Structure of Hybrid Polyhedral Oligomeric Silsesquioxane Polymethacrylate Oligomers Using Ion Mobility Mass Spectrometry and Molecular Mechanics

摘要

Ion mobility and molecular modeling methods were used to examine the gas phase conformational properties of POSS (Polyhedral Oligomeric Silsesquioxanes) propylmethacrylate (PMA) oligomers. MALDI was utilized to generate sodiated (PMA)Cp7T8xNa+ ions, and their collision cross-sections were measured in helium using ion mobility based methods. Results for x = 1, 2, and 3 were consistent with only one conformer occurring for the Na+1-mer and Na+3- mer, but two or more conformers are present for the Na+2-mer. Theoretical modeling of the Na+1-mer using the AMBER suite of programs indicates only one family of low-energy structures is found, in which the sodium ion binds to the carbonyl oxygen on the PMA and 4 oxygens on one face of the POSS cage. The calculated cross-section of this family agrees very well with the experimental value, with.