Study of the Flow-induced Structure and Anisotropy in Lyotropic Liquid Crystals for Hierarchical Composites PDF Download
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Category :
Languages : en
Pages : 44
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Author:
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ISBN:
Category :
Languages : en
Pages : 44
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Author: Qing Zhang (Mechanical engineer)
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The natural world is full of patterns that spontaneously emerge across length scales and material properties. Examples range from microscopic dendritic snowflakes to macroscopic sand ripples and intricate river networks. Central to the formation of patterns is the concept of an instability; complex forms spontaneously develop when a system is driven out of equilibrium. Nature leverages instabilities to 'fabricate' complex structures that maximize performance using minimal resources, exploiting the self-amplification of small perturbations. The potential to use instabilities in practical applications, for example to engineer or assemble structured materials, is barely exploited due to the notorious difficulty and limited available strategies to control the self-amplified and non-linear growth that characterizes instabilities. In this thesis, we focus on fluid instabilities due to the adaptivity of fluids to their environments, and establish novel strategies to tune the growth morphology of interfacial instabilities and flow-induced structures at different length scales. At the macroscale, we induce a morphology transition from the generic dense-branching growth characterized by repeated tip-splitting of the growing fingers to dendritic growth characterized by stable fingertips in the presence of anisotropy in the viscous-fingering instability. This instability arises when a less viscous fluid displaces a more viscous one in a confined environment. When the growth environment is rendered anisotropic by engraving a lattice of channels on a Hele-Shaw cell, we show that the morphology transition and the global symmetry of the dendrites can be controlled by tuning the viscosity ratio between the two fluids or the degree of anisotropy set by the lattice topography. We further exploit a material with shear-enhanced anisotropy where the anisotropy is intrinsic to the fluid, a lyotropic chromonic liquid crystal (LCLC) in the nematic phase. For high enough flow velocities, the tumbling behavior of LCLC solutions can be suppressed, which results in a flow-alignment of the material. This microscopic change in the director field macroscopically enhances the liquid crystal anisotropy to induce the transition from dense-branching to dendritic growth. Microscopically, we discover the emergence of flow-induced defects and structures in LCLC solutions. Pure-twist disclination loops form in a range of shear rates as a consequence of the low twist elastic constant of LCLC solutions. We demonstrate that the size of the pure-twist disclination loops is governed by the balance between nucleation and annihilation forces, which can be tuned by controlling the flow velocity. Strikingly, at lower shear rates, chiral periodic double-twist structures spontaneously emerge, even though the LCLC is achiral. We show that the mirror symmetry breaking is triggered at regions of biaxial-splay deformations that are unstable and evolve into the energetically cheaper double-twist elastic mode. Our results reveal a novel path to structural chirality in an achiral system. The control gained over the pattern morphology and structure formation from fluid instabilities can open pathways to harnessing unstable growth to design programmable microstructures in materials and to control assembly and flow of biological systems in microfluidic devices.
Author: Antônio M. Figueiredo Neto
Publisher: Oxford University Press, USA
ISBN: 0198525508
Category : Science
Languages : en
Pages : 317
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Book Description
This book presents a comprehensive review of structural properties and phase transition phenomena in lyotropic mixtures. It includes a wealth of experimental results, in addition to the main theoretical models and a number of technological applications, such as cosmetics, detergents and techniques of oil recovery. It is suitable for use as a pedagogical introduction to the subject.
Author: Heberth A. Diestra Cruz
Publisher:
ISBN:
Category : Anisotropy
Languages : en
Pages : 234
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Author: Glenn Halstead Brown
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 106
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Author: Nissim Garti
Publisher: John Wiley & Sons
ISBN: 9780470281758
Category : Science
Languages : en
Pages : 0
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This book will describe fundamentals and recent developments in the area of Self-Assembled Supramolecular Architecture and their relevance to the understanding of the functionality of membranes as delivery systems for active ingredients. As the heirarchial architectures determine their performance capabilities, attention will be paid to theoretical and design aspects related to the construction of lyotropic liquid crystals: mesophases such as lamellar, hexagonal, cubic, sponge phase micellosomes. The book will bring to the reader mechanistic aspects, compositional considerations, transition within phases, solubilization capacities, drug entrapment and release mechanisms and transmembrane, transdermal, and other transport phenomena. It will stress the importance of these mesostructures to crystallization and polymorphism of drugs, fats, and nutraceuticals and will discuss regioselectivity of organic and enzymatic reactions that take place at interfaces and within the channels of the mesophase. The book will bring studies on the use of these mesophase as crystallization or particulation media for the formation of nanoparticles and nanocrystals. Chapters will discuss applications in the areas of pharmaceuticals, food, cosmetics, plastics, paper, agro-chemistry and industrial applications.
Author: Igor Muševič
Publisher: Springer Science & Business Media
ISBN: 9783540207894
Category : Mathematics
Languages : en
Pages : 320
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Book Description
This book describes the state of the art of our understanding of liquid-crystal interfaces on a molecular level. The interactions of liquid crystal molecules with a surface play an essential role in the operation of liquid crystal displays (LCD's) and other LC devices that are based on the controllable anchoring of LC molecules on polymer coated surfaces. This book addresses the microscopic interaction between a macromolecule (liquid crystal, polymer) and a wall, using state of the art surface and interface-sensitive experimental techniques, such as Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (STM), Linear and Nonlinear Optical Microscopy and (Dynamic) Light Scattering (DLS). These experimental techniques were complemented with computer simulations and supra molecular chemistry methods to develop controllable polymeric surfaces.
Author: P. S. Pershan
Publisher: World Scientific
ISBN: 9789971507053
Category : Science
Languages : en
Pages : 450
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Book Description
Current understanding of different phases as well as the phase transitions between them has only been achieved following recent theoretical advances on the effects of dimensionality in statistical physics. P S Pershan explains the connection between these two separate areas and gives some examples of problems where the understanding is still not complete. The most important example is the second order phase transition between the nematic and smectic-A phase. Others include the relation between the several hexatic phases that have been observed and the first order restacking transitions between phases that were all previously identified as smectic-B, but which should more properly be identified as crystalline-B. Some relatively recent experimental developments on the discotic phase, liquid crystal surfaces and lyotropic phases are also included. The book includes 41 major reprints of some of the recent seminal work on the structure of liquid crystals. They are introduced by a brief review of the symmetries and other properties of liquid crystalline phases. In addition, there is a discussion of the differences between true liquid crystalline phases and others that were described as liquid crystalline in the early literature, but which have since been shown to be true three-dimensional crystals. The progression from the isotropic fluid, through the nematic, smectic, and various crystalline phases can be understood in terms of a systematic decrease in symmetry, together with an accompanying variation in structure is explained. A guide to the selected reprints and a sort of ?Rosetta Stone? for these various phases is provided. The goal of this book is to explain the systematics of this progression to students and others that are new to this field, as well as to provide a useful handbook for people already working in the field.
Author: George W. Gray
Publisher: John Wiley & Sons
ISBN: 3527613951
Category : Technology & Engineering
Languages : en
Pages : 522
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Book Description
This handbook is a unique compendium of knowledge on all aspects of the physics of liquid crystals. In over 500 pages it provides detailed information on the physical properties of liquid crystals as well as the recent theories and results on phase transitions, defects and textures of different types of liquid crystals. An in-depth understanding of the physical fundamentals is a prerequisite for everyone working in the field of liquid crystal research. With this book the experts as well as graduate students entering the field get all the information they need.
Author: David Neal Lewis
Publisher:
ISBN:
Category : Liquid crystals
Languages : en
Pages : 604
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Book Description
