POSS molecules

The reactions of POSS molecules fall into two categories, those involving the silsesquioxane core of the molecule and those involving reactions of the peripheral substituents. The silsesquioxane core in POSS compounds is fairly unreactive to many reaction conditions and this inertness has led to the successful application of POSS species in many materials (see Section V for further... 

The alkene groups in TsICH = CH2]s have allowed a wider variety of chemistry to be carried out than for either TsHs or TsPhs. For example, Feher s group have prepared a variety of unsaturated POSS molecules via olefin cross-metathesis... 

Chigwada et al.36 have combined polyhedral oligosilsesquioxanes (POSS), which are cage-like hybrid molecules of silicon and oxygen, with TCP (tricresylphosphate) in poly(vinyl ester) resins (PVE). POSS molecule contains nonreactive organic functionalities allowing solubility and compatibility of the POSS with various polymers. POSS was incorporated alone (3-10 wt %) in PVE, and four compositions were made with TCP at 4wt % POSS + 4wt % TCP and 5wt % POSS + 5, 10, 15 wt % TCP. Fligh reductions in PHRR and THR were noticed. Nevertheless, the POSS/ TCP combination did not exhibit better performances than compositions with only 5 or 10 wt % of TCP alone. 

Experimental and theoretical parameters have been successfully developed to accurately model the gas-phase conformations of a variety of POSS compounds with different Si - O cage sizes and substituent groups. Incompletely condensed POSS molecules are commonly used to create specific condensed POSS systems by capping with the appropriate reactive functional group. Some of the POSS compounds were functionalized with cyclohexyl groups, but data has also been obtained for POSS functionalized with cyclopropyl, vinyl and phenyl groups [71]. 

Fu et al. [85] studied the structural development of a unique polyurethane system having inorganic POSS molecules attached to the hard segments as... 

Simultaneous WAXD and SAXS techniques were applied to reveal the POSS crystal structural and POSS-PU morphological changes under deformation. The WAXD data indicated that POSS molecules formed nanoscale crystals in the hard segment domains. Under stretching, the full-width at half-maximum of the POSS crystal peak was found to decrease, which suggested the destruction of POSS crystals and also the hard segments. 

Ion mobility is based on the measurement of the amount of time it takes for an ion to drift through a buffer gas under the influence of a weak electric field. This drift time inherently contains information about the conformation of the ion. Differently shaped ions have various collision cross sections and hence different mobilities (and drift times) when drifting through the gas. Thus, various computational methods are then used to generate model structures of the ions and calculate their cross sections for comparison to experiment. For instance. X-ray crystallography and NMR spectroscopy are usually used to obtain structural data on POSS molecules. However, POSS-polymer systems can be difficult to examine with these methods since synthetic polymers exist as a mixture of chain lengths data can thus only be obtained for the entire polymer distribution as a collective using these methods. In this respect, detailed information about how POSS interacts with one particular... 

Polyhedral oligomeric silsesquioxane (POSS) has been described as a three-dimensional "cage-shaped molecule composed of a silicon-oxygen framework bonded to organic groups that make it compatible with a polymer matrix. Unlike conventional nanofillers that must be dispersed and exfoliated to be useful, POSS molecules formulated in the resin are induced by shear to "self-assemble ... 

A more convenient method of incorporating POSS into organic polymers is physical blending. Since each POSS molecule has a SigOi2 core covered with alterable organic side groups, it is believed that better dispersion may... 

Since a POSS molecule has both defined structure and specific functional groups, it provides the possibility of preparing nanocomposites with controlled structures. There has been considerable effort using POSS cages as building blocks to make controlled structure materials. 

Figure 23.1 POSS molecule showing the central rigid cage and surrounding methyl groups.

Figure 23.3 POSS dissolves molecularly and spontaneously each black dot is a 1.5 nm POSS molecule (scale bar is 50 nm).

POSS molecule contains organic substituents, which make the POSS structure compatible with polymers, biological systems, or surfaces. The availability of diverse nanocomponents, which are easily made and whose properties can be closely controlled, can have a signiflcant impact on the development of nanomaterials and nanotechnologies. 

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