scholarly journals Spinnability of Silica Sols: the Role of Alkoxy Group Exchange

1994 ◽  
Vol 346 ◽  
Author(s):  
S. Prabakar ◽  
R.A. Assink ◽  
A.D. Irwin
Keyword(s):  
Sol Gel ◽  
Alkoxy Group ◽  
Condensation Reactions ◽  
Hydrolysis And Condensation ◽  
Silica Sols

ABSTRACTThe exchange and spinnability of several systems with the general form Si(OR)4 (where R = CH3, C2H5) in ethanol, propanol and butanol were investigated. We have followed the alkoxy group exchange, the hydrolysis and condensation reactions and the Q distributions of these systems using 29Si and 17O NMR. The observed differences in spinnability of the various sol-gel systems are attributed to the effect of the bulkiness of the alkoxy group on its reactivity.

Organic–inorganic hybrids having a talc-like structure as suitable hosts to guest a wide range of species

2018 ◽  
Vol 47 (9) ◽  
pp. 2925-2932 ◽  
Author(s):  
J. Brendlé
Keyword(s):  
Hybrid Materials ◽  
Sol Gel ◽  
Step Method ◽  
Mild Conditions ◽  
Condensation Reactions ◽  
Wide Range ◽  
Sol Gel Process ◽  
Hydrolysis And Condensation ◽  
One Step

The sol–gel process involving hydrolysis and condensation reactions is an attractive way to form siloxane based hybrid materials since it is a one-step method performed under mild conditions.

Sol-Gel Polymerization of Tetraalkoxygermanium and Organotrialkoxygermanium Monomers

1996 ◽  
Vol 431 ◽  
Author(s):  
Brigitta M. Baugher ◽  
Douglas A. Loy
Keyword(s):  
Chemical Modification ◽  
Sol Gel ◽  
Silica Gels ◽  
Germanium Oxide ◽  
Oxide Materials ◽  
Siloxane Bond ◽  
Mild Conditions ◽  
Condensation Reactions ◽  
Hydrolysis And Condensation ◽  
Opening Up

AbstractWhile the sol-gel polymerizations of tetraalkoxy- and organotrialkoxysilanes have been extensively studied, there have been few reports of similar investigations with the analogous tetraalkoxygermanium and organotrialkoxygermanium compounds. Germanium alkoxides have received less attention due, in part to their higher cost, but also their greater reactivity towards hydrolysis and condensation reactions. Germanium oxide materials are potentially interesting because the Ge-O-Ge linkage is labile (compared with the siloxane bond in silica gels and polysilsesquioxanes) opening up the possibility of further chemical modification of the polymeric architecture. This may permit hydrolytic reorganization of germanium oxide networks under relatively mild conditions. In this paper, we will present the results of our investigations of the solgel polymerizations of tetraethoxygermanium 1, tetraisopropoxygermanium 2, and methyltriethoxy-germanium 3 to afford network materials as both xerogels and aerogels.

scholarly journals Preparation of sol–gel hybrid materials from γ-methacryloxypropyltrimethoxysilane and tetramethyl orthosilicate: study of the hydrolysis and condensation reactions

2011 ◽  
Vol 289 (17-18) ◽  
pp. 1875-1883 ◽  
Author(s):  
Amir A. El hadad ◽  
Diogenes Carbonell ◽  
Violeta Barranco ◽  
Antonia Jiménez-Morales ◽  
Blanca Casal ◽  
...  
Keyword(s):  
Hybrid Materials ◽  
Sol Gel ◽  
Condensation Reactions ◽  
Hydrolysis And Condensation

Influence of the nature of the R Group on the Hydrolysis and Condensation Process of Trifunctional Silicon Alkoxides, R-Si(OR')3

1994 ◽  
Vol 346 ◽  
Author(s):  
Laurent Delattre ◽  
Florence Babonneau
Keyword(s):  
Nuclear Magnetic Resonance ◽  
The Other ◽  
Cross Linking ◽  
Condensation Process ◽  
Alkyl Chains ◽  
Condensation Reactions ◽  
Hydrolysis And Condensation ◽  
Silicon Alkoxides ◽  
Degree Of Condensation

ABSTRACTThe hydrolysis and condensation reactions of three trifunctional silicon alkoxides, R-Si(OEt)3, with various R alkyl chains (R = CH3, C2H5, C8H17), was followed by 29Si and 1H Nuclear Magnetic Resonance. The condensation reactions are faster for methyltriethoxysilane and the degree of condensation of the system is higher. The other two systems have similar behaviors during the first hours, with lowest degree of condensation. The condensation reactions slow down for the octyltriethoxysilane, due to the presence of the long alkyl chains which prevent condensation reactions between oligomeric species. The influence of the addition of tetraethoxysilane (TEOS) was studied: for all three systems, the degree of condensation of the network is higher, indicating the role of cross-linking played by TEOS.

Tailoring of Transition Metal Alkoxides Via complexation For The Synthesis of Hybrid Organic-Inorganic Sols and Gels

1992 ◽  
Vol 271 ◽  
Author(s):  
C. Sanchez ◽  
M. In ◽  
P. Toledano ◽  
P. Griesmar
Keyword(s):  
Transition Metal ◽  
Chemical Control ◽  
Sol Gel ◽  
Particle Growth ◽  
Metal Alkoxides ◽  
Network Modifier ◽  
Surface Protection ◽  
Nlo Properties ◽  
Condensation Reactions

ABSTRACTThe chemical control of hydrolysis-condensation reactions of transition metal alkoxides can be performed through the modification of the transition metal coordination sphere by using strong complexing ligands (SCL). Complexing organic groups can be bonded to the transition metal oxide network in two different ways, as network modifiers or network formers. Different illustrations of the role of complexing ligands on Ti(IV) and Zr(IV) alkoxides are presented. As a network modifier, SCL act as termination agents for condensation reactions allowing a control of particle growth. The complexing ligands being located at the periphery of the oxo core open many opportunities for colloid surface protection. SCL carrying organofunctional groups which exhibit non linear optical (NLO) properties have also been used as probes to study sol-gel transformations. SCL functionalized with organic polymerizable functions act as network formers. Hybrid organic-inorganic copolymers intimately interpenetrated on a nanometer size scale were synthesized from zirconium oxo polymers chemically bonded to polymeric methacrylate chains via a complexing function.

Sol-Gel Chemistry of Hydrogenosiliconates: The Role of Hypervalent Silicon Species

1990 ◽  
Vol 180 ◽  
Author(s):  
V. Belot ◽  
R. Corriu ◽  
C. Guerin ◽  
B. Henner ◽  
D. Leclercq ◽  
...  
Keyword(s):  
Sol Gel ◽  
Condensation Reactions ◽  
Sol Gel Process ◽  
Redistribution Reactions ◽  
Hydrolysis Of

ABSTRACTThe hydrolysis of organic silicates ( mainly Si(OEt)4: [TEOS] and Si(OMe)4: [TMOS]) is the key reaction in sol gel process for preparation of silica. The mechanism of this reaction is not well known because of the competition taking place between hydrolysis itself and condensation reactions (homo or heterocondensations) but also because of redistribution reactions which take place competitively. Furthermore the competition between these steps depends also on the catalysis (acid,basic or nucleophilic) [1, 3].

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