Polyhedral oligomeric silsesquioxane nanoparticles

Fig. 7 Examples of polyhedral oligomeric silsesquioxane (POSS) nanoparticles used to induce homeotropic alignment in nematic liquid crystals...

The 0-d nanoparticles can be nano-metal oxides (such as silica,1 titania,2 alumina3), nano-metal carbide,4 and polyhedral oligomeric silsesquioxanes (POSS),5 to name just a few the 1-d nanofibers can be carbon nanofiber,6 and carbon nanotubes (CNT),7 which could be single-wall CNTs (SWCNT) or multiwall CNTs (MWCNT) etc. the 2-d nano-layers include, but are not limited to, layered silicates,8 layered double hydroxides (LDH),9 layered zirconium phosphate,10 and layered titanates,11 etc. 3-d nano-networks are rarely used and thus examples are not provided here. 

Broadband dielectric spectroscopy is a powerful tool to investigate polymeric systems (see [38]) including polymer-based nanocomposites with different nanofillers like silica [39], polyhedral oligomeric silsesquioxane (POSS) [40-42], and layered silica systems [43-47] just to mention a few. Recently, this method was applied to study the behavior of nanocomposites based on polyethylene and Al-Mg LDH (AlMg-LDH) [48]. The properties of nanocomposites are related to the small size of the filler and its dispersion on the nanometer scale. Besides this, the interfacial area between the nanoparticles and the matrix is crucial for the properties of nanocomposites. Because of the high surface-to-volume ratio of the nanoparticles, the volume fraction of the interfacial area is high. For polyolefin systems, this interfacial area might be accessible by dielectric spectroscopy because polyolefins are nonpolar and, therefore, the polymeric matrix is dielectrically invisible [48]. 

Mabry, J. M. Vij, A. Viers, B. D. Grabow, W. W. Marchant, D. lacono, S. C. Ruth, P. N. Vij, I., Hydrophobic Silsesquioxane Nanoparticles and Nanocomposite Surfaces Overview of the Synthesis and Properties of Fluorinated Polyhedral Oligomeric Silsesquioxane (POSS) and Fluorinated POSS Nanocomposites. In Science and Technology of Silicones and Silicone-Modified Materials, Clarson, S. J. Fitzgerald, J. J. Owen, M. J. Smith, S. D. Van Dyke, M. E., Eds. American Chemical Society Washington, DC, 2007 Vol. 964,... 

Compositematerialcontainingatleastonephasewithconstituentsofl-lOOmn in size can be termed nanocomposites. Nanoparticles commonly used in the nanocomposite include single-walled carbon nanotube (SWCNT), double-walled carbon nanotube (DWCNT), multi-walled carbon nanotubes (MWCNT), carbon nanofiber (CNF), graphite nanoplatelet (GNP), mont-morillonite (MMT), nanoclay and polyhedral oligomeric silsesquioxanes (POSS). Other nanoparticles, such as SiOj, AljOj, TiOj and nanosilica are also used in the nanocomposite. The potential benefits of the nanoparticles for structural and multifunctional nanocomposites are sunamarized below. 

It is of interest to determine the flame retardant effectiveness of shapes or types of nanoparticles other than layered silicates, to find what shape or type of nanoparticle is most effective for improving the flammability properties of commodity polymers. In this chapter, flammability properties of nanocomposites containing nanoscale oxides such as nanoscale silica particles and metal oxides, polyhedral oligomeric silsesquioxanes (POSSs), and carbon-based nanoparticles such as graphite, single-walled carbon nanotubes (SWNTs), multiwalled carbon nanotubes (MWNTs), and carbon nanofibers (CNFs) are described and a flame retardant mechanism of these nanoparticles is discussed. 

Carroll, J. B., Frankamp, B. L., Srivastava, S., Rotello, V. M. (2004), Electrostatic self-assembly of structured gold nanoparticle/polyhedral oligomeric silsesquioxane (ROSS) nanocomposites, JoMwa/ of Materials Chemistry, 14, 690. ... 

Zhang, Y.W. and Ye, Z.B. (2008a) Homogeneous polyhedral oligomeric silsesquioxane (POSS)-suppdiimine complex and synthesis of polyethylenes end-tethered with a POSS nanoparticle via ethylene living polymerization. Chemical Communications, 1178-1180. 

In recent times, polyhedral oligomeric silsesquioxane (POSS) has been used as organic modifier, for montmorillonite nanoparticles in nanocomposite preparation [120-123]. However, much of the literature is on monopolymer nanocomposites. 

Current synthesis techniques provide an unprecedented level of control over nanoparticle shape and composition, resulting in an almost limitless catalog of nanoparticles with varying geometry and interactions.Examples of different shapes include spheres, rods, cubes and other polyhedra, plates, ° and multipods, along with molecular nanoparticles such as carbon fullerenes, porphyrin squares, polyhedral oligomeric silsesquioxane (POSS)... 

Carroll JB, Frankamp BL, Srivastava S, Rotello VM (2004) Electrostatic self-assembly of stmctured gold nanoparticle/polyhedral oligomeric silsesquioxane (POSS) nanocomposites. J Mater Chem 14(4) 690-694. doi 10.1039/b311423f... 

Rotello et al. used a similar system, relying mainly on multiple thymine/2,6-diamino-pyridine interactions (Fig. 72). Small molecules (such as flavines [241], ferrocenes [242]) can be boimd via a single, thymine/2,6-di-aminopyridine interaction. This can lead to materials with reversible properties, where the redox activity of the surface-bound functional moiety can interact with a current form of the (Au-) surface. The concept has been extended to nanoparticles (Au-NP) [243] and polyhedral ohgomeric silsesquioxanes [244]. The presence of the oligomeric silsesquioxanes was proven by XPS measurements, detecting the Si(2p) peak on the surface after deposition. 

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