Ordered droplet structures at the liquid crystal surface and elastic-capillary colloidal interactions.
TL;DR: In this article, a variety of ordered structures, including hexagonal structures and chains, formed by colloidal particles (droplets) at the free surface of a nematic liquid crystal (LC).
Abstract: We demonstrate a variety of ordered patterns, including hexagonal structures and chains, formed by colloidal particles (droplets) at the free surface of a nematic liquid crystal (LC). The surface placement introduces a new type of particle interaction as compared to particles entirely in the LC bulk. Namely, director deformations caused by the particles lead to distortions of the interface and thus to capillary attraction. The elastic-capillary coupling is strong enough to remain relevant even at the micron-scale when its buoyancy-capillary counterpart becomes irrelevant.
Citations
More filters
TL;DR: In this article, a review examines physico-chemical requirements necessary to achieve stimuli-responsiveness in heterogeneous polymer networks as well as discusses recent developments and future trends while individual structural components of polymeric networks are responsible for localized chainresponsiveness, desirable spatial and energetic network properties are necessary for collective and orchestrated responsiveness to external or internal stimuli.
866 citations
TL;DR: It is shown that colloidal particles confined to a few-micrometer-thick layer of a nematic liquid crystal form two-dimensional crystal structures that are bound by topological defects.
Abstract: The ability to generate regular spatial arrangements of particles is an important technological and fundamental aspect of colloidal science We showed that colloidal particles confined to a few-micrometer-thick layer of a nematic liquid crystal form two-dimensional crystal structures that are bound by topological defects Two basic crystalline structures were observed, depending on the ordering of the liquid crystal around the particle Colloids inducing quadrupolar order crystallize into weakly bound two-dimensional ordered structure, where the particle interaction is mediated by the sharing of localized topological defects Colloids inducing dipolar order are strongly bound into antiferroelectric-like two-dimensional crystallites of dipolar colloidal chains Self-assembly by topological defects could be applied to other systems with similar symmetry
699 citations
TL;DR: A review of liquid crystal nanoscience can be found in this article, where a short overview of current research efforts in liquid crystal nano-nanoscience is given, including the synthesis of nanomaterials using LCs as templates, the design of liquid crystals (LCs) and self-assembly of LCs, defect formation in LC-nanoparticle suspensions and potential applications.
Abstract: Revolutionary developments in the fabrication of nanosized particles have created enormous expectations in the last few years for the use of such materials in areas such as medical diagnostics and drug-delivery, and in high-tech devices. By its very nature, nanotechnology is of immense academic and industrial interest as it involves the creation and exploitation of materials with structural features in between those of atoms and bulk materials, with at least one dimension limited to between 1 and 100 nm. Most importantly, the properties of materials with nanometric dimensions are, in most instances, significantly different from those of atoms or bulk materials. Research efforts geared towards new synthetic procedures for shape and size-uniform nanoscale building blocks as well as efficient self-assembly protocols for manipulation of these building blocks into functional materials has created enormous excitement in the field of liquid crystal research. Liquid crystals (LCs) by their very nature are suitable candidates for matrix-guided synthesis and self-assembly of nanoscale materials, since the liquid crystalline state combines order and mobility at the molecular (nanoscale) level. Based on selected relevant examples, this review attempts to give a short overview of current research efforts in LC-nanoscience. The areas addressed in this review include the synthesis of nanomaterials using LCs as templates, the design of LC nanomaterials, self-assembly of nanomaterials using LC phases, defect formation in LC-nanoparticle suspensions, and potential applications. Despite the seeming diversity of these research topics, this review will make an effort to establish logical links between these different research areas.
333 citations
TL;DR: In this article, the free energy of nematic liquid crystal colloids is discussed and the numerical finite difference relaxation technique is explained as an efficient tool for the minimisation of the energy.
Abstract: Phenomenological Landau–de Gennes modelling based on the free energy of nematic liquid crystal colloids is reviewed. Nematic phase, gradient of order, and surface anchoring contributions to the total free energy are used. The numerical finite difference relaxation technique is explained as an efficient tool for the minimisation of the free energy. Effects of the mesh and mesh allocation are discussed. Various conceptually different colloidal structures are calculated to show the universality of the model. Single particles, dipolar–quadrupolar dimers, entangled dimers, dimers bound by escaped hyperbolic rings, and hierarchically patterned Saturn-ring colloidal superstructures are presented.
246 citations
TL;DR: Qualitative and quantitative aspects of the effective interactions between micrometer-sized colloids of different types trapped at fluid interfaces are discussed, with a particular emphasis on the relation between experimental and theoretical results.
