Core composite particles

The benefit of the LbL technique is that the properties of the assemblies, such as thickness, composition, and function, can be tuned by varying the layer number, the species deposited, and the assembly conditions. Further, this technique can be readily transferred from planar substrates (e.g., silicon and quartz slides) [53,54] to three-dimensional substrates with various morphologies and structures, such as colloids [55] and biological cells [56]. Application of the LbL technique to colloids provides a simple and effective method to prepare core-shell particles, and hollow capsules, after removal of the sacrificial core template particles. The properties of the capsules prepared by the LbL procedure, such as diameter, shell thickness and permeability, can be readily adjusted through selection of the core size, the layer number, and the nature of the species deposited [57]. Such capsules are ideal candidates for applications in the areas of drug delivery, sensing, and catalysis [48-51,57]. 

The chemical composition of particles can be just as varied as their shape. Commercial particles can consist of polymers or copolymers, inorganic constructs, metals and semiconductors, superparamagnetic composites, biodegradable constructs, and synthetic dendrimers and dendrons. Often, both the composition of a particle and its shape govern its suitability for a particular purpose. For instance, composite particles containing superparamagnetic iron oxide typically are used for small-scale affinity separations, especially for cell separations followed by flow cytometry analysis or fluorescence-activated cell sorting (FACS). Core-shell semiconductor particles, by... 

Suzuki, D. Kawaguchi, H., Modification of gold nanoparticle composite nanostructures using thermosensitive core shell particles as a template, Langmuir. 2005, 21, 8175 8179... 

Suspension arrays are based on addressable nano- or micrometric beads of various chemical natures (polymeric, silica, gold) and architectures (uniform composition, core-shell particles) to which NAs can be immobilized by means of activating chemistries similar to those described for fiat supports [64,65] depending on the composition of the particles outmost layer. 

Figure 13.3.7 shows scanning electron microscopy (SEM) photographs of the surface of the polyethylene particle after the silica particles were peeled off. The specimen was prepared in the following way. After the composite particles were potted in epoxy resin, the dried resin block was cut using a microtome to produce fine sections. The fracture surface appearance of the polyethylene was then observed under a microscope. The mean depth penetration into the surface of the core particles could be measured using the SEM photographs. Silica 0.3 pan in diameter was embedded in the surface of the polyethylene particles at a depth of 0.03 xm. In... 

The interfacial adhesion between dispersed particles and the matrix can be improved by functionalizing the core-shell particles with any chemical group that can react with the thermosetting polymer. For example, glycidyl methacrylate can be introduced in the shell composition to incorporate functional groups that can react with epoxy formulations. 

The copolymer composition in miniemulsion copolymerization of vinyl acetate and butyl acrylate during the initial 70% conversion was found to be less rich in vinyl acetate monomer units [34]. Miniemulsion polymerization also allowed the synthesis of particles in which butyl acrylate and a PMMA macromonomer [83, 84] or styrene and a PMMA macromonomer [85] were copolymerized. The macromonomer acts as compatibilizing agent for the preparation of core/shell PBA/PMMA particles. The degree of phase separation between the two polymers in the composite particles is affected by the amount of macromonomer used in the seed latex preparation. 

Fig. 8 Composite particles consisting of thermosensitive core-shell particles in which metallic nanoparticles are embedded. Left The composite particles are suspended in water, which swells the thermosensitive network attached to the surface of the core particles. In this state, the reagents can diffuse freely to the nanoparticles, which act as catalysts. Right At higher temperatures (T > 32°C) the network shrinks and the catalytic activity of the nanoparticles is strongly diminished...

Connelly, P. W., and Kuksis, A. (1981), Effect of core composition and particle size of lipid emulsions on apolipoprotein transfer of plasma lipoproteins in vivo, Biochim. Biophys. Acta, 666, 80-89. 

For composite particles in water, the three extreme morphologies may be considered as core-shell, with the more hydrophilic component interfacing with water, inverted core-shell, with the more hydrophobic component interfacing with water, and separated particles. 

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