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Surface modification offers a straightforward means to alter and enhance the properties and performance of materials, such as nanofiltration membranes for water softening. Herein, we demonstrate how a membrane's surface charge can be altered by grafting different electrostatically varying copolymers onto commercial membrane surfaces using perfluorophenylazide (PFPA) photochemistry for enhanced ion separation performance. The native membrane's performance-i.e., in terms of divalent cation separation-with copolymer coatings containing a positively charged quaternary ammonium (-N(Me)3+), a negatively charged sulfonate (-SO3-), and an essentially neutral zwitterion (sulfobetaine, -N(Me)2R2+, and -SO3-), respectively, indicates that: (a) the sulfonated polymer induces robust Coulombic exclusion of divalent anions as compared to the negatively charged native membrane surface on account of its higher negative charge; (b) the positively charged ammonium coating induces exclusion of cations more effectively than the native membrane; and significantly, (c) the zwitterion polymer coating, which reduces the surface roughness and improves wettability, in spite of its near-neutral charge enhances exclusion of both divalent cations and anions on account of aperture sieving by the compact zwitterion polymer that arises from its ability to limit the size of ions that transport through the polymer along with dielectric exclusion. The outcomes thereby inform new pathways to achieve size- and charge-based exclusion of ionic, molecular, and other species contained in liquid streams.

Graphene oxide (GO) membranes have great potential for separation applications due to their low-friction water permeation combined with unique molecular sieving ability. However, the practical use of deposited GO membranes is limited by the inferior mechanical robustness of the membrane composite structure derived from conventional deposition methods. Here, we report a nanostructured GO membrane that possesses great permeability and mechanical robustness. This composite membrane consists of an ultrathin selective GO nanofilm (as low as 32 nm thick) and a postsynthesized macroporous support layer that exhibits excellent stability in water and under practical permeability testing. By utilizing thin-film lift off (T-FLO) to fabricate membranes with precise optimizations in both selective and support layers, unprecedented water permeability (47 L·m-2·hr-1·bar-1) and high retention (>98% of solutes with hydrated radii larger than 4.9 A) were obtained.

Conjugated polyaniline has shown anticorrosive, hydrophilic, antibacterial, pH-responsive, and pseudocapacitive properties making it of interest in many fields. However, in situ grafting of polyaniline without harsh chemical treatments is challenging. In this study, we report a simple, fast, and non-destructive surface modification method for grafting tetraaniline (TANI), the smallest conjugated repeat unit of polyaniline, onto several materials via perfluorophenylazide photochemistry. The new materials are characterized by nuclear magnetic resonance (NMR) and electrospray ionization (ESI) mass spectroscopy. TANI is shown to be covalently bonded to important carbon materials including graphite, carbon nanotubes (CNTs), and reduced graphene oxide (rGO), as confirmed by transmission electron microscopy (TEM). Furthermore, large area modifications on polyethylene terephthalate (PET) films through dip-coating or spray-coating demonstrate the potential applicability in biomedical applications where high transparency, patternability, and low bio-adhesion are needed. Another important application is preventing biofouling in membranes for water purification. Here we report the first oligoaniline grafted water filtration membranes by modifying commercially available polyethersulfone (PES) ultrafiltration (UF) membranes. The modified membranes are hydrophilic as demonstrated by captive bubble experiments and exhibit extraordinarily low bovine serum albumin (BSA) and Escherichia coli adhesions. Superior membrane performance in terms of flux, BSA rejection and flux recovery after biofouling are demonstrated using a cross-flow system and dead-end cells, showing excellent fouling resistance produced by the in situ modification.

