Effect of pH on the Gelation Time of Hexylene-Bridged Polysilsesquioxanes

Abstract

The effect of pH on the gelation time of hexylene-bridged polysilsesquioxanes was determined with the sol−gel polymerization of 1,6-bis(trimethoxysilyl)hexane (1) in methanol. Gel times formed a crude bell curve plotted against pH with the longest gel times of 660 h near pH 5. This represents the first systematic study of the effects of pH on the gelation of polysilsesquioxanes.

Hexylene‐ and Octylene‐Bridged Polysilsesquioxane Hybrid Crystals Self‐Assembled by Dimeric Building Blocks with Ring Structures

“…14 In previous reports, the bridged polysilsesquioxanes with ordered structures were usually synthesized under conditions that may decrease the hydrolysis and condensation rate, for example, by utilizing a low concentration of precursors or by using inert solvents. Importantly, in previous reports, use of the same precursors as in our synthesis resulted in only amorphous materials 8b. 9c…”

“…The hydrolysis and condensation of organosilica species is different from that of pure silica and are commonly known as induction and steric effects 13. By varying the experimental conditions of hydrolysis and condensation, such as the concentration of precursors, catalysts, synthetic temperature, pH value of the reaction system, and solvent, the final structures and physicochemical properties of the products can be changed 8b. 14 In previous reports, the bridged polysilsesquioxanes with ordered structures were usually synthesized under conditions that may decrease the hydrolysis and condensation rate, for example, by utilizing a low concentration of precursors or by using inert solvents.…”

Mechanically robust aerogels derived from an amine-bridged silsesquioxane precursor

“…Different catalysts provide aerogels distinct properties [38][39][40]. In this work, the influences of base catalysis, two-step acid/base catalysis, acid catalysis/base aging and acid catalysis on the DC of the precursor (Fig.…”

Fabrication of highly transparent and superhydrophobic silica-based surface by TEOS/PPG hybrid with adjustment of the pH value

“…In general, condensation reaction is quite slow when the pH value is about 2 (the point of zero charge (PZC) where the surface charge is zero; isoelectric point (IEP)), implying that the gel time is very long [46]. The most important factor for the precursor solution which influences the sol-gel process is the catalyst [47]. The rate coefficient of condensation is the lowest when pH = IEP [46].…”