Small-angle scattering investigation of silica xerogels and sonogels prepared with ionic liquid pyridinium tetrafluoroborate

Silica matrices were prepared via acid catalysed sol-gel processing augmented with sonocatalysis. As silica precursors, a mixture of tetra-functionalized alkoxide (TMOS) and three-functionalized alkoxide methyl-trimethoxysilane (MTMS) were employed. Ionic liquid N-butyl-3-methylpyridinium tetrafluoroborate ([bmPy][BF4]), was used in various proportions, aiming to catalyse the sol-gel reactions, and to influence the mesoporous silica materials properties, serving as pore template. Small-angle neutron (SANS) and small-angle X-ray scattering (SAXS) techniques were used to explore the xerogels and sonogels microstructure evolution as a function of the IL/Si molar ratio. The results show a strong increase of the primary particle size under the influence of the ionic liquid. Ultrasonic agitation leads to further size increase by ca. 10%

Solvent-free synthesis of reactive inorganic precursors for preparation of organic/inorganic hybrid materials

International audiencePrehydrolyzed-condensed precursors containing amino or glycido groups were prepared via sol gel process using various alkoxysilanes in the bulk, without addition of solvent in any step of their preparation. The influence of the experimental set-up, the functionality and ratio of alkoxysilanes, and type of catalyst, on the structure buildup was studied. In the case of amino precursors, the sol-gel process was carried out at weak basic conditions while in the case of glycido precursors the sol-gel process was catalyzed by acid or neutral pH. The sol-gel process was monitored by (29)Si NMR in solution and the structure of the prehydrolysed-condensed precursors was characterized by small-angle X-Ray scattering. The systems with high content of tetraethoxysilane led to the fast gel formation. In weak acid medium tetraethoxysilane formed larger, more condensed species as well as small structures (based on Q (1), Q (2) and Q (3) species) with silanol groups. Strong acidic conditions led to the fast formation of insoluble silica particles in liquid (sol) phase containing monomeric alkoxysilanes. The most suitable precursor formulations based on the alkoxysilanes with amino groups, as well as the most efficient set-up, were selected and used to prepare hybrid organic/inorganic networks based on an epoxy matrix. These networks were characterized using dynamic mechanical analysis

Preparation and characterization of organic/inorganic hybrid epoxy networks from reactive inorganic precursors

International audienceOrganic/inorganic hybrid networks were prepared by a novel solvent-free two-step synthesis method. In the first step, prehydrolyzedcondensed reactive inorganic precursors (clusters) were prepared by a solgel process from monomeric alkoxysilanes with amino and glycido groups. The second step comprised their addition into epoxy resin and amine hardener, followed by the reaction of all components giving the final hybrid crosslinked materials. Their structure was evaluated by small-angle X-ray scattering, transmission electron microscopy, scanning electron microscopy, and dynamic mechanical and thermal analysis. The morphology of the organic/inorganic hybrid structures formed from glycidoprecursor revealed spherical silica-rich domains forming agglomerates with diameter from 100 to 500 nm. The aminoprecursor led to large highly condensed and branched silicon-rich structures. The organic/inorganic hybrid networks obtained from this precursor consisted of mixed siliconorganic phases covalently interconnected via epoxyamine bonds. Such hybrid networks showed significantly improved thermomechanical properties and better resistance against thermooxidation when compared with the neat epoxyamine network. Thin films as well as bulk materials were successfully prepared by this process

Fast synthesis of nanostructured microspheres of a bridged silsesquioxane via ultrasound-assisted sol-gel processing

Microspheres of a nanostructured bridged silsesquioxane were synthesized by employing ultrasound-assisted self-assembly of a bridged monomer via sol-gel processing. The bridged precursor was synthesized from glycidoxypropyl(trimethoxysilane) (GPMS) (2 mol) and cyclohexylamine (1 mol). The main factor controlling the generation of a stable dispersion of microspheres was the time at which the phase separation of the silsesquioxane was produced during the hydrolytic condensation. An appropriate blend of THF/n-hexane as a solvent enabled to rapidly generate a stable dispersion exhibiting a low polydispersity. The mild reaction conditions produced the nanostructuring of the silsesquioxane characterized by a fine structure in SAXS spectrum. Inorganic domains were arranged in a two-dimensional hexagonal system leading to the formation of cavities in the microspheres which could be employed as host-guest systems in advanced technologies. © 2009 WILEY-VCH Verlag GmbH & Co. KCaA.Fil: Romeo, Hernan Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Fanovich, Maria Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Williams, Roberto Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Matejka, Libor. Academy of Sciences of the Czech Republic; República ChecaFil: Plestil, Josef. Academy of Sciences of the Czech Republic; República ChecaFil: Brus, Jirí. Academy of Sciences of the Czech Republic; República Chec