Thin-film composite (TFC) membranes are favored for precise molecular sieving in liquid-phase separations; they possess high permeability due to the minimal thickness of the active layer and the high porosity of the support layer. However, current TFC membrane fabrication techniques are limited by the available materials for the selective layer and do not demonstrate the level of structural control needed to substantially advance organic solvent nanofiltration (OSN) membrane technology. In this work, we employ the newly developed thin-film lift-off (T-FLO) technique to fabricate polybenzimidazole (PBI) TFC membranes with porous support layers uniquely tailored to OSN. The drop-cast dense PBI selective layers endow the membranes with an almost complete rejection of common small dye molecules. The polymeric support layer is optimized by a combinatorial approach using four different monomers that alter the cross-linking density and polymer chain flexibility of the final composite. These two properties substantially affect the porogen holding capacity of the reticular polymer network, leading to the formation of different macropore structures. With a 150 nm thick PBI selective layer and fine-tuning of the support layer, the resulting membrane achieves stable and superior permeance of 14.0, 11.7, 16.4, 11.4, 17.1, and 19.7 L m-2 h-1 bar-1 for water, ethanol, methanol, isopropanol, tetrahydrofuran (THF), and acetonitrile, respectively.

Tungsten tetraboride alloys with Y, Sc, Gd, Tb, Dy, Ho, and Er were prepared by arc-melting and investigated for their thermal stability and mechanical properties. The phase composition and purity were confirmed by powder X-ray diffraction (PXRD) and energy dispersive X-ray spectroscopy (EDS). In all cases, except for Sc, a change to a “dendritic” morphology was observed. For alloys with Sc, the metal boride and boron grains became smaller; however, no patterning was observed. This shows that tuning the composition of the alloys of WB4 with transition metals and lanthanides results in a modification of the morphology leading to patterning and smaller grains that enhance mechanical and thermal properties. For alloys of WB4 with Y, Sc, Gd, Dy, Tb, Ho, and Er, an increase in hardness to 50.2 ± 2.4, 48.9 ± 2.5, 48.0 ± 2.1, 46.3 ± 2.6, 48.5 ± 2.3, 46.4 ± 3.4, and 47.2 ± 2.9 GPa at low load, respectively, compared to 41.2 ± 1.4 GPa for WB4 is observed. Moreover, the alloys of WB4 with Y, Sc, and Gd showed an in...

This chapter focuses on applications of conjugated polymers for selected separations. It introduces conjugated polymer–based gas separation membranes using polyaniline, followed by the use of other conjugated polymers and then composite membranes. The chapter discusses conjugated polymer–based membranes for water purification, followed by the emerging field of capacitive deionization. It highlights the synthesis, mechanisms, and performances of membrane technologies that specifically use conjugated polymers. The driving forces for separation can be the gradients of concentration, temperature, pressure, and/or external/internal electric potential. Polymeric membranes used for gas separations can be categorized into two types: rubbery polymers and glassy polymers. Gas molecules are small in size; hence, making a sufficiently dense polymeric membrane with angstrom-size pores for gas separation is crucial. For an as-cast membrane, the permeability of gases mainly depends on the kinetic diameter of the gas molecules due to the effect of molecular sieving.

2D nanomaterials are finding numerous applications in next-generation electronics, consumer goods, energy generation and storage, and healthcare. The rapid rise of utility and applications for 2D nanomaterials necessitates developing means for their mass production. This study details a new compressible flow exfoliation method for producing 2D nanomaterials using a multiphase flow of 2D layered materials suspended in a high-pressure gas undergoing expansion. The expanded gassolid mixture is sprayed in a suitable solvent, where a significant portion (up to 10% yield) of the initial hexagonal boron nitride material is found to be exfoliated with a mean thickness of 4.2 nm. The exfoliation is attributed to the high shear rates ((Formula presented.) > 105 s−1) generated by supersonic flow of compressible gases inside narrow orifices and converging-diverging channels. This method has significant advantages over current 2D material exfoliation methods, such as chemical intercalation and exfoliation, as well as liquid phase shear exfoliation, with the most obvious benefit being the fast, continuous nature of the process. Other advantages include environmentally friendly processing, reduced occurrence of defects, and the versatility to be applied to any 2D layered material using any gaseous medium. Scaling this process to industrial production has a strong possibility of reducing the cost of creating 2D nanomaterials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim