A new bis(amino)-functionalized POSS monomer was prepared and characterized with the formula diexo-(c-C5H9)8Si8O11(p-C6H4NH2)2 . The new POSS monomer (1−10 mol %) along with diamines ...1,3-bis(3-aminophenoxy)benzene (APB) and 3,4‘-oxydianiline (ODA) and were copolymerized with 4,4‘-oxydiphthalic anhydride (ODPA) and two reactive end-caps, 4-(arylethynyl)phthalic anhydride {where aryl = phenyl and 9-anthracenyl} to afford a series of new inorganic/organic imide oligomers. The oligomers containing 1% and 10% POSS gave similar T g data (≈191 and 203 °C) as the pure organic imide oligomers and were shown to thermally cure to afford solvent-resistant and high T g resins. The thermal curing kinetic data for the 10%-POSS-containing imide was obtained. The kinetic data showed the rate of thermal curing to be unaffected (within experimental deviation) by the addition of the POSS units.
Synthesis, chain characteristics, and time-dependent viscoelastic response of polyhedral oligomeric silsesquioxanes (POSS)-containing hybrid polymers were investigated. Unlike many other reported ...POSS hybrid copolymers works, the POSS-grafted copolymers used in this study, although having different amounts of POSS attachments, have the same degrees of polymerization and molecular weight distribution. This was accomplished by grafting different amounts of aluminosilsesquioxane onto a previously synthesized, random copolymer of styrene and vinyl−diphenylphosphine oxide, PSP. The coordination bonding between aluminum and phosphine oxide is quantitative, which enables the investigation of physical characteristics and viscoelastic response of polymers as influenced only by the POSS attachments. Similar to other hybrid polymers with covalently bonded POSS, we observed a systemic increase in the characteristic relaxation time of polymers at the terminal zone due to the POSS attachment. Linear viscoelastic response at different temperatures above T g was studied using the small-strain amplitude oscillatory shear technique. It was found that these POSS-grafted copolymers obey the time−temperature superposition principle. In addition, for isothermal experiments, the linear viscoelastic response obtained for copolymer with varying amounts of POSS attachment were able to be superposed, thus demonstrating that these hybrid copolymers obey the time−POSS content superposition principle. We also examine the effect of POSS−POSS interactions on the long-term viscoelastic response of these copolymers. It was found that copolymers with high POSS attachments exhibit a slow gelation response when held isothermally at temperatures above T g for extended periods of time, while copolymers with low POSS attachments remain unchanged for the same periods of time. Therefore, this observed gel-like behavior is due to the intrachain POSS−POSS interaction.
In direct conflict with theoretical predictions, thiophene monolayers were adsorbed onto Au(111) by immersing an evaporated thin film of mica supported gold in an ethanolic solution of thiophene. The ...resulting self-assembled Monolayer (SAM) was shown to be annealable and to be comprised of large domains adopting the unit cell (2√19×√3)R30°. The SAMs can be removed by photooxidation in air and rinsing with ethanol to afford clean reconstructed Au(111).
The reactions of Os3(CO)10(μ-H)(μ-OH) (3) with the incompletely condensed silsesquioxanes (c-C6H11)7Si7O9(OH)3 (1) and (c-C6H11)8Si8O11(OH)2 (2) afford in high yield ...{Os3(CO)10(μ-H)(μ-O)Si7O10(c-C6H11)7} (4) and the new compounds {Os3(CO)10(μ-H)(μ-O)Si7O9(OH)2(c-C6H11)7} (5), {Os3(CO)10(μ-H)2(μ-O)2Si7O9(OH)(c-C6H11)7} (6), {Os3(CO)10(μ-H)(μ-O)Si8O11(OH)(c-C6H11)8} (8), and {Os3(CO)10(μ-H)2(μ-O)2Si8O11(c-C6H11)8} (9), which are discrete molecular models of silica-anchored Os3(CO)10(μ-H)(μ-OSi⋮). Compounds 6 and 9 represent the first examples of complexes containing two Os3(CO)10(μ-H) cluster cores. The X-ray structures of 5, 8, and 9 are reported.
Silsesquioxanes as models for silica surfaces Feher, Frank J; Newman, David A; Walzer, John F
Journal of the American Chemical Society,
03/1989, Letnik:
111, Številka:
5
Journal Article
Methanethiol adsorption onto Au(111) was studied in situ by scanning tunneling microscopy in air at room temperature. By maintaining registry on the surface during adsorption, it was demonstrated ...that gold vacancy islands (i.e., “etch pits”), which are created by the chemisorption of methanethiol, exist in rows that exactly follow the (22×√3) gold reconstruction. Ostwald ripening produces larger gold vacancy islands that are no longer coincident with the original Au(111) reconstruction. Further annealing produces well-ordered domains of methanethiol that have the same surface structures observed for other alkanethiol-based self-assembled monolayers on Au(111). The results demonstrate for the first time that at high rates of dosing, the structure of a fully-formed thiol monolayer on Au(111) is influenced by the original (22×√3) reconstruction of the underlying gold surface. These data strongly suggest that the gold vacancy islands observed in methanethiol, thiophene, and other alkanethiol-based monolayers are not the result of chemical etching.
Self-assembled monolayers were formed by immersing Au(111) surfaces into solutions of benzeneselenol and diphenyl diselenide. Chemisorption of benzeneselenol produced numerous gold islands (20−200 Å ...in diameter) on the surface and a selenium-containing monolayer with a fundamental repeat unit of (3√3 × 2√3)R30°. Upon annealing at 60 °C in air, these gold islands coalesce to form larger, hexagonal-shaped islands. Chemisorption of diphenyl diselenide is qualitatively similar and upon annealing appears to produce the same surface structures observed with benzeneselenol. These organoselenium-modified surfaces were investigated by scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES).
