Phase Behavior of a Carbon Dioxide/Methyl Trimethoxy Silane/Polystyrene Ternary System

Recently, polymeric foams filled with a silica aerogel have been developed. The phase behavior of CO2/silicon alkoxide binary systems and CO2/silicon alkoxide/polymer ternary systems is an important factor that affects the design of novel processes. The phase behavior of a carbon dioxide (CO2)/methyl trimethoxy silane (MTMS)/polystyrene (PS) ternary system was measured using a synthetic method involving the observation of the bubble and cloud point. The phase boundaries were measured at temperatures ranging from 313.2 to 393.2 K and CO2 weight fractions between 0.01 and 0.08. The CO2/MTMS/PS system showed a similar CO2 mass fraction dependence of the phase behavior to that observed for the CO2/tetramethyl orthosilicate (TMOS)/PS system. When the phase boundaries of these systems were compared, the vapor-liquid (VL) and vapor-liquid-liquid (VLL) lines were found to be nearly identical, while the liquid-liquid (LL) lines were different. These results indicate that the affinity between the silicon alkoxide and polymer greatly influences the liquid-liquid phase separation.

Pseudoboehmite Nanorod–Polymethylsilsesquioxane Monoliths Formed by Colloidal Gelation

The addition of a trifunctional silicon alkoxide methyltrimethoxysilane (MTMS) to aluminum oxide hydroxide pseudoboehmite nanorod (PBNR) aqueous dispersions resulted in adhesion between the PBNR colloids to form macroporous monoliths. The use of greater amounts of MTMS led to coarsening of the skeleton and strengthening of the skeletal structure, and the monoliths got water resistance. When a dispersion of zirconium oxide nanoparticles and MTMS was used as a starting material, a macroporous monolith was also obtained by the same simple process. The colloidal gelation occurs because the silanol moiety is more likely to react with the colloid surface of ceramic materials than with other silanols derived from MTMS and their oligomer. Due to the development of material chemistry, colloidal dispersions having various shapes and compositions are becoming available as products. Based on this mechanism, it is expected to be feasible to fabricate various porous monoliths with characteristic morphologies and properties depending on the colloid.<br>

Pseudoboehmite Nanorod–Polymethylsilsesquioxane Monoliths Formed by Colloidal Gelation

The addition of a trifunctional silicon alkoxide methyltrimethoxysilane (MTMS) to aluminum oxide hydroxide pseudoboehmite nanorod (PBNR) aqueous dispersions resulted in adhesion between the PBNR colloids to form macroporous monoliths. The use of greater amounts of MTMS led to coarsening of the skeleton and strengthening of the skeletal structure, and the monoliths got water resistance. When a dispersion of zirconium oxide nanoparticles and MTMS was used as a starting material, a macroporous monolith was also obtained by the same simple process. The colloidal gelation occurs because the silanol moiety is more likely to react with the colloid surface of ceramic materials than with other silanols derived from MTMS and their oligomer. Due to the development of material chemistry, colloidal dispersions having various shapes and compositions are becoming available as products. Based on this mechanism, it is expected to be feasible to fabricate various porous monoliths with characteristic morphologies and properties depending on the colloid.<br>

Facile fabrication of marshmallow-like gels as flexible thermal insulators and liquid nitrogen retention materials: Application to a cryopreserved embryo container

<p>Low bulk density porous monoliths were prepared by using two types of silicon alkoxide methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) as precursors and controlling phase separation under appropriate conditions. By changing the ratio of the aqueous solution to the precursors in the starting composition, it was possible to control the microstructure of the resulting porous monoliths or to prepare microparticles. Those marshmallow-like monoliths with a skeleton diameter of a few micrometers and pore diameter of several tens micrometers has high flexibility against compression and bending, and shows low thermal conductivity of ~30 mW m⁻¹ K⁻¹ at room temperature. We show that those materials can be used as a simple cryopreserved embryo container like small dry shippers by packing gels and adsorbing liquid nitrogen in a vacuum-insulated water bottle.</p>

Facile fabrication of marshmallow-like gels as flexible thermal insulators and liquid nitrogen retention materials: Application to a cryopreserved embryo container

<p>Low bulk density porous monoliths were prepared by using two types of silicon alkoxide methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) as precursors and controlling phase separation under appropriate conditions. By changing the ratio of the aqueous solution to the precursors in the starting composition, it was possible to control the microstructure of the resulting porous monoliths or to prepare microparticles. Those marshmallow-like monoliths with a skeleton diameter of a few micrometers and pore diameter of several tens micrometers has high flexibility against compression and bending, and shows low thermal conductivity of ~30 mW m⁻¹ K⁻¹ at room temperature. We show that those materials can be used as a simple cryopreserved embryo container like small dry shippers by packing gels and adsorbing liquid nitrogen in a vacuum-insulated water bottle.</p>

Monodispersed strontium containing bioactive glass nanoparticles and MC3T3-E1 cellular response

Non-porous monodispersed strontium containing bioactive glass (Si2O-CaO-SrO) nanoparticles (Sr- BGNPs), were synthesised using a modified Stöber process. Silica nanoparticles (Si-NPs) with diameters 90 ± 10 nm were produced through hydrolysis and polycondensation reactions of the silicon alkoxide precursor, tetraethyl orthosilicate (TEOS), prior to the incorporation of cations; calcium (Ca) and strontium (Sr), into the silica networks through heat treatment (calcination). Sr was substituted for Ca on a mole basis from non- (0SrBGNPs) to fullsubstitution (100SrBGNPs) in order to increase the amount of network modifiers in the Si-NPs. The different ratios of Si: Ca; 1:1.3 and 1:8.0, presented various elemental compositions (i.e. 77–92 mol% of SiO

Synthesis and characterization of the first transparent silicon oxycarbide aerogel obtained through H2decarbonization

The first transparent silicon oxycarbide aerogel has been obtained through H2decarbonzation at 800 °C starting from an alkylene-bridged silicon alkoxide precursor.

Porous Polyimide-Silica Composite: A New Thermal Resistant Flexible Material

ABSTRACTWe developed a new highly porous polyimide (PI) -silica composite with high flexibility, mechanical strength, and heat resistance. The composite was prepared by a new process consisting of (1) phase separation of a mixture of PI precursor (polyamic acid), solvent, and silicon alkoxide, induced by high-pressure CO2 (40 °C, 20 MPa), (2) silicate formation by sol-gel reaction, and (3) supercritical CO2 extraction of the solvent. The composite had a bimodal porous structure with micropores of 10-30 μm and nanopores of ∼50 nm. In the PI matrix, silica nanoparticles (< 100 nm in diameter) were highly dispersed. Porosity of the composite was 78%, which is higher than that of conventional porous PI prepared by physical foaming technique. Relative dielectric constant of the material was lower than 1.4 at 1 MHz. The porous PI-silica composite sheet was flexible enough to be folded without cracking. Notably, the Young’s modulus (0.80 GPa) and the onset decomposition temperature (600 °C) of the PI-silica composite were higher than those of conventional porous PI with similar porosity, respectively. The porous PI-silica composite is promising as a flexible thermal insulator for high-temperature use and as a thermal resistant low-k material.