Colloidal particles act in many ways like surfactant molecules, particularly if adsorbed to a fluid–fluid interface. Just as the water or oil-liking tendency of a surfactant is quantified in terms of the hydrophile–lipophile balance (HLB) number, so can that of a spherical particle be described in terms of its wettability via contact angle. Important differences exist, however, between the two types of surface-active material, due in part to the fact that particles are strongly held at interfaces. This review attempts to correlate the behaviour observed in systems containing either particles or surfactant molecules in the areas of adsorption to interfaces, partitioning between phases and solid-stabilised emulsions and foams.

Particles as surfactants—similarities and differences

We present an approach to fabricate solid capsules with precise control of size, permeability, mechanical strength, and compatibility. The capsules are fabricated by the self-assembly of colloidal particles onto the interface of emulsion droplets. After the particles are locked together to form elastic shells, the emulsion droplets are transferred to a fresh continuous-phase fluid that is the same as that inside the droplets. The resultant structures, which we call "colloidosomes," are hollow, elastic shells whose permeability and elasticity can be precisely controlled. The generality and robustness of these structures and their potential for cellular immunoisolation are demonstrated by the use of a variety of solvents, particles, and contents.

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Colloidosomes: Selectively Permeable Capsules Composed of Colloidal Particles

Blue phases are types of liquid crystal phases that appear in a temperature range between a chiral nematic phase and an isotropic liquid phase. Because blue phases have a three-dimensional cubic structure with lattice periods of several hundred nanometres, they exhibit selective Bragg reflections in the range of visible light corresponding to the cubic lattice. From the viewpoint of applications, although blue phases are of interest for fast light modulators or tunable photonic crystals, the very narrow temperature range, usually less than a few kelvin, within which blue phases exist has always been a problem. Here we show the stabilization of blue phases over a temperature range of more than 60 K including room temperature (260–326 K). Furthermore, we demonstrate an electro-optical switching with a response time of the order of 10−4 s for the stabilized blue phases at room temperature.

Polymer-stabilized liquid crystal blue phases

Janus particles: synthesis, self-assembly, physical properties, and applications.

Just as nanoparticles display properties that differ from those of bulk samples of the same material, ensembles of nanoparticles can have collective properties that are different to those displayed by individual nanoparticles and bulk samples. Self-assembly has emerged as a powerful technique for controlling the structure and properties of ensembles of inorganic nanoparticles. Here we review different strategies for nanoparticle self-assembly, the properties of self-assembled structures of nanoparticles, and potential applications of such structures. Many of these properties and possible applications rely on our ability to control the interactions between the electronic, magnetic and optical properties of the individual nanoparticles. Self-assembly is a powerful technique for controlling the structure and properties of ensembles of inorganic nanoparticles. This article reviews the properties and potential applications of self-assembled structures made from nanoparticles.

Properties and emerging applications of self-assembled structures made from inorganic nanoparticles

Polystyrene spheres (2450 \AA{} in diameter) are trapped in a surface energy well at water/air interface. Because of asymmetry of charge distribution, electrical dipoles are associated with each interfacial particle. The dipole-dipole repulsive interactions organize the polystyrene spheres into a two-dimensional triangular lattice. The direct microscopic observations of such an interfacial colloidal crystal are reported for the first time.

