ISSN:
1572-8870
Keywords:
inorganic-organic hybrids
;
the sol-gel process
;
29Si and 13C NMR spectroscopies
;
hydrolysis and condensation of T and Q silicon species
;
abrasion resistant coatings
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Inorganic-organic hybrid materials were prepared by hydrolysis and condensation of triethoxysilylated diethylenetriamine (f-DETA) and tetramethoxysilane (TMOS). The prehydrolysis stage of this f-DETA/TMOS system was monitored by 29Si NMR spectroscopy. The NMR experiments indicated that f-DETA hydrolyzes and condenses nearly as fast as TMOS at pH 0–1, but lags far behind the latter at pH~4.2. Gels derived from f-DETA and TMOS were studied using 13C or 29Si solid state NMR spectroscopy. The concentration of the alkoxy groups and the extent of condensation of the T & Q species in the cured gels were estimated. The contents of the Si–OMe group and Si–OEt group were barely detectable in most water-abundant systems (equivalent ratio of water to alkoxysilane ~4.0). However, a significant amount of Si–O i Pr groups was found if the reactant f-DETA was stored at room temperature in solvent 2-propanol for three weeks or longer. The relative composition of each Tz or Qz species was estimated for gels prepared in media of different acidity levels and water concentrations and then cured at 125–130°C for 4 h. As the acidity of the medium increased from pH 0–2 to pH 4–5, the extent of condensation of the T species decreased but that of the Q species increased. The hydrolysis of urea groups in f-DETA during the sol-gel process was also evaluated by 13C solid state NMR spectroscopy. The results indicated that only a very small fraction of urea groups was hydrolyzed during the sol-gel process.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1021435232746
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