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Your search keyword '"Ogieglo, Wojciech"' showing total 172 results
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172 results on '"Ogieglo, Wojciech"'

4. Disentangling Thermal from Electronic Contributions in the Spectral Response of Photoexcited Perovskite Materials

Author

Wang, Lijie, primary, Nughays, Razan, additional, Rossi, Thomas C., additional, Oppermann, Malte, additional, Ogieglo, Wojciech, additional, Bian, Tieyuan, additional, Shih, Chun-Hua, additional, Guo, Tzung-Fang, additional, Pinnau, Ingo, additional, Yin, Jun, additional, Bakr, Osman M., additional, Mohammed, Omar F., additional, and Chergui, Majed, additional

Published
2024
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5. Identifying orientation-dependent optical properties of single-crystalline β-Ga2O3 films.

Author

Upadhyaya, Kishor, Gudelli, Vijay Kumar, Ogieglo, Wojciech, Alamoudi, Hadeel, Alreshidi, Fatimah, and Roqan, Iman S.

Subjects
REFRACTIVE index, X-ray diffraction measurement, THIN films, OPTICAL properties, DENSITY functional theory
Abstract

We explore the effect of crystallographic anisotropy on the optical properties of high-quality β-Ga2O3 thin films by conducting experimental measurements and theoretical simulations. High resolution x-ray diffraction measurements confirm the high-quality and the single crystalline quality, ruling out the effect of defects for all films. Raman spectra reveal the presence of anisotropy, as evident from a stronger B g (2) mode related to GaIO4 chain libration in (100) orientation. Conversely, a stronger A g (10) mode corresponding to tetrahedral bonds is evident in the (010) orientation, while it is suppressed in the (100) orientation. Low-temperature photoluminescence spectra indicate the presence of intrinsic impurity-related emissions in the ultraviolet and blue regions for all films. An anisotropic bandgap is observed, wherein the lowest bandgap value is related to the (010) oriented sample. Spectroscopic ellipsometry measurements confirm different refractive indices and extinction coefficient values depending on crystallographic orientation, which are in good agreement with the theoretical values obtained by density functional theory, confirming the anisotropic characteristics. The theoretical calculations of charge density show that the strength of covalent bonding depends on the β-Ga2O3 orientation, while experimental findings demonstrate that as the covalent bonding character increases, the film bandgap and the refractive index decrease. The anisotropy of β-Ga2O3 with respect to the crystal orientation leads to variations in the extinction coefficient, refractive index, and bandgap energy. [ABSTRACT FROM AUTHOR]

Published
2024
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7. Unlocking complex chemical and morphological transformations during thermal treatment of O-hydroxyl-substituted polyimide of intrinsic microporosity: Impact on ethanol/cyclohexane separation

Author

Ogieglo, Wojciech, primary, Knozowska, Katarzyna, additional, Puspasari, Tiara, additional, Ali, Zain, additional, Kujawa, Joanna, additional, Korczeniewski, Emil, additional, Terzyk, Artur P., additional, Kujawski, Wojciech, additional, and Pinnau, Ingo, additional

Published
2023
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27. Exploring physical aging in PIM-1 using molecular dynamics.

Author

Balcik, Marcel, Ogieglo, Wojciech, Wang, Yingge, and Pinnau, Ingo

Subjects
*MOLECULAR dynamics, *AGING, *POLYMER structure, *POLYMERS, *CARBON dioxide, *POLYIMIDES
Abstract

