A surface science model for the phillips ethylene polymerization catalyst

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In situ ATR-FTIR studies on MgCl2-Diisobutyl phthalate interactions in thin film Ziegler-Natta catalysts

To study the surface structure of MgCl2 support and its interaction with other active components in Ziegler–Natta catalyst, such as electron donors, we prepared a thin film analogue for Ziegler–Natta ethylene polymerization catalyst support by spin-coating a solution of MgCl2 in ethanol, optionally containing a diester internal donor (diisobutyl-ortho-phthalate, DIBP) on a flat Si crystal surface. The donor content of these films was quantified by applying attenuated total internal reflection–Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Changes in the interaction of DIBP with MgCl2 at various temperatures were monitored by in situ ATR-FTIR. Upon increasing the temperature, a shift in the (C-O) band toward lower wavenumbers was observed together with the depletion of (O–H) stretching band due to the desorption of residual ethanol. We assign this shift to gradual redistribution of adsorbed DIBP from adsorption sites on the MgCl2 (104) surface toward the more acidic MgCl2 (110) surface. The morphologies of MgCl2 and MgCl2/DIBP films were studied by transmission electron microscopy (TEM) revealing a preferential orientation of ClMgCl layers (001) parallel to the lateral film dimensions. This orientation becomes more pronounced upon annealing. In the absence of donor, the MgCl2 grow in to large crystals aligned in large domains upon annealing. Both crystal growth and alignment is impeded by the presence of donor

In situ ATR-FTIR studies on MgCl2-Diisobutyl phthalate interactions in thin film Ziegler-Natta catalysts

To study the surface structure of MgCl2 support and its interaction with other active components in Ziegler–Natta catalyst, such as electron donors, we prepared a thin film analogue for Ziegler–Natta ethylene polymerization catalyst support by spin-coating a solution of MgCl2 in ethanol, optionally containing a diester internal donor (diisobutyl-ortho-phthalate, DIBP) on a flat Si crystal surface. The donor content of these films was quantified by applying attenuated total internal reflection–Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Changes in the interaction of DIBP with MgCl2 at various temperatures were monitored by in situ ATR-FTIR. Upon increasing the temperature, a shift in the (C-O) band toward lower wavenumbers was observed together with the depletion of (O–H) stretching band due to the desorption of residual ethanol. We assign this shift to gradual redistribution of adsorbed DIBP from adsorption sites on the MgCl2 (104) surface toward the more acidic MgCl2 (110) surface. The morphologies of MgCl2 and MgCl2/DIBP films were studied by transmission electron microscopy (TEM) revealing a preferential orientation of ClMgCl layers (001) parallel to the lateral film dimensions. This orientation becomes more pronounced upon annealing. In the absence of donor, the MgCl2 grow in to large crystals aligned in large domains upon annealing. Both crystal growth and alignment is impeded by the presence of donor

A new approach to silver-catalysed aerobic oxidation of octadecanol: probing catalysts utilising a flat, two-dimensional silicon-based model support system

Aerobic oxidation of a thin film of octadecanol at 105 °C and ambient pressures to its corresponding carbonyl derivatives (a mixture of aldehyde and carboxylic acid) was for the first time performed over a flat-model (i.e. two-dimensional), silicon wafer-supported metallic silver catalyst. The experimental set-up was extraordinary simple. An open-to-the-atmosphere glass beaker was used as reactor. Just enough octadecanol was placed on the silicon-supported catalytic surface to cover it with a thin film when melted. Reaction progress was monitored by ATR-FTIR analyses to identify the appearance of octadecanal and octadecanoic acid carbonyl stretching peaks at 1730 and 1710 cm- 1 respectively. The successful demonstration of this simple approach in studying catalysed small-molecule condensed organic reactions opens a new avenue towards simplified catalytic mechanistic studies of such processes. The catalyst was prepared by spin coating silver nitrate on a flat silicon wafer with (100) surface orientation, pretreated to have 4-5 silanol (SiOH) groups per nm2. Reduction by hydrogen at 350 °C afforded metallic silver particles on the two-dimensional support at a nominal surface concentration of ca. 21–23 silver atoms/nm2. XPS differentiation between the catalyst precursor, AgNO3, and the metallic silver catalytic surface required use of the Auger MNN kinetic energies. TEM studies of the active catalyst showed no serious aggregation of metallic Ag particles occurred during reduction

