Heeju Lee

Formation of Frustrated Lewis Pairs in Ptx‐Loaded Zeolite NaY

The formation of a frustrated Lewis pair consisting of sodium hydride (Na(+) H(-) ) and a framework-bound hydroxy proton O(H(+) ) is reported upon H2 treatment of zeolite NaY loaded with Pt nanoparticles (Ptx /NaY). Frustrated Lewis pair formation was confirmed using in situ neutron diffraction and spectroscopic measurements. The activity of the intrazeolite NaH as a size-selective catalyst was verified by the efficient esterification of acetaldehyde (a small aldehyde) to form the corresponding ester ethyl acetate, whereas esterification of the larger molecule benzaldehyde was unsuccessful. The frustrated Lewis pair (consisting of Na(+) H(-) and O(H(+) )) generated within zeolite NaY may be a useful catalyst for various catalytic reactions which require both H(-) and H(+) ions, such as catalytic hydrogenation or dehydrogenation of organic compounds and activation of small molecules.

Surface Dynamics of Block Copolymer Films by X‐ray Photon Correlation Spectroscopy (abstract)

We investigated the structure and dynamics of supported block copolymer films of poly(styrene)‐b‐poly(dimethylsiloxane) (PS‐b‐PDMS) in the spherical phase by x‐ray photon correlation spectroscopy (XPCS) in grazing angle geometry. The temperature range studied was between 160° and 210° C, much higher than glass transition temperature (Tg), with thickness from 40 nm to 600 nm. Using x‐ray reflectivity and x‐ray photoelectron spectroscopy (XPS), we found that the PDMS‐rich layer near the surface appeared at a temperature higher than Tg. Universal scaling of the dynamics, even with the bilayer model, was observed. From the fitting with the bilayer model, viscosities from both layers were obtained. The results from the surface dynamics are compared with the theory of overdamped thermal capillary waves on thin films.