped building blocks; H-field: magnetic field; PR: planar radial director configuration; PP: planar polar director configuration; RR: right handed – right handed; LL: left handed – left handed; RL: right handed – left handed; LR: left handed – right handed.","PeriodicalId":18110,"journal":{"name":"Liquid Crystals Today","volume":"30 1","pages":"2 - 14"},"PeriodicalIF":3.1,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1358314X.2021.1928961","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45971327","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 : 2020-10-01DOI: 10.1080/1358314X.2021.1886781
C. Rosenblatt
{"title":"Conference report on the 2nd international online conference on crystals 10 – 20 november 2020","authors":"C. Rosenblatt","doi":"10.1080/1358314X.2021.1886781","DOIUrl":"https://doi.org/10.1080/1358314X.2021.1886781","url":null,"abstract":"","PeriodicalId":18110,"journal":{"name":"Liquid Crystals Today","volume":"29 1","pages":"84 - 84"},"PeriodicalIF":3.1,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1358314X.2021.1886781","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42639974","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 : 2020-10-01DOI: 10.1080/1358314X.2020.1886779
D. Dardas, I. Dierking
{"title":"Obituary professor Wojciech Kuczyński (1941-2020)","authors":"D. Dardas, I. Dierking","doi":"10.1080/1358314X.2020.1886779","DOIUrl":"https://doi.org/10.1080/1358314X.2020.1886779","url":null,"abstract":"","PeriodicalId":18110,"journal":{"name":"Liquid Crystals Today","volume":"29 1","pages":"60 - 64"},"PeriodicalIF":3.1,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1358314X.2020.1886779","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46357379","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 : 2020-10-01DOI: 10.1080/1358314X.2020.1886780
I. Nys
ABSTRACT Combining liquid crystals (LCs) with well-designed anchoring patterns at the substrates offers tremendous potential for the development of functional electro-optic devices or stimuli-responsive actuators. Photo-alignment techniques nowadays allow an almost arbitrary control over the surface anchoring and this flexibility is used to design highly efficient flat optical LC components with different functionalities. Part of this research, dealing with nematic and chiral nematic LC between substrates with patterned azimuthal anchoring, is reviewed here. The focus is on understanding the self-assembly of complex structures, steered by an interplay between surface anchoring and LC elasticity. Additional insight into the LC bulk behaviour is obtained by comparing experimental results with numerical simulations of the director configuration. Periodic anchoring patterns with azimuthal rotation at the top and bottom substrate are studied, as well as ring-shaped alignment patterns with a 180° or 360° azimuthal rotation in a confined region in space. Different combinations of anchoring patterns at the top and bottom substrates are investigated and in addition to nematic liquid crystal (NLC), also short and long-pitch chiral nematic liquid crystal (CLC) is considered.
{"title":"Patterned surface alignment to create complex three-dimensional nematic and chiral nematic liquid crystal structures","authors":"I. Nys","doi":"10.1080/1358314X.2020.1886780","DOIUrl":"https://doi.org/10.1080/1358314X.2020.1886780","url":null,"abstract":"ABSTRACT Combining liquid crystals (LCs) with well-designed anchoring patterns at the substrates offers tremendous potential for the development of functional electro-optic devices or stimuli-responsive actuators. Photo-alignment techniques nowadays allow an almost arbitrary control over the surface anchoring and this flexibility is used to design highly efficient flat optical LC components with different functionalities. Part of this research, dealing with nematic and chiral nematic LC between substrates with patterned azimuthal anchoring, is reviewed here. The focus is on understanding the self-assembly of complex structures, steered by an interplay between surface anchoring and LC elasticity. Additional insight into the LC bulk behaviour is obtained by comparing experimental results with numerical simulations of the director configuration. Periodic anchoring patterns with azimuthal rotation at the top and bottom substrate are studied, as well as ring-shaped alignment patterns with a 180° or 360° azimuthal rotation in a confined region in space. Different combinations of anchoring patterns at the top and bottom substrates are investigated and in addition to nematic liquid crystal (NLC), also short and long-pitch chiral nematic liquid crystal (CLC) is considered.","PeriodicalId":18110,"journal":{"name":"Liquid Crystals Today","volume":"29 1","pages":"65 - 83"},"PeriodicalIF":3.1,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1358314X.2020.1886780","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41888421","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}
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