NMR spectroscopic studies of dimethyldiethoxy silane hydrolysis and polysiloxane conversion

Abstract

ABSTRACT:The hydrolysis rate of alkoxy silane (dimethyldiethoxy silane, DMDES, etc.) is a linear relationship vs. the reaction time under the moisture flux control. The hydrolysis process results in formation of the linear polysiloxane products by a subsequent condensation reaction. An amidized alkoxy silane (3-(2-aminoethyl)aminopropylmethyldimethoxy silane, KLM-602 or ␥-aminopropyl-triethoxy silane, ␥-APS) serves as an internal standard of DMDES hydrolysis kinetics measurements. The hydrolysis kinetics of DMDES with the amidized alkoxy silane and the subsequent linear polysiloxanes conversion have been evaluated and characterized by 29 Si-and 13 C-NMR NMR spectroscopic measurements.

Evolution of surface chemistry and morphology of hyperbranched polysiloxane polyimides in simulated atomic oxygen environment

“…d Weight loss at 500 • C aging for 10 h in nitrogen flow. and condensation, the initial reaction must run in dilute solution at low temperature (0 • C) without catalyst (base or acid), since catalyst addition could significantly accelerate the hydrolysis and easily induces gelation, while higher initial reaction temperature generally results in oxidation of amino groups [28,29]. After low-temperature hydrolysis for 1 h, silanols would undergo condensation reactions at 50 • C for 2 h to produce HBPSi precursors.…”

Influence of coating bath chemistry on the deposition of 3-mercaptopropyl trimethoxysilane films deposited on magnesium alloy

“…The rates of hydrolysis for MPTS at pH 4, 7 and 10 were examined with 1 H NMR. It is generally accepted that at low pH, hydrolysis will be complete before condensation occurs while at high pH, the condensation process begins with incomplete hydrolysis [11,18,[21][22][23][24][25][26][27]31]. Under acidic conditions, the rate of hydrolysis has previously been reported to be faster than condensation.…”

“…The rates and extent of these reactions depend on a number of factors such as the organosilane of interest, the solvent, water availability, solution pH, silane concentration and the surface to be coated [11,18,[21][22][23][24][25][26][27]. These factors can also affect the quality of the deposited silane film.…”

“…The availability of water, solution pH and silane concentration also affect the rates of hydrolysis and condensation [11,18,[21][22][23][24][25][26][27]. The rate of hydrolysis is faster than condensation when water is in excess and the pH of the solution is low [21,22,27,31].…”

“…The deposition of organosilane molecules onto solid surfaces requires two reactions. Both hydrolysis and condensation of the molecules must occur as shown in the reactions below [11,18,[21][22][23][24][25][26][27]:…”