Controlled Localized Metal-Organic Framework Synthesis on Anion Exchange Membranes.

Metal-organic framework (MOF) films can be used in various applications. In this work, we propose a method that can be used to synthesize MOF films localized on a single side of an anion exchange membrane, preventing the transport of the metal precursor via Donnan exclusion. This is advantageous compared to the related contra-diffusion method that results in the growth of a MOF film on both sides of the support, differing in quality on both sides.

Comparison of Eight Classical Lennard-Jones-Based H Molecular Models in the Gas Phase at Temperatures and Pressures Relevant to Hydrogen On-Board Storage Tanks.

This work compares eight classical H molecular models in the gas phase taken from the existing literature. All models are based on Lennard-Jones (LJ) 12-6 terms for the van der Waals interactions and hence easier to transfer to multiphase molecular simulations than more sophisticated potentials. The H potentials tested include one-site, two-site, three-site, and five-site models, with the sites being either the H atoms, the center-of-mass of the H molecule, or massless sites.

Teachers' and students' perceptions of a sense of community in blended education.

Universities have renewed interest in blended learning in preparation for post-COVID education. However, unsatisfactory social interactions hinder the quality of blended learning, despite its potential for flexible and personalized learning. In this situation, a sense of community would provide essential academic and social benefits.

Nonaqueous Interfacial Polymerization-Derived Polyphosphazene Films for Sieving or Blocking Hydrogen Gas.

A series of cyclomatrix polyphosphazene films have been prepared by nonaqueous interfacial polymerization (IP) of small aromatic hydroxyl compounds in a potassium hydroxide dimethylsulfoxide solution and hexachlorocyclotriphosphazene in cyclohexane on top of ceramic supports. Via the amount of dissolved potassium hydroxide, the extent of deprotonation of the aromatic hydroxyl compounds can be changed, in turn affecting the molecular structure and permselective properties of the thin polymer networks ranging from hydrogen/oxygen barriers to membranes with persisting hydrogen permselectivities at high temperatures. Barrier films are obtained with a high potassium hydroxide concentration, revealing permeabilities as low as 9.

Molecular Characterization of Membrane Gas Separation under Very High Temperatures and Pressure: Single- and Mixed-Gas CO/CH and CO/N Permselectivities in Hybrid Networks.

This work illustrates the potential of using atomistic molecular dynamics (MD) and grand-canonical Monte Carlo (GCMC) simulations prior to experiments in order to pre-screen candidate membrane structures for gas separation, under harsh conditions of temperature and pressure. It compares at 300 °C and 400 °C the CO/CH and CO/N sieving properties of a series of hybrid networks based on inorganic silsesquioxanes hyper-cross-linked with small organic PMDA or 6FDA imides. The inorganic precursors are the octa(aminopropyl)silsesquioxane (POSS), which degrades above 300 °C, and the octa(aminophenyl)silsesquioxane (OAPS), which has three possible , or isomers and is expected to resist well above 400 °C.

Development of Thin-Film Composite Membranes for Nanofiltration at Extreme pH.

Water recycling is one of the most sustainable solutions to growing water scarcity challenges. However, wastewaters usually contain organic pollutants and often are at extreme pH, which complicates the treatment of these streams with conventional membranes. In this work, we report the synthesis of a robust membrane material that can withstand prolonged exposure to extreme pH (of 1 or 13 for 2 months).

Poly(aryl cyanurate)-Based Thin-Film Composite Nanofiltration Membranes.

The successful synthesis of poly(aryl cyanurate) nanofiltration membranes via the interfacial polymerization reaction between cyanuric chloride and 1,1,1-tris(4-hydroxyphenyl)ethane (TPE), atop a polyethersulfone ultrafiltration support, is demonstrated. The use of cyanuric chloride allows for the formation of a polymer that does not contain hydrolysis-susceptible amide bonds that inherently limit the stability of polyamide nanofiltration membranes. In order to achieve a thin defect-free cross-linked film via interfacial polymerization, a sufficient number of each monomer should react.

High-temperature molecular screening of hybrid polyOAPS-imide networks based on octa(aminophenyl)silsesquioxane for increased thermomechanical resistance.

A new family of hybrid hyper-cross-linked thin films based on inorganic polyhedral oligomeric silsesquioxane (POSS) cages covalently bound with short organic imides has recently been developed using interfacial polycondensation followed by high-temperature imidization. These polyPOSS-imide networks were aimed at gas separations under harsh conditions, but the aliphatic arms of the initial POSS precursor, octa(aminopropyl)silsesquioxane, were found to be a weak link. This work investigates the replacement of the aliphatic arm by a phenyl derivative, octa(aminophenyl)silsesquioxane (OAPS).

Polyoctahedral Silsesquioxane Hexachlorocyclotriphosphazene Membranes for Hot Gas Separation.

There is a need for gas separation membranes that can perform at high temperatures, for example, for CO capture in industrial processes. Polyphosphazenes classify as interesting materials for use under these conditions because of their high thermal stability, hybrid nature, and postfunctionalization options. In this work, thin-film composite cyclomatrix polyphosphazene membranes are prepared via the interfacial polymerization reaction between polyhedral oligomeric silsesquioxane and hexachlorocyclotriphosphazene on top of a ceramic support.

Swelling of Poly(methyl acrylate) Brushes in Acetone Vapor.

