Study of three‐dimensional configurations of ( γ ‐methacryloxypropyl)‐silsesquioxanes by ultraviolet laser matrix‐assisted desorption/ionization time‐of‐flight mass spectrometry and quantum chemical calculation

[(3‐Methacryloxy)propyl]silsesquioxanes (MSSO) were prepared from the hydrolytic condensation of [(3‐methacryloxy)‐propyl]trimethoxysilane (MPMS) in the presence of an acid catalyst (HCOOH). The proposed MSSO structures were characterized with Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) ( 1 H, 13 C and 29 Si), and were assigned by ultraviolet laser matrix‐assisted desorption/ionization time‐of‐flight mass spectrometry (UV‐MALDI‐TOF MS). The large organic group connected to silicon was simplified for the quantum chemical calculation (QCC), and the correlation of the calculated total energies ( E T ) before and after simplification was analyzed by multiple linear regression, verifying no significant influence on the final conclusions of the research of structural formulas by a correlation coefficient ( r ). The geometric parameters (Si–O bond length and Si–O–Si, O–Si–O bond angles) and E T of the simplified MSSO were calculated by QCC to determine the relative stability of various MSSO structures. The structural geometry (silicon ring), the fraction of intramolecular cycles ( f ) and the number of the silicon rings ( F ) were also employed to qualitatively determine the relative stability. The results of the calculation showed that almost all of the cage structures had a lower E T than the isomeric ladder structures; therefore, most MSSO structures are of the cage type. Copyright © 2011 John Wiley & Sons, Ltd.