Latex opal

Figure 13-19, SEM images of (a) a bare latex opal, (b) a latex opal infiltrated with a barium titanate precursor and (c) a barium titanate inverse opal obtained at 750 C (Soten, 2002).

Similar mirrorless laser-like emission was observed for silica inverse opals infiltrated with rhodamine 6G [105]. Figure 30.15 shows the latex opal obtained... 

Figure 30.15 Scanning electron microscopy images of (a) latex opal and (b) silica inverse opal. (Adapted with permission from Ref. [103].)...

Rogach AL, Kotov NA, Koktysh DS, Ostrander W, Ragoisha GA (2000) Electrophoretic deposition of latex-based 3D colloidal photonic crystals A technique for rapid production of high-quality opals. Chem Mater 12 2721-2726... 

Figure 3.5 shows aTEM picture of the core/double shell latex particles incorporated into an styrene/acrylonitrile (SAN) copolymer matrix (thin cut through the particle-filled matrix).The particles are very homogeneous in size and can also be used to prepare ar-tifical opals. 

Ordered macroporous materials (OMMs) are a new family of porous materials that can be synthesized by using colloidal microspheies as the template. - The most unique characteristics of OMMs are their uniformly sized macropores arranged at micrometer length scale in three dimensions. Colloidal microspheres (latex polymer or silica) can self assemble into ordered arrays (synthetic opals) with a three-dimensional crystalline structure. The interstices in the colloidal crystals are infiltrated with a precursor material such as metal alkoxide. Upon removal of the template, a skeleton of the infiltrated material with a three-dimensionally ordered macroporous structure (inverse opals) is obtained. Because of the 30 periodicity of the materials, these structures have been extensively studied for photonic applications. In this paper, the synthesis and characterization of highly ordered macroporous materials with various compositions and functionalities (silica, organosilica, titana, titanosilicate, alumina) are presented. The application potential of OMMS in adsorption/separation is analyzed and discussed. 

The simplest photonic crystal is nature s opal. The artificial opal is composed of monodispersed spheres of a dielectric, usually silica. Considerable work has been done using latex or polystyrene spheres, but we largely will restrict ourselves here to ceramics. In producing high-quality photonic crystals, care must be taken in each of the three main steps particle synthesis, sedimentation, and sintering. 

Inverse opals are formed by the use of micro- or nanospheres to template a structure containing spherical cavities. One way of doing this is to use monodisperse latex spheres. These latex spheres are prepared by slow addition of an aqueous precursor solution into a reservoir of hydrophobic silicone liquid, forming emulsion droplets. The size of the droplets is controlled by the concentration of the aqueous latex, the speed at which the suspension is stirred and ratio between the silicone liquid and latex. Polymerisation results in latex spheres of well defined size of the order of a few hundred nanometers, and spherical shape. As the concentration of the latex spheres increases to its critical concentration... 

Similarly to the codeposition procedure above, the metal can also be delivered as nanoparticles to the colloidal crystal template, but in this case after preparation of the template. This was demonstrated for gold nanoparticles, which were filled into the interstitial sites of a polymer opal by filtering a gold nanoparticle suspension through the preassembled opal with a filter small enough to hold back the nanoparticles [33]. The templating opal was prepared before in very much the same way by filtration of a PS latex suspension. 

Opals are synthesized commercially by allowing monosized SiOi spheres to slowly settle from a dispersion in the lab. Since the structure is quite open, it is easy to diffuse a dye into the matrix to change the overall color. We can produce inverse opals in a similar way using latex spheres instead of SiOi and then various sols such as Ti02 instead of the dye. When the impregnated polymer is burned out, the inverse opal has potential as a photonic... 

One obvious example of this is opal, the gemstone formed by adhesion of silica particles over geological time. The colors seen by diffraction of white light from the particles suggest that the structuring of the particles extends for millimetres, a milhon times further than would be expected from the range of atomic forces. The same sorts of colors can be seen in polymer latex dispersions. It is important to inquire about the origins of such structures. 

PPy inverse opal patterns (ordered two-dimensional rings, hexagonal or honeycomb monolayers) over wide areas are accomplished by using a colloidal template method. The templates are made ofpoly(styrene/sodium p-styrene sulphonate) latex particles that drive the opal structure upon modulation of their packing density, thus inducing a modulation of the polymer properties [166, 167]. 

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