Sensor platforms can benefit from the incorporation of polymer brushes since brushes can concentrate the analyte near the sensor surface. Brushes that absorb acetone vapor are of particular interest since acetone is an important marker for biological processes. We present a simple procedure to synthesize acetone-responsive poly(methyl acrylate) brushes.

Preparation of Ti, Ti/TiC or Ti/TiN based hollow fibres with extremely low electrical resistivity.

Porous Ti based hollow fibres with extremely low electrical resistivity (4.1-9.6 μΩ m), orders of magnitude smaller than reported for Ti-fibres in the literature, were produced by dry-wet spinning of a mixture of Ti-particles, polyethersulfone (PES), and -methylpyrrolidone (NMP).

Triple-Layer Nanofiber Membranes for Treating High Salinity Brines Using Direct Contact Membrane Distillation.

A composite, three-layered membrane for membrane distillation was prepared from electrospun polyvinylidene fluoride (PVDF) nanofibers supported by commercial polyethersulfone (PES) nanofiber based nonwoven from E.I. duPont de Nemours company (DuPont).

Relaxation Dynamics of Thin Matrimid 5218 Films in Organic Solvents.

Polyimides are interesting polymer materials for organic solvent nanofiltration (OSN) applications because of their high excess free volume and high chemical and temperature resistance. However, an open challenge that remains for glassy polymer materials (i.e.

Synergic Swelling of Interactive Network Support and Block Copolymer Films during Solvent Vapor Annealing.

We report the effect of "interactive" polymer network (PN) supports on the solvent-vapor processing of thin polymer films. Densely cross-linked surface-attached network exhibits under experimental time scale a glassy swelling behavior with the conformational states and solvent-uptake clearly sensitive to the degree of solvent vapor saturation in the atmosphere. Pretreatment of the thermally cured PN films by complete immersion or by swelling in saturated chloroform vapors facilitates relaxation of the residual stresses and induces irreversible changes to the network structure as revealed by the swelling/deswelling tests.

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

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 influence of the dianhydride precursor in hyper-cross-linked hybrid polyPOSS-imide networks.

Hybrid organic/inorganic hyper-cross-linked membranes based on imides covalently bonded with polyhedral oligomeric silsesquioxanes (POSS) have recently been developed for gas-separation applications under high pressure and/or temperature conditions. Their molecular sieving capabilities have been shown to depend on the nature of the organic dianhydride precursor. In the present work, realistic molecular models of such polyPOSS-imide films based on the flexible 6FDA dianhydride are compared to those based on the shorter and more rigid PMDA dianhydride.

Three-dimensional porous hollow fibre copper electrodes for efficient and high-rate electrochemical carbon dioxide reduction.

Aqueous-phase electrochemical reduction of carbon dioxide requires an active, earth-abundant electrocatalyst, as well as highly efficient mass transport. Here we report the design of a porous hollow fibre copper electrode with a compact three-dimensional geometry, which provides a large area, three-phase boundary for gas-liquid reactions. The performance of the copper electrode is significantly enhanced; at overpotentials between 200 and 400 mV, faradaic efficiencies for carbon dioxide reduction up to 85% are obtained.

Sorption Behavior of Compressed CO2 and CH4 on Ultrathin Hybrid Poly(POSS-imide) Layers.

Sorption of compressed gases into thin polymeric films is essential for applications including gas sensors and membrane based gas separation. For glassy polymers, the sorption behavior is dependent on the nonequilibrium status of the polymer. The uptake of molecules by a polymer is generally accompanied by dilation, or swelling, of the polymer material.

Formation and prevention of fractures in sol-gel-derived thin films.

Sol-gel-derived thin films play an important role as the functional coatings for various applications that require crack-free films to fully function. However, the fast drying process of a standard sol-gel coating often induces mechanical stresses, which may fracture the thin films. An experimental study on the crack formation in sol-gel-derived silica and organosilica ultrathin (submicron) films is presented.

Visualization and characterization of interfacial polymerization layer formation.

We present a microfluidic platform to visualize the formation of free-standing films by interfacial polymerization. A microfluidic device is fabricated, with an array of micropillars to stabilize an aqueous-organic interface that allows a direct observation of the films formation process via optical microscopy. Three different amines are selected to react with trimesoyl chloride: piperazine, JEFFAMINE(®)D-230, and an ammonium functionalized polyhedral oligomeric silsesquioxane.

Synthesis of porous inorganic hollow fibers without harmful solvents.

A route for the fabrication of porous inorganic hollow fibers with high surface-area-to-volume ratio that avoids harmful solvents is presented. The approach is based on bio-ionic gelation of an aqueous mixture of inorganic particles and sodium alginate during wet spinning. In a subsequent thermal treatment, the bio-organic material is removed and the inorganic particles are sintered.

Dynamic response of ultrathin highly dense ZIF-8 nanofilms.

Ultrathin ZIF-8 nanofilms are prepared by facile step-by-step dip coating. A critical withdrawal speed allows for films with a very uniform minimum thickness. The high refractive index of the films denotes the absence of mesopores.

Kinetic analysis of the thermal processing of silica and organosilica.

The incorporation of an organic group into sol-gel-derived silica causes significant changes in the structure and properties of these materials. Therefore, the thermal treatment of organosilica materials may require a different approach. In the present paper, kinetic parameters (activation energy, pre-exponential constant, and reaction models) have been determined from mass loss data for the dehydration, dehydroxylation, and decomposition reactions that take place upon heating silica and organosilica.