Cagelike precursors of high-molar-mass silsesquioxanes formed by the hydrolytic condensation of trialkoxysilanes

Citation
P. Eisenberg et al., Cagelike precursors of high-molar-mass silsesquioxanes formed by the hydrolytic condensation of trialkoxysilanes, MACROMOLEC, 33(6), 2000, pp. 1940-1947
Citations number
25
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
MACROMOLECULES
ISSN journal
0024-9297 → ACNP
Volume
33
Issue
6
Year of publication
2000
Pages
1940 - 1947
Database
ISI
SICI code
0024-9297(20000321)33:6<1940:CPOHSF>2.0.ZU;2-#
Abstract
High-molar-mass silsesquioxanes (SSQO) based on (3-glycidoxypropyl)trimetho xysilane (GPMS) and (3-methacryloxypropyl)trimethoxysilane (MPMS) were synt hesized. The hydrolytic condensation of GPMS was performed using HCOOH (0.1 N) as catalyst, keeping the molar ratio H2O/Si = 3. A first step was perfo rmed in tetrahydrofuran (THF) at 50 degrees C, followed by a second step in diglycidyl ether of bisphenol A (DGEBA), where temperature was increased i n steps up to 140 degrees C. The hydrolytic condensation of MPMS was perfor med in bulk with HCOOH 98%, at T = 50 or 70 degrees C, using molar ratios o f HCOOH/Si = 3 or 6. Homogeneous solutions were obtained for both silanes. The reaction was followed by size exclusion chromatography (SEC), and final products were characterized by matrix-assisted ultraviolet laser desorptio n/ionization time-of-flight mass spectrometry (UV-MALDI-TOF MS). FTIR, and H-1 and Si-29 NMR. Molar-mass distributions showed the presence of clusters corresponding to products formed in different generations. With the aid of UV-MALDI-TOF MS, the different: species present in every cluster could be identified for one of the silsesquioxanes derived from MPMS. During the ini tial stage of the hydrolytic condensation, species with 7-12 Si atoms were produced. They mainly consisted of incompletely condensed polyhedra (specie s with 1-3 OH per molecule) and ladder-type structures (species with 4 OH p er molecule). Species with more OH groups were condensed with a higher prob ability. giving place to a second generation of products. This process acco unts for the presence of a cluster of species with 14-24 Si atoms and the e nrichment of the first cluster in the more condensed structures (T-7(OH), T -8(OH)(2), and T-9(OH)). Third and fourth generations of condensation produ cts were also present. Structures of different species may be depicted as c ombinations of incompletely condensed polyhedra with ladder fragments.