From understanding structures in antiferro-ferri and ferroelelectric liquid crystals to an unusual electro-optic effect in a bent-core nematic; a celebration of innovative materials

ABSTRACT

The field of liquid crystals is truly multidisciplinary with numerous examples of virtuous circles of interaction between chemistry, physics, theory and engineering resulting in breakthroughs in both fundamental understanding and novel applications. This paper, written to mark John Goodby’s 65th birthday, offers a personal perspective of the synergy between chemistry and physics from a collaboration that has spanned three decades. The first part of the paper reviews some of the physics insights that resulted from chiral liquid crystals fundamental to understanding structures in ferroelectric, ferrielectric and antiferroelectric systems. The second part of the paper describes some of the remarkable consequences of the anomalous elasticity and flexoelectricity found in the nematic phases of bent-core materials. In particular, we present unusual bowing of disclination lines in the nematic phase of a bent-core material in the presence of a field. Finally, the paper summarises some future prospects relating for bent-core materials. The paper by no means captures the amazing breadth of contribution that John’s chemistry has made to the subject, but aims to exemplify how his generous collaborative approach coupled with innovative chemistry and physical insight has led to paradigm changes in our subject.     

Atomistic simulations of the tensile strength of a disclinated bicrystalline nanofilm

The tensile strength of a metallic bicrystalline nanofilm containing a wedge disclination in the middle of a grain boundary (GB) terminating at the film surfaces was studied via atomistic simulations. The results show that an increase in the disclination power strengthens the film, which is contrary to intuition, if a crack initiates at one end of the terminated GB, whereas it weakens the film if a crack initiates at the disclination core. Both the strengthening and weakening demonstrate a size effect for film thickness in the range 10–20 nm, and are also significantly influenced by the GB misorientation. It is further shown that the strength can be increased to ～80% of the theoretical strength of a defect-free film by introducing a disclination of moderate power in the GB.     

二代树状碳硅烷液晶研究I.端基含36个丁氧基偶氮苯介晶基元

用发散法合成周边含36个丁氧基偶氮苯介晶基元（M5）端基新的二代树状碳硅 烷液晶（D_2），并用元素分析，氢谱，激光质谱，红外，紫外，偏光显微镜，DSC和WAXD法表 征D2为向列相，与M5相同，二代树状物相态由介晶基定．D2液晶态相行为是 K85N107I103N69K，其熔点比M5降低27-41℃，清亮点比M5降低17-18宽10-23℃．二 代碳硅烷（D2）与一代碳硅烷（D1）相比熔点增加2-3℃，清亮点降低26-29℃，液 晶态温区减少℃．在二代树状物中观察到S＝＋3／2的高强向错．     

Textures and disclinations in the cholesteric liquid‐crystalline phase of a cyanoethyl chitosan solution

Disclinations in the fingerprint‐like cholesteric texture of a natural polymer derivative, cyanoethyl chitosan, were observed and studied by both polarizing optical microscopy and scanning electron microscopy. In the latter technique, permanganic etching was developed for this cholesteric texture to increase the contrast. A special mechanism for cholesteric phase etching is suggested and discussed. Some χ, λ, and τ disclinations and domain walls were observed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 980–986, 2000     

Elastic behaviour of a wedge disclination dipole near a sharp crack emanating from a semi-elliptical blunt crack

The interaction between a wedge disclination dipole and a crack emanating from a semi-elliptic hole is investigated. Utilising the complex variable method, the closed form solutions are derived for complex potentials and stress fields. The stress intensity factor at the tip of the crack and the image force acting on the disclination dipole center are also calculated. The influence of the morphology of the blunt crack and the position of the disclination dipole on the shielding effect to the crack and the image force is examined in detail. The results indicate that the shielding or anti-shielding effect to the stress intensity factor increases when the wedge disclination dipole approaches the tip of the crack. The effects of the morphology of the blunt crack on the stress intensity factor of the crack and the image force are very significant.     

一代碳硅烷树枝状大分子钯配合物的液晶性

合成了新的周边含12个4-硝基偶氮苯端基一代碳硅烷树枝状大分子的钯(II)配合物(G1Pd), 并用元素分析、核磁共振氢谱、碳谱、红外、紫外-可见光谱、能量色散X射线分析(EDXRA)、偏光显微镜、差示扫描量热法和广角X射线衍射法对其结构和液晶性质进行了表征. 配合物G1Pd的相行为是K122ch189I166ch90K. 给出一种具有新的结构特点的液晶性树枝状大分子, 它兼有配位金属和介晶基元. 在液晶和液晶高分子界观察到首例胆甾相的高强向错和首例树枝状大分子配合物的高强向错现象.     

非对称塑性力学的物理理论

实验观察到塑性变形中的旋转现象。这种塑性旋转是由旋错,位错的特殊排列和微观结构上缺陷滑动所产生的非均匀性,本文基于塑性旋转的微观机制,建立了缺陷(位错和旋错)运动所满足的守恒方程。基于非对称连续介质力学理论,导出了缺陷运动所满足的扩散方程。利用塑性功的最大耗散过程和尺度不变性,推出了Cosserat塑性力学中的各种模型。     

缺陷连续统理论及其在本构方程研究中的应用 Ⅰ.一般概述,运动学和变形几何学

缺陷连续统理论即缺陷场论是当代固体力学的一个重要分支,其主要任务是对物质的弹性和非弹性性质的宏、微观研究之间架起一座桥梁。它也被认为是由固体力学、近代物理和数学之间交互作用而发展起来的一门交缘学科。本文分三部分较系统地介绍了它的主要发展和最近结果。第Ⅰ部分讨论具有位错和旋错连续统的运动学和变形几何学,包括Nye,Kondo,Bilby和Krner等人的早期结果以及我们利用4维物质流形上Cartan结构方程推导出的非线性动力学方程的最近结果。第Ⅱ部分详细介绍了缺陷连续统的规范场理论,主要强调对该连续统动力学方程的发展。第Ⅲ部分研究缺陷场论对构造弹塑性物质本构关系的应用。      

On the wedge dispiration in an inhomogeneous isotropic nonlinear elastic solid

In this short note we find the stress field of a wedge dispiration (a combination of a screw dislocation and a wedge dislocation along the same line) in an inhomogeneous incompressible isotropic nonlinear solid. We discuss the effect of the radial inhomogeneity of energy function on both the stress field and the energy per unit length of the dispiration and compare with those in an isotropic linear elastic solid.     

Lithium-an impurity of interest in radiation effects of silicon

The introduction and annealing of defects produced in lithium-diffused float-zone n-type silicon by 30-MeV electrons and fission neutrons are studied. The introduction rate of recombination centers produced by electron irradiation is dependent on lithium concentration and for neutron irradiation is independent of lithium concentration. The introduction rate of Si-B1 centers also depends on the lithium concentration. The annealing of electron- and neutron-produced recombination centers, Si-B1, and Si-G7 centers in lithium-diffused silicon occurs at much lower temperatures than in nondiffused material.