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![Macrocyclic compounds (cyclic-(R6Si8O13)n) obtained by intermolecular condensation of disilanol functionalized D4R siloxanes. The R groups are omitted for clarity. Reprinted with permission from Inorg. Chem. 2018, 57, 14686−14691 [60]. Copyright 2018 American Chemical Society.](publication/338846076/figure/fig7/AS:852114788057088@1580171405181/Macrocyclic-compounds-cyclic-R6Si8O13n-obtained-by-intermolecular-condensation-of.jpg)
Macrocyclic compounds (cyclic-(R6Si8O13)n) obtained by intermolecular condensation of disilanol functionalized D4R siloxanes. The R groups are omitted for clarity. Reprinted with permission from Inorg. Chem. 2018, 57, 14686−14691 [60]. Copyright 2018 American Chemical Society.
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Siloxane-based materials have a wide range of applications. Cage-type oligosiloxanes have attracted significant attention as molecular building blocks to construct novel siloxane-based nanoporous materials with promising applications such as in catalysis and adsorption. This paper reviews recent progress in the preparation of siloxane-based nanopor...
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... key to this success was the use of a di-hydroxy organic compound that can bridge the adjacent corner Si atoms by the reaction with Si-H groups. After the hydrolysis of the Si-O-C bonds to form silanol groups, cyclic siloxanes with well-defined cavities (cyclic-(R6Si8O13)n; R = alkyl, n = 3, 4, and 5) were obtained by intermolecular condensation (Figure 7). These cyclic compounds can be regarded as "molecular zeolites". ...
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... Depending on a way of synthesis and used substrates, especially the one that contributes the silica-derivative component, the obtained hybrid and composite materials may significantly differ from each other in terms of structural properties. Silica or silicate species can create varied forms ranging from completely disordered and amorphous [12,13], through partially ordered (composed of defective octamers or ladder-like fragments [14,15]), to crystalline [16,17] or channel-like highly ordered [3,18]. Their rigid structure not only allows to construct internal three-dimensional frameworks, which constitute an element reinforcing the material [19], but also influences its thermochemical and insulation properties contributing to the increase in thermal and fire resistance [4,5,9,20]. ...
The TGA-EGA technique was used to study the influence of sulphanilic acid (SA) on the carbonisation process of the hybrid
terpolymeric precursors composed of methacrylamide, divinylbenzene, and trimethoxyvinylsilane. The pristine polymers
were impregnated with saturated solution of SA, dried, and carbonized at 600 °C under N2
atmosphere. The characteristic
properties of both the pristine hybrid polymers and the resulting carbons were based on FTIR, Raman, and PXRD analyses,
which revealed the materials were composed of amorphous polymeric or carbon phase interpenetrated by silica/silicate
disordered network. The porosimetric analysis showed the resulted carbons possessed homogeneous supermicropores with
the average pore width of 0.7 nm and reduced number of mesopores compared to pristine precursors. From the TGA results,
it was followed that impregnated polymers decomposed in two stages, instead of one like pristine precursors did. Moreover,
IDT of impregnated polymers was reduced by about 100 °C, and their Tmax
was increased by 2–5.5 °C. Their decomposition
proceeded slower by 22–37% that caused increase in efficiency of the process by 10–48%. The EGA showed the decomposition
of the impregnated precursors started from the degradation of the amide groups, then SA destruction took place,
followed by further decomposition of the polymer. The studies led to the conclusion that SA had the protective effect on
the surface of the carbonized polymers. During impregnation and thermal treatment, SA produced a deposit in pores of the
precursors. This resulted in narrowing of the pore width, delaying and slowing down the polymer thermal decomposition
process, as well as increasing its efficiency.
... Organosilica compounds are of particular interest due to the inherent properties of silicon-containing compounds, as well as the possibility of precise control of their properties by varying the structure of organic fragments [14,15]. In particular, materials containing Si-O-Si networks are interesting because of their low-toxicity, structural diversity and abundant resources [16]. Silicon-based porous materials are notable for their low cost, adjustable particle size and scalability. ...
... cis-trans- (4), and all-trans-(5) (Figure 1) have been performed. All reactions were monitored with APCI-MS and 29 Si NMR spectrosco tions of 1 were conducted at 4 °C with the concentration of HCl between 0 mol L −1 . ...
