Spectroscopic analysis of interactions between alkylated silanes and alumina nanoporous membranes

Hardin, Jonathan L.; Oyler, Nathan A.; Steinle, Erich D.; Meints, Gary A.

doi:10.1016/j.jcis.2009.10.083

Cited by 10 publications

(6 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In both cases, however, the monodentate binding mode was preferential to the bidentate binding mode by about 1 eV . A similar conclusion was reached by Hardin et al who performed a spectroscopic analysis of the interactions between alkylated silanes and alumina nanoporous membranes. On the basis of the amount of methanol side product formed, they reasoned that a single covalent bond is formed between the standalone silane and the surface.…”

Section: Introductionsupporting

confidence: 78%

Insight into the Bonding of Silanols to Oxidized Aluminum Surfaces

2018

View full text Add to dashboard Cite

In the context of elucidating the mechanism by which siloxane-based sol−gel coatings adhere to the surface, the adsorption of a model silanol molecule, CH 3 Si(OH) 3 , and its oligomers (up to the trimer) on oxidized and fully hydroxylated aluminum substrates is described using density functional theory (DFT). To link our calculations with the synthesis of siloxane-based sol−gel coatings, the focus is given on the condensation mechanism. We find that the formation of a monodentate bonding mode with the hydroxylated surface via the condensation mechanism is exothermic by ≥0.5 eV in all considered cases. In contrast, the formation of a bidentate bonding mode is exothermic only for the trimer. However, taking entropic contributions into account, we find that the formation of the bidentate bonding mode is exergonic already for the dimer due to favorable entropic effects of a liberated water molecule during the reaction. In contrast, the reaction entropy is unfavorable for the monodentate formation because the effects of the immobilized silanol molecule counteract and surpass those of the liberated water molecule. The monodentate to bidentate transformation is therefore determined by the interplay between entropy and energy, and we find that the longer the oligomer chain, the more likely is the bidentate formation due to increasingly favorable reaction energies. These results further reveal that for the silanol monomer, additional molecule−surface chemical bonds do not form via the condensation mechanism due to the strained configuration it has to adopt in the bidentate bonding mode.

show abstract

Section: Introductionsupporting

confidence: 78%

Insight into the Bonding of Silanols to Oxidized Aluminum Surfaces

2018

View full text Add to dashboard Cite

show abstract

“…Similarly, alkylsilanes have been shown forming a multilayer attachment to the surface of hydroxylated alumina, being the alkylsilane adsorbate on the lowest layer linked to the surface by a single Al−O−Si covalent bond. 62 The γ-AlOOH (010) surface presents only one monodentate adsorption site (ms1; Figure 4) because of the symmetry of the hydroxyl groups, which are equally accessible to bind either MePA or Si(OH) 4 molecules. However, there are three different bidentate coordination sites (bs1, bs2, and bs3).…”

Section: Resultsmentioning

confidence: 99%

How Organophosphonic Acid Promotes Silane Deposition onto Aluminum Surface: A Detailed Investigation on Adsorption Mechanism

et al. 2014

View full text Add to dashboard Cite

Many research works have evidenced the importance in using inorganic–organic hybrid materials to protect metal surface or to serve as intermediate adhesion promoter layer for further coating deposition. The main aim of the present work was to elucidate the mechanism of silane deposition onto aluminum surface, in the presence of organophosphonic acid as adhesion promoter and using experimental and theoretical techniques. Transparent thin films of layered inorganic–organic composites were prepared by the sol–gel synthesis of tetraethylorthosilicate and vinyltrimethoxysilane in the presence of 1,2-diaminoethanetetrakis-methylenephosphonic acid. Aluminum surface was characterized by X-ray diffraction, SEM and XPS techniques. On the other hand, inorganic–organic coating was characterized by FTIR and XPS spectroscopies. Density functional theory was employed to evaluate three simplified molecules, orthosilicic acid (Si(OH)4), methylphosphonic acid (MePA), and Si(OH)3OMePA, by using different coordination modes, in order to approach the most stable chemical bonding between silane-phosphonic groups with modified aluminum surface (i.e., with boehmite as oxidized layer).

show abstract

“…Between 1700 and 1200 cm À1 the difference spectra for all three samples very much resemble the pure APTMS spectra, suggesting the presence of large oligomers on the surface of the c-alumina. c-alumina [44]. However, the covalent attachment of silanes on calumina substrate has been confirmed by NMR investigations [44].…”

Section: Ftir Characterizationmentioning

confidence: 92%

“…c-alumina [44]. However, the covalent attachment of silanes on calumina substrate has been confirmed by NMR investigations [44].…”

Section: Ftir Characterizationmentioning

confidence: 92%