Nanoestructured bridged silsesquioxanes via sol-gel synthesis

Two types of hybrid materials with different degree of nanoestructuring (a bridged silsesquioxane (BS) and hybrid microspheres (MS)) were obtained from a bridged precursor (P) synthesized by the reaction of glycidoxypropyl(trimethoxysilane) with cyclohexylamine. The polycondensation of P in presence of formic acid produced a hybrid material (BS) exhibiting a short-range order based on elongated organic channels, accommodating the cyclohexyl fragments pending from the organic bridge, bounded by inorganic domains. Also, nanostructured hybrid microspheres (MS) were synthesized from P by employing ultrasound-assisted sol-gel processing. The mild reaction conditions produced the nanostructuring of the silsesquioxane characterized by a fine structure in SAXS spectrum. Inorganic domains were arranged in a twodimensional hexagonal system leading to the formation of cavities in the microspheres which could be employed as host-guest systems in advanced technologies.Dos tipos de materiales híbridos con diferente grado de nano-estructuración (un silsesquioxano puenteado (BS) y microesferas híbridas (MS)) fueron obtenidos a partir de un precursor puenteado (P) sintetizado mediante la reacción de glicidoxipropil (trimetoxisilano) con ciclohexilamina. La policondensación del precursor (P) en presencia de ácido fórmico produjo un material híbrido (BS) que presenta un ordenamiento de corto alcance basado en canales orgánicos alargados, que acomodan grupos ciclohexilo pendientes del puente orgánico, enlazados por dominios inorgánicos. También, a partir del precursor P fueron sintetizadas microesferas híbridas nanoestructuradas (MS) empleando una vía de síntesis sol-gel asistida por irradiación ultrasónica. Las suaves condiciones de reacción produjeron la nanoestructuración del silsesquioxano caracterizado por una estructura fina en el espectro SAXS. Los dominios inorgánicos presentaron un arreglo bidimensional hexagonal que dio lugar a la formación de cavidades en las microesferas, las que podrían ser empleadas para contener pequeñas moléculas útiles en tecnologías avanzadas.Fil: Romeo, Hernan Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Williams, Roberto Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Matejka, Libor. Academy of Sciences of the Czech Republic; República ChecaFil: Plestil, Josef. Academy of Sciences of the Czech Republic; República ChecaFil: Brus, Jirí. Academy of Sciences of the Czech Republic; República ChecaFil: Fanovich, Maria Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Macromolecular HPMA-Based Nanoparticles with Cholesterol for Solid-Tumor Targeting: Detailed Study of the Inner Structure of a Highly Efficient Drug Delivery System

We report a rigorous investigation into the detailed structure of nanoparticles already shown to be successful drug delivery nanocarriers. The basic structure of the drug conjugates consists of an <i>N</i>-(2-hydroxypropyl)­methacrylamide (HPMA) copolymer bearing the anticancer drug doxorubicin (Dox) bound via a pH-sensitive hydrazone bond and a defined amount of cholesterol moieties that vary in hydrophobicity. The results show that size, anisotropy, and aggregation number <i>N</i>_aggr of the nanoparticles grows with increasing cholesterol content. From ab initio calculations, we conclude that the most probable structure of HPMA copolymer–cholesterol nanoparticles is a pearl necklace structure, where ellipsoidal pearls mainly composed of cholesterol are covered by a HPMA shell; pearls are connected by bridges composed of hydrophilic HPMA copolymer chains. Using a combination of techniques, we unambiguously show that the Dox moieties are not impregnated inside a cholesterol core but are instead uniformly distributed across the whole nanoparticle, including the hydrophilic HPMA shell surface