The PIMs are for the first time incorporated into an arylether-type PBI (OPBI) matrix to form some novel partially miscible alloy membranes containing a special intrinsic "porous" structure. A proton ...conductivity of 313 mS cm
−1
at 200 °C and a peak power density of 438 mW cm
−2
at 160 °C can be obtained under anhydrous conditions.
Polymers of intrinsic microporosity are for the first time incorporated into PBIs to form some novel alloys for HT-PEMFC applications.
High-free-volume glassy polymers, such as polymers of intrinsic microporosity (PIMs) and poly(trimethylsilylpropyne), have attracted attention as membrane materials due to their high permeability. ...However, loss of free volume over time, or aging, limits their applicability. Introduction of a secondary filler phase can reduce this aging but either cost or instability rules out scale up for many fillers. Here, we report a cheap, acid-tolerant, nanoparticulate hypercrosslinked polymer 'sponge' as an alternative filler. On adding the filler, permeability is enhanced and aging is strongly retarded. This is accompanied by a CO2/N2 selectivity that increases over time, surpassing the Robeson upper bound.
HintergrundAktuelle Untersuchungen belegen den Zusammenhang zwischen der Verordnung potenziell inadäquater Medikamente (PIM) an Patienten ab 65 Jahren und einem erhöhten Risiko dieser Patienten für ...unerwünschte Ereignisse, insbesondere Krankenhausaufnahmen. Die bevölkerungsrepräsentative Stichprobe der DEGS1-Studie („Studie zur Gesundheit Erwachsener in Deutschland“ des RKI) bietet die Möglichkeit, die mit der Anwendung von PIM assoziierten Faktoren zu identifizieren.FragestellungenWas charakterisiert ältere Menschen in Deutschland, die aktuell PIM anwenden, und gibt es Subpopulationen, bei denen eine PIM-Anwendung besonders häufig ist?Material und MethodenIm Rahmen der DEGS1-Studie wurden 175 Variablen zu gesundheitlichen und sozialen Aspekten von 1392 im eigenen Haushalt lebenden Personen im Alter von 65 bis 79 Jahren erhoben und die Medikation der letzten sieben Tage dokumentiert. PIM konnten mit Hilfe der PRISCUS-Liste identifiziert werden. Mögliche Zusammenhänge zwischen PIM-Einnahme und den erhobenen Variablen wurden in einem multivariablen Modell überprüft.Ergebnisse und DiskussionIn den letzten sieben Tagen vor Befragung wurden von 13,0 % (95 %-KI: 10,7–15,6) der Befragten PIM eingenommen. Folgende Faktoren begünstigen signifikant die PIM-Einnahme: Gesamtzahl der in den letzten sieben Tagen eingenommenen Medikamente; Zahl niedergelassener Arztgruppen, die in den letzten 12 Monaten aufgesucht worden sind; Einschlafstörungen; die Krankheitsgruppen Psyche und Gelenke/Knochen. Die am häufigsten eingenommenen PIM-Wirkstoffe kommen aus der Gruppe der Antidepressiva und Anxiolytika/Sedativa. Besonders betroffen von einer erhöhten PIM-Einnahme sind ältere Frauen mit Depressionen, Einschlafstörungen und Analgetikabedarf. Sie bedürfen einer besonderen Aufmerksamkeit.
The promise of ultrapermeable polymers, such as poly(trimethylsilylpropyne) (PTMSP), for reducing the size and increasing the efficiency of membranes for gas separations remains unfulfilled due to ...their poor selectivity. We report an ultrapermeable polymer of intrinsic microporosity (PIM-TMN-Trip) that is substantially more selective than PTMSP. From molecular simulations and experimental measurement we find that the inefficient packing of the two-dimensional (2D) chains of PIM-TMN-Trip generates a high concentration of both small (<0.7 nm) and large (0.7-1.0 nm) micropores, the former enhancing selectivity and the latter permeability. Gas permeability data for PIM-TMN-Trip surpass the 2008 Robeson upper bounds for O
/N
, H
/N
, CO
/N
, H
/CH
and CO
/CH
, with the potential for biogas purification and carbon capture demonstrated for relevant gas mixtures. Comparisons between PIM-TMN-Trip and structurally similar polymers with three-dimensional (3D) contorted chains confirm that its additional intrinsic microporosity is generated from the awkward packing of its 2D polymer chains in a 3D amorphous solid. This strategy of shape-directed packing of chains of microporous polymers may be applied to other rigid polymers for gas separations.
