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

Abstract

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...

Synthesis and Characterization of Monofunctionalized Polyhedral Oligomeric Silsesquioxanes by Cohydrolytic and Cocondensation of Propyltrimethoxysilane and Vinyltrimethoxysilane

“…The remaining peaks are produced by the rhombohedral crystal structure of POSS molecules (14,15). These results indicated that the product had good crystallinity and the structure was high symmetry (16).…”

Influence of Monomer Connectivity, Network Flexibility, and Hydrophobicity on the Hydrothermal Stability of Organosilicas

“…The high condensation degree of MTMS-derived powder (98%) suggests a densely packed network in which the methyl group fits well, as also indicated by the ability of methylated silica to crystallize. 61 , 62 Interestingly, the addition of terminal methyl groups in BMDESE-derived material as compared to BTESE-derived powder increased the rotational freedom of molecular segments but did not increase the condensation degree. The methyl groups did not preferentially replace noncondensed hydroxyl groups, suggesting that the hydroxyl groups had little freedom to rearrange or that the ethylene bridges introduced too much spacing to enable higher condensation degrees.…”

Anionic hydrogen‐transfer polymerization of N‐isopropylacrylamide under microwave irradiation

“…This method allows rapid and direct heating of the reaction media. In most cases, microwave can dramatically reduce reaction times and increase product yields . In our previous research, we found that the anionic hydrogen‐transfer polymerization of AAm utilizing microwave irradiation easily provides poly( β ‐alanine) as a resulting polymer in a short space of time .…”

“…In most cases, microwave can dramatically reduce reaction times and increase product yields. [20][21][22][23] In our previous research, we found that the anionic hydrogen-transfer polymerization of AAm utilizing microwave irradiation easily provides poly(β-alanine) as a resulting polymer in a short space of time. 24 When N-substituted amides with low reactivity as described above are polymerized, the anionic polymerization of N-substituted amides proceeds via a hydrogen-transfer process when using microwave irradiation.…”