Abstract:Partial polycondensation of RSi(OMe) 3 (R = C 6 H 5 , CH 3 ) by the reaction with АсOH in the presence of HCl is studied. Oligoorganomethoxysiloxanes are obtained of the average composition [RSi(OMe)O] 4 , [RSi (OMe) 4/6 O 7/6 ] 6 , RSi(OMe) 0.5 O 1.25 ] 8 , and [RSi(OMe) 0.4 O 1.3 ] 10 . Using the method of 29 Si NMR spectroscopy they were shown to contain three types of structural fragments: RSi(OMe) 2 O-, RSiOMe(O-) 2 , RSi(O-) 3 . Based on the kinetic data, on the composition, properties, and the 29 Si NMR… Show more
“…Under alternative conditions, such as omitting THF, resolution of the silanes can be readily achieved in the 29 Si dimension. 21 The in situ Raman spectra of the MTMS hydrolysis showed a remarkable similarity to that observed for the PTMS. All peaks are shifted to lower frequencies due to the change from phenyl to methyl group.…”
Section: Ab Initio Calculationsupporting
confidence: 52%
“…Under alternative conditions, such as omitting THF, resolution of the silanes can be readily achieved in the 29 Si dimension. 21 Figure 5.H–Si HMBC spectral series displayed right and 1 H NMR spectral series displayed left.…”
Section: Resultsmentioning
confidence: 99%
“…It is challenging to investigate the kinetics of sol-gel reactions that form silsesquioxanes due to the many transient intermediate species. 10 Many different analytical techniques have been employed such as Raman spectroscopy, [11][12][13][14][15] infrared (IR) spectroscopy, [16][17][18][19] nuclear magnetic resonance (NMR), [20][21][22][23] and computational calculations. 18,19,[24][25][26][27] This is an example where the combination of NMR, Raman, and IR provide complimentary information.…”
Sol-gels are found in many different scientific fields and have very broad applications. They are often prepared by the hydrolysis and condensation of alkoxysilanes such as trimethoxysilanes, which are commonly used as precursors in the preparation of silsequioxanes via the sol-gel process. The reaction rates of such reactions are influenced by a wide range of experimental factors such as temperature, pH, catalyst, etc. In this study, we combined multiple in situ spectroscopic techniques to monitor the hydrolysis and partial condensation reactions of methyltrimethoxysilane and phenyltrimethoxysilane. A rich set of kinetics information on intermediate species of the hydrolysis reactions were obtained and used for kinetics modeling. Raman and nuclear magnetic resonance (NMR) spectroscopy provided the most information about hydrolysis and NMR provided the most information about condensation. A quantitative method based on Raman spectra to quantify the various transient intermediate hydrolysis products was developed using NMR as the primary method, which can be deployed in the field where it is impractical to carry out NMR measurements.
“…Under alternative conditions, such as omitting THF, resolution of the silanes can be readily achieved in the 29 Si dimension. 21 The in situ Raman spectra of the MTMS hydrolysis showed a remarkable similarity to that observed for the PTMS. All peaks are shifted to lower frequencies due to the change from phenyl to methyl group.…”
Section: Ab Initio Calculationsupporting
confidence: 52%
“…Under alternative conditions, such as omitting THF, resolution of the silanes can be readily achieved in the 29 Si dimension. 21 Figure 5.H–Si HMBC spectral series displayed right and 1 H NMR spectral series displayed left.…”
Section: Resultsmentioning
confidence: 99%
“…It is challenging to investigate the kinetics of sol-gel reactions that form silsesquioxanes due to the many transient intermediate species. 10 Many different analytical techniques have been employed such as Raman spectroscopy, [11][12][13][14][15] infrared (IR) spectroscopy, [16][17][18][19] nuclear magnetic resonance (NMR), [20][21][22][23] and computational calculations. 18,19,[24][25][26][27] This is an example where the combination of NMR, Raman, and IR provide complimentary information.…”
Sol-gels are found in many different scientific fields and have very broad applications. They are often prepared by the hydrolysis and condensation of alkoxysilanes such as trimethoxysilanes, which are commonly used as precursors in the preparation of silsequioxanes via the sol-gel process. The reaction rates of such reactions are influenced by a wide range of experimental factors such as temperature, pH, catalyst, etc. In this study, we combined multiple in situ spectroscopic techniques to monitor the hydrolysis and partial condensation reactions of methyltrimethoxysilane and phenyltrimethoxysilane. A rich set of kinetics information on intermediate species of the hydrolysis reactions were obtained and used for kinetics modeling. Raman and nuclear magnetic resonance (NMR) spectroscopy provided the most information about hydrolysis and NMR provided the most information about condensation. A quantitative method based on Raman spectra to quantify the various transient intermediate hydrolysis products was developed using NMR as the primary method, which can be deployed in the field where it is impractical to carry out NMR measurements.
“…The reaction has an induction period that could be substantially shortened by the addition of HCl or methanol. 10 These studies and related work by Muzafarov demonstrated that siloxane bond formation can be elicited by acidic transesterification processes. 11 As noted, the reaction is slow in the absence of strong acids.…”
Section: ■ Introductionmentioning
confidence: 89%
“…The reaction has an induction period that could be substantially shortened by the addition of HCl or methanol. 10…”
We
describe a versatile cascade route for manufacturing MQ resins
using alkoxysilanes (e.g., tetraethoxysilane (TEOS)) or equivalent
oligomers (e.g., ethyl polysilicate (polyTEOS)), a carboxylic acid
(typically acetic acid), and hexamethyldisiloxane (MM) as starting
materials; a strong acid catalyst is also employed in the one-pot
reaction. The siloxane resin synthesis is accompanied by esterification
of the carboxylic acid to give ethyl acetate, which acts as an important
solvent, making the process more controllable. Contrary to traditional
sol–gel methods, no water is introduced in the experiments,
but is generated in situ. The strategy offers several advantages,
including reproducibility, high yields of siloxane resins with excellent
batch-to-batch consistency and without gel formation, narrow dispersity,
low Si-hydroxyl residues in the final products, and the ability of
increasing the molecular weight by thermal treatment. The process
utilizes the green chemistry concepts of lower pollutant formation
and higher atom efficiency.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
