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Mechanism and Kinetics of Oligosilsesquioxane Growth in the In Situ Water Production Sol–Gel Route: Dependence on Water Availability
Author(s) -
Borovin Evgeny,
Callone Emanuela,
Ribot Francois,
Diré Sandra
Publication year - 2016
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201501220
Subject(s) - chemistry , heteronuclear single quantum coherence spectroscopy , nuclear magnetic resonance spectroscopy , heteronuclear molecule , two dimensional nuclear magnetic resonance spectroscopy , hydrolysis , gel permeation chromatography , spectroscopy , precipitation , diffusion , analytical chemistry (journal) , organic chemistry , stereochemistry , polymer , physics , quantum mechanics , meteorology , thermodynamics
Thiol‐functionalized nanobuilding blocks (NBBs) were synthesized from 3‐mercaptopropyltrimethoxysilane by using the in situ water production (ISWP) process in which the water needed to hydrolyze the precursor was provided by means of an esterification reaction. In the present study the reaction between 1‐propanol and chloroacetic acid was used. Whereas the growth of the Si oligomers was followed at room temperature and 100 °C using 1D 29 Si and 2D 1 H– 29 Si heteronuclear single quantum correlation (HSQC) NMR spectroscopic experiments, the amount of water delivered along the process was followed by means of 1 H NMR spectroscopy. The results show a good correlation between the evolution of the degree of condensation and the amount of water produced in situ. They also point to the preferential formation of cagelike structures and the narrowing of the species distribution over long reaction times. The average size of the growing oligomers was estimated from their diffusion coefficient, which was measured by means of 1 H diffusion‐ordered NMR spectroscopy (DOSY NMR). Like gel permeation chromatography, DOSY NNR showed a plateau between 70 to 100 hours in the growth of the oligomers, a time at which, according to 29 Si NMR spectroscopy, the well‐defined octakis(3‐mercaptopropylsilsesquioxane) is the major species.