... Recently, the stereoisomerization of all cis-[iso-C 4 H 9 Si(OH)O] 4 in an acetone solution under the action of HCl taken in concentrations from 0.01 M to 5 M was studied. It was found that after 10 min, regardless of the C HCl , three isomers were formed and the ratio between the four isomers changed insignificantly with the change in C HCl [30]. ...
The rate of hydrolysis–condensation reaction of phenyltrichlorosilane in water-acetone solutions and the product yields were shown to significantly depend on the concentration of HCl (CHCl) in the solutions. The main product of the reaction was all-cis-(tetrahydroxy)(tetraphenyl)cyclotetrasiloxane. This was different from the earlier published results of analogous reactions of m-tolylSiCl3, m-ClPhSiCl3, and a-naphtylSiCl, in which some products of other types were formed. For example, trans-1,1,3,3-tetrahydroxy-1,3-di-α-naphtyldisiloxane was obtained in the case of a-naphtylSiCl3. All-cis-(tetrahydroxy)(tetraphenyl)cyclotetrasiloxane was treated in acetone with HCl to give the other three geometric isomers (cis-cis-trans-, cis-trans-, and all-trans-). The thermal self-condensation of these four isomers under “pseudo”-equilibrium conditions (under atmospheric pressure) was investigated in different solvents, in quartz or molybdenum glass flasks. The compositions of the products were monitored by APCI-MS and 29Si NMR spectroscopy. It was shown that all-cis- and cis-cis-trans-isomers in toluene or anisole mostly gave the cage-like Ph-T8,10,12,14 and uncompleted cage-like Ph-T10,12OSi(HO)Ph compounds. In contrast to these two isomers, the cis-trans–isomer in toluene mainly formed dimers with the loss of one or two molecules of water. However, in acetonitrile, significant amounts of Ph-T10,12 and Ph-T10,12OSi(HO)Ph species were formed along with the dimers. All-trans-isomer did not enter into the reaction at all.
... In recent years a large number of studies into microporous POSS compounds have been reported. However, only a few structural analyses have been conducted as these materials do not usually crystallise in a manner similar to metal-organic-frameworks (MOFs), and thus, techniques such as X-ray diffraction and Raman spectroscopy are of limited use in their characterisation (Stein, 2003;Shimojima and Kuroda, 2020). ...
Microporous organosilicas assembled from polysilsesquioxane (POSS) building blocks are promising materials that are yet to be explored in-depth. Here, we investigate the processing and molecular structure of bispropylurea bridged POSS (POSS-urea), synthesised through the acidic condensation of 1,3-bis(3-(triethoxysilyl)propyl)urea (BTPU). Experimentally, we show that POSS-urea has excellent functionality for molecular recognition toward acetonitrile with an adsorption level of 74 mmol/g, which compares favourably to MOFs and zeolites, with applications in volatile organic compounds (VOC). The acetonitrile adsorption capacity was 132-fold higher relative to adsorption capacity for toluene, which shows the pores are highly selective towards acetonitrile adsorption due to their size and arrangement. Theoretically, our tight-binding density functional and molecular dynamics calculations demonstrated that this BTPU based POSS is microporous with an irregular placement of the pores. Structural studies confirm maximal pore sizes of around 1 nm, with POSS cages possessing an approximate edge length of approximately 3.16 Angstrom
... In recent years a large number of studies into microporous POSS compounds have been reported. However, only a few structural analyses have been conducted as these materials do not usually crystallise in a manner similar to metal-organic-frameworks (MOFs), and thus, techniques such as X-ray diffraction and Raman spectroscopy are of limited use in their characterisation (Stein, 2003;Shimojima and Kuroda, 2020). ...
Microporous organosilicas assembled from polysilsesquioxane (POSS) building blocks are promising materials that are yet to be explored in-depth. Here, we investigate the processing and molecular structure of bispropylurea bridged POSS (POSS-urea), synthesised through the acidic condensation of 1,3-bis(3-(triethoxysilyl)propyl)urea (BTPU). Experimentally, we show that POSS-urea has excellent functionality for molecular recognition toward acetonitrile with an adsorption level of 74 mmol/g, which compares favourably to MOFs and zeolites, with applications in volatile organic compounds (VOC). The acetonitrile adsorption capacity was 132-fold higher relative to adsorption capacities for methanol and toluene, which shows the pores are highly selective towards acetonitrile adsorption due to their size and arrangement. Theoretically, our tight-binding density functional and molecular dynamics calculations demonstrated that this BTPU based POSS is microporous with an irregular placement of the pores. Structural studies confirm maximal pore sizes of ∼ 1 nm, with POSS cages possessing an approximate edge length of ∼ 3.16 Å.
