In situ formed methyl-co-(bis-R) silsesquioxane based polymer networks with solvent controlled pore size distributions and high surface areas

Abstract

Specific pore size distributions of synthesized methylsilsesquioxane-based network materials stem from a combination of the solvation of monomers and growing oligomers, as well as miscibility of water in tested solvents; enabling specific analyte uptake materials.

R-Silsesquioxane-Based Network Polymers by Fluoride Catalyzed Synthesis: An Investigation of Cross-Linker Structure and Its Influence on Porosity

“…Changing to larger cage corners for each of the cross-linkers tended to show decreases in overall surface area, except when both corners and cross-linkers contained π-bonds. These studies will enable further understanding of post-synthesis modifiable silsesquioxane networks.Materials 2020, 13, 1849 2 of 13 of reaction solvent and water content in modifying the overall pore size distributions of a single cross-linker system [29]. Though many reports speculate that the pore sizes obtained in sol-gel reactions are directly related to the bridging groups used, especially for rigid spacers [2,26,[30][31][32], we found that multiple pore size distributions (0.5 to 100 nm) could be obtained by simply changing the reaction solvent for the same bridge.…”

“…Sol-gel reaction efficiencies were measured by TGA, based on analysis of post-curing wt. % drops at~200 • C. We compared three cross-linkers against BTSE systems: [29] bis-triethoxysilylhexane (BTSH), bis-triethoxysilylethene (BTSEE), and bis-triethoxysilylacetylene (BTSA). We used a ratio of 1:0.36 of R-Si(OEt) 3 to cross-linker for our standard conditions, as they have been found to offer the highest surface areas and best overall reaction completion [29].…”

“…Specific surface area (SSA) and porosity analyses: A Micromeritics 3FLEX surface and catalyst characterization analyzer (Micromeritics Inc., Norcross, GA, USA) was used to analyze the surface area and porosity of all samples [29,52]. Samples were degassed at room temperature for 2 h with an N 2 flush.…”

“…The sample was heated under air (60 mL/min) from room temperature to 1000 • C at a rate of 10 • C/min. Solid state nuclear magnetic resonance: solid state 29 Si NMR was measured by a Bruker Avance III NMR spectrometer (Bruker, Inc., Billerica, MA, USA). A multinuclear double resonance CP-MAS probe was tuned to 119.23 MHz with a 4 mm top-loading rotor.…”

“…For example, Corma et al have found good synthetic control with fluoride catalysis methods and showing bridging moiety control of porosity [23]. These improvements are due to the rapid equilibration processes that occur, which allow for the facile generation of more uniform porosity in materials as well as controlled swellability [13,15,[24][25][26][27][28][29].…”