UV-MALDI-TOF and ESI-TOF mass spectrometry characterization of silsesquioxanes obtained by the hydrolytic condensation of (3-glycidoxypropyl)-trimethoxysilane in an epoxidized solvent

Full Paper: Silsesquioxanes obtained by the hyrolytic condensation of (3-gl ycidoxypropyl)trimethoxysilane (GPMS) in diglycidyl ether of bisphenol A (D GEBA) were characterized by electrospray ionization time-of- flight mass sp ectrometry (ESI-TOF MS) and matrix assisted ultraviolet laser desorption/io nization, ti flight mass spectrometry (UV-MALDI-TOF MS) employing two diffe rent matrices and both positive negative ion modes. A bimodal distribution of in the 1300-6400 m/z range, was observed in mass spectra. This distribut ion accounted gomers formed in two successive generations but I include a c luster of higher molar-mass species pre SEC chromatograms. Most of the peak s present and MALDI mass spectra could be described by eric formula T-n(OCH 3)(m) with in = 0, 2, and 4 for n = even, m = 1, 3, 5 for n = odd, and T = RSiO(3n-m)/2n corresponds to completely condensed polyhedra (incompletely h ydrolyzed polyhedra (m = 1 to 3). ar precursors (in = 4). Predominant speci es in the first contained 10 to 14 Si atoms whereas those in: the cluster h ad 18 to 23 Si atoms. Small amounts of following species: T-8(OH)(OCH3), T- 9(OH), T-10(OH)(OCH3) and T-11(OH) could be identified in MALDI MS 9H-pyrid o[3,4-b]indole (nor-harmane) as matrix ! negative ion mode. It was inferred that some, of the species had a relevant participation in the generation, second cluster of higher molar masses. The stability of the silsequioxane s olution in DGEBA was the result of the very small concentration of free SiO H groups available small concentration of free SiOH groups available for fu rther condensation.