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.

/pdf/colloidosomes-selectively-permeable-capsules-composed-of-147a06bk70.pdf

Colloidosomes: Selectively Permeable Capsules Composed of Colloidal Particles

5. In Situ Polymerization 3907 5.1. General Polymerization 3907 5.2. Photopolymerization 3910 5.3. Surface-Initiated Polymerization 3912 5.4. Other Methods 3913 6. Colloidal Nanocomposites 3913 6.1. Sol-Gel Process 3914 6.2. In Situ Polymerization 3916 6.2.1. Emulsion Polymerization 3917 6.2.2. Emulsifier-Free Emulsion Polymerization 3919 6.2.3. Miniemulsion Polymerization 3920 6.2.4. Dispersion Polymerization 3921 6.2.5. Other Polymerization Methods 3923 6.2.6. Conducting Nanocomposites 3924 6.3. Self Assembly 3926 7. Other Preparative Methods 3926 8. Characterization and Properties 3928 8.1. Chemical Structure 3928 8.2. Microstructure and Morphology 3929 8.3. Mechanical Properties 3933 8.3.1. Tensile, Impact, and Flexural Properties 3933 8.3.2. Hardness 3936 8.3.3. Fracture Toughness 3937 8.3.4. Friction and Wear Properties 3937 8.4. Thermal Properties 3938 8.5. Flame-Retardant Properties 3941 8.6. Optical Properties 3942 8.7. Gas Transport Properties 3943 8.8. Rheological Properties 3945 8.9. Electrical Properties 3945 8.10. Other Characterization Techniques 3946 9. Applications 3947 9.1. Coatings 3947 9.2. Proton Exchange Membranes 3948 9.3. Pervaporation Membranes 3948 9.4. Encapsulation of Organic Light-Emitting Devices 3948

Polymer/Silica Nanocomposites: Preparation, Characterization, Properties, and Applications

Emulsions stabilized with solid nanoparticles: Pickering emulsions

An overview of the wide range of nanoreactors that have been constructed from synthetic and biological building blocks using both covalent and noncovalent approaches is given. Focus is on self-assembled systems, varying in size from a few nanometers to tens of micrometers. The review is divided into several sections that cover the development of tailor-made nanoreactors, starting from small organic molecular containers expanding to large compartment-containing assemblies. First, the construction of capsules from low molecular weight compounds by means of covalent synthesis and self-assembly by highly directive and pre-designed interactions is discussed. Second, nanocapsules based on micellar and vesicular assemblies that are built up frow low molecular weight molecules are described. Finally, the construction of nanoreactors from macromolecular building blocks, as well as recent developments in the use of viruses as nanocontainers and reactors are outlined.

/pdf/self-assembled-nanoreactors-4el5gc5op7.pdf

Self-Assembled Nanoreactors

Design and Production of Nanoparticles Formulated From Nano-Emulsion Templates-A Review

This paper reports on the convenient one-step synthesis of hollow polymer nanocapsules by miniemulsion polymerization of different monomers in the presence of larger amounts of a hydrophobe. The idea of the procedure is that the hydrophobe and monomer form a common miniemulsion, whereas the polymer is immiscible with the hydrophobe and demixes throughout polymerization to form the hollow polymer structure surrounding the hydrophobe. The primary objective of this work was to study the effect of different monomers and monomer mixtures, of the type and amount of surfactant, and of the hydrophobe on the morphological characteristics of the polymer/oil composite particle, using dynamic light scattering, scanning and transmission electron microscopies, and atomic force microscopy. It was found that the structure can be adjusted to cover the whole range from independent particles over partially engulfed structures to structurally integer nanocapsules of high uniformity.

Preparation of polymeric nanocapsules by miniemulsion polymerization.

Polystyrene latexes in a size range of 30−180 nm can be synthesized by polymerization in miniemulsions where the particle size responds to the amount of the surfactant sodium dodecyl sulfate (SDS) which was varied between 0.5 and 50 wt % with respect to monomer. Turbidity and surface tension measurements were used to characterize the miniemulsification by ultrasonication and the approach to a steady state of droplet size. Since size equilibrium seems to be established by a rate equation of collision-induced droplet fusion and ultrasound fission, miniemulsions realize the minimal droplet size for the distinct amount of surfactant; i.e., they are “critically stabilized” with respect to collisions (τ2 process). Complete stability against Ostwald ripening (τ1 process) is obtained by the addition of a hydrophobe, which was varied over a broad structural range. The efficiency of this hydrophobic agent is given mainly by a very low water solubility. The growth of the critically stabilized miniemulsion droplets i...

Formulation and stability mechanisms of polymerizable miniemulsions

Polymer dispersions made of a variety of monomers, including styrene, butyl acrylate, and methyl methacrylate, were generated by the miniemulsion process in the presence of a coupling comonomer, a hydrophobe, and silica nanoparticles. Depending on the reaction conditions and the surfactants employed, different hybrid morphologies were obtained, comprising a “hedgehog” structure where the silica surrounds the latex droplet and provides stabilization even without any low molecular weight surfactant. In other parts of the composition diagram noncoupled structures as well as “raspberry” hybrids where whole clusters of silica nanoparticles are completely embedded in the polymer particle can be made. The resulting structures are promising for a number of applications, e.g. the increase of scratch resistance in water-based coatings.

Silica Nanoparticles as Surfactants and Fillers for Latexes Made by Miniemulsion Polymerization

Full Paper: In this paper the effective encapsulation of carbon black with polymers by co-sonication of a carbon black dispersion and a typical miniemulsion polymerization recipe is described. The carbon containing polymer particles are analyzed in detail by particle size measurements, transmission electron microscopy, density distributions experiments with the ultracentrifuge, and by nitrogen adsorption. The final particle size was in the range of 50 to 170 nm, the weight ratio polymer to carbon was changed between 20 : 80 and 90 : 10. In all cases, the surface tension of the final dispersion is above the minimal surface tension of SDS indicating the absence of micelles and the incomplete coverage of the polymer coated carbon particles with surfactant. The amount and type of an added hydrophobe needed for osmotic stabilization as well as the type of monomer have a large influence on the encapsulation process. The encapsulation process can be described by a scenario where the fusion/fission by ultrasound splits the monomer droplets, whereas the monomer coated carbon stays intact. The thickness of the monomer film depends on the amount of monomer and has to be optimized since there is an optimal range of monomer layer thickness in order to preserve the morphology. Too low amounts of monomer result in incompletely covered particles which aggregate with polymer whereas too much monomer results in the formation of a second species of pure polymer particles. The process can be described as a polymerization in an adsorbed monomer layer created and stabilized as a miniemulsion (“ad-miniemulsion polymerization”).

Franca Tiarks

Papers

Preparation of polymeric nanocapsules by miniemulsion polymerization.

Formulation and stability mechanisms of polymerizable miniemulsions

Silica Nanoparticles as Surfactants and Fillers for Latexes Made by Miniemulsion Polymerization

Encapsulation of carbon black by miniemulsion polymerization.

Miniemulsion polymerization: Applications and new materials.