Crystalline Organosilsesquioxanes<sup>*</sup>

Barry, Arthur J.; Daudt, William H.; Domicone, Joseph J.; Gilkey, John W.

doi:10.1021/ja01621a025

Cited by 178 publications

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“…1,[3][4][5][6][7] Most of the interests have been focused on hydrido, vinyl and epoxy functional polysilsesquioxane, and the products have been used in high porous materials, 8 nano-composite materials, 9 and catalyst for polymerization, 10 although many unidentified products still exist in the system. During the reaction, both ''intermolecular'' to give randomly branched polymers and ladder polymers, 11 and ''intramolecular'' to give loop structure which eventually forms cyclic polyhedral cage products occur 4,5,12,13 ( Figure 1). The products usually contain unreacted silanol groups depending on their structures.…”

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confidence: 99%

Tendency of Loop Formation of Oligosilsesquioxanes Obtained from (4-Substituted phenyl)trimethoxysilane Catalyzed by Benzyltrimethylammonium Hydroxide in Benzene

Pakjamsai

Kawakami

2004

Polym J

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ABSTRACT:Products in hydrolysis of (4-substituted phenyl)trimethoxysilane in the presence of benzyltrimethylammonium hydroxide in benzene was studied by matrix-assisted laser desorption/ionization-time of flight mass spectroscopy. In the benzene soluble fraction of 4 h reaction, oligosilsesquioxanes containing 6 to 9 silicon atoms with or without loops were observed. (4-Dimethylaminophenyl)trimethoxysilane gave the fraction containing 6 silicon atoms the least (3%), and 9 silicon fraction the most (36%). Oligosilsesquioxanes containing 9 silicon atoms were formed the least among the products for [4-methoxy-(10%), 4-methyl-(22%), non-(3%), and 4-phenyl-(13%) substituted phenyl]trimethoxysilanes. Oligosilsesquioxanes containing 6 to 8 silicon atoms were the major components of the product irrespective of the substituent. Maximum degree of condensation ( f ) was 0.8 for S 8 , and fully condensed structure was not found. The maximum f ¼ 1:00, and completely closed loop was found in S 9 with one OH group remaining.

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confidence: 99%

Tendency of Loop Formation of Oligosilsesquioxanes Obtained from (4-Substituted phenyl)trimethoxysilane Catalyzed by Benzyltrimethylammonium Hydroxide in Benzene

Pakjamsai

Kawakami

2004

Polym J

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“…On 29Si n. m. r. spectra of partially and fully hydrolyzed products of tetramethoxy-or ethoxy silane, peaks shift to higher frequency when the degree of hydrolysis of tetraalkoxysilane in creases, in other words, the number of hydroxyl groups which displace for alkoxyl groups increases.28),29) For example, Pouxviel et al 2 reported that the resonance due to Si(OC2H5)4 appears at -82.0 p. p. m., that due to Si(OC2H5)3 (OH) at -78.9 p. p. m., that due to Si(OC2H5)2 (OH)2 at -76.2 p. p. m., that due to Si(OC2H5) (OH)3 at -74.2 p. p. m., and that due to Si(OH)4 at -72.4 p. p. m. The value of the chemical shift of CH3Si(OC2H5)3 is measured to be -42.38 p. p. m. In addition, there is enough amount of water in the solution for hydrolyzing methyl triethoxysilane completely. These facts suggest that the peak at -41.2 p. p. m. may be assigned to the completely hydrolyzed product of methyl triethoxysilane, CH3SiO33-.…”

Section: Resultsmentioning

confidence: 99%

Polymerization of Hydrolysis Products of Methyltriethoxysilane in Aqueous Solutions

Hasegawa

Sakka

Sugahara

et al. 1990

J. Ceram. Soc. Japan

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The structure and distribution of chemical species of hydrolysis and polycondensation products of methyltriethoxysilane in aqueous solutions containing sodium ions have been studied with the trimethylsilylation technique and by 29Si n. m. r. spectros copy. 11 trimethylsilylated derivatives of the products were obtained from the solutions. The recovery of methyltrisilanol (CH3Si(OH)3) was much higher than that of the monosilicic acid in an aqueous sodium silicate solution at the same Si con centration and the same sodium ion-to-silicon molar ratio, suggesting that the polymerization of silicate anions is easier than that of hydrolysis products of methyltriethoxysilane in aqueous solutions. On the basis of the distribution, assignment of 29Si n. m. r. peaks corresponding to low-molecular weight species formed from methyltriethoxysilane has been discussed. [Received March 6, 1990; Accepted April 13, 1990] Key-words: Methyltriethoxysilane, Hydrolysis, Polymerization, Trimethylsilylation, 29Si n. m. r. spectroscopy IntroductionTrifunctional alkoxysilanes, R1Si(OR2)3, where R1 is an alkyl or aryl group and R2 is an alkyl group, have been used as raw materials for preparation of polyhedral or ladder-like organyl silsesquioxanes.1)-4) Recently, they are also noted as starting materials for producing ceramics, such as silica fibers and silicon carbide powders through the sol-gel processing.5)-8) Since the structures would affect the properties of precur sors and resultant materials, it is necessary to investigate structures of hydrolysis and polycon densation products of trifunctional silanes.It is known that the polymerization of silicate anions in aqueous solutions is affected by various factors, such as the SiO2 concentration, the nature of coexisting cations, the cation-to-silica molar ratio, the pH and the temperature. So far, trimethylsilylation9)-13) and 29Si n. m. r. spectros copy14)-17) have successfully been utilized to in vestigate the structure and distribution of silicate species in solutions. It is expected that these methods would be applicable to the study on hydrolysis and polycondensation products of tri functional alkoxysilanes present in solutions as well.In this study, methyltriethoxysilane (CH3Si (OC2H5)3) has been selected as a trifunctional alkoxysilane in order to obtain basic information on the structure and distribution of the hydrolysis and polycondensation products in aqueous solu tions containing sodium ions. First, the structure and distribution have been investigated with the trimethylsilylation technique combined with gas liquid and gel permeation chromatographies. It was demonstrated that trimethylsilylation by the method of Lentz was adaptable to the investiga tion on species formed by hydrolysis and polymerization of methyltriethoxysilane in solu tions.18) Then, on the basis of the trimethylsilyl ation study, assignment of signals on 29Si n. m. r. spectra of the solutions has been discussed. Although assignment of the signals to each structure unit of methylsilsesquioxanes has been ...

