Polyhedral Oligomeric Silsesquioxane

Octavinyloctasilsesquioxane was first prepared in 1978 with a yield of <10% by K. Andrianov 1  and co-workers in the trichlorovinylsilane hydrolysis reaction. Since then, many groups have tried to improve the method of obtaining it. 2-4  In 1997, P. Harrison and Ch. Hall, when examining the hydrolysis of CH 2 =CHSiCl 3  in ethanol, they obtained (CH 2 =CHSiO 1.5 ) 8  with an efficiency of 30%. 5  The use of an ion exchange resin as a catalyst for the hydrolysis and condensation of CH 2 =CHSiCl 3  contributed to an increase in the reaction efficiency to 40%. 6  Compound (CH 2 =CHSiO 1.5 ) 8  was obtained with a yield of 80% using CH 2 =CHSi(OEt) 3  during hydrolysis and tetramethylammonium hydroxide as a phase transfer reagent. 7 Octavinyloctaasilsesquioxane derivatives can be obtained as a result of typical alkene reactions, such as: thiolation, phosphination, hydrosilylation, epoxidation, as shown in scheme below. Thiolation with reagents such as thiophenol or thiocyclohexane can b

There is little information available in the literature concerning pure, isolated larger cages like the aforementioned heptahedral T 10 . A small amount of T 10  type POSS is usually formed as a by-product during the preparation of T 8  type silsesquioxanes. For example, during the preparation of T 8 H 8  by the hydrolytic condensation of HSiCl 3 , a small amount of T 10 H 10 . 1  is formed in addition to the main product. The formation of more thermodynamically unstable POSS of the T 10  or even T 12  type occurs primarily as a result of the reorganization of the core of the T 8  cage. The transformation of the T 8  cage into a larger one has been published by several research groups. 2–4  For example, V. Ervithayasuporn observed the reorganization of octakis (3-chloropropyl) octasilsesquioxane by reaction with sodium methacrylate, 5  sodium phenoxides, 6  or potassium phthalimide. 7  These reactions resulted in the formation of mixture of compounds of the type T 8 , T 10  and T 12  

Octa(3-aminopropyl)silsesquioxane hydrochloride (OAS) was first described in a patent from Wacker-Chemie GmbH. 1  However, this document does not describe the method of its preparation, nor the spectroscopic data allowing its full identification. 2  Seven years late F. Feher 3  investigated the hydrolytic condensation of (3-aminopropyl) triethoxysilane in a methanolic solution using hydrochloric acid as a catalyst to obtain octakis (3-aminopropyl) octasilsesquioxane chloride salt. The yield of the reaction under these conditions is 30%, and the duration is 4 weeks. Modifications to this procedure can be found in the literature based on the change of the hydrolysable group to the methoxy group or the addition of PtCl 4  cocatalyst. However, these treatments do not significantly increase the yield of the reaction. 4–6  Kaneko and co-workers achieved another valuable approach. 7  They investigated the hydrolytic condensation of APTMS using a number of different acid catalysts. The best ef

Quantum-mechanical calculations of octhydrooctasilsesquioxane showed that the highest occupied molecular orbital (HOMO) of this compound consists of atomic orbitals of free electron pairs of oxygen atoms, while the lowest energetically unfilled molecular orbital (LUMO) The lowest unoccupied molecular orbital) is spherical and is located in the center of the silsesquioxane core as shown in figure belowe. The calculations also showed that the energy gap between the HOMO and LUMO orbitals is approximately 6-7 eV. This value is higher than the limit for conductivity (3 eV), which proves that the silsesquioxane core is an insulator. Figure of molecular orbitals: (a) HOMO and (b) LUMO octhydrocarbonoctasilsesquioxane Taking into account the low electronegativity of silicon atoms (1.90 compared with 2.55 for the carbon atom according to the Pauling scale), it can be assumed that the POSS core will behave like an electron donor group. However, experimental studies have shown that the silses

There are many synthetic methods for the preparation of POSS, other than the methods used in the first attempts to synthesize this type of compounds. These methods can be divided into three categories. The first is the hydrolysis and condensation of silanes, the second is the preparation of a polyhedron compound from silanols containing less than eight silicon atoms, the third is the modification of the side arms of the already existing polyhedric silsesquioxane or the substitution of a hydrogen atom in octahydrooctasilsesquioxane. Synthesis of POSS Compounds   Synthesis of POSS Compounds

