The dynamics of the surface height fluctuations on layers of covalently tethered, nearly monodisperse polymer chains synthesized by atom transfer radical polymerization were studied using X-ray photon correlation spectroscopy. The data reveal that both polystyrene and poly(n-butyl acrylate) "brushes" have structure at the surface with length scales in the region of 620-3100 nm, but the surface features show no relaxation in a time window of 0.1-1000 s, even at temperatures more than 130 °C above the glass transition temperature of the corresponding untethered chains. This remarkable alteration of the dynamics is compared with the suppression of fluctuations on this length scale anticipated by thermodynamic theories. The alteration of surface dynamics by tethering has implications for wetting, friction, and adhesion.

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The formation of af rustrated Lewis pair consisting of sodium hydride (Na +

Recent research on hydrogen storage in metal–organic frameworks focuses on how to achieve increased hydrogen binding energies by using doped metal, using unsaturated metal ions, or forming composites comprising Pt-doped carbon materials. In particular, noticeable progress using MOFs and Pt-doped carbons has been achieved to enhance the hydrogen storage capacity near room temperature. A three-component composite material, Pt-MWCNT-MOF5 (PMM5), which is a metal–organic framework (MOF-5) hybridized with Pt nanoparticles on multiwalled carbon nanotubes (MWCNT), stores 0.22 wt % hydrogen at 320 K and 30 bar, which is larger than 0.13 wt % at 300 K and 30 bar. Although the increased quantity is small, it is possible to detect the origin of uptake increase based on various analyses. In situ neutron diffraction experiments of deuterium-sorbed PMM5 with a temperature cycling process (D2 loading at 50 K → 4 K → 320 K, 2 h → 50 K → 4 K) result in a significant background increase owing to both chemisorbed deuterium atoms and a local deformation of the MOF-5 framework. Hydrogen loading in PMM5 induces significant binding energy shifts in C 1s and Zn 2p3/2 electrons in the X-ray photoelectron spectra, suggesting the chemical environment change in Zn4O(COO)6 coordination sphere in MOF-5. All accumulated experimental data support the fact that the hydrogen receptor is the oxygen atoms of benzene-1,4-dicarboxylates of MOF-5, which is facilitated by the embedded Pt-MWCNT.

The unprecedented ternary nanocomposites have been synthesized as a single platform via cross-linking of two nanoporous materials, MOFs and Pt nanoparticle (NP) loaded zeolite. The heterojunction of the novel nanocomposites is anticipated to work as a chemical platform for size selective catalytic hydrogenation or deuteration of small molecules.

Although thermal expansion is a key factor in relation to the host-guest interaction of clathrate hydrates, few studies have investigated the thermal behavior of ionic clathrate hydrates. The existence of ionic species in these hydrates creates a unique host-guest interaction compared to that of nonionic clathrate hydrates. It was revealed that X-ray diffraction cannot be used for research of tetramethylammonium hydroxide clathrate hydrates due to damage of the cations by the X-ray, which results in abnormal thermal expansion of the ionic clathrate hydrates. Hence, in the present work, the thermal expansivities of binary sII Me(4)NOD·16D(2)O and sI DClO(4)·5.5D(2)O were measured by neutron powder diffraction (NPD) in order to shed light on their thermal behavior. General correlations for the thermal behaviors of given structures were established and lattice expansions depending on the guests were compared between ionic and nonionic clathrate hydrates. The peculiar change in the thermal expansivity of binary DClO(4)·5.5D(2)O was also considered in relation to the host-guest configuration.

Zeolites are three-dimensional aluminosilicates having unique properties from the size and connectivity of their sub-nanometer pores, the Si/Al ratio of the anionic framework, and the charge-balancing cations. The inhomogeneous distribution of the cations affects their catalytic performances because it influences the intra-crystalline diffusion rates of the reactants and products. However, the structural deformation regarding inhomogeneous active regions during the catalysis is not yet observed by conventional analytical tools. Here we employ in situ X-ray free electron laser-based time-resolved coherent X-ray diffraction imaging to investigate the internal deformations originating from the inhomogeneous Cu ion distributions in Cu-exchanged ZSM-5 zeolite crystals during the deoxygenation of nitrogen oxides with propene. We show that the interactions between the reactants and the active sites lead to an unusual strain distribution, confirmed by density functional theory simulations. These observations provide insights into the role of structural inhomogeneity in zeolites during catalysis and will assist the future design of zeolites for their applications.

We have measured the viscosity of thin polymer films as a function of film thickness using three independent techniques. The results of all methods indicated that the viscosity of the film increases about two orders of magnitude near the solid substrate. Measurements performed on split layer substrates indicated that a layer of polymer chains remained permanently adsorbed at the Si substrate. This layer was responsible for trapping subsequent layers, and propagating the effect of surface interactions to chains without direct contacts to the solid substrate. If this layer was applied prior to the rest of the film, it can screen the surface interactions and even initiate auto-dewetting of other chemically identical layers above it.