Abstract
We fabricated a series of mesoporous silicas and mesoporous organosilicates with hierarchical porosity through evaporation-induced self-assembly using Pluronic F127 as a template in this study. We could tailor the mesophase of each mesoporous silica sample by varying the weight ratio of its two silica sources: tetraethyl orthosilicate (TEOS) and triethoxysilane hydrosilylated octavinyl polyhedral oligomeric silsesquioxane (OV-POSS-SILY). The mesophases ranged from an ordered body-centered cubic (bcc) structure (TEOS alone) to ordered face-centered cubic (fcc) structure (10 and 20 wt.% of OV-POSS-SILY) and finally to disordered spherical pores (≥30 wt.% of OV-POSS-SILY). We used small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) to study the transformations of these mesophases, while N2 isotherm sorption curves revealed the porosities of these mesoporous silicate samples. Moreover, 29Si CP/MAS solid state nuclear magnetic resonance spectroscopy allowed us to analyze the compositions of the POSS-containing silicate frameworks. Such functional mesoporous silica samples incorporating microporous POSS building units have potential applications in various systems, including optical and electronic devices.
Highlights
Polyhedral oligomeric silsesquioxane (POSS) has received much attention recently because of its unique cage-like structure and its interesting phase behavior and properties at multiple length scales [1,2,3,4,5,6,7,8,9,10,11,12,13,14]
In the 29Si nuclear magnetic resonance (NMR) spectra (Figure 3), the peak at −80 ppm for OV-POSS disappeared completely, with new signals appearing for OV-POSS-SILY at −66.8 and −45.4 ppm
The 1H, 13C, and 29Si NMR spectra collectively confirmed the successful synthesis of OV-POSS-SILY
Summary
Polyhedral oligomeric silsesquioxane (POSS) has received much attention recently because of its unique cage-like structure (intramolecular pore size: ca. 0.3 nm) and its interesting phase behavior and properties at multiple length scales [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. (PEO20PPO70PEO20, P123) micelles to fabricate a mesoporous organic/inorganic hybrid material having a hierarchical architecture and various functionality (including the cubic silsesquioxane cage, the bridging ethylene groups, and the pendant vinyl groups) [21]. They performed more detailed characterization and examined the deeper applications of a bifunctional super-microporous organosilica prepared through the assembly of predefined POSS nano building blocks around a poly(ethylene glycol) octadecyl ether (Brij-76) template [22]. Scheme 1. (a) Synthesis of triethoxysilane hydrosilylated octavinyl polyhedral oligomeric silsesquioxane (OV-POSS-SILY); and (b) The preparation of mesoporous silicas with different amounts of polyhedral oligomeric silsesquioxane (POSS) building units tempalted by F127 triblock copolymers
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