Synthesis of Polycyclic and Cage Siloxanes by Hydrolysis and Intramolecular Condensation of Alkoxysilylated Cyclosiloxanes

Abstract

The controlled synthesis of oligosiloxanes with well‐defined structures is important for the bottom‐up design of siloxane‐based nanomaterials. This work reports the synthesis of various polycyclic and cage siloxanes by the hydrolysis and intramolecular condensation of monocyclic tetra‐ and hexasiloxanes functionalized with various alkoxysilyl groups. An investigation of monoalkoxysilylated cyclosiloxanes revealed that intramolecular condensation occurred preferentially between adjacent alkoxysilyl groups to form new tetrasiloxane rings. The study of dialkoxy‐ and trialkoxysilylated cyclotetrasiloxanes revealed multistep intramolecular condensation reactions to form cubic octasiloxanes in relatively high yields. Unlike conventional methods starting from organosilane monomers, intramolecular condensation enables the introduction of different organic substituents in controlled arrangements. So‐called Janus cubes have been successfully obtained, that is, Ph4R4Si8O12, in which R=Me, OSiMe3, and OSiMe2Vi (Vi=vinyl). These findings will enable the creation of siloxane‐based materials with diverse functions.

Cyanostilbene‐Based AIEgen Smart Film: Optical Switching by Engineering Molecular Packing Structure and Molecular Conformation Through Thermal and Photoinduced Monotropic Phase Transition

“…For the development of smart organic materials with target properties, many material scientists and engineers have tried to understand the thermodynamic and kinetic relationships between chemical structure, molecular packing structure and for meso-nanostructure, organic-inorganic hybrids, and functional amphiphiles. [39][40][41][42][43][44][45] In this context, there have been several reports about the synthesis and application of cyclosiloxanebased molecules, but the thermodynamic and kinetic relationships between the chemical structure, molecular packing structure, and resulting material properties of cyclosiloxane-based functional molecules need to be further studied.…”

“…[ 32–38 ] In particular, it is notable that cyclosiloxanes have advantages in view of geometry and dimensional diversity, multifunctionalization, relatively flexible building unit for meso‐nanostructure, organic–inorganic hybrids, and functional amphiphiles. [ 39–45 ] In this context, there have been several reports about the synthesis and application of cyclosiloxane‐based molecules, but the thermodynamic and kinetic relationships between the chemical structure, molecular packing structure, and resulting material properties of cyclosiloxane‐based functional molecules need to be further studied.…”

The Influence of HCl Concentration on the Rate of the Hydrolysis–Condensation Reaction of Phenyltrichlorosilane and the Yield of (Tetrahydroxy)(Tetraphenyl)Cyclotetrasiloxanes, Synthesis of All Its Geometrical Isomers and Thermal Self-Condensation of Them under “Pseudo”-Equilibrium Conditions

“…Octaarylsilsesquioxanes with reactive or non-reactive organic groups were synthesized from cyclotetrasiloxanetetraols and their sodium salts in the presence of ammonium catalysts [ 17 ]. Unsymmetrical silsesquioxane double-deckers of new types [ 17 , 18 , 19 , 20 , 21 , 22 ], the basket [ 23 ] and butterfly types [ 24 ], or siloxane cages were reported to be obtained by simple hydrolytic condensations of two cyclosiloxanes with an organomonosilane. They can be building blocks for diverse applications since materials based on them should have low dielectric constants and excellent thermal stability.…”

Synthesis and Characterization of Unsymmetrical Double-Decker Siloxane (Basket Cage)

“…In contrast, only a few studies on unsymmetrical silsesquioxane or siloxane cages have been reported because of the difficulty in obtaining a perfect Janus structure via a simple hydrolytic condensation of two organomonosilane precursors. Due to its unique chemical/physical properties related to type, number, and position of organic functional groups on a single molecule, the synthesis of asymmetrical structures has recently become an essential subject in chemistry [30,31,32,33,34,35]. Since the first report by the Laine group [30], to the most recent by the Kuroda group [31], on the synthesis of Janus cube octasilsesquioxane by the hydrolytic condensation of trimethoxy groups on cyclotetrasiloxanes rings, only our group has successfully synthesized a Janus cube from two different organic functional groups on cyclotetrasiloxane precursors [32].…”

“…Due to its unique chemical/physical properties related to type, number, and position of organic functional groups on a single molecule, the synthesis of asymmetrical structures has recently become an essential subject in chemistry [30,31,32,33,34,35]. Since the first report by the Laine group [30], to the most recent by the Kuroda group [31], on the synthesis of Janus cube octasilsesquioxane by the hydrolytic condensation of trimethoxy groups on cyclotetrasiloxanes rings, only our group has successfully synthesized a Janus cube from two different organic functional groups on cyclotetrasiloxane precursors [32]. Furthermore, we also expanded to the synthesizing of an elongated core-sized Lantern Cage siloxane with the similar capping reaction between tetrakis(bromodimethylsiloxy)tetraphenylcyclotetrasiloxane and cyclotetrasiloxanetetraol [33].…”