Liquid Crystals

New Perspectives

Inbunden, Engelska, 2021

Av Pawel Pieranski, Maria Helena Godinho, Pawel Pieranski, Maria Helena Godinho

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This book on liquid crystals reports on the new perspectives that have been brought about by the recent expansion of frontiers and overhaul of common beliefs.First, it explores the interaction of light with mesophases, when the light or matter is endowed with topological defects. It goes on to show how electrophoresis, electro-osmosis and the swimming of flagellated bacteria are affected by the anisotropic properties of liquid crystals.It also reports on the recent progress in the understanding of thermomechanical and thermohydrodynamical effects in cholesterics and deformed nematics and refutes the common belief that these effects could explain Lehmann’s observations of the rotation of cholesteric droplets subjected to a temperature gradient. It then studies the physics of the dowser texture, which has remarkable properties. This is of particular interest in regards to nematic monopoles, which can easily be generated, set into motion and collided within it.Finally, this book deals with the spontaneous emergence of chirality in nematics made of achiral molecules, and provides a brief historical context of chirality

Produktinformation

Utgivningsdatum2021-11-19
Mått10 x 10 x 10 mm
Vikt454 g
FormatInbunden
SpråkEngelska
Antal sidor368
FörlagISTE Ltd
ISBN9781789450408

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Fysik inom Naturvetenskap och teknik

Pawel Pieranski works at Laboratoire de Physique des Solides in Orsay, France. He has published a two-volume textbook on liquid crystals, written in collaboration with Patrick Oswald, and has conducted extensive research in many different areas of the field of liquid crystals.Maria Helena Godinho is Associate Professor at NOVA University Lisbon, Portugal. Between 2016 and 2020 she was Vice President of the International Liquid Crystal Society. In 2019 she was awarded the “Fréedericksz Medal” by the Russian Liquid Crystal Society.

