POSS Structure Research Articles

Synthesis of dithienogermole-containing oligo- and polysilsesquioxanes as luminescent materials.

Dithienogermole (DTG)-containing oligo- and polysilsesquioxanes were prepared by hydrolysis/condensation of DTGs bearing one () or two trialkoxysilyl group(s) (). The reaction of gave a cage-type octasilsesquioxane with eight DTG groups at the edges () as a viscous oil, whereas the reaction of yielded a network polymer () as a self-standing film. showed a photoluminescence (PL) quantum yield (Φ) of 56% in THF. This value was as high as that of (Φ = 58%), in spite of the accumulation of DTG units in the molecule, as characteristics of the POSS structure. The PL of in THF was suppressed by contact with nitrobenzene, showing the potential of for sensing nitroaromatic explosives. Polymer exhibited a relatively low Φ of 2% as a film, but Φ was improved to 38% by copolymerization with trimethoxymethylsilane. was also copolymerized with a trimethoxysilyl-substituted carbazole derivative () to provide polysilsesquioxanes with DTG and carbazole units, which showed efficient photo-energy transfer from carbazole to DTG in the films. Similar copolymerization of with in the presence of poly(9-vinylcarbazole) provided a composite material with hole-transporting electroluminescence properties, applicable in multi-layered organic light emitting diodes.

Rheological and optical properties of solar absorbing paints with POSS-treated pigments

Thickness sensitive spectrally selective (TSSS) coatings should be capable of absorbing high amounts of solar energy, i.e. they should exhibit high solar absorptivity. However, due to their sensitivity to thickness, it is extremely difficult to prepare uniform, smooth and thin coatings with dense distribution. In our study, we prepared black TSSS paints at various PVC ratios by using a pigment that was treated with trisilanol POSS dispersants. Various POSS dispersants were used for pigment treatment in order to determine the influence of POSS structure on the rheological behavior of liquid paints and the solar absorptivity of applied coatings. Liquid paints were prepared at various PVC ratios in order to examine the effect of pigment loading on the rheological behavior of the paint. The rheological properties were correlated to the solar absorptivity of coatings applied on the substrate. The results revealed that POSS dispersants enable the preparation of dispersions with particularly high pigment loadings (above PVC = 51), which still exhibit liquid-like viscoelastic behavior and are sufficiently flowable to enable proper leveling, uniform distribution of pigment particles inside dry coating and, therefore, excellent solar absorptivity.

There once was a verb

This dissertation presents two extensive case studies in the morpho-syntactic structure of American Sign Language (ASL) based on original fieldwork conducted with native, deaf signers.The first case study focuses on the structure of attributive and predicative POSS possessives. Based on language-internal diagnostics, this study shows that the possessive marker, POSS, functions as a verbal predicate of possession, not as a DP-internal marker of the possessive relation. The structure and interpretation of predicative POSS possessives are reduced to the interaction of the verbal POSS structure with two functional components of the predicative domain: (i) locative structure and (ii) licensing positions of definite objects. Attributive POSS possessives are derived as prenominal reduced relative clause modifiers formed from this underlying predicative structure. The second case study presented here addresses the structural uniformity and semantic ambiguity of two classes of deverbal nominals formed via reduplication in ASL: concrete object-denoting nominals and result-denoting nominals. Based on a morpho-semantic decomposition of verbal structure that is transparent in the surface form of verbal predicates in ASL, it is shown that nominalization via reduplication targets the lowest constituent of the verbal structure (VP-Res ). Nominalization of VP-Res yields the class of result-denoting nominals, while concrete object-denoting nominals are derived as relative clause structures headed by a nominal argument that is introduced by the classifier structure present in the relevant verbal forms.