Two-Dimensional Interfacial Colloidal Crystals

Foreword Preface to the English edition Nematic and Cholesteric Liquid Crystals PART A: OVERVIEW Some History Georges Friedel and Liquid Crystals The Discovery of Birefringence in Fluid Biological Substances by Buffon, Virchow, and Mettenheimer: Lyotropic Liquid Crystals Observation of the Surprising Behavior of Cholesteryl Esters by Planer and Reinitzer: Thermotropic Liquid Crystals Fliessende Kristalle or "The Flowing Crystals" of Otto Lehmann Modern Classification of Liquid Crystals The Terminology Introduced by Georges Friedel Modern Definition of Mesophases Broken Symmetries Short- and Long-Distance Order Classification of Smectic Phases Classification of Columnar Phases Chiral Smectic Phases Mesogenic anatomy Thermotropic Liquid Crystals Lyotropic Liquid Crystals Liquid Crystal Diblock Copolymers Colloidal Liquid Crystals PART B: MESOPHASES WITH AN ORIENTATIONAL ORDER Structure and Dielectric Properties of the Nematic Phase Quadrupolar Order Parameter The Uniaxial Nematic-Isotropic Liquid Phase Transition The Uniaxial Nematic-Biaxial Nematic Phase Transition Low-Frequency Dielectric Properties Optical Properties Nematoelasticity: Frederiks Transition and Light Scattering Grupp Experiment Frank-Oseen Free Energy Free Energy Minimization: Molecular Field and Elastic Torques Interpretation of the Grupp Experiment Magnetic Field Action Action of an Electric Field: Displays Elastic Light Scattering and the Determination of the Frank Constants Nonlinear Optics Appendix 1: Calculating the Scattering Cross-Section Appendix 2: Free Energy Expression in the Fourier Space Nematodynamics and Flow Instabilities Preliminary Observations Illustrating Some Fundamental Differences Between a Nematic and an Ordinary Liquid Equations of the Linear Nematodynamics Laminary Couette and Poiseuille Flows Laminary Flows and Their Stability Convective Instabilities of Electrohydrodynamic Origin Thermal Instabilities Appendix 1: "Derivation Under the Integral" Theorem Appendix 2: Rotational Identity Appendix 3: Calculation of the Irreversible Entropy Production Appendix 4: Energy Dissipation and Constitutive Laws in the Formalism of Leslie-Ericksen-Parodi Appendix 5: The Rayleigh-Benard Instability in Isotropic Fluids Defects and Textures in Nematics Polarizing Microscope Observations The Volterra-de Gennes-Friedel process Energy of a Wedge Planar Line in Isotropic Elasticity Continuous Core Model: Landau-Ginzburg-de Gennes Free Energy Interaction Energy Between Two Parallel Wedge Lines Dynamics of a Planar Wedge Line: Calculating the Friction Force Wedge line Stability: Escape in the Third Dimension Bloch and Ising Walls Induced by the Frederiks Instability Anchoring and Anchoring Transitions of Nematics on Solid Surfaces Precursors On the Notion of Interface Interface Symmetry and Classification of the Different Types of Anchoring Wetting and Anchoring Selection Anchoring Transitions Measuring the Anchoring Energy in the Homeotropic Case The nematic-isotropic liquid interface:static properties and directional growth instabilities. Anchoring Angle, Surface Tension, and Width of the Nematic-Isotropic Interface Landau-Ginzburg-de Gennes Theory Instabilities in Confined Geometry Elastic Correction to the Gibbs-Thomson Relation Directional Growth of the Nematic-Isotropic Liquid Front Cholesterics: the First Example of a Frustrated Mesophase Cholesteric Frustration Cholesteric Order Parameter and the Cholesteric-Isotropic Liquid Phase Transition Optical Properties of the Cholesteric Phase Defects and Textures of the Cholesteric Phase Unwinding Transition Cholesteric Hydrodynamics Blue Phases: a Second Example of a Frustrated Mesophase Experimental Evidence for the Cubic Symmetry of Blue Phases I and II Uniaxial Models for the Blue Phases: Disclination Lattices Biaxial Model of the Blue Phases by Grebel, Hornreich, and Shtrikman Landau Theory of the Blue Phases by Grebel, Hornreich, and Shtrikman Experiments BPIII or Blue Fog Overview of Growth Phenomena and _the Mullins-Sekerka Instability Gibbs-Thomson Relation and the Phase Diagram of a Diluted Binary Mixture The Minimal Model Stationary Plane Front Plane Front in the Diffusive Regime (GBPG

Nematic and Cholesteric Liquid Crystals: Concepts and Physical Properties Illustrated by Experiments

Colloidal crystals, made of large polystyrene particles (1.1 \ensuremath{\mu}m in diameter), are confined into a thin layer between two glass boundaries. When the thickness $h$ of the layer is increased progressively from zero, a sequence of structures $S(h)$ is detected from direct observations in an optical microscope. These structures are stacks of $n$ square (\ensuremath{\square})---or triangular $(\ensuremath{\Delta})$---ordered layers. For $nl~7$, the sequence $S(h)$ is $\dots{}n\ensuremath{\Delta}\ensuremath{\rightarrow}(n+1)\ensuremath{\square}\ensuremath{\rightarrow}(n+1)\ensuremath{\Delta}\ensuremath{\rightarrow}\dots{}$.

Thin Colloidal Crystals

2014 The dynamics of the distortion of a well-oriented nematic liquid crystal film in a perpendicular field around the Freedericks critical field value is studied both theoretically and experimentally. The experimental thermal and optical techniques have already been used for the description of the equilibrium properties of the transition. Their use for the measurement of transition rates leads to an accurate verification of the Leslie-Ericksen hydrodynamic theory and to a demonstration of the role of back flow effects. The divergence of the characteristic time close to the critical value follows accurately the general Landau model of second order phase transitions. The value of the twist viscosity coefficient 03B31 is obtained. LE JOURNAL DE PHYSIQUE TOME 34, JANVIER 1973,

Static and dynamic behavior of a nematic liquid crystal in a magnetic field. Part II : Dynamics

A new photonic structure is produced from cellulose nanocrystal iridescent films reflecting both right and left circularly polarized light. Micrometer-scale planar gaps perpendicular to the films' cross-section between two different left-handed films' cholesteric domains are impregnated with a nematic liquid crystal. This photonic feature is reversibly tuned by the application of an electric field or a temperature variation.

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Pawel Pieranski

Papers

Two-Dimensional Interfacial Colloidal Crystals

Nematic and Cholesteric Liquid Crystals: Concepts and Physical Properties Illustrated by Experiments

Thin Colloidal Crystals

Static and dynamic behavior of a nematic liquid crystal in a magnetic field. Part II : Dynamics

Mind the Microgap in Iridescent Cellulose Nanocrystal Films.