https://ir.nctu.edu.tw:443/bitstream/11536/14909/1/000297489400002.pdf

POSS related polymer nanocomposites

A new class of epoxy nanocomposites with completely defined organic/inorganic phases was prepared by reacting octakis(glycidyldimethylsiloxy)octasilsesquioxane [(glydicylMe2SiOSiO1.5)8] (OG) with diaminodiphenylmethane (DDM) at various compositional ratios. The effects of reaction curing conditions on nanostructural organization and mechanical properties were explored. A commercial epoxy resin based on the diglycidyl ether of bisphenol A (DGEBA) was used as a reference material throughout these studies. FTIR was used to follow the curing process and to demonstrate that the silsesquioxane structure is preserved during processing. OG/DDM composites possess comparable tensile moduli (E) and fracture toughness (KIC) to, and better thermal stabilities than, DGEBA/DDM cured under similar conditions. Dynamic mechanical analysis and model reaction studies suggest that the maximum cross-link density is obtained at N = 0.5 (NH2:epoxy groups = 0.5) whereas the mechanical properties are maximized at N = 1.0. Digestio...

Organic/Inorganic Hybrid Composites from Cubic Silsesquioxanes

The dissolution of high surface area silica with tetralkylammonium hydroxides at concentrations greater than 0.2 M, produces polyanionic cage structures, [R4N+][−OSiO1.5]x or Qx, where x
				= 6, 8 or 10. The value x depends on the type of alkyl or alkanol group. If R = Me or Me3NCH2CH2OH+ group (choline)
				x
				= 8 is favored. These silicate anions can be functionalized by reaction with chlorosilanes or siloxanes to produce [RSiMe2OSiO1.5]x. The octafunctional molecules are 1.2–1.4 nm in diameter, each functional group occupies a different octant in Cartesian space and as such all functional groups are either orthogonal to or opposite each other. This highly symmetrical structure offers the opportunity to construct multiple kinds of materials one nanometer at a time in one, two or three dimensions. In this review, we discuss methods of synthesizing the polyanionic silicates, their transformation into octafunctional building blocks, “cubes,” and their use in formulating polyfunctional compounds and nanocomposites therefrom. Examples of tailoring global properties by tailoring the chemistries used to link cubes are given.

Nanobuilding blocks based on the [OSiO1.5]x (x= 6, 8, 10) octasilsesquioxanes

Polyhedral oligosilsesquioxane (POSS)-based hybrid polymers have generated much interest recently, both from the academic and industrial points of view. POSS are completely defined molecules of nanoscale dimensions that may be functionalized with reactive groups suitable for the synthesis of new organic–inorganic hybrids, thus providing the opportunity to design and build materials with extremely well-defined dimensions possessing nanophase behavior. POSS have been successfully incorporated into common polymers via copolymerization, grafting or blending. A variety of POSS-containing copolymers have been prepared and they have displayed great potential in the development of a wide range of hybrid nanomaterials with diverse properties. This work has critically evaluated the recent developments in syntheses of POSS polymer materials leading to POSS nanocomposites. The syntheses of POSS cages, monomers containing POSS cages, POSS-dendrimers' cores, POSS-containing polymers (nanobuilding blocks) and POSS nanocomposites are described in detail. This work also assesses the properties of POSS nanobuilding blocks that can be otherwise used for developing nanocomposites. Such properties include mechanical, thermal, flame-retardant and viscoelastic properties. Investigations into the structure, morphology and compatibility of POSS nanobuilding blocks have been reviewed. Other properties covered include the ion-mobility and swelling characteristics as well as porosity of POSS nanobuilding blocks. Lastly, existing and possible future applications are highlighted and final conclusions are drawn.

Polyhedral Oligomeric Silsesquioxanes (POSS)-Containing Nanohybrid Polymers

Polyimide/POSS nanocomposites: interfacial interaction, thermal properties and mechanical properties

R.M. LAINE, M. ASUNCION, S. BALIAT,t N.L. DIAS FILHO, J. HARCUP, A.C.SUTORIK,t L. VICULIS, A.F. YEE, C. ZHANG, and Q. ZHU,Depts. of Materials Science and Eng., Chemistry and the Macromolecular Science and Eng. Cen-ter, University of Michigan, Ann Arbor, MI 48109-2136, U.S.A and tTal Materials, Inc., 912 N.Main St., Ann Arbor, MI 48104ABSTRACTOctafunctionalized silsesquioxanes [(RSiO!.5)8, cubes] offer potential as rigid, hard nanoplat-forms to which a variety of organofunctional groups can be appended. Crosslinking these groupsleads to novel organic/inorganic nanocomposites that consist primarily of interfacial interactions.These materials can be 100% interphase. We present efforts to develop nanocomposite materialsthat consist of both continuous and discontinuous organic/inorganic phases. We then discussmethods of probing the properties of these materials.INTRODUCTIONTwo general principles are often used to describe the origin of macroscopic properties in ma-terials. The first is, "Intrinsic materials properties and processing taken together define micro-structure." The second is,"Intrinsic materials properties and microstructure together define globalproperties."With the advent of chemical processing of materials, one can often replace the termmicrostructure with nanostructure.A less encompassing general principle is that "Control at the finest scales gives the highesthomogeneity, thereby providing the highest reproducibility, predictability and ability to tailor prop-erties." This principle is less encompassing because we often would like to prepare materials with"controlled heterogeneity," ie. composite materials. We may generally describe composites asmaterials that combine two (or more) materials and microstructures. In composite manufacture, thegoal is usually to achieve properties that are more than the sum of the properties of the individualcomponents; however, it is often possible to estimate the properties of typical composites using therule of mixtures. The utility of the rule of mixtures in predicting properties is greatly diminishedwhen applied to nanocomposites.

Jason Harcup

Papers

Organic/Inorganic Hybrid Composites from Cubic Silsesquioxanes

Organic/Inorganic Molecular Hybrid Materials From Cubic Silsesquioxanes