Chokbunpiam T.,Chulalongkorn University |
Chokbunpiam T.,University of Leipzig |
Chanajaree R.,Chulalongkorn University |
Remsungnen T.,Khon Kaen University |
And 7 more authors.
Microporous and Mesoporous Materials | Year: 2014
In the field of nanoporous materials, guest-induced structural changes in metal-organic frameworks (MOFs) attracted great attention over the last years. One example concerns a gate-opening effect in MOF ZIF-8 which was found to occur upon sorption of N2. To mirror these structural changes in molecular simulations, suitable force fields for the proper description of framework flexibility are required. We demonstrate that our previously published force field is able to reproduce these structural changes in classical MD simulations. In particular, with our parameter set the diameter of the windows connecting adjacent cavities is found to match the X-ray values almost perfectly. We focus on investigating the impact of the structural changes on the mobility of N 2 molecules in ZIF-8 framework and compare the results with those of another parameter set, which was published recently by Zhang and coworkers. The size of the windows increases notably, when the critical "gate- opening" loading is surpassed. Most surprisingly, this pronounced increase does not result in a speed-up of the N2 self-diffusivity. It appears, that a complex interplay of host-host and host-guest interactions increases the mutual hindrance of the N2 molecules and counter balance the acceleration of the mobility due to the larger window size. © 2013 Elsevier Inc. All rights reserved. Source
Schierz P.,University of Leipzig |
Fritzsche S.,University of Leipzig |
Fritzsche S.,Chulalongkorn University |
Janke W.,University of Leipzig |
And 4 more authors.
Microporous and Mesoporous Materials | Year: 2015
Adsorption and diffusion of hydrogen in the metal organic framework ZIF-11 will be discussed in this paper using molecular dynamics (MD) and Gibbs Monte Carlo (GMC) computer simulations. Reliable force fields, needed for these simulations, are only partially available. Adsorption simulations, in comparison with experiments, have been used to fit some missing interaction parameters. The lattice flexibility turns out to have relatively small influence on adsorption. The obtained parameter set has been used to investigate the structure of ZIF-11 and the self-diffusion of hydrogen within the flexible framework. © 2014 Elsevier Inc. All rights reserved. Source
IRPC Public Company Ltd | Date: 2013-09-04
IRPC PUBLIC COMPANY Ltd | Date: 2012-07-02
In accordance with the present disclosure, a method of preparing a solid support for a transition metal catalyst is disclosed. The solid support may have a unique morphology that may be derived from contacting the magnesium compound and an electron donor in the presence of a fluorinated organic compound to form the solid support. The solid support may be used to form an enhanced catalyst. The enhanced catalyst may be used, in combination with an organoaluminum compound, as a Ziegler-Natta (ZN) catalyst. The ZN catalyst including the enhanced catalyst may be used to form a UHMWPE.
Prachum Y.,Chulalongkorn University |
Prachum Y.,IRPC Public Company Ltd |
Adam Strauss R.H.,IRPC Public Company Ltd |
Kiatkamjornwong S.,Chulalongkorn University
Journal of Applied Polymer Science | Year: 2011
Polypropylene (PP) and polypropylene/polypropylene-g-maleic anhydride/ organomontmorillonite (PP/PP-g-MA/OMMT) nanocomposites were modified with 0.05 to 0.3% (w/w) of the aryl amide β-nucleator to promote the formation of hexagonal crystal modification (β-phase) during melt crystallization. The nonisothermal crystallization behavior of PP, PP/PP-g-MA/OMMT and β-nucleated PP/PP-g-MA/OMMT nanocomposites were studied by means of differential scanning calorimetry. Structure-property relationships of the PP nanocomposites prepared by melt compounding were mainly focused on the effect and quantity of the aryl amide nucleator. The morphological observations, obtained from scanning electron microscopy, transmission electron microscopy and X-ray diffraction analyses are presented in conjunction with the thermal, rheological, and mechanical properties of these nanocomposites. Chemical interactions in the nanocomposites were observed by FT-IR. It was found that the β-crystal modification affected the thermal and mechanical properties of PP and PP/PP-g-MA/OMMT nanocomposites, while the PP/PP-g-MA/OMMT nanocomposites of the study gained both a higher impact strength (50%) and flexural modulus (30%) compared to that of the neat PP. β-nucleation of the PP/PP-g-MA/OMMT nanocomposites provided a slight reduction in density and some 207% improvement in the very low tensile elongation at break at 92% beta nucleation. The crystallization peak temperature (Tcp) of the PP/PP-g-MA/OMMT nanocomposite was slightly higher (116°C) than the neat PP (113°C), whereas the β-nucleation increased the crystallization temperature of the PP/PP-g-MA/OMMT/aryl amide to 128°C, which is of great advantage in a commercial-scale mold processing of the nanocomposites with the resulting lower cycle times. The beta nucleation of PP nanocomposites can thus be optimized to obtain a better balance between thermal and mechanical properties. © 2011 Wiley Periodicals, Inc. Source