Thiolated Janus silsesquioxane tetrapod : new precursors for functional materials

Herein, we report synthetic strategies for the development of a bifunctional Janus T4 tetrapod (Janus ring), in which the orthogonal silsesquioxane and organic faces are independently functionalized. An all‐cis T4 tetrasilanolate was functionalized to introduce thiol moieties on the silsesquioxane face and naphthyl groups on the organic face to introduce luminescent and self‐or‐ ganization properties. The stepwise synthesis conditions required to prepare such perfectly defined oligomers via a suite of well‐defined intermediates and to avoid polymerization or reactions over all eight positions of the tetrapod are explored via 29Si, 13C and 1H NMR, FTIR and TOF‐ESI mass spectroscopy. To the best of our knowledge, this is one of the few reports of Janus T4 tetrapods, with different functional groups located on both faces of the molecule, thus expanding the potential range of applications for these versatile precursors

Self-structuring of lamellar bridged silsesquioxanes with long side spacers

Diurea cross-linked bridged silsesquioxanes (BSs) C(10)C(11)C(10) derived from organosilane precursors, including decylene chains as side spacers and alkylene chains with variable length as central spacers (EtO)(3)Si- (CH(2))(10)-Y(CH(2))(n)-Y-(CH(2))(10)-Si(OEt)(3) (n = 7, 9-12; Y = urea group and Et = ethyl), have been synthesized through the combination of self-directed assembly and an acid-catalyzed sol gel route involving the addition of dimethylsulfoxide (DMSO) and a large excess of water. This new family of hybrids has enabled us to conclude that the length of the side spacers plays a unique role in the structuring of alkylene-based BSs, although their morphology remains unaffected. All the samples adopt a lamellar structure. While the alkylene chains are totally disordered in the case of the C(10)C(7)C(10) sample, a variable proportion of all-trans and gauche conformers exists in the materials with longer central spacers. The highest degree of structuring occurs for n = 9. The inclusion of decylene instead of propylene chains as side spacers leads to the formation of a stronger hydrogen-bonded urea-urea array as evidenced by two dimensional correlation Fourier transform infrared spectroscopic analysis. The emission spectra and emission quantum yields of the C(10)C(n)C(10) Cm materials are similar to those reported for diurea cross-linked alkylene-based BSs incorporating propylene chains as side spacers and prepared under different experimental conditions. The emission of the C(10)C(n)C(10) hybrids is ascribed to the overlap of two distinct components that occur within the urea cross-linkages and within the siliceous nanodomains. Time-resolved photoluminescence spectroscopy has provided evidence that the average distance between the siliceous domains and the urea cross-links is similar in the C(10)C(n)C(10) BSs and in oxyethylene-based hybrid analogues incorporating propylene chains as side spacers (diureasils), an indication that the longer side chains in the former materials adopt gauche conformations. It has also allowed us to demonstrate for the first time that the emission features of the urea-related component of the emission of alkylene-based BSs depend critically on the length of the side spacers

Synthèse d'oligoTTF à lien saturé, fonctionnalisé et conjugué (Caractérisation électrochimique et formation de matériaux)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Mesoporous-Silica-Functionalized Nanoparticles for Drug Delivery

International audienceThe ever-growing interest for finding efficient and reliable methods for treatment of diseases has set a precedent for the design and synthesis of new functional hybrid materials, namely porous nanoparticles, for controlled drug delivery. Mesoporous silica nanoparticles (MSNPs) represent one of the most promising nanocarriers for drug delivery as they possess interesting chemical and physical properties, thermal and mechanical stabilities, and are biocompatibile. In particular, their easily functionalizable surface allows a large number of property modifications further improving their efficiency in this field. This Concept article deals with the advances on the novel methods of functionalizing MSNPs, inside or outside the pores, as well as within the walls, to produce efficient and smart drug carriers for therap

Evonik P25 photoactivation in the visible range by surface grafting of modified porphyrins for p-nitrophenol elimination in water

peer reviewedAn Evonik P25 TiO2 material is modified using a porphyrin containing Si-(OR)3 extremities to extend its absorption spectrum in the visible range. Two different loadings of porphyrin are grafted at the surface of P25. The results show that the crystallinity and the texture of the P25 are not modified with the porphyrin grafting and the presence of the latter is confirmed by FTIR measurements. All three samples are composed of anatase/rutile titania nanoparticles around 20 nm with a spherical shape. The absorption spectra of the porphyrin modified samples show visible absorption with the characteristic Soret and Q bands of porphyrin despite slightly shifted peak values. The 29Si solid state NMR spectra show that the porphyrin is linked with Ti–O–C and Ti–O–Si bonds with the Evonik P25, allowing for a direct electron transfer between the two materials. Finally, the photoactivity of the materials is assessed on the degradation of a model pollutant in water, the p-nitrophenol (PNP). Whereas a very low activity is evidenced for P25, the degradation is substantially enhanced when the porphyrin is grafted at its surface. Indeed, with the best sample, the activity increases from 9% to 38% under visible light illumination. This improvement is due to the activation of the porphyrin under visible light that produces electrons that are transferred to the TiO2 to generate radicals able to degrade organic pollutants. The observed degradation is confirmed to be a mineralization of the PNP. Recycling experiments show a constant PNP degradation after 5 cycles of photocatalysis of 24 h each