The microscopic interfacial structures for a series of metal-organic framework/polymer composites consisting of the Zr-based UiO-66 coupled with different polymers are systematically explored by ...applying a computational methodology that integrates density functional theory calculations and force field-based molecular dynamics simulations. These predictions are correlated with experimental findings to unravel the structure-compatibility relationship of the MOF/polymer pairs. The relative contributions of the intermolecular MOF/polymer interactions and the flexibility/rigidity of the polymer with respect to the microscopic structure of the interface are rationalized, and their impact on the compatibility of the two components in the resulting composite is discussed. The most compatible pairs among those investigated involve more flexible polymers,
polyvinylidene fluoride (PVDF) and polyethylene glycol (PEG). These polymers exhibit an enhanced contact surface, due to a better adaptation of their configuration to the MOF surface. In these cases, the irregularities at the MOF surface are filled by the polymer, and even some penetration of the terminal groups of the polymer into the pores of the MOF can be observed. As a result, the affinity between the MOF and the polymer is very high; however, the pores of the MOF may be sterically blocked due to the strong MOF/polymer interactions, as evidenced by UiO-66/PEG composites. In contrast, composites involving polymers that exhibit higher rigidity, such as the polymer of intrinsic microporosity-1 (PIM-1) or polystyrene (PS), present interfacial microvoids that contribute to a decrease in the contact surface between the two components, thus reducing the MOF/polymer affinity.
The molecular imprinting technology yields artificial materials capable of antibody-like molecular recognition. Molecularly imprinted materials are attractive because procedures for their preparation ...and use are comparatively simple. The number of research reports concerning molecularly imprinted polymers (MIPs) have been increasing yearly, attracting a great deal of interest in various fields. However, as most MIPs have been generated by relatively simple methods developed from the 1970s to the 2000s, resulting in MIPs bearing a single function, their capabilities are limited compared to those of multi-functionalised naturally occurring materials. Proteins are biosynthesised through multiple steps, including fabrication of peptide backbone and subsequent post-translational modifications that introduce additional functionalities, finally producing the mature protein. Post-imprinting modification (PIM) is an innovative strategy for generating MIPs analogous to biosynthetic proteins. New functionalities are introduced, in a site-directed manner, into a molecular imprinted cavity. Monomer residues in the cavity are chemically modified to incorporate new features, such as on/off switching of binding activity, fluorescence signalling, photoresponsivity, and finely tuned binding characteristics. In this Feature Article, we provide an overview of multifunctional MIPs prepared
via
PIMs developed earlier and the currently used state-of-the-art ones.
Post-imprinting modification (PIM) is an innovative strategy for generating MIPs analogous to biosynthesising proteins to introduce new functionalities in a site-directed manner.
Microporous polymers are a class of microporous materials with high free volume elements and large surface areas. Microporous polymers have received much attention for various applications in gas ...separation, gas storage, and for clean energy resources due to their easy processability for mass production, as well as microporosity for high performance. This review describes recent research trends of microporous polymers in various energy related applications, especially for gas separations and gas storages. The new classes of microporous polymers, so-called thermally rearranged (TR) polymers and polymers of intrinsic microporosity (PIMs), have been developed by enhancing polymer rigidity to improve microporosity with sufficient free volume sizes. Their rigidity improves separation performance and efficiency with extraordinary gas permeability. Moreover, their solubility in organic solvents allows them to have potential use in large-scale industrial applications.
