摘要(英) |
Silsesquioxane is molecular spherosilicates with the formula [RSiO2.5]n, where R is an inorganic or organic group and n can be between 4 and about 30, but typically 6, 8, 10 or 12. We focus our effort to modify D4R silicate (Si8O20)8- with dimethylchlorosilane and trimethylchlorosilane to make dimethylsilylated D4R unit ((HSiMe2O)8-Si8O12) and trimethylsilylated D4R unit ((SiMe3O)8-Si8O12) respectively. Dimethylsilylated D4R unit ((HSiMe2O)8-Si8O12) can be used as an intermediate for synthesizing spherical siloxanes owing the chemical reactivity of the a H-terminated D4R unit to connect with another function for example; methacrylate, epoxy group, or long chain alkyl group.
The silanation of octaanion is typically carried out in a two phase system, where the hydrated tetramethyl ammomium salt of octaanion exists in the aqueous phase, while the silane dissolved in an organic phase. The yield for octaanion silanized with dimethylchlorosilane and trimethylchlorosilane was 83% and 93% respectively (molar ratio chlorosilane to Si in octaanion = 4 : 1). Since they used a large excess of chlorosilane, there is a large room to improve the reaction system.
We will start by examining the phase diagram of hexane-methanol-water tertiary system and identify the region where a single phase is formed, and test the shift of phase boundary when octaanion salt is included. The reaction will then be carried out as much as possible in the single phase domain to facilitate the dissolution of the salt as well as its immediate reaction with silane. We believe that through such modification higher yield can be achieved with less amount of chlorosilane. The result will then be characterized with FTIR, DSC, TGA, and NMR.
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