This comprehensive study explored the aging process of PIM-1, a ladder polymer of intrinsic microporosity (PIM), by applying molecular dynamics simulations for the first time. Through detailed analysis, our work illustrates the evolution of the polymer structure from a loosely packed, less dense state of the pristine polymer to a more tightly packed configuration due to physical aging. For this purpose, a novel molecular dynamics (MD) methodology was employed in the process toward equilibration of PIM-1. This structural transition was quantitatively captured by measuring key parameters such as density, fractional free volume (FFV), cohesive energy density (CED), d -spacing, surface area, and gas permeabilities. The simulations demonstrate a noticeable increase in density by approximately 7 % in aged PIM-1 compared to a fresh sample. This increase in density is accompanied by a corresponding decrease in FFV, suggesting a more compact molecular arrangement. The impact of these structural changes is evident in the gas transport properties. Permeabilities of all gases tested, He, H 2 , O 2 , N 2 , CO 2 and CH 4 , decreased by 33 %–80 %. Moreover, the selectivity of gas pairs like CO 2 /CH 4 and O 2 /N 2 exhibited increasing trends due to aging, as previously reported in experimental work. Structural analysis performed on the fresh and aged structures indicated collapse of free volume over aging, by disappearance of pores larger than ∼6.5 Å. Furthermore, no intrachain rearrangement was observed during physical aging in the ladder PIM-1 structure; rather, the aging resulted in increased interchain packing efficiency. Our methodology can be employed to other PIM architectures, such as polyimides of intrinsic microporosity (PIM-PIs) as well as low-free volume glassy polymers. [Display omitted] • Physical aging in PIM-1 was successfully simulated by MD. • Simulated fresh and aged pure-gas transport properties matched experimental data. • Effect of aging on density, d-spacing, FFV, PSD was analyzed. • Aging resulted in more efficient interchain packing without significantly affecting intrachain packing. • Our methodology was extended to other high-free-volume glassy polymers. [ABSTRACT FROM AUTHOR]

Published
2024
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28. Effect of the 3D Swelling of Microgels on Their 2D Phase Behavior at the Liquid–Liquid Interface

Author

Bochenek, Steffen, primary, Scotti, Andrea, additional, Ogieglo, Wojciech, additional, Fernández-Rodríguez, Miguel Ángel, additional, Schulte, M. Friederike, additional, Gumerov, Rustam A., additional, Bushuev, Nikita V., additional, Potemkin, Igor I., additional, Wessling, Matthias, additional, Isa, Lucio, additional, and Richtering, Walter, additional

Published
2019
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39. Carbon molecular sieve gas separation materials and membranes: A comprehensive review.

Author

Genduso, Giuseppe, Ogieglo, Wojciech, Wang, Yingge, and Pinnau, Ingo

Subjects
*GAS separation membranes, *MOLECULAR sieves, *POLYMERIC membranes, *SEPARATION of gases, *CHEMICAL precursors
Abstract

Carbon molecular sieve (CMS) membranes offer some of the best combinations of high selectivity and permeability for molecular separations of permanent and condensable gases available to date. In addition, the fabrication of CMS membranes benefits from the well-established solution processing methods developed for fabrication of high-performance commercial polymeric membranes. In this review, we critically evaluate the extensive data set on CMS membranes available in the peer-reviewed literature published since the 1980s. In the first part, we focus on the material perspectives and evaluate how various polymer chemistries were used as precursors for generation of CMS films. We highlight the role of fluorinated and non-fluorinated polyimides as well as polymers of intrinsic microporosity (PIMs) which tend to dominate the more recent literature. In addition, we identify the most important parameters that determine the gas separation performance of CMS membranes, such as (i) pyrolysis temperature, (ii) pyrolysis atmosphere, or (iii) pre- and post-treatments and others. We collected and evaluated the CMS membrane performance for the separation of permanent gases (He, H 2 , O 2 , N 2 , CH 4 , CO 2) and highly energy-intensive olefin/paraffin separation. In the second part, we highlight the currently available data on CMS thin-film composite and integrally-skinned asymmetric membranes, which exhibit excellent permeance and selectivity in many important industrial separations. Finally, we provide a set of recommendations for future research in the area of CMS materials and membranes based on a critical evaluation of the reported data. [Display omitted] • Comprehensive review of CMS materials and membranes since 1980s. • Detailed material-oriented perspective on the role of various CMS precursor chemistries. • Highlight of the emerging CMS precursors such as PIMs. • Insights on relevant pyrolysis parameters: temperature, atmosphere, pre-/post-treatment. • Examination of the effect of selective layer thickness in composite CMS membranes. [ABSTRACT FROM AUTHOR]

Published
2024
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40. Evidence of a Transition Layer between the Free Surface and the Bulk

Author

Ogieglo, Wojciech, Tempelman, Kristianne, Napolitano, Simone, Benes, Nieck N.E., Ogieglo, Wojciech, Tempelman, Kristianne, Napolitano, Simone, and Benes, Nieck N.E.