Context. When a planet becomes massive enough, it gradually carves a partial gap around its orbit in the protoplanetary disk. A pressure maximum can be formed outside the gap where solids that are ...loosely coupled to the gas, typically in the pebble size range, can be trapped. The minimum planet mass for building such a trap, which is called the pebble isolation mass (PIM), is important for two reasons: it marks the end of planetary growth by pebble accretion, and the trapped dust forms a ring that may be observed with millimetre observations. Aims. We study the effect of disk turbulence on the PIM and find its dependence on the gas turbulent viscosity, aspect ratio, and particles Stokes number. Methods. By means of 2D gas hydrodynamical simulations, we found the minimum planet mass to form a radial pressure maximum beyond the orbit of the planet, which is the necessary condition to trap pebbles. We then carried out 2D gas plus dust hydrodynamical simulations to examine how dust turbulent diffusion impacts particles trapping at the pressure maximum. We finally provide a semi-analytical calculation of the PIM based on comparing the radial drift velocity of solids and the root mean square turbulent velocity fluctuations around the pressure maximum. Results. From our results of gas simulations, we provide an expression for the PIM vs. disk aspect ratio and turbulent viscosity. Our gas plus dust simulations show that the effective PIM can be nearly an order of magnitude larger in high-viscosity disks because turbulence diffuse particles out of the pressure maximum. This is quantified by our semi-analytical calculation, which gives an explicit dependence of the PIM with Stokes number of particles. Conclusions. Disk turbulence can significantly alter the PIM, depending on the level of turbulence in regions of planet formation.
The moldability of titanium-based feedstocks used in low-pressure powder injection molding process was investigated using numerical simulation and real-scale injections. Feedstock characterization ...and injection were conducted using a feedstock formulated from a Ti-6Al-4 V powder and a low-viscosity binder system. The thermal characteristics of the feedstock, including the specific heat capacity and the thermal conductivity, were measured over a 20–120 °C temperature range, while rheological profiles were experimentally measured at 80, 90, and 100 °C to establish the constitutive equations to be implemented in the model. The mold filling stage of a complex shape part was numerically simulated using Autodesk Moldflow Synergy 2019. The predicted filling time and magnitude of powder segregation after an injection were validated using a laboratory injection press and thermogravimetric analysis. The melt front location and filling completion predicted by the numerical model at different short shots were in good agreement with the experimental observations, with relative differences below 9%. Moldflow was also used to identify the high shear rate zones experienced by the feedstock, in which a predicted segregation of 2 vol% was validated by experimental tests. A halo shape segregation pattern was determined as resulting from a solidified skin and/or a segregation band passing near the interface of the shear rate gradient.
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•Ti-based LPIM feedstock was numerically simulated for the first time in this paper.•Melt front shape and injection time were accurately predicted (relative error < 9%).•Segregation area and its magnitude were correctly assessed (2 vol% of powder).•The shape of the segregation bands was not clearly predicted by simulations.•The segregation bands were attributable to the segregation of coarse powder.
Porous titanium-hydroxyapatite (Ti/HA) composite is a developed composite material suitable for bio-medical applications. Powder injection molding (PIM) with space holder method is used to produce ...porous Ti/HA with mechanical properties, similar to human bone, and pores helps to initiate tissue growth. However, the differences in physical and mechanical properties of these composites are the main challenges during debinding and sintering. Therefore, the main objective is to determine effects of binder systems and processing parameters on formability of Ti/HA composite. In PIM, a binder system is necessary to produce green and ultimately sintered part. There are two binder systems and variation of sintering temperature has been used. Results revealed that Polyethylene glycol (PEG)-based binder system is applicable with NaCl space holder and optimum sintering parameters, including temperature, heating rate, and holding time of 1300°C, 10°C/min, and 5h, respectively. The fabricated porous Ti/HA exhibits average porosity, pore size distribution, compressive strength, and roughness values of 55%, 60μm to 170μm, 370MPa, and 0.323μm, respectively. FESEM results showed that the pores are interconnected. It may be an appropriate material for future bio-medical applications.
FEMSEM micrograph of porous Ti/HA composite sintered at 1300°C showing interconnected pores the neck formation between the particles. Display omitted
•Porous Ti/HA composite was successfully fabricated through powder injection molding technique using space holder.•PEG-based binder system with NaCl as space holder is suitable for PIM.•Porous Ti/HA composite fabricated through PIM using NaCl space holder showed pore size half of the space holder size.
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