HPLC Characterization of cis and trans Mixtures of Double-Decker Shaped Silsesquioxanes
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HPLC was used as the quantitative analysis technique in determining the molar ratio of cis and trans isomers in the double-decker shaped silsesquioxanes (DDSQ). Different experiments were performed to analyze the effects in the retention times of the polarity of moieties bonded to the DDSQ, as well as other possible adsorption driving forces. As expected, the use of adsorption HPLC was successful in separating cis and trans DDSQ isomers with the resolution of elution better than 1.5. Interestingly, the molecular size of moiety attached to the DDSQ resulted in significant reduction of the retention time suggesting the sterics constraint plays a critical role in the separation of these cage-like structures along with the strength of hydrogen bonding. In partition HPLC using Si bonded with CN groups as a normal phase resulted in a partial separation for one of the selected systems, which indicates the extent of polarity plays a secondary role in the separation mechanism.
KeywordsDouble-decker shaped silsesquioxane (DDSQ) Polarity Cis and trans isomers Separation HPLC
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We thank the Office of Naval Research (N00014-16-2109) for funding and Program Manager Mr. William Nickerson for the support. We also acknowledge Dr. Beth Schoen and Ms. Gayanthi Attanayake for their collaboration synthesizing and providing the DDSQ-(Ph)8(aniline)(R2) materials.
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