Prof. Kazuki NAKANISHI, Silsesquioxane-based Hybrid Macroporous Monoliths for Heat-insulation, Oil-water Separation and Supported Metal Nanoparticles
Date: Fri 14 Jun 2013, 09:30 - 10:30
Location: UPC (Engineering Room 148A)
SEMINAR: Silsesquioxane-based Hybrid Macroporous Monoliths for Heat-insulation, Oil-water Separation and Supported Metal Nanoparticles
Prof. Kazuki NAKANISHI
Department of Chemistry, Graduate School of Science, Kyoto University
Organic-inorganic hybrids derived from partially substituted alkoxysilane precursors can offer a variety of monolithic porous materials via a sol-gel process when their hydrolysis-polycondensation reactions are appropriately controlled to parallel the polymerization-induced phase separation. Some of our recent developments are described below.
Using methyltrimethoxysilane, MTMS, as a single precursor, monolithic poly(methylsilsesquioxane), PMSQ gels are prepared in the presence of surfactants via acid-base one pot reaction route. Through the preparation optimized for low-density, pure PMSQ aerogels are obtained to exhibit comparable properties with those of tranditional silica aerogels. Moreover, the monolithic PMSQ aerogels can reversibly recover to the original size when uniaxially compressed. Utilizing this “spring-back” property, PMSQ aerogels can be prepared by drying at ambient conditions.
K. KANAMORI and K. NAKANISHI, Chem. Soc. Rev., 40, 754-770 (2011). doi: 10.1039/C0CS00068J
Marshmallow-like Macroporous Monoliths
As an extension of PMSQ monoliths, a co-polymerization of MTMS with dimethyldimethoxysilane, DMDMS, was attempted. With an increase of DMDMS/MTMS ratio, the Young’s modulus drastically decreased to give very soft reversibly deformable monolith (marshmallow-like monolith) with larger macropores. Due to its inherent surface hydrophobicity, the marshmallow-like monolith can selectively absorb nonpolar liquid from a physical mixture of oil/water.
G. HAYASE et al, Angew. Chem. Int. Ed., 52 (7), 1986-1989 (2013). doi: 10.1002/anie.201207969
The simplest silsesquioxane, hydrogen silsesquioxane HSQ, has been studied for a long time. Using the polymerization-induced phase separation technique, we have succeeded to prepare monoliths with well-defined continuous macropores while preserving all the Si-H bonds contained in the precursor. Liquid-phase contact of noble metal ions onto the Si-H resulted in an instantaneous formation of metal nanoparticles firmly immobilized in the mesopores of HSQ monoliths. An application of embedded noble metal nanoparticles to various catalytic reactions is now under way.
N. MOITRA et al., Adv. Func. Mater., published online. doi: 10.1002/adfm.201202558