Structural Study of Poly(phenylsilsesquioxane) Sol-Gel Materials

Smaïhi, M.; Jermoumi, T.; Marignan, J.

doi:10.1021/cm00060a017

Cited by 43 publications

(40 citation statements)

References 1 publication

(1 reference statement)

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“…NMR spectra were acquired on a CMX-500 spectrometer (Chemagnetics, Ft. Collins, CO) operating at 11.7 tesla and a 29 Si frequency of 99.06 MHz referenced to tetramethylsilane (9). The single-pulse spectrum was acquired for 22 h with an 8.35-s single pulse and a recycle delay of 300 s, under conditions of magic-angle sample spinning at 3.5 kHz.…”

Section: Isolation Of Silicatein Filaments and Analysis Of Reactionsmentioning

confidence: 99%

Silicatein filaments and subunits from a marine sponge direct the polymerization of silica and silicones in vitro

Jennifer

Shimizu

Zhou

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

778

780

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Nanoscale control of the polymerization of silicon and oxygen determines the structures and properties of a wide range of siloxane-based materials, including glasses, ceramics, mesoporous molecular sieves and catalysts, elastomers, resins, insulators, optical coatings, and photoluminescent polymers. In contrast to anthropogenic and geological syntheses of these materials that require extremes of temperature, pressure, or pH, living systems produce a remarkable diversity of nanostructured silicates at ambient temperatures and pressures and at near-neutral pH. We show here that the protein filaments and their constituent subunits comprising the axial cores of silica spicules in a marine sponge chemically and spatially direct the polymerization of silica and silicone polymer networks from the corresponding alkoxide substrates in vitro, under conditions in which such syntheses otherwise require either an acid or base catalyst. Homology of the principal protein to the well known enzyme cathepsin L points to a possible reaction mechanism that is supported by recent site-directed mutagenesis experiments. The catalytic activity of the ''silicatein'' (silica protein) molecule suggests new routes to the synthesis of silicon-based materials.Silicon, the second most abundant element in the earth's crust, interacts with living systems by mechanisms that have remained poorly understood (1-6). Evidence suggests that silicon is essential for normal growth and biological function in a diversity of plant, animal, and microbial systems (2); silicon compounds have been shown to modulate these activities (1, 2), but the molecular mechanisms of these effects have proved elusive. Studies of marine organisms that produce relatively large masses of silicified structures (3) show the underlying molecular and genetic mechanisms by which living systems process silicon. Hildebrand et al. (7) recently characterized the cDNAs coding for a family of silicon transporters in diatoms and showed that the transporters are likely transmembrane proteins. We have found that the marine sponge Tethya aurantia produces copious silica spicules (1-2 mm in length and 30 m in diameter) that constitute 75% of the dry weight of the organism and that each of these spicules contains a central axial filament of protein (1-2 mm in length and 2 m in diameter) consisting of three very similar subunits that we have named silicateins (for silica proteins; ref. 8). Characterization of silicatein ␣ (the subunit comprising nearly 70% of the mass of the filaments) and its cloned cDNA indicated that it is homologous to members of the cathepsin L subfamily of the papain family of proteolytic enzymes (8).We show here that, at neutral pH, the silicatein filaments and their constituent subunits catalyze the in vitro polymerization of silica and silsesquioxanes from tetraethoxysilane and organically modified silicon triethoxides, respectively. These substrates were chosen because of their stability at neutral pH and the similarity of their chemical reactivity to that of...

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Section: Isolation Of Silicatein Filaments and Analysis Of Reactionsmentioning

confidence: 99%

Silicatein filaments and subunits from a marine sponge direct the polymerization of silica and silicones in vitro

Jennifer

Shimizu

Zhou

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

778

780

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“…[31][32][33][34] In 1992, Mobil researchers disclosed the first family of highly ordered mesoporous molecular sieves, M41S (pore size in the range 2-10 nm), in which long chain cationic surfactants were used as the template or pore forming agents during the hydrothermal sol-gel synthesis. 35 Depending on starting materials and synthesis conditions, different mesoporous silica oxides with ordered structures in the form of hexagonal (denoted as MCM-41), 18,20,[35][36][37][38][39][40][41][42] cubic (denoted as MCM-48), [36][37][38][39][40][41][42] and lamella (denoted as MCM-50), 20,43,44 were formed (see Figure 1). Since then, many synthetic routes and strategies have been developed to yield a wide variety of materials of various frameworks with different chemical compositions and pore structures.…”

Section: Historymentioning

confidence: 99%

Silica-Based Mesoporous Nanospheres

Bhattacharyya

Ducheyne

2011

Comprehensive Biomaterials

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“…In recent years, organic-inorganic hybrid membranes have attracted considerable attention due to their extraordinary properties with improved physical, mechanical, and thermal properties as compared with pure polymeric membranes or inorganic membranes [7,8]. Peng et al [9,10] attempted to introduce γ-glycidyloxypropyltrimethoxysilane (GPTMS) into a matrix of either chitosan or polyvinyl alcohol (PVA).…”

Section: Introductionmentioning

confidence: 99%

Alternative proton-conducting electrolytes and their electrochemical performances

Uma

Parrondo

Rambabu

2012

J Solid State Electrochem

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This study was focused on the performances of membrane electrode assemblies (MEAs) consisting of the proton-conducting 90PVA/3PWA/4GPTMS/1P 2 O 5 /2Gl and 80PVA/10PWA/6GPTMS/2P 2 O 5 /2Gl hybrid membranes as electrolytes together with a Pt/C electrode for proton exchange membrane fuel cells. The MEAs were fabricated and tested as a function of temperature and humidity, and yielded a current density value of about 350 mA cm −2 at 60°C and 100% relative humidity (RH) for the membrane electrolyte 80PVA/10PWA/6GPTMS/2P 2 O 5 /2Gl. These values were compared with Nafion® membranes, and the single-cell performances based on proton-conducting organic/inorganic hybrid electrolytes were discussed. The test conditions employed were equivalent for each MEA that had an active area of 5 cm 2 . These hybrid membranes showed a high proton conductivity in the range of 10 −3 -10 −2 S cm −1 at low temperatures, i.e., 60, 80, and 90°C, and 50%, 75%, and 100% RH.

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Structural Study of Poly(phenylsilsesquioxane) Sol-Gel Materials

Cited by 43 publications

References 1 publication

Silicatein filaments and subunits from a marine sponge direct the polymerization of silica and silicones in vitro

Silicatein filaments and subunits from a marine sponge direct the polymerization of silica and silicones in vitro

Silica-Based Mesoporous Nanospheres

Alternative proton-conducting electrolytes and their electrochemical performances

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