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“…20 These results suggest that the microwave irradiation gave a cubic octamethylsilsesquioxane. As compared with an authentic sample, the cubic particles had good crystallinity from the…”

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confidence: 92%

“…24 The XRD patterns of the cubic particles agreed with the patterns of the authentic sample and also the reported data. 20 These results suggest that the microwave irradiation gave a cubic octamethylsilsesquioxane. As compared with an authentic sample, the cubic particles had good crystallinity from the Si NMR spectrum of octamethylsilsesquioxane has two well-resolved lines with an intensity ratio of 3:1 at ¹66.1 and ¹66.8 ppm, respectively.…”

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confidence: 92%

Simple and Rapid Eco-friendly Synthesis of Cubic Octamethylsilsesquioxane Using Microwave Irradiation

Iwamura¹,

Adachi²,

Chujo³

2010

Chemistry Letters

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Octamethylsilsesquioxane (Me 8 Si 8 O 12 ) having a cage structure was rapidly prepared by means of microwave-assisted solgel reaction of methyltrimethoxysilane as a trifunctional alkoxysilane with an aqueous basic solution in diglyme as a solvent. Moreover, octamethylsilsesquioxane was obtained as cubic particles in a good yield. Cubic octamethylsilsesquioxane could be formed under microwave irradiation owing to the formation of micelles which are organized by eight methyltrimethoxysilane molecules in diglyme.Silsesquioxane chemistry has been the subject of intense interest for more than half a century. 18 The term silsesquioxane is the general name for organosiloxide species with an empirical formula (RSiO 1.5 ) n (R = H, hydrocarbon) and closely related compounds. In particular, silsesquioxane structures, which are random, ladder, cage (cubic), or partial cage, are interesting. 9Since the caged part of silsesquioxane has a structure similar to silica gel, these compounds can be regarded as a model of inorganic compounds. Silsesquioxane and its derivatives have a wide range of potential applications. In recent years, the polyhedral oligomeric silsesquioxanes (POSS) have been attracting a great deal of attention. However, a long reaction time is usually required to obtain silsesquioxanes. Moreover, the yields of silsesquioxanes are not so high in general. Due to increasing environmental concern, green chemistry has been receiving progressively more attention since the 1990s.1012 Therefore, there is a great necessity for the advancement of novel methodologies for chemical reactions using an environmentally ecofriendly method. A promising approach from this standpoint would be to search for new processes and technologies which from the very beginning are aimed at sharply curtailing environmental pollution by reducing the volumes of chemical production wastes. Microwave irradiation has been applied to various chemical reactions. Many review papers have been published about microwave-assisted chemical reactions. 1316 The microwave method provides fast and direct heating. In many cases, it can dramatically reduce the reaction time from hours to minutes, and would increase the product yields and enhance the product purity. For example, the monodisperse submicrometer silica spheres were prepared rapidly by the microwave-assisted solgel reaction of tetramethoxysilane.17 Silica mixed oxide such as Mg 2 SiO 4 , 18 and organic polymersilica hybrid 19 were also synthesized using microwave-assisted solgel reaction. In this study, we tried to overcome the difficulties in synthesis of silsesquioxanes, using microwave irradiation (Scheme 1).To find suitable reaction conditions, experiments were carried out using different catalysts. As a preliminary experiment, the reactions of methyltrimethoxysilane (MeTMOS) with various solgel reaction catalysts (0.1 M LiOH aq., 0.1 M NaOH aq., or 0.1 M KOH aq.) were carried out in a PTFE beaker in a microwave oven. Into a 50-mL glass bottle, diglyme (40 mL) was added followed by addition o...

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Crystalline Organosilsesquioxanes^*

Cited by 178 publications

References 0 publications

Tendency of Loop Formation of Oligosilsesquioxanes Obtained from (4-Substituted phenyl)trimethoxysilane Catalyzed by Benzyltrimethylammonium Hydroxide in Benzene

Tendency of Loop Formation of Oligosilsesquioxanes Obtained from (4-Substituted phenyl)trimethoxysilane Catalyzed by Benzyltrimethylammonium Hydroxide in Benzene

Polymerization of Hydrolysis Products of Methyltriethoxysilane in Aqueous Solutions

Simple and Rapid Eco-friendly Synthesis of Cubic Octamethylsilsesquioxane Using Microwave Irradiation

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Crystalline Organosilsesquioxanes*

Cited by 178 publications

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Tendency of Loop Formation of Oligosilsesquioxanes Obtained from (4-Substituted phenyl)trimethoxysilane Catalyzed by Benzyltrimethylammonium Hydroxide in Benzene

Tendency of Loop Formation of Oligosilsesquioxanes Obtained from (4-Substituted phenyl)trimethoxysilane Catalyzed by Benzyltrimethylammonium Hydroxide in Benzene

Polymerization of Hydrolysis Products of Methyltriethoxysilane in Aqueous Solutions

Simple and Rapid Eco-friendly Synthesis of Cubic Octamethylsilsesquioxane Using Microwave Irradiation

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Crystalline Organosilsesquioxanes^*