Preface xiChapter 1. Singular Optics of Liquid Crystal Defects 1Etienne BRASSELET1.1. Prelude from carrots 11.2. Liquid crystals, optics and defects: a long-standing trilogy 11.3. Polarization optics of liquid crystals: basic ingredients 31.3.1. The few liquid crystal phases at play in this chapter 31.3.2. Liquid crystals anisotropy and its main optical consequence 31.3.3. Polarization state representation in the paraxial regime 51.3.4. Polarization state evolution through uniform director fields 61.3.5. Effective birefringence 81.3.6. Polarization state evolution through twisted director fields 91.4. Liquid crystal reorientation under external fields 151.5. Customary optics from liquid crystal defects 161.5.1. Localized defects structures in frustrated cholesteric films 171.5.2. Elongated defects structures in frustrated cholesteric films 201.5.3. Regular optics from other topological structures 241.5.4. Assembling photonic building blocks with liquid crystal defects 311.6. From regular to singular optics 341.6.1. What is singular optics? 341.6.2. A nod to liquid crystal defects 371.6.3. Singular paraxial light beams 381.6.4. Generic singular beam shaping strategies 411.7. Advent of self-engineered singular optical elements enabled by liquid crystals defects 441.7.1. Optical vortices from a cholesteric slab: dynamic phase option 441.7.2. Optical vortices from a nematic droplet: geometric phase option 451.8. Singular optical functions based on defects: a decade of advances 471.8.1. Custom-made singular dynamic phase diffractive optics 471.8.2. Spontaneous singular geometric phase optics 471.8.3. Directed self-engineered geometric phase optics 521.8.4. From single to arrays of optical vortices 581.9. Emerging optical functionalities enabled by liquid crystal defects 581.9.1. Spectrally and spatially adaptive optical vortex coronagraphy 591.9.2. Multispectral management of optical orbital angular momentum 671.10. Conclusion 691.11. References 70Chapter 2. Control of Micro-Particles with Liquid Crystals 81Chenhui PENG and Oleg D. LAVRENTOVICH2.1. Introduction 812.2. Control of micro-particles by liquid crystal-enabled electrokinetics 822.2.1. Liquid-crystal enabled electrophoresis 852.2.2. Liquid crystal-enabled electro-osmosis 912.3. Controlled dynamics of microswimmers in nematic liquid crystals 962.4. Conclusion 1042.5. Acknowledgments 1072.6. References 107Chapter 3. Thermomechanical Effects in Liquid Crystals 117Patrick OSWALD, Alain DEQUIDT and Guilhem POY3.1. Introduction 1173.2. The Ericksen–Leslie equations 1213.2.1. Conservation equations 1213.2.2. Molecular field 1233.2.3. Constitutive equations 1253.3. Molecular dynamics simulations of the thermomechanical effect 1303.3.1. Molecular models 1303.3.2. Constrained ensembles 1313.3.3. Computation of the transport coefficients 1333.3.4. Analysis of the results 1343.4. Experimental evidence of the thermomechanical effect 1353.4.1. The static Éber and Jánossy experiment 1363.4.2. Another static experiment proposed in the literature 1403.4.3. Continuous rotation of translationally invariant configurations 1423.4.4. Drift of cholesteric fingers under homeotropic anchoring 1653.5. The thermohydrodynamical effect 1743.5.1. A proposal for measuring the TH Leslie coefficient μ: theoretical prediction 1753.5.2. About the measurement of the TH Akopyan and Zel’dovich coefficients 1783.6. Conclusions and perspectives 1843.7. References 185Chapter 4. Physics of the Dowser Texture 193Pawel PIERANSKI and Maria Helena GODINHO4.1. Introduction 1934.1.1. Disclinations and monopoles 1934.1.2. Road to the dowser texture 1974.1.3. The dowser texture 2014.2. Generation of the dowser texture 2074.2.1. Setups called “Dowsons Colliders” 2074.2.2. “Classical” generation of the dowser texture 2084.2.3. Accelerated generation of the dowser texture using the DDC2 setup 2084.3. Flow-assisted homeotropic ⇒ dowser transition 2104.3.1. Experiment using the DDC2 setup 2104.3.2. Flow-assisted bowser-dowser transformation in capillaries 2124.3.3. Flow-assisted homeotropic-dowser transition in the CDC2 setup 2134.3.4. Theory of the flow-assisted homeotropic-dowser transition 2144.3.5. Summary and discussion of experimental results 2164.4. Rheotropism 2174.4.1. The first evidence of the rheotropism 2174.4.2. Synchronous winding of the dowser field 2194.4.3. Asynchronous winding of the dowser field 2254.4.4. Hybrid winding of the dowser field with CDC2 2284.4.5. Rheotropic behavior of π- and 2π-walls 2284.4.6. Action of an alternating Poiseuille flow on wound up dowser fields 2314.5. Cuneitropism, solitary 2π-walls 2334.5.1. Generation of π-walls by a magnetic field 2334.5.2. Generation and relaxation of circular 2π-walls 2364.5.3. Cuneitropic origin of the circular 2π-wall 2364.6. Electrotropism 2394.6.1. Definition of the electrotropism 2394.6.2. Flexo-electric polarization 2414.6.3. Setup 2414.6.4. The first evidence of the flexo-electric polarization 2424.6.5. Measurements of the flexo-electric polarization 2434.7. Electro-osmosis 2464.7.1. One-gap system of electrodes 2464.7.2. Two-gap system of electrodes 2504.7.3. Convection of the dowser field 2524.8. Dowser texture as a natural universe of nematic monopoles 2534.8.1. Structures and topological charges of nematic monopoles 2534.8.2. Pair of dowsons d+ and d- seen as a pair of monopoles 2554.8.3. Generation of monopole–antimonopole pairs by breaking 2π-walls 2574.9. Motions of dowsons in a wound up dowser field 2624.9.1. Single dowson in a wound up dowser field 2624.9.2. The Lorentz-like force 2634.9.3. Velocity of dowsons in wound up dowser fields 2664.9.4. The race of dowsons 2664.9.5. Trajectories of dowsons observed in natural light 2704.9.6. Trajectories of dowsons observed in polarized light 2724.10. Collisions of dowsons 2794.10.1. Pair of dowsons (d+,d-) inserted in a wound up dowser field 2804.10.2. Cross-section for annihilation of dowsons’ pairs 2824.10.3. Rheotropic control of the collisions outcome 2834.11. Motions of dowsons in homogeneous fields 2854.12. Stabilization of dowsons systems by inhomogeneous fields with defects 2874.12.1. Gedanken experiment 2874.12.2. Triplet of dowsons stabilized in MBBA by a quadrupolar electric field 2894.12.3. Septet of dowsons in MBBA stabilized by a quadrupolar electric field` 2904.12.4. Dowsons d+ stabilized by corner singularities of the electric field 2904.13. Dowser field submitted to boundary conditions with more complex geometries and topologies 2914.13.1. Ground state of the dowser field in an annular droplet 2914.13.2. Wound up metastable states of the dowser field in the annular droplet 2934.13.3. Dowser field in a square network of channels, four-arm junctions 2934.13.4. Triangular network, six-arm junctions 2944.13.5. Three-arm junctions 2964.13.6. General discussion of n-arm junctions 2964.14. Flow-induced bowson-dowson transformation 2984.15. Instability of the dowson’s d- position in the stagnation point 3014.16. Appendix 1: equation of motion of the dowser field 3034.16.1. Elastic torque 3034.16.2. Viscous torques 3044.16.3. Magnetic torque 3064.16.4. Electric torque 3064.17. References 306Chapter 5. Spontaneous Emergence of Chirality 311Mohan SRINIVASARAO5.1. Introduction 3115.2. Chirality: a historical tour 3125.2.1. Chirality and optics 3165.2.2. Chiral symmetry breaking and its misuse 3225.2.3. Spontaneous emergence of chirality or chiral structures in liquid crystals 3235.2.4. Spontaneous emergence of chirality due to confinement 3265.2.5. Spontaneous emergence of chirality due to cylindrical confinement 3295.2.6. Some misconceptions about optical rotation 3395.3. Concluding remarks 3415.4. Acknowledgments 3425.5. References 342List of Authors 347Index 349