... The Si-O bond is a highly versatile chemical linkage that can be found in a great variety of materials and molecules, linking together inorganic [1][2][3] and organic species [4][5][6], as well as being a building block for polymers [7][8][9] and sophisticated 3D oligomers [10,11]. In the role of linkage, the siloxane bond is robust, chemically resistant to an array of environments and easily established, e.g., via the reaction of silanes with organic or inorganic hydroxyl groups [6,12,13]. ...
Siloxanes are adaptable species that have found extensive applications as versatile materials for functionalising various surfaces and as building blocks for polymers and hybrid organic-inorganic systems. The primary goal of this review is to report on and briefly explain the most relevant recent developments related to siloxanes and their applications, particularly regarding surface modification and the synthesis of graft copolymers bearing siloxane or polysiloxane segments. The key strategies for both functionalisation and synthesis of siloxane-bearing polymers are highlighted, and the various trends in the development of siloxane-based materials and the intended directions of their applications are explored.
While a variety of functional zeolites have been synthesized using hydrothermal methods with conventional discrete Al and Si sources, control of the composition, structure, and function of the targeted zeolites often involves costly and time-consuming trial-and-error approaches. Despite ongoing efforts to manipulate zeolite formation by adjusting Al and Si sources and reaction conditions, limited attention has been given to studies on zeolite synthesis using molecular precursors (MPs) with pre-organized Al–O–Si bonds. Here, we demonstrate the synthesis of LTA-type zeolites using [TMA]4[Al4Si4O12(OH)8]·13H2O ([MP]; TMA = tetramethylammonium cation) with a double-four-ring (D4R)-type core structure, which is known to be a secondary building unit (SBU) in the LTA-type zeolite, as a MP. Here, we demonstrate the successful synthesis of LTA-type zeolites using [MP] under hydrothermal conditions at 100–200 °C in the presence of 1 equivalent of NaOH or NaCl. Notably, when discrete Al and Si sources were used instead of [MP] under otherwise identical conditions (the same Si/Al ratio, Na+ content, and temperature), GIS-, SOD-, and FAU-type zeolites lacking the D4R structure were obtained in addition to the LTA-type zeolites.
Octaalkoxy-substituted polyhedral oligomeric silsesquioxane (8RO-POSS) is an attractive starting material for producing silicone resins. However, polymers derived from 8RO-POSS via the sol–gel process have seldom been reported owing to their...
The photoresist is one of the key materials for the development of the modern semiconductor industry, and it not only affects the chip manufacturing process but also has an important impact on performance. Photoresists with low dielectric properties have a critical impact on the fabrication process and performance of various chips and devices. In this paper, a silicone encapsulated photoresist with low dielectric properties is reported, and it demonstrates excellent film-forming properties and lithography patterning effects, with a line width of 10 μm and a line spacing, a low dielectric constant (Dk = 2.75), a high thermal decomposition temperature (T5 = 503.5 °C), a low coefficient of thermal expansion (CTE = 33.61 ppm per °C), and excellent mechanical properties of thin films. This type of resin has a photo-crosslinked double bond structure and a thermally cross-linked benzocyclobutene structure, in which the silicone branched structure gives the photoresist excellent patterning properties and the thermally crosslinked structure gives the film excellent thermal, electrical, and mechanical properties. The resin is expected to replace traditional polyimide photoresists and has important applications in the semiconductor industry.
This present work investigates the corrosion performance of hybrid organic/inorganic Si/Zr sol-gel doped with various cerium nitrate concentrations applied on hot-dip galvanized steel. The Si/Zr sol-gel solution was prepared from tetraethyl orthosilicate (TEOS), 3-(trimethoxysilyl)propyl methacrylate (MAPTMS), and zirconium (IV) propoxide (ZTP). The effect of the addition of cerium nitrate was evaluated by electrochemical impedance spectroscopy (EIS) versus immersion in 0.1 M NaCl solution and salt spray test. The results indicated that cerium nitrate contents affected the protective behavior of sol-gel coating in long term. Additionally, the sol-gel doped with 650 ppm Ce (III) presented the optimal corrosion protection of the sol-gel coating formed on hot-dip galvanized steel substrate.