Abstract: We discuss qualitative and quantitative aspects of the effective interactions between micrometer-sized colloids of different types trapped at fluid interfaces, with a particular emphasis on the relation between experimental and theoretical results. For colloids of that size, the interactions can broadly be classified into "direct" ones such as electrostatic, magnetic, or elastic ones. Such interactions appear also for colloids in bulk systems, but they are modified at interfaces. On the other hand, the presence of a fluid interface generates in addition interface-mediated (capillary) interactions which are either induced by nonspherical colloid shapes or by the "direct" interactions.
230 citations
References
More filters
TL;DR: Small water droplets dispersed in a nematic liquid crystal exhibit a novel class of colloidal interactions, arising from the orientational elastic energy of the anisotropic host fluid, which can lead to novel mechanisms for colloid stabilization.
Abstract: Small water droplets dispersed in a nematic liquid crystal exhibit a novel class of colloidal interactions, arising from the orientational elastic energy of the anisotropic host fluid. These interactions include a short-range repulsion and a long-range dipolar attraction, and they lead to the formation of anisotropic chainlike structures by the colloidal particles. The repulsive interaction can lead to novel mechanisms for colloid stabilization.
1,032 citations
Book•
25 Apr 2013
TL;DR: This book discusses Condensed Matter, The Chemical Bond, Particle Interactions, and Polymers: Structural Properties, which describes how particles interact with each other to form molecules that have different properties.
Abstract: CHAPTER 1 Condensed Matter: General Characters, The Chemical Bond, Particle Interactions. / CHAPTER 2 Atomic and Molecular Arrangements. / CHAPTER 3 The Order Parameter: Amplitude and Phase. / CHAPTER 4 Phase Transitions. / CHAPTER 5 Elasticity of Mesomorphic Phases. / CHAPTER 6 Dynamics of Isotropic and Anisotropic Fluids. / CHAPTER 7 Fractals and Growth Phenomena. / CHAPTER 8 Dislocations in Solids. Plastic Relaxation. / CHAPTER 9 Dislocations in Smectic and Columnar Phases. / CHAPTER 10 Curvature Defects in Smectics and Columnar Phases. / CHAPTER 11 Disclinations and Topological Point Defects. Fluid Relaxation. / CHAPTER 12 Topological Theory of Defects. / CHAPTER 13 Surface Phenomena. / CHAPTER 14 Stability of Colloidal Systems. / CHAPTER 15 Polymers: Structural Properties.
693 citations
TL;DR: This article is devoted to an overview, comparison and discussion of recent results (both theoretical and experimental) about lateral capillary forces, when the contact of particles or other bodies with a fluid phase boundary causes perturbations in the interfacial shape.
655 citations
TL;DR: A mechanism for attraction which is based on nonuniform wetting causing an irregular shape of the particle meniscus is proposed, including the cluster dissolution caused by addition of detergent to the subphase and the formation of linear aggregates.
Abstract: Recent observations of charged colloidal particles trapped at the air-water interface revealed long-range interparticle attractive forces, not accounted for by the standard theories of colloidal interactions. We propose a mechanism for attraction which is based on nonuniform wetting causing an irregular shape of the particle meniscus. The excess water surface area created by these distortions can be minimized when two adjacent particles assume an optimum relative orientation and distance. Typically, for spheres with diameter of 1 mm at an interparticle distance of 2 mm, deviations from the ideal contact line by as little as 50 nm result in an interaction energy of the order of 10(4)kT. Roughness-induced capillarity explains the experimental findings, including the cluster dissolution caused by addition of detergent to the subphase and the formation of linear aggregates. This kind of interaction should also be of importance in particle-stabilized foams and emulsions.
428 citations
TL;DR: It is reported that a binary mixture consisting of an isotropic fluid and a liquid crystal forming the continuous phase does not fully separate into two phases, but self-organizes into highly ordered arrays of monodisperse colloidal droplet chains.
Abstract: Some binary mixtures exist as a single phase at high temperatures and as two phases at lower temperatures; rapid cooling therefore induces phase separation that proceeds through the initial formation of small particles and subsequent growth and coarsening. In solid and liquid media, this process leads to growing particles with a range of sizes, which eventually separate to form a macroscopically distinct phase. Such behaviour is of particular interest in systems composed of an isotropic fluid and a liquid crystal, where the random distribution of liquid-crystal droplets in an isotropic polymer matrix may give rise to interesting electro-optical properties. Here we report that a binary mixture consisting of an isotropic fluid and a liquid crystal forming the continuous phase does not fully separate into two phases, but self-organizes into highly ordered arrays of monodisperse colloidal droplet chains. We find that the size and spatial organization of the droplets are controlled by the orientational elasticity of the liquid-crystal phase and the defects caused by droplets exceeding a critical size. We expect that our approach to forming monodisperse, spatially ordered droplets in liquid crystals will allow the controlled design of ordered composites that may have useful rheological and optical properties.
404 citations