Alkoxysilane coupling

Brebner, K.I. and Schneider, M.H. (1985). Wood-polymer combinations bonding of alkoxysilane coupling agents to wood. Wood Science and Technology, 19(1), 75-81. 

A maximum initial formation of M—O—Si. Kaas and Kardos [13] reported that condensation of neutral alkoxysilane coupling agents with glass and... 

Schneider MH, Brebner KI (1985) Wood-polymer combinations the chemical modification of wood by alkoxysilane coupling agents. Wood Sci Technol 19 67-73... 

Figure 24.4 TEM micrographs of systems containing 15 wt% SiOi, both produced from a bisphenol-A epoxy resin grafted with an amine alkoxysilane-coupling agent (a) epoxy/silica hybrid (cocontinuous domains) and (b) epoxy/silica nanocomposite (particulate silica domains).

Masda. L. and Kionl, A. (1994) CompatibUity of polyimide-silica hybrids induced by alkoxysilane coupling agents. /. Cryst. Solids, 175. 169. 

Wheeler, G., Mendez-Vivar, J., Goins, E. S., Fleming, S. A., et al. (2000). Evaluation of alkoxysilane coupling agents in the consolidation of limestone. In V. Fassina (Ed.), 9th international congress on deterioration and conservation of stone, Venice, June 19-24, 2000 Vol. 2. Proceedings (pp. 541-545). Elsevier Science. 

The use of tri-tert-butylphosphine has produced still higher selectivities, allowing near total control in the synthesis of (A)-vinylsilanes, including alkoxysilanes and disiloxanes.38,39 In the context of a total synthesis of an HMG-CoA reductase inhibitor, hydrosilylation with a chlorosilane catalyzed by a platinum(O) olefin complex, Pt2 [(CH2=CH)Me2Si]20 3 (also known as Karstadt s catalyst), followed by coupling with a 2,6-disubstituted aryl iodide forged a key intermediate shown in Scheme 6.38... 

A series of studies were conducted to define parameters related to reactivity, solubility, and stability of alkoxysilane hydrolysis mixtures for the purpose of generating model compounds stable in water solution and maintaining coupling agent activity. 

The common uses of alkoxysilanes as coupling agents or crosslinkers depend on hydrolysis and condensation reactions. 

Keywords Alkoxysilanes hydrolysis alcoholysis siliconium coupling agents. 

Our interest in silane coupling agents and in the preparation of silicates has led us to study the mechanisms involved in the various reactions. In a previous paper, we investigated the kinetics and mechanism of the alcoholysis of TMOS [13]. This present work studies the effects of changing the substituents on a para-substituted phenyl attached directly to the alkoxysilane. The alkoxysilane silanes used have only one alkoxy group present to eliminate complications from a competing second or third alcoholysis reaction. The resulting Hammett plot yields additional information on the mechanism of this reaction. 

Morrall2 used a HPLC system with two columns. The first column was loaded with the controlled pore glass (CPG) to be modified. The second column was used for separation of the reaction effluents. This column was coupled to a refractive index detector, allowing for quantitative detection of the effluents. The reaction was initiated by injecting an APTS/toluene mixture and stopped by injection of pure toluene. With this so-called stop-flow mechanism reaction times down to 18 seconds could be used. From these analyses it became evident that upon mixing of the aminosilane with the silica, a very rapid physisorption occurs. The initial adsorption of the APTS (from toluene solution on dried CPG) occurred before the 18 second minimum time delay of the stop-flow apparatus. For non-aminated silanes the adsorption proved to be much slower. This study also revealed the pivotal role of surface water in the modification of siliceous surfaces with alkoxysilanes, as discussed in the previous chapter. 

A mild method has been developed to synthesize unsymmetrical bis-alkoxysilanes (silyl ketals). This method utilizes three different catalysts to synthesize a variety silyl ketals in a stepwise manner. We were able to achieve our initial goal of finding catalytic systems that are mild, compatible with carbon-carbon multiple bonds, easily accessible and cost effective. Our method can couple tertiary alcohols in moderate to high yields. 

---