Synthesis of incompletely caged silsesquioxane (T7-POSS) compounds via a versatile three-step approach
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Three kinds of incompletely condensed polyhedral oligomeric silsesquioxanes (T7-POSS) with three Si–OH groups: (i-C4H9)7Si7O9(OH)3, (i-C8H17)7Si7O9(OH)3 and (C6H5)7Si7O9(OH)3 were prepared by a versatile three-step approach (hydrolysis, condensation, and neutralization) from i-C4H9Si(OEt)3, i-C8H17Si(OEt)3, and C6H5Si(OEt)3, respectively, with the LiOH·H2O as catalyst. The structures of the three T7-POSS were characterized by FTIR, 1H NMR, 13C NMR, 29Si NMR, MALDI-TOF MS and XRD. The accurate incompletely caged structure of the three T7-POSS indicated that the built-up three-step approach is a versatile and effective way to synthesize T7-POSS with high yield. The best reaction conditions to synthesize the isobutyl-T7, isooctyl-T7 and phenyl-T7 POSS have been suggested, involving acetone and a co-solvent, the molar ratio of the RSi(OEt)3: LiOH·H2O: H2O and the reaction temperature. The thermal stability of the three T7-POSS were characterized by TGA, showing different degradation behaviors. The thermal stability of phenyl-T7 POSS was the highest among the three T7-POSS.
KeywordsTriethoxysilane Incompletely caged silsesquioxane Polyhedral oligomeric silsesquioxanes T7-POSS POSS
This project was funded by the National Program on Key Research Project (No. 2016YFB0302101), the National Natural Science Foundation of China (No. 51603011), and the International Science and Technology Cooperation Program of China (No. S2014ZR0465).
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