Cellulose nanocrystal submonolayers by spin coating

Dilute concentrations of cellulose nanocrystal solutions were spin coated onto different substrates to investigate the effect of the substrate on the nanocrystal submonolayers. Three substrates were probed: silica, titania, and amorphous cellulose. According to atomic force microscopy (AFM) images, anionic cellulose nanocrystals formed small aggregates on the anionic silica substrate, whereas a uniform two-dimensional distribution of nanocrystals was achieved on the cationic titania substrate. The uniform distribution of cellulose nanocrystal submonolayers on titania is an important factor when dimensional analysis of the nanocrystals is desired. Furthermore, the amount of nanocrystals deposited on titania was multifold in comparison to the amounts on silica, as revealed by AFM image analysis and X-ray photoelectron spectroscopy. Amorphous cellulose, the third substrate, resulted in a somewhat homogeneous distribution of the nanocrystal submonolayers, but the amounts were as low as those on the silica substrate. These differences in the cellulose nanocrystal deposition were attributed to electrostatic effects: anionic cellulose nanocrystals are adsorbed on cationic titania in addition to the normal spin coating deposition. The anionic silica surface, on the other hand, causes aggregation of the weakly anionic cellulose nanocrystals which are forced on the repulsive substrate by spin coating. The electrostatically driven adsorption also influences the film thickness of continuous ultrathin films of cellulose nanocrystals. The thicker films of charged nanocrystals on a substrate of opposite charge means that the film thickness is not independent of the substrate when spin coating cellulose nanocrystals in the ultrathin regime

Cellulose nanocrystal submonolayers by spin coating

Dilute concentrations of cellulose nanocrystal solutions were spin coated onto different substrates to investigate the effect of the substrate on the nanocrystal submonolayers. Three substrates were probed: silica, titania, and amorphous cellulose. According to atomic force microscopy (AFM) images, anionic cellulose nanocrystals formed small aggregates on the anionic silica substrate, whereas a uniform two-dimensional distribution of nanocrystals was achieved on the cationic titania substrate. The uniform distribution of cellulose nanocrystal submonolayers on titania is an important factor when dimensional analysis of the nanocrystals is desired. Furthermore, the amount of nanocrystals deposited on titania was multifold in comparison to the amounts on silica, as revealed by AFM image analysis and X-ray photoelectron spectroscopy. Amorphous cellulose, the third substrate, resulted in a somewhat homogeneous distribution of the nanocrystal submonolayers, but the amounts were as low as those on the silica substrate. These differences in the cellulose nanocrystal deposition were attributed to electrostatic effects: anionic cellulose nanocrystals are adsorbed on cationic titania in addition to the normal spin coating deposition. The anionic silica surface, on the other hand, causes aggregation of the weakly anionic cellulose nanocrystals which are forced on the repulsive substrate by spin coating. The electrostatically driven adsorption also influences the film thickness of continuous ultrathin films of cellulose nanocrystals. The thicker films of charged nanocrystals on a substrate of opposite charge means that the film thickness is not independent of the substrate when spin coating cellulose nanocrystals in the ultrathin regime

An injectable calcium phosphate cement for the local delivery of paclitaxel to bone

Item does not contain fulltextBone metastases are usually treated by surgical removal, fixation and chemotherapeutic treatment. Bone cement is used to fill the resection voids. The aim of this study was to develop a local drug delivery system using a calcium phosphate cement (CPC) as carrier for chemotherapeutic agents. CPC consisted of alpha-tricalcium phosphate, calcium phosphate dibasic and precipitated hydroxyapatite powders and a 2% Na(2)HPO(4) hardening solution. Scanning electron microscopy (SEM) was used to observe CPC morphology. X-ray diffraction (XRD) was used to follow CPC transformation. The loading/release capacity of the CPC was studied by a bovine serum albumin-loading model. Release/retention was measured by high performance liquid chromatography and X-ray photoelectron spectrometry. For chemotherapeutic loading, paclitaxel (PX) was loaded onto the CPC discs by absorption. Viability of osteosarcoma U2OS and metastatic breast cancer MDA-MB-231 cells was measured by an AlamarBlue assay. Results of SEM and XRD showed changes in CPC due to its transformation. The loading model indicated a high retention behavior by the CPC composition. Cell viability tests indicated a PX minimal lethal dose of 90 mug/ml. PX released from CPC remained active to influence cell viability. In conclusion, this study demonstrated that CPC is a feasible delivery vector for chemotherapeutic agents