Bridged Silsesquioxanes with Organic Domains Self‐Assembled as Functionalized Molecular Channels

Abstract

A bridged silsesquioxane was obtained from a precursor synthesized by the reaction of glycidoxypropyl(trimethoxysilane) (2 mol) with cyclohexylamine (1 mol). The polycondensation in the presence of formic acid produced a hybrid material exhibiting a short‐range order based on elongated organic channels accommodating the pendant cyclohexyl fragments, bounded by inorganic domains. The presence of functional groups in the organic channels (tertiary amine, ether, hydroxyl), can be used to retain small organic molecules capable of forming hydrogen bonds. Aspirin was used as a probe to illustrate this possibility.magnified image

Fast Synthesis of Nanostructured Microspheres of a Bridged Silsesquioxane via Ultrasound‐Assisted Sol–Gel Processing

“…1D 29 Si MAS NMR spectra were measured using a Bruker Avance 500 WB/US spectrometer at MAS frequency v r /2p ¼ 10 kHz and B 1 ( 13 C) field intensity v 1 /2p ¼ 62.5 kHz. B 1 ( 1 H) field intensity of TPPM (two-pulse phase-modulated) decoupling corresponds to v 1 /2p ¼ 89.3 kHz.…”

“…Single-pulse experiments were used with 45 8pulse length (2 ms) and 60 s repetition delay. The 29 Si NMR scale was calibrated by external standard M 8 Q 8 (À109.8 ppm; the highest field signal).…”

“…Finally, the broad-band centered at about 3 400 cm À1 was assigned to C-OH groups including the small fraction of unreacted Si-OH groups. 29 Si NMR spectrum provides information related to the condensation degree of the silsesquioxane (Figure 4). Four signals were obtained from the deconvolution of the spectrum.…”

“…[29] In that case, a less defined nanostructuration was observed characterized by the appearance of a single peak in the SAXS spectrum, assigned to the length (19 Å ) of the organic bridge. In the conformation of minimum energy, organic bridges were curved to accommodate the cyclohexyl groups in the hybrid structure (as estimated using the software ACD Labs/3D Viewer) leading to the formation of a hybrid material exhibiting a short-range ordering based on elongated organic channels accommodating the cyclohexyl fragments.…”

“…In comparison to the previously reported organicinorganic material, [29] the method of synthesis used in this study led not only to a stable dispersion of microspheres but also to a much better nanostructuration of the hybrid material. The high definition of the SAXS spectrum enabled us to propose a more reliable structure for the cavities generated in the microspheres.…”