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11.
《Current Applied Physics》2020,20(12):1391-1395
Muscovite mica is a widely accepted substrate for scanning probe microscopy (SPM) investigations. However, mica has intrinsic properties that alter samples and obstruct their analysis due to free charges build-up, ionic exchange and water adsorption taking place at the surface. In addition to interfacial phenomena, there is a growing interest in electrostatic charges on insulators as they are crucial in diverse applications. Despite the high demand for studies of this nature, experimental set-ups capable of resolving charge build-up at the micro-scale are still scarce and technically limited. Here, we report the imaging of surface charge dissipation on freshly cleaved mica by Kelvin-probe Force Microscopy (KPFM). A local electrostatic charge micro-domain was generated by friction between an atomic force microscope (AFM) tip and mica, and its decay was tracked by two-dimensional mapping using KPFM. We found time-dependent charge dissipation, which is attributed to the adsorption of water molecules on mica surface. 相似文献
12.
Formation of porous polymer morphology by microsyneresis during divinylbenzene polymerization 下载免费PDF全文
Libuše Hanková Ladislav Holub Karel Jeřábek 《Journal of Polymer Science.Polymer Physics》2015,53(11):774-781
This article describes the investigation of the importance of various reaction conditions on microsyneretic pore formation during polymerization of divinylbenzene (DVB) under so‐called “solvothermal” conditions. To induce microsyneretic pore formation, the most important parameter is an unusually high dilution of monomers with a “good” porogen solvating the polymer chains. High dilution and solvation of the growing poly(DVB) chains promote the prolongation of the polymer chains rather than their interconnection by crosslinking. Consequently, when the polymer gel density reaches the point where syneresis starts, the polymer network is geometrically too extensive to be broken up into precipitating entities and, instead, porogen droplets are formed within the continuous polymer gel. The pore geometry created by microsyneresis offers high surface area in wide mesopores and hence, high capacity for supporting functional groups or reactions with much better accessibility than narrow pores between polymer microspheres produced by macrosyneresis in conventional styrenic polymer supports. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 774–781 相似文献
13.
Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol‐ene photochemistry 下载免费PDF全文
Victor A. Kusuma Elliot A. Roth William P. Clafshenkel Steven S. Klara Xu Zhou Surendar R. Venna Erik Albenze David R. Luebke Meagan S. Mauter Richard R. Koepsel Alan J. Russell David Hopkinson Hunaid B. Nulwala 《Journal of polymer science. Part A, Polymer chemistry》2015,53(13):1548-1557
Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO2/N2 selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557 相似文献
14.
Vsevolod Khikhlovskyi Albert J. J. M. van Breemen Jasper J. Michels René A. J. Janssen Gerwin H. Gelinck Martijn Kemerink 《Journal of Polymer Science.Polymer Physics》2015,53(17):1231-1237
In many organic electronic devices functionality is achieved by blending two or more materials, typically polymers or molecules, with distinctly different optical or electrical properties in a single film. The local scale morphology of such blends is vital for the device performance. Here, a simple approach to study the full 3D morphology of phase‐separated blends, taking advantage of the possibility to selectively dissolve the different components is introduced. This method is applied in combination with AFM to investigate a blend of a semiconducting and ferroelectric polymer typically used as active layer in organic ferroelectric resistive switches. It is found that the blend consists of a ferroelectric matrix with three types of embedded semiconductor domains and a thin wetting layer at the bottom electrode. Statistical analysis of the obtained images excludes the presence of a fourth type of domains. The criteria for the applicability of the presented technique are discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1231–1237 相似文献
15.
A novel metal-doped metal–organic framework (MOF) was developed by incorporating salen–Mg into NH2–MIL-101(Cr) structure under ambient conditions. The Schiff base complex was successfully prepared by condensing salicylaldehyde with a free amino group and then coordinating metal ions. Such a structure can endow the sample with higher CO2 adsorption performance. At 0°C and 1 bar, the salen–Mg-modified sample achieves the maximum adsorption capacity of 2.18 mmol g−1 for CO2, which was 5.8% higher than the pristine salen–MOF under the same conditions. Notably, the Freundlich model indicates that the CO2 adsorption process of all samples conforms to reversible adsorption. However, the correlation coefficients (R2) of the Mg-doped sample are lower than that of the pristine sample. Besides, the CO2/N2 adsorption selectivity and isosteric heat also show a similar trend. These results indicate that the salen–Mg can enhance the interaction between the material and CO2 molecules. 相似文献
16.
Morgan A. Higgins Christopher R. Maroon Jacob Townsend Xinyi Wang Konstantinos D. Vogiatzis Brian K. Long 《Journal of polymer science. Part A, Polymer chemistry》2020,58(18):2644-2653
Polymeric membranes have shown tremendous promise for the separation of CO2 from flue gas streams. However, few systematic studies have been conducted to better understand the impact that chemical functionalities have on membrane-based gas separation performance. To address this gap, we herein describe the synthesis and gas separation performance of a series of vinyl-addition polynorbornenes bearing various CO2-philic functional groups. To facilitate direct comparison between functional groups, each material was designed to maintain a common polymer backbone. Though the incorporation of CO2-philic moieties within a dense polymeric membrane is frequently hypothesized to enhance CO2 solubility, and thereby increase CO2/N2 selectivity, our results demonstrate that the incorporation of CO2-philic groups onto a common polymer backbone do not necessarily result in increased gas separation performance. Experimental and computational results demonstrate that the incorporation of amidoxime groups onto a polynorbornene backbone increase CO2/N2 selectivity, whereas commonly employed ethereal side chains only increased permeability. 相似文献
17.