Thermal decomposition of polyhedral oligomeric octaphenyl, octa(nitrophenyl), and octa(aminophenyl) silsesquioxanes

The mechanisms of the thermal degradation of polyhedral oligomeric octaphenylsilsesquioxane (OPS), octa(nitrophenyl)silsesquioxane (ONPS), and octa(aminophenyl)silsesquioxane (OAPS) were investigated. The –NO2 or –NH2 substituents on the phenyl group affected the mechanism of the POSS thermal degradation. The thermal stabilities of OPS, ONPS, and OAPS were characterized by TG and FTIR. Thermal degradation of OPS included mainly the degradation of caged polyhedral oligomeric silsesquioxane structures and phenyl groups. Nitro or amino substituents decreased its thermal stability. The thermal degradation processes of OPS, ONPS, and OAPS differed. Phenyl groups and cyclobutadiene were observed in the OPS degradation products. Oxygen radicals that caused intensive CO2 release between 350 and 450 °C were generated by the degradation of ONPS –NO2. OAPS released mainly aminophenyl groups at 370 °C, whereas a small number of phenyl groups decomposed at 500 °C. The OAPS reactivity could enhance the thermal stability of POSS structure in the polyimide OAPS composites.

Syntheses of silsesquioxane (POSS)-based inorganic/organic hybrid and the application in reinforcement for an epoxy resin

A new inorganic/organic hybrid material containing silsesquioxane was prepared by the reaction of caged octa (aminopropyl silsesquioxane) (POSS-NH2) with n-butyl glycidyl ether (nBGE) and 1,4-butanediol diglycidyl ether (BDGE). The copolymers of POSS, nBGE, and BDGE could be obtained with varied feed ratio of POSS-NH2, nBGE, and BDGE in the preparation. The hybrid material was added into an epoxy resin (E51) for enhancing the toughening and thermal properties of the epoxy resin. The results showed that the toughening and the thermal properties of the cured epoxy resin were greatly improved by the addition of the hybrid. The enhancement was ascribed to nano-scale effect of the POSS structure and the formation of anchor structure in the cured network. The investigation of kinetics for the curing process of the hybrid-modified epoxy resin revealed that two kinds of curing reactions occurred in different temperature ranges. They were attributed to the reactions between amino groups of the curing agent with epoxy groups of E51 and with residue epoxy groups in the hybrid. The reacting activation energies were calculated based on Kissinger’s and Flynn–Wall–Ozawa’s methods, respectively.

Synthesis of N-Phenylaminomethyl POSS and Its Utilization in Polyurethane

A new functional N-phenylaminomethyl POSS was synthesized by traditionally controlled hydrolytic condensation in one step reaction. The POSS structure was ascribed to a T10 and T12 derivative mixture as main component by varied characterization methods such as 1H NMR, 13C NMR, 29Si NMR, gel permeation chromatography (GPC) and matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI−TOF MS). Then based on this new POSS reacted with polyether diisocyanate, a series of POSS−PU composites with different POSS concentration was prepared and characterized. The POSS−PU composites showed no macrophase separation up to 52 wt % POSS concentration. The high resolution transmission electron microscopy (HRTEM) images of POSS−PU composites showed a well separated nanostructure of POSS with a typical phase size of 5−10 nm. A critical POSS concentration of 26 wt % was found by DMA, beyond which the POSS−PU showed a permanent network at high temperature. Tg and storage modulus of POSS−PU composites increased with increasing POSS concentration. Young’s modulus largely enhanced with increasing POSS concentration at constant Ttest − Tg. All the enhanced mechanical properties could be ascribed to the synergetic effect of POSS and PU, where POSS played a role as the nanoscale cross-linker in the PU system and formed a network, thus hindering the motion of the PU chain.

Novel epoxy nanocomposite of low Dk introduced fluorine‐containing POSS structure

AbstractA nanoporous additives, polyhedral oilgomeric silisesquioxane containing eight functional hexafluorine groups, octakis(dimethylsiloxyhexafluoropropyl ether)silsesquioxane (OF) has been synthesized and blended with the UV‐cured epoxy resin. The OF containing (10%) epoxy has significantly lower dielectric constant (2.65) than the plain epoxy (3.71). The incorporation of fluorine containing additives is well‐known to reduce dielectric constant due to lower its polarizability. In addition, the presence of the bulky POSS structure is able to create additional free space or pores and further reduces the dielectric constant of the epoxy matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 502–510, 2007