pH-Responsive Bridged Silsesquioxane

International audienceABSTRACT: A pH-responsive bridged silsesquioxane was obtained via the sol gel process from a bis-silylated triazine derivative bearing a triple DAD (donor- acceptor- donor) moiety which was strongly hydrogen-bonded to the three ADA (acceptor- donor- acceptor) sites of cyanuric acid. The latter template molecule was easily removed from the resulting hybrid material upon acidic treatment, which yielded the template-free bridged silsesquioxane with preserved morphology and unaltered particle size as demonstrated by SEM. As expected, the surface area of the acid-treated hybrid was significantly higher than that of the untreated material, as demonstrated by nitrogen adsorption measurements. The absence of cyanuric acid in this material was confirmed by solid state NMR and by IR. It was shown that amild acidic medium (pH = 5.5) is sufficient to release the cyanuric acid template, thus providing a novel route to new hybrid materials with potential applications as efficient carriers for pH-responsive delivery systems

Hybrid silica with molecular recognition properties

International audienc

Silylated Melamine and Cyanuric Acid as Precursors for Imprinted and Hybrid Silica Materials with Molecular-Recognition Properties

International audienceTwo monotrialkoxysilylated compounds that consist of complementary fragments of melamine (M) and cyanuric acid (CA) have been synthesised. The molecular-recognition properties of the M and CA fragments through complementary hydrogen bonds (DAD and ADA; D=donor, A=acceptor) are the key factor used to direct the formation of hybrid silica materials by using a sol–gel process. These materials were synthesised following two methods: First, an organobridged silsesquioxane was obtained by the hydrolysis of the two complementary monotrialkoxysilylated melamine and cyanuric acid derivatives, with fluoride ions as a catalyst. The hydrogen-bonding interactions between the two organic fragments are responsible for the formation of the bridging unit. The transcription of the assembly into the hybrid material was characterised and evidenced by solid-state NMR (29Si, 13C) and FTIR spectroscopic experiments. Second, the molecular recognition was exploited to synthesise an imprinted hybrid silica. This material was prepared by cocondensation of tetraethyl orthosilicate (TEOS) with the monosilylated cyanuric acid derivative (CA)templated by nonsilylated melamine. The melamine template was completely removed by treating the solid material with hydrochloric acid. The reintroduction of the template was performed by treating the resulting material with an aqueous suspension of melamine. These steps were monitored and analysed by several techniques, such as solid-state NMR (29Si, 13C) and FTIR spectroscopic analysis and nitrogen adsorption–desorption isotherms

Post-synthesis modification of functionalised polyhedral oligomeric silsesquioxanes with encapsulated fluoride – enhancing reactivity of T 8 -F POSS for materials synthesis

International audienc

Sol-gel processing of polyhedral oligomeric silsesquioxanes : nanohybrid materials incorporating T8 and T10 cages

Polyhedral oligomeric silsesquioxanes (POSS, T8 and T10) have been incorporated in hybrid silica materials via hydrolysiscondensation of octa- and deca(triethoxysilylated)-POSS precursors, respectively. The precursors were synthesized via a thiol-ene Click reaction involving the corresponding octastyryl-T8 or decastyryl-T10 molecules and thiopropyltriethoxysilane. Following addition of water and HCl (as catalyst) to a solution of the precursors, gels were formed within a few minutes. The resulting hybrids were characterized by TEM, FTIR, N2 physisorption analyses, solid-state NMR (29Si and 13C), and TGA, which indicated that the T8 and T10 cages were incorporated and remained intact within the hybrid gel network, with no Si–C cleavage being observed via 29Si NMR. FTIR data indicated that water retained within the gels following drying and aging at ambient temperature exhibited an unusual “connective”, ice-like structure, suggesting that it is initially retained as a key component of the gel network during consolidation and aging at ambient temperature. Following aging, the water was readily removed by evacuation at 100 °C without significantly modifying the network structure, on the basis of the FTIR spectrum of the gel. To the best of our knowledge, this is the first report of the incorporation of T10 cages in such gels