Formation of nanostructured silicas through the fluoride catalysed self-polymerization of Q-type functional silica cages

Abstract

Octa(dimethylsiloxy)silsesquioxane (Q8M8H) undergoes rapid self-polymerization in the presence of a fluoride catalyst to form complex 3D porous structural network materials with specific surface areas up to 650 m2g-1. This establishes...

Overview of the challenges and current solutions in organic and hybrid coatings for historical monuments and architecture

“…However, these units are often combined to install unique side chains or crosslinking sites to modify properties. [122][123][124][125][126] Sol-gel and/or hydrosilylation processes are most commonly utilized to form siloxane-type polymer coatings, where the suspension of the alkoxysilanes in a solvent forms a solid film upon condensation reaction and drying which provides a more environmentally friendly route to coating formation compared to epoxies and acrylics. 122,[127][128][129][130] For the same reasons, these materials are susceptible to hydrolyzation over time, resulting in crack formation in strained systems, and requiring the surface to be retreated.…”

“…Two types of siloxane polymers are commonly formed depending on the monomers used: linear chains derived from M and D units and three‐dimensional networks with silsesquioxanes formed from T types or silica components from Q units. However, these units are often combined to install unique side chains or crosslinking sites to modify properties 122–126 . Sol–gel and/or hydrosilylation processes are most commonly utilized to form siloxane‐type polymer coatings, where the suspension of the alkoxysilanes in a solvent forms a solid film upon condensation reaction and drying which provides a more environmentally friendly route to coating formation compared to epoxies and acrylics 122,127–130 .…”

Direct cross-linking of silyl-functionalized cage siloxanes via nonhydrolytic siloxane bond formation for preparing nanoporous materials

“…A problem of such hydrolytic condensation reactions is the possible cleavage of the siloxane bonds within the cage frameworks and/or between the silyl groups and cage frameworks. Self-polymerization of D4R siloxanes modified with dimethylsilyl groups (Si 8 O 12 (OSiMe 2 H) 8 , D4R-SiMe 2 H ) in the presence of a fluoride ion catalyst 7 has also been reported. However, it is still difficult to completely prevent the cleavage of the cage framework and the elimination of terminal silyl groups caused by the presence of water in the systems.…”

Cage-rearranged and cage-intact syntheses of azido-functionalized larger T10 and T12 POSSs

“…), are a class of well-defined nanoparticles consisting of an inorganic siloxane cage [(SiO 1.5 ) n , T n ] and multiple organic substituents (R = H, alkyl, vinyl, phenyl, etc .). 1 Due to their cage-like shape-persistent three-dimensional structures, hybrid characteristics, and diverse functionalities, POSSs have garnered significant attention in the materials chemistry community and find wide-ranging applications in diverse fields such as polymer nanocomposites, 2 self-assembly, 3 biomedicine, 4 catalysis, 5 dielectrics, 6 absorbents, 7 and coatings. 8 Typically, the properties of POSSs are determined by the T n cage and the substituents attached to it.…”