The effects of the peripheral architecture on the macroscopic properties of eight symmetric and asymmetric aryl polyhedral oligomeric silsesquioxane (POSS) molecules are described. These POSS materials were synthesized in our laboratory and characterized by single-crystal and powder Xray diffraction techniques, as well as differential scanning calorimetry, thermogravimetric analysis, mass spectrometry, and Fourier transform infrared spectroscopy. The peripheral aryl architecture, although similar in most cases, was found to significantly influence observed thermally induced phase transitions, mass loss during decomposition, and heat capacity. These properties are correlated to POSS assembly, molecular interactions, and the specific attributes of peripheral structure and connectivity to the inorganic core.

Four new asymmetric Polyhedral Oligomeric SilSesquioxanes (POSS) with the formula (Aryl)Phenyl7Si8O12, where Aryl = 1-naphthyl, 2-naphthyl, 9-phenanthrenyl, and 1-pyrenyl, have been synthesized in reasonable yield and high purity. These compounds were characterized with 1H, 13C, 29Si NMR and elemental combustion analysis. These compounds possess polycyclic aromatic functionality, which disrupts symmetry to improve solubility in organic solvents and aromatic polymers, without significant impact on thermal stability.

: New POSS compounds with high temperature capability and good solubility in various organic solvents have been developed. By placing a single polycyclic aromatic group (naphthyl, phenanthryl, or pyrenyl) on a corner (via a corner-capping reaction) of (phenyl)7Si7O9(OH)3, cage symmetry is disrupted, which significantly increases solubility over (phenyl)8Si8O12. Thermal characteristics are retained, which makes these materials suitable for use in high performance polymers. Reasonable yields (29- 95%) were obtained for the reactions.

The design of robust omniphobic surfaces, which are not wetted by low-surface-tension liquids such as octane (gamma(lv) = 21.6 mN/m) and methanol (gamma(lv) = 22.7 mN/m), requires an appropriately chosen surface micro/nanotexture in addition to a low solid-surface energy (gamma(sv)). 1H, 1H, 2H, 2H- Heptadecafluorodecyl polyhedral oligomeric silsesquioxane (fluorodecyl POSS) offers one of the lowest solid-surface energy values ever reported (gamma(sv) approximate to 10 mN/m) and has become the molecule of choice for coating textured surfaces. In this work, we synthesize and evaluate a series of related molecules that either retain the POSS cage and differ in fluoroalkyl chain length or that retain the fluorodecyl chains surrounding a linear or cyclic molecular structure. The solid-surface energy (gamma(sv)) of these molecules was estimated using contact angle measurements on flat spin-coated silicon wafer surfaces. Zisman analysis was performed using a homologous series of n-alkanes (15.5 <= gamma(lv) <= 27.5 mN/m), whereas Girifalco-Good analysis was performed using a set of polar and nonpolar liquids with a wider range of liquid surface tension (15.5 <= gamma(lv) <= 72.1 mN/m). The hydrogen-bond-donating, hydrogen-bond-accepting, polar, and nonpolar (dispersion) contributions to the solid-surface energy of each compound were determined by probing the surfaces using a set of three liquid droplets of either acetone, chloroform, and dodecane or diiodomethane, dimethyl sulfoxide, and water.

Abstract : Polyhedral Oligomeric Silsesquioxanes (POSS) are nanoparticles that are used to enhance the thermal and mechanical properties of many polymeric systems. Starting in 1993, there has been extensive research in understanding how POSS affects these properties. Certain POSS macromers can be copolymerized with organic monomers to form nanocomposite type materials. A model is emerging for how addition-polymerized POSS copolymers can undergo a type of self-assembly to form a nanocomposite. The R-group on the POSS moiety plays a critical role in determining the properties of the nanocomposite, as it determines the level of compatibility of the POSS with the comonomer and how strongly the POSS cages associate. A common (but not always observed) phenomenon with POSS in glassy polymers, is that cyclohexyl POSS often increases thermal transitions while isobutyl POSS frequently plasticizes. It is possible that this is due to the length scale of the POSS-cage domains and/or their level of compatibility with the polymer matrix.