Leiqing Hu Sankhajit Pal Hien Nguyen Vinh Bui Haiqing Lin 《Journal of polymer science. Part A, Polymer chemistry》2020,58(18):2467-2481
Over the last two decades, polymers with superior H2/CO2 separation properties at 100–300 °C have gathered significant interest for H2 purification and CO2 capture. This timely review presents various strategies adopted to molecularly engineer polymers for this application. We first elucidate the Robeson's upper bound at elevated temperatures for H2/CO2 separation and the advantages of high-temperature operation (such as improved solubility selectivity and absence of CO2 plasticization), compared with conventional membrane gas separations at ~35 °C. Second, we describe commercially relevant membranes for the separation and highlight materials with free volumes tuned to discriminate H2 and CO2, including functional polymers (such as polybenzimidazole) and engineered polymers by cross-linking, blending, thermal treatment, thermal rearrangement, and carbonization. Third, we succinctly discuss mixed matrix materials containing size-sieving or H2-sorptive nanofillers with attractive H2/CO2 separation properties. 相似文献
18.
Ding Tian Taliehsadat Alebrahim Gregory K. Kline Liwen Chen Haiqing Lin Chulsung Bae 《Journal of polymer science. Part A, Polymer chemistry》2020,58(18):2654-2663
Polymeric membrane-based gas separation technology has significant advantages compared with traditional amine-based CO2 separation method. In this work, SEBS block copolymer is used as a polymer matrix to incorporate triethylene oxide (TEO) functionality. The short ethylene oxide segment is chosen to avoid crystallization, which is confirmed by differential scanning calorimetry and wide-angle X-ray scattering characterizations. The gas permeability results reveal that CO2/N2 selectivity increased with increasing content of TEO functional group. The highest CO2 permeability (281 Barrer) and CO2/N2 selectivity (31) were obtained for the membrane with the highest TEO incorporation (57 mol%). Increasing the TEO content in these copolymers results in an increase in CO2 solubility and a decrease in C2H6 solubility. For example, as the grafted TEO content increased from 0 to 57 mol%, the CO2 solubility and CO2/C2H6 solubility selectivity increased from 0.72 to 1.3 cm3(STP)/cm3 atm and 0.47 to 1.3 at 35°C, respectively. The polar ether linkage in TEO-grafted SEBS copolymers exhibits favorable interaction with CO2 and unfavorable interaction with nonpolar C2H6, thus enhancing CO2/C2H6 solubility selectivity. 相似文献
19.
Zhentao Hao Chuchu Chen Ting Shen Jiaxing Lu Hao-Cheng Yang Weihua Li 《Journal of polymer science. Part A, Polymer chemistry》2020,58(21):3031-3041
Slippery liquid-infused porous surface (SLIPS) is a rising star in corrosion protection owing to its outstanding corrosive medium resistance and self-healing property. The large-area and facile fabrication of SLIPS remains a challenge lying on the way of its practical application. Herein, we develop a novel SLIPS based on a porous polyvinylidene fluoride (PVDF) substrate fabricated by thermally induced phase separation. A sphere-packing structure can be easily obtained by blade-coating followed by cooling. The SLIPS exhibits an extremely low sliding angle of 5.8° so that it can resist the fouling of even the Chinese ink, ascribing to its slippery dynamic surface with low surface energy. We also evaluated the anti-corrosion performance of the SLIPS and superhydrophobic PVDF coating by electrochemical impedance spectroscopy (EIS) and scanning Kelvin probe technique (SKP), both of which exhibited enhanced corrosion resistance in 3.5 wt% NaCl solution due to the physical oil and air barriers against the corrosive medium penetration. Nevertheless, the SLIPS coatings performed outstanding self-healing properties because of the high fluidity of infused oil to recover the surface damages, and the self-healing process was recorded by the SKP. 相似文献
20.
Shuhao Zhang Mercedes K. Taylor Lingchang Jiang Prof. Hao Ren Prof. Guangshan Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(15):3205-3221
Light hydrocarbons (C1–C3) are used as basic energy feedstocks and as commodity organic compounds for the production of many industrially necessary chemicals. Due to the nature of the raw materials and production processes, light hydrocarbons are generated as mixtures, but the high-purity single-component products are of vital importance to the petrochemical industry. Consequently, the separation of these C1–C3 products is a crucial industrial procedure that comprises a significant share of the total global energy consumption per year. As a complement to traditional separation methods (distillation, partial hydrogenation, etc.), adsorptive separations using porous solids have received widespread attention due to their lower energy costs and higher efficiency. Extensive research has been devoted to the use of porous materials such as zeolites and metal-organic frameworks (MOFs) as solid adsorbents for these key separations, owing to the high porosity, tunable pore structures, and unsaturated metal sites present in these materials. Recently, porous organic framework (POF) materials composed of organic building blocks linked by covalent bonds have also shown excellent properties in light hydrocarbon adsorption and separation, sparking interest in the use of these materials as adsorbents in separation processes. This Minireview summarizes the recent advances in the use of POFs for light hydrocarbon separations, including the separation of mixtures of methane/ethane, methane/propane, ethylene/ethane, acetylene/ethylene, and propylene/propane, while highlighting the relationships between the structural features of these materials and their separation performances. Finally, the difficulties, challenges, and opportunities associated with leveraging POFs for light hydrocarbon separations are discussed to conclude the review. 相似文献