Sodium montmorillonite silylation: unexpected effect of the aminosilane chain length.
In this work, the silylation of sodium montmorillonite (Na-MMT) was performed in glycerol using 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 3-[2-(2-aminoethylamino)ethylamino]-propyl-trimethoxysilane. The effects on the d-spacing of sodium montmorillonite (Na-MMT) upon reaction with three aminosilanes of different chain length were studied in details by combining experimental and computational techniques. Infrared spectroscopy was used to monitor the grafting process, while the degree of grafting was calculated using thermogravimetric analysis. X-ray diffraction experiments were carried out to evaluate the shift of the (0 0 1) basal spacing. It was found that the degree of silylation of Na-MMT increases with increasing the length of the aminosilane organic moieties, the overall aminosilane concentration, and temperature. The same beneficial effects were observed on the silicate d-spacing, as its value increases with increasing silane concentration and reaction temperature. Remarkably, however, increasing the length of the organic chains in the silane modifiers resulted in decreasing values of the Na-MMT interlayer distance. A rationale for this behavior is proposed on the basis of atomistic molecular dynamics simulation evidences.
Piscitelli
Filomena
F
Department of Materials Engineering and Production, University of Naples Federico II, Piazzale Tecchio 80, 80125 Naples, Italy. Filomena.Piscitelli@imcb.cnr.it
Posocco
Paola
P
Toth
Radovan
R
Fermeglia
Maurizio
M
Pricl
Sabrina
S
Mensitieri
Giuseppe
G
Lavorgna
Marino
M
D001546:Bentonite / Q000737:chemistry*; D005990:Glycerol / Q000737:chemistry; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D012821:Silanes / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
D012821:Silanes; D001546:Bentonite; D005990:Glycerol