Кластеризація води в міжчастинковому просторі гідрофобного нанокремнезему АМ-1

The processes occurring in hydrated powders and concentrated suspensions of hydrophobic silica were studied by 1H NMR spectroscopy. It is shown that a mixture of methyl silica and water with a hydration of less than 1 g / g is a wet powder, where water is in the form of submicron clusters filling the interparticle voids of nanosilica, and the interfacial energy is directly proportional to the amount of added water. It was found that at high water concentrations there is a spontaneous increase in the size of water structures, which is accompanied by a sharp decrease in interfacial energy, that may reflect the disappearance of narrow interparticle voids or their filling with air. It is shown that aqueous suspensions of AM-1 are easily mixed with a weakly polar organic solvent chloroform, forming a stable suspension with close the amounts both of water and chloroform. It was revealed that the aqueous suspension of methyl silica has high thixotropic properties, which depend on the time and the magnitude of the applied mechanical loads.Методом 1Н ЯМР спектроскопії було досліджено процеси, що відбуваються в гідратованих порошках і концентрованих суспензіях гідрофобного кремнезему. Показано, що суміш метилкремнезему та води при гідратованості менше 1 г/г являє собою вологий поршок, де вода знаходиться у вигляді субмікронних кластерів, що заповнюють міжчастинкові проміжки нанокремнезему, а міжфазна енергія прямо пропорційна кількості води, що додається. Виявлено, що при великих концентраціях води відбувається спонтанне збільшення розміру водних структур, яке супроводжується різким зменшенням міжфазної енергії, що може відображати зникнення вузьких міжчастинкових зазорів або заповнення їх повітрям. В роботі показано, що водні суспензії АМ-1 легко змішуються із слабополярним органічним розчинником хлороформом, формуючи стійку суспензію, де кількість води та хлороформу може бути близьким. Виявлено, що водна суспензія метилкремнезему має високі тиксотропні властивості, які залежать від часу та від величини прикладених механічних навантажень

Polyurethane–poly(2-hydroxyethyl methacrylate) semi- IPN–nanooxide composites

Two sets of hybrid polyurethane–poly(2-hydroxyethyl methacrylate) semi-interpenetrating polymer network–nanooxide composites with 0.25 or 3 wt% nanosilica or nanoalumina functionalised with OH, NH2 or CHLCH2 groups were prepared. A combination of atomic force microscopy, infrared spectroscopy, thermally stimulated depolarisation current measurement, differential scanning calorimetry and creep rate spectroscopy analysis of the nanostructure and properties of the composites was performed. The pronounced dynamic heterogeneity and the strong impact of oxide additives, basically suppression of the dynamics and temperature-dependent increasing modulus of elasticity, were observed. The effects correlated with either interfacial interactions (for silica) or the nanostructure (for alumina). A low oxide content strongly affected the matrix due to the formation of an unusual cross-linked, via double covalent hybridisation of three components, structure of the nanocomposites

Interactions of single and multi-layer graphene oxides with water, methane, organic solvents and HCl studied by 1H NMR

Abstract Contemporary characterisation techniques for graphenes are often performed for samples in a dried state or vacuum, which can lead to significant structural changes and difficulty in assessing the actual physical or physicochemical characteristics of graphenes in a colloid state. The interfacial phenomena between water or mixtures (of water with benzene, methane, or HCl) bound to single-layer graphene oxide (SLGO) and multi-layer graphene oxide (MLGO) in different dispersion media (CDCl3, CCl4, CDCl3/DMSO, air) were studied using low-temperature (200–280K) 1H NMR spectroscopy. Use of the NMR cryoporometry method allows determination of the textural characteristics of SLGO and MLGO depending on their hydration degree. It was found that SLGO in diluted suspensions is more agglomerated after freezing-thawing. This effect could be assigned to cryogelation of carbon sheets leading to a decrease in the specific surface area (from 1841 to 533m2/g) representing the area of sheets that are accessible for water that is unfrozen at subzero temperatures. The results obtained show that the cryoporometry method is appropriate for the investigation of the texture of both wetted and suspended graphene oxides