Abstract

The free surface, a very thin layer at the interface between polymer and air, is considered the main source of the perturbations in the properties of ultrathin polymer films, i.e. nanoconfinement effects. The structural relaxation of such a layer is decoupled from the molecular dynamics of the bulk. The free surface is, in fact, able to stay liquid even below the temperature where the polymer resides in the glassy state. Importantly, this surface layer is expected to have a very sharp interface with the underlying bulk. Here, by analyzing the penetration of n-hexane into polystyrene films, we report on the existence of a transition region, not observed by previous investigations, extending for 12 nm below the free surface. The presence of such a layer permits reconciling the behavior of interfacial layers with current models and has profound implications on the performance of ultrathin membranes. We show that the expected increase in the flux of the permeating species is actually overruled by nanoconfinement., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2018

44. Thermal Stability of Sulfonated Poly(Ether Ether Ketone) Films: on the Role of Protodesulfonation

Author

Koziara, Beata T., Kappert, Emiel J., Ogieglo, Wojciech, Nijmeijer, Kitty, Hempenius, Mark A., Benes, Nieck E., Faculty of Science and Technology, Membrane Science & Technology, Inorganic Membranes, and Materials Science and Technology of Polymers

Subjects
SPEEK, Thermal stability, Desulfonation, Thin film membranes, Thermo-ellipsometric analysis
Abstract

Thin film and bulk, sulfonated poly(ether ether ketone) (SPEEK) have been subjected to a thermal treatment at 160–250 °C for up to 15 h. Exposing the films to 160 °C already causes partial desulfonation, and heating to temperatures exceeding 200 °C results in increased conjugation in the material, most likely via a slight cross-linking by H-substitution. It is well-known that the sulfonate proton plays a major role in the desulfonation reactions, and exchanging the protons with other cations can inhibit both protodesulfonation as well as electrophilic cross-linking reactions of the sulfonate group with other chains. Yet, the implications of such ion-exchange for the thermal processing of sulfonated polymer films has not been recognized. Our study demonstrates that the ion exchange stabilizes thin films and bulk SPEEK up to temperatures exceeding 200 °C, opening up ways for the thermal processing of SPEEK in the temperature range of 160–220 °C without adverse effects.

Published
2016

49. CO2/CH4Pure- and Mixed-Gas Dilation and Sorption in Thin (∼500 nm) and Ultrathin (∼50 nm) Polymers of Intrinsic Microporosity

Author

Ogieglo, Wojciech, Genduso, Giuseppe, Rubner, Jens, Hofmann-Préveraud de Vaumas, Jacques, Wessling, Matthias, and Pinnau, Ingo

Abstract

In this work, we present (i) the dilation and refractive index variation associated with changes in film density and (ii) gas uptake of pure CO2and CH4, as well as their equimolar mixture in thin films of two polymers of intrinsic microporosity (PIMs), that is, PIM-1 and poly(trimethylsilyl)propyne (PTMSP). A conventional low-free-volume glassy polymer, cellulose triacetate, was also investigated as the reference material. All experiments were performed with ∼50 and ∼500 nm-thick films up to partial pressures of 25 bar using in situinterference-enhanced spectroscopic ellipsometry. In all cases, film thickness reduction promoted the collapse of the frozen-in free volume. Particularly for thin PIM-1 and PTMSP films, the CO2and CH4pure-gas uptakes were generally lower than in bulk samples. In the most extreme case of the ultrathin ∼50 nm PTMSP film, we could detect a strikingly similar qualitative behavior to the penetrant partial molar volume and dilation in rubbery polymers. Remarkably, in PIM-1, the collapse of the frozen-in free volume seemed to be opposed by its ultra-micropores (<7 Å), which was not the case in PTMSP with larger micropores (>10 Å). In mixed-gas experiments, the refractive index response of all investigated films closely followed the trend observed during CO2pure-gas sorption. In both thickness ranges and throughout the entire pressure range, the samples dilated less in the multicomponent environment than under the corresponding ideal pure-gas conditions. We found this phenomenon consistent with the pure- and mixed-gas uptake behavior of PIM-1 and PTMSP bulk films reported in the literature.

Published
2020
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