Polymeric spheres

Colloidal crystals . At the end of Section 2.1.4, there is a brief account of regular, crystal-like structures formed spontaneously by two differently sized populations of hard (polymeric) spheres, typically near 0.5 nm in diameter, depositing out of a colloidal solution. Binary superlattices of composition AB2 and ABn are found. Experiment has allowed phase diagrams to be constructed, showing the crystal structures formed for a fixed radius ratio of the two populations but for variable volume fractions in solution of the two populations, and a computer simulation (Eldridge et al. 1995) has been used to examine how nearly theory and experiment match up. The agreement is not bad, but there are some unexpected differences from which lessons were learned. 

However, the free acid quickly starts to condense with itself, accompanied by the elimination of water to form dimers, trimers and eventually polymeric silicic acid. The polymer continues to grow, initially forming polymer aggregates and then polymer spheres, a few Angstroms in diameter. These polymeric spheres are termed the primary particles of silica gel and must not to be confused with the macro-particles of silica gel that are packed into the LC column. 

Recently, a new procedure was reported for the preparation of nanoporous polymeric spheres (NPSs) with well-controlled structure via the LbL infiltration and coating of MS spheres with preformed polymers (Figure 7.7) [69]. A main advantage of this approach is that it offers a general and versatile route to the preparation of NPSs of different and tailored compositions, as it is based on electrostatic assembly [69,109]. 

Abstract In this paper we report on AFM force spectroscopy measurements on hollow polymeric spheres of colloidal dimensions made from polyelectrolyte multilayers of polyal-lylamine and polystyrenesulfonate in water. We find that the shells show a linear force-deformation characteristic for deformations of the order of the shell wall thickness. This experimental outcome is discussed in terms of analytical results of continuum mechanics, in particular the scaling behaviour of the shell spring constant with wall thickness, shell radius and speed of the deformation is analysed. The experimental results agree well with the predictions of Reissner for thin shells and allow... 

Polymer nanoparticles with diameters of 50-500 nm are now widely used. As with microspheres and microcapsules, one can differentiate between solid polymeric spheres (nanoparticles) and those spheres with thin polymeric walls (nanocapsules). The locus of polymerisation is not an emulsion droplet as in microencapsulation, hut a micelle. The process involves the soluhilisation of a water-soluhle monomer such as acrylamide along with the dmg or other agent such as antigen to he encapsulated. An organic liquid such as n-hexane serves as the outer phase. Polymerisation is induced hy irradiation (y-rays. X-rays, UV light), exposure to visible light or heating with an initiator. 

McKelvey, C.A., Kaler, E.W., Zasadzinski, J.A., Coldren, B. and Jung, H.T. (2000) Templating hollow polymeric spheres from catanionic equilibrium vesicles Synthesis and characterization. Langmuir, 16, 8285-8290. 

FIGURE 20.13 Examples of multiple emulsions formed in microfluidic systems (a) multiple shells-multiple cores configurations of monodisperse triple emulsions made with cascaded microcapillary devices results. (Reproduced with permission from Utada, A.S. et al.. Bull. MRS, 32(09), 702, 2007.), (b) composite emulsion formed by droplets of different composition and different volumes. (Reproduced with permission from Hashimoto, M. et al.. Small, 3(10), 1792, 2007.), and (c) examples of anisotropic particles formed by either polymerization (spheres and disks, rods) of droplets of monomer or thermal setting of droplets. (Reproduced with permission from Xu, S. et al., Angew. Chem. Int. Ed. Engl, 44(5), 724, 2005.)... 

Stmctures with micrometer or submicrometer dimensions can be created using different templating methods [4, 5]. A large variety of approaches have been developed and employed to prepare microporous structured materials, including the use of templates such as ordered arrays of colloidal particles to produce inverse opal structures [6-9], from transformed polymeric sphere arrays [10, 11], using emulsion droplets as templates [12], employing natural biological templates [13-16], by... 

Fusaoka et al. [12] observed a structure composed of fused and deformed polymeric spheres using FE-SEM in a cross section of the membranes, cast and dried from solutions of poly(l-trimethyl-silyl-l-propyne), poly(4-methyl-l-pentene), and some other polymers. 

Fujii et al. [13] studied morphological structures of the cross section of various hollow fibers and fiat sheet membranes by high-resolution field emission scanning electron microscopy. Figure 6.8 shows a cross-sectional structure of a flat sheet cellulose acetate RO membrane. The layer near the top surface is composed of a densely packed monolayer of polymeric spheres, which is supported by a layer formed with completely packed spheres. The contours of the spheres in the top layer can be observed. The middle layer is also composed of loosely packed and partly fused spheres, which are larger than the spheres in the surface layer. In the middle layer, there are many microvoids, the sizes of which are the same as the spheres. The layer near the bottom is denser than the middle layer, and the spheres are deformed and fused. Interstitial void spaces between the spheres, which may be called microvoids, are clearly observed. This structure seems common for the flat sheet as well as the hollow fiber membranes. For example. Fig. 6.9 shows a cross section of a hollow fiber made of PMMA B-2 (a copolymer containing methyl methacrylate and a small amount of sulfonate groups). The inside surface layer is composed of the dense structure of compactly packed fine polymeric particles. The particle structure of the middle layer... 

Membranes prepared by the dry-wet phase inversion method from glassy polymers are composed of polymeric spheres. 

Figure 12 The attraction force between a polymeric sphere and a flat electrode vs. the applied electric field at various values of the particle-to-liquid conductivity ratio, T = Gphj ,. Reproduced with permission from J-...

Ahnog Y, Reich S, Levy M. Monodisperse polymeric spheres in the micron size range by a single step process. Braz Polym J 1982 14 131-136. 

Smith, Jr., J. G Smith, T. WUUams, M. Youngquist, R. and Mendell, W., Potential polymeric sphere construction materials for a spacecraft electrostatic shield, National Aeronautics and Space Administration Langley Research Center, Hampton, VA 23681, NASA/TM-2006-214302. 

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