Condensation of alkoxysilanes in alcoholic media: I. Oligomerization of dimethyldiethoxysilane

Abstract

In the context of the preservation of cultural heritage, the treatment of paper by an aminoalkylalkoxysilane, or its mixture with dimethyldiethoxysilane, has given encouraging results. Diluting the monomer bearing the amino function could contribute to obtaining a flexible network interpenetrating the fibre network. Due to the complexity of the system, the work presented here begins with a study of dimethyldiethoxysilane condensation under the conditions used for the paper deacidification (alcoholic medium, neutral condition, etc.). No detectable exchange reaction with ethanol was observed in anhydrous systems of dimethyldiethoxysilane for 24 h, but in the presence of water, hydrolysis and exchange were observed, the rate constant of the former being higher than that of the latter by one order of magnitude. In methanol, in the presence of water, condensation leading to dimerization was observed within less than three days, with polycondensation requiring a much longer time. From the rate constant measurements, in the presence of water, it appears that the condensation reaction is the slowest reaction. It can be concluded that with freshly prepared dimethyldiethoxysilane solutions in ethanol, this monomer cannot homopolymerize. The next step will be to determine to what extent it can be integrated into the network formed by the polycondensation of aminoalkylalkoxysilane.www.soci.org V Bennevault-Celton et al.material, i.e. inside paper. The next step of this research is to investigate the behaviour of mixtures of DMDES with an AAAS under the same conditions.

Condensation of alkoxysilanes in alcoholic media: II. Oligomerization of aminopropylmethyldiethoxysilane and co‐oligomerization with dimethyldiethoxysilane

“…With pure DMDES, they showed that beyond an ethanol volume fraction of 0.5 no emulsion droplets were formed, and the reaction mixture remained as a single phase. This situation is similar to that reported in a previous study 19. As for the degree of polymerization of polydimethylsiloxane formed in oil‐in‐water emulsion, Vincent and co‐workers showed that it mainly consists of the stable cyclic tetramer D 4 .…”

A New Insight into the Mechanism of 1,3‐Dienes Cationic Polymerization I: Polymerization of 1,3‐Pentadiene with tBuCl/TiCl4 Initiating System: Kinetic and Mechanistic Study

“…It is known that the cationic polymerization of 1,3-pentadiene is co-initiated by a wide range of Lewis acids such as AlCl 3 , [11][12][13][14][15][16][17] FeCl 3 , [ 18 ] SnCl 4 , [ 19,20 ] BF 3 OEt 2 , [ 20,21 ] VOCl 3 , [ 22 ] and TiCl 4 . [ 1,[23][24][25][26] The main feature of TiCl 4 -based initiating systems is their low activity in the polymerization of 1,3-dienes in the absence of purposely added initiators such as water, hydrochloric acid, organic acids, and so on, while the addition to the system of protic compounds or cationogens allowed to increase the rate of polymerization of 1,3-dienes signifi cantly.…”

Hybrid Sol–Gel Glasses with Glass‐Transition Temperatures Below Room Temperature

“…found that the silica surface was covalently grafted with methyl groups, when using MTES or DMDES, which increased the hydrophobicity of the silica surface. Bennevault‐Celton et al . showed that DMDES along with aminoalkylaloxysilane were used to preserve the flexibility of aging cellulosic paper in items of cultural heritage.…”

“…11 Using 29 Si NMR, Monredon-Senani et al 12 found that the silica surface was covalently grafted with methyl groups, when using MTES or DMDES, which increased the hydrophobicity of the silica surface. Bennevault-Celton et al 13 showed that DMDES along with aminoalkylaloxysilane were used to preserve the flexibility of aging cellulosic paper in items of cultural heritage. Weiser et al used TEOS and DMDES 14 to incorporate Lipase AK in a sol-gel procedure to enhance its thermal stability and long-term operational stability.…”