Silsesquioxane-Based Nanoparticles Formed via Hydrolytic Condensation of Organotriethoxysilane Containing Hydroxy Groups

Abstract

Silsesquioxanes-based nanoparticles synthesized by hydrolytic condensation of a functionalized precursor, N,N-di(2,3-dihydroxypropyl)(aminopropyl)triethoxysilane, (HOCH2CH(OH)CH2)2NCH2CH2CH2Si(OCH2CH3)3, were characterized using MALDI-TOF MS, NMR, elemental analysis, FT-IR, transmission electron microscopy (TEM), and scanning force microscopy (SFM). MALDI-TOF MS analysis indicated that the product consists of many species having 12−18 Si atoms with different numbers of intramolecular cyclizations, and Si−O−C bonds are formed through the reaction of SiOH (or SiOEt) groups with the hydroxyl functionalities of an organic moiety bonded to a Si atom. The species having high number of intermolecular cyclization (f ≥ 0.5 at 10 ≥ n ≥ 7) were predominantly detected, suggesting that the product mainly consists of complete and incomplete cagelike structures. The chemical composition of the product was consistent with that calculated from the structure, (R−SiO1.5) n , indicating that the nanoparticles belong to a family of silsesquioxanes characterized by a ratio of 1.5 between the silicon and oxygen atoms. Reasonable NMR and FT-IR spectra were observed, corresponding to the structure assuming that majority of the alkyl chain attached on a Si atom was intact during the hydrolytic condensation. The resulting particles have relatively narrow size distribution with average particle diameter less than 3.0 nm, as confirmed by TEM and SFM.

Architecture of Silsesquioxanes

“…It is based on the molecular arrangement of silsesquioxanes obtained under acid-catalyzed polycondensation of bulky organoalkoxysilanes (Mori et al 2004). They proposed the approach to silsesquioxane nano-objects as an alternative to time-consuming and low efficient syntheses of POSS.…”

“…The synthetic protocol with small amounts of aqueous HF in methanol, ethanol, or acetone was applied, among many examples (Mori 2012), to the preparation of cationic (Mori Fig. 3 Various silsesquioxane structures in hydrophilic nanoparticles prepared by the condensation of the addition product of aminopropyltriethoxysilane and glycidol (Reprinted with permission from Mori et al 2004, # 2016 and Yamada 2012), fluorinated (Mori et al 2011), and S-functionalized silsesquioxane nanoparticles (Mori et al 2013). Moreover, the preparation of films with tunable amphiphilicity and variable refractive index by co-condensation of fluorinated and hydroxyl-functionalized triethoxysilane precursors (Fig.…”

Synthesis of Processable Inorganic‐Organic Hybrid Polymers Based on Poly(silsesquioxanes): Grafting from Polymerization Using ATRP

“…[16] Furthermore, well-defined inorganic/organic hybrid materials with pH induced reversible complexation of weak electrolytes could be obtained by the sol-gel method. [17,18] Synthesizing defined architectures of silica can also be realized by using inorganic/organic hybrid polymers. For example, by addition of different additives to a bio-inspired silification process, defined silica structures can be obtained.…”

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

“…[12,13] The bridged silsesquioxane family is now recognized to have an enormous potential as a building block for various advanced materials, and their applications can be found in areas such as catalysis, optics, electronics, and biosciences, among others. [14] Different kinds of organic structures with self-assembling capabilities, leading to nanostructured bridged silsesquioxanes after hydrolytic condensation, have been reported in the literature. Strong hydrogen bonds as those formed among urea groups, alone or combined with aromatic p-stacking or hydrophobic interactions produce a variety of self-assembled structures.…”