Special Issue: New Challenges in Thin-Film Nanocomposite Membranes

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Thermally stable anion-exchange materials

Anion-exchange materials are of great interest in a broad field of applications like water treatment, catalysis or electrochemical devices like electro dialysis or fuel cells. The anion-exchange materials are widely based on (cross-linked) polystyrene functionalized with trimethyl ammonium groups fixed via a methylene bridge to the benzene ring. Nearly all anion-exchange materials have in common, that they are thermally unstable at elevated temperature and high pH. However, in electrochemical applications like fuel cells or in electro dialysis high temperatures are desired for competitive performances. In a recent study Marino and Kreuer1 investigated the thermal stability of quaternary ammonium model compounds. Among the various compounds those based on piperidine (Fig. 1) turned out to be most stable ones. Pham and Jannasch2 reported on polymeric anion-exchange materials based on poly(ether sulfone)s bearing N-spirocyclic quaternary ammonium groups similar to those reported by Marino and Kreuer. However, these polymers showed only a low thermal stability. Please click Additional Files below to see the full abstract

Ultrafiltration membranes based on PES-PEG block copolymers

Although subject to research for decades, fouling is still one of the major limiting factors in membrane applications. Numerous methods have been suggested to overcome this shortcoming, like crossflow filtration, backflushing, air sparging, all of them in combination with chemical cleaning. However many of these techniques imply off-production cycles, resulting in lower yield, shorter lifetime of membranes and therefore higher costs. Another approach to reduce fouling involves the modification of membranes with charged and / or hydrophilic polymers. These are either added to the casting solution or subsequently grafted onto the membrane surface. However, both methods have their specific drawbacks. Adding hydrophilic polymers to the dope solution leads to a significant loss during membrane preparation step (coagulation). On the other hand graft modification involves most often several steps and bears the risk of damaging (degrading) the membrane material resulting in loss of mechanical stability. In this work we report on UF membranes prepared from poly(ether sulfone)-poly(ethylene glycol) block copolymers with poly(ethylene glycols) of molecular weights varying from 200 g/mol to 4000 g/mol but constant molar fraction of 5 mol%. Furthermore, block copolymers with increasing content of PEG-200 up to 20 mol% were prepared. This approach has the advantage over surface modification that the degree of functionalization can be easily controlled by the monomer composition. UF-membranes from block copolymers were prepared by conventional NIPS process using NMP as solvent and water as non-solvent. The effect co-monomer type (molecular weight of PEG) and co-monomer concentration on the morphology of the resulting membranes (Figure 1) as well as their filtration properties including protein fouling will be discussed in detail. Please click Additional Files below to see the full abstract

Surface Modification of Membranes for Fouling Reduction

Despite great effort that has been made to reduce and understand fouling, this phenomenon is still a major problem in membrane applications. Numerous methods, both from a chemical and engineering point of view, have been introduced to overcome this problem. In this contribution, we report on the modification of membranes with polyelectrolytes and polyelectrolyte multilayers utilizing two of the mentioned strategies. The effect of surface modification on the fouling behavior as well as on the critical flux will be discussed on two examples, microfiltration membranes and RO membranes

Straightforward Approach for Preparing Durable Antibacterial ZnO Nanoparticle Coatings on Flexible Substrates

Flexible antibacterial materials have gained utmost importance in protection from the distribution of bacteria and viruses due to the exceptional variety of applications. Herein, we demonstrate a readily scalable and rapid single-step approach for producing durable ZnO nanoparticle antibacterial coating on flexible polymer substrates at room temperature. Substrates used are polystyrene, poly(ethylene-co-vinyl acetate) copolymer, poly(methyl methacrylate), polypropylene, high density polyethylene and a commercial acrylate type adhesive tape. The deposition was achieved by a spin-coating process using a slurry of ZnO nanoparticles in toluene. A stable modification layer was obtained when toluene was a solvent for the polymer substrates, namely polystyrene and poly(ethylene-co-vinyl acetate). These coatings show high antibacterial efficiency causing >5 log decrease in the viable counts of Gram-negative bacteria Escherichia. coli and Gram-positive bacteria Staphylococcus aureus in 120 min. Even after tapping these coated surfaces 500 times, the antibacterial properties remained unchanged, showing that the coating obtained by the presented method is very robust. In contrast to the above findings, the coatings are unstable when toluene is not a solvent for the substrate. © 2022 by the authors. --//-- This is an open access article Šutka A, Mežule L, Denisova V, Meier-Haack J, Kulkarni A, Bitina S, Smits K, Vihodceva S., "Straightforward Approach for Preparing Durable Antibacterial ZnO Nanoparticle Coatings on Flexible Substrates", Molecules, 2022 Nov 8;27(22):7672, doi: 10.3390/molecules27227672 published under the CC BY 4.0 licence.ERA-NET Cofound M-era.Net Project CaFeOx No. ES RTD/2021/11; Institute of Solid-State Physics, University of Latvia has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2

Straightforward Approach for Preparing Durable Antibacterial ZnO Nanoparticle Coatings on Flexible Substrates

Flexible antibacterial materials have gained utmost importance in protection from the distribution of bacteria and viruses due to the exceptional variety of applications. Herein, we demonstrate a readily scalable and rapid single-step approach for producing durable ZnO nanoparticle antibacterial coating on flexible polymer substrates at room temperature. Substrates used are polystyrene, poly(ethylene-co-vinyl acetate) copolymer, poly(methyl methacrylate), polypropylene, high density polyethylene and a commercial acrylate type adhesive tape. The deposition was achieved by a spin-coating process using a slurry of ZnO nanoparticles in toluene. A stable modification layer was obtained when toluene was a solvent for the polymer substrates, namely polystyrene and poly(ethylene-co-vinyl acetate). These coatings show high antibacterial efficiency causing >5 log decrease in the viable counts of Gram-negative bacteria Escherichia. coli and Gram-positive bacteria Staphylococcus aureus in 120 min. Even after tapping these coated surfaces 500 times, the antibacterial properties remained unchanged, showing that the coating obtained by the presented method is very robust. In contrast to the above findings, the coatings are unstable when toluene is not a solvent for the substrate

Special Issue: New Challenges in Thin-Film Nanocomposite Membranes

Rapid population growth and the associated rise in industrialization and food production have resulted in a tremendously increased demand for clean water