Polyhedral oligomeric silsesquioxanes (POSS) compounds described by the chemical formula (RSiO 3/2 ) n  (where n = 6, 8, 10, 12; R = H, alkyl, aryl), constitute a family of three-dimensional organosilicon compounds containing siloxane Si–O–Si moieties. Such species possess various structures including ladder-like, cage-like, and open-cage motifs. Their molecular structure strictly depends on reaction conditions. Because of the well-defined 3D structure, the most promising seem the cage-like systems. It is possible to obtain these type of compounds with a variety of structural frameworks like hexamers (T 6 ),octamers (T 8 ), decamers (T 10 ), and dodecamers (T 12 ). Their synthesis is challenging and in many cases cumbersome due to the formation of variety of structures derived from different Si–O connections types. Molecular silsesquioxanes are organosilicon are considered as the smallest existing silica nanoparticles, due to their diameters in the range of 1–3 nm. Another advantage of

The English name silsesquioxane comes from Latin and can be translated as: sil icium (silicon), sesqui (one and a half), ox ygenium (oxygen), which means that the ratio of atoms to silicon atoms is one and a half. The use of system names for polyhedra silsesquioxanes can be cumbersome, therefore the literature uses the nomenclature for siloxanes. This classification distinguishes five silicon atoms (see figure below). Type "M" symbol one connected with three organic groups and an atom connected. A silicon atom of type "D" is linked to two atoms, type "T" is linked to three atoms, and type "Q" is linked to four atoms manually. Si–O connections can form siloxane (Si–O–Si) or silanol (Si–OH) groups. To distinguish them, a superscript is used, which defines the number of Si–O–Si bonds formed by the silicon atom, eg T 3 represents a silicon atom containing one organic group and three siloxane bonds. Polyhedral silsesquioxanes have T 3 type silico

Research on compounds containing Si–O bond for years has been dominated by silicon oxide, minerals containing the repeating fragment of SiO 2 and silicones made of repeating units of R 2 SiO (R = alkane or phenyl). Over the past 20–30 years, research has been developing on silsesquioxanes containing the RSiO 1.5 group. Due to the presence of an inorganic fragment and an organic group, these compounds have hybrid properties. The inorganic Si–O–Si fragment gives these compounds chemical and thermal resistance, while the organic R group increases their solubility and gives them appropriate reactivity. It is possible to obtain many polymeric structures with the general formula (RSiO 1.5 ) n , but the most interesting are those with polyhedron structure. 1 The first reports of compounds composed of repeating CH 3 SiO 1.5 groups appeared in 1946 in the work of D. Scott. 2 Scott described the thermal depolymerization of polymethylsiloxane obtained during the condensation of trichlorometh

The presence of Si–O bonds in the central core of POSS imparts superior thermal, mechanical, and chemical stability, which makes these compounds extremely interesting from an industrial point of view. From the many valuable properties of POSS the ones that are responsible for improvement of oxidation resistance of polymers doped with POSS are of special interest. From this reason a deeper insight into thermal properties and their dependence on the POSS structure is highly needed. Already in 1997 Bolln et al. studied thermal properties of alkyl substituted T 8  POSS cages, which showed that their thermal stability increases with longer chain length (from 166 °C for octapropyl up to 355 °C for octadecyl derivatives). He also showed that the degradation processes performed in dinitrogen or in oxidative environment differ signifi­cantly. POSS degradation studies concentrating on the gas and char analysis were undertaken by Mantz et al. and gave an insight into details of the POSS degrada

Porous Silsesquioxane-Imine Frameworks (PSIF) was designed and synthesized by imine condensation approach starting from octa(3-aminopropyl)silsesquioxane cage compound (OAS-POSS) and selected multitopic aldehydes. The resulting PSIFs possess 3D micro-mesoporous structures with permanent porosity and high thermal stability. These aerogels were tested in sorption of I 2  vapor. For PSIF-1a I 2 uptake of 481%wt was obtained, which is the highest value reported to date. Preferential interaction of I 2  with PSIFs can be attributed to the cooperative interactions of POSS cages and imine moieties in the porous framework. Schematic representation of the synthesis of PSIF-1–5; bifunctional and trifunctional prolinkers used in the synthesis ACS Appl. Mater. Interfaces 2018, 23, 19964-19973

The simplest method of preparing amides is by reacting the amines with carboxylic acids (for example in the presence of DCC as a coupling agent), acid anhydrides, esters or acyl halides. In the work by Janeta et all ( Chemistry - A European Journal 2014, 20, 15966-15974 ), the reactions were carried out with the use of acid chlorides, which were selected because these reactions do not require an additional coupling agent, the reaction is rapid even at reduced temperature, and the resulting by-product (ammonium salt) is easy to remove. The reaction of amines with acid chlorides, the products of which are amides (Schotten-Baumann reaction), is usually carried out in a two-phase system. The alkaline aqueous phase containing sodium hydroxide neutralizes the acid ammonium salt and the product remains in the organic phase. However, as under these conditions the silsesquioxane core decomposes (a strong base breaks the Si–O–Si bonds), the solution was to use triethylamine as a neutralizing age