Dual effective organic/inorganic hybrid star-shaped polymer coatings on ultrafiltration membrane for bio- and oil-fouling resistance

Functionalization of octaspherosilicate (HSiMe2O)8Si8O12 with buta-1,3-diynes by hydrosilylation

Hydrosilylation with octaspherosilicate (HSiMe2O)8Si8O12 (1) has provided hundreds of molecular and macromolecular systems so far, making this method the most popular in the synthesis of siloxane-based, nanometric, cubic, and reactive building blocks. However, there are no reports on its selective reaction with 1,3-diynes, which allows for the formation of new products with unique properties. Therefore, herein we present an efficient protocol for monohydrosilylation of symmetrically and non-symmetrically 1,4-disubstituted buta-1,3-diynes with 1. The compounds obtained bear double and triple bonds and other functionalities (e.g., Br, F, OH, SiR3), making them highly desirable, giant building blocks in organic synthesis and material chemistry. These compounds were fully characterized by 1H, 13C, 29Si, 1D NOE, 1H-13C HSQC NMR, FT-IR, and MALDI TOF MS, EA, UV-Vis, and TGA analysis. The TGA proved their high thermal stability up to 427 ℃ (Td10%) for compound 3j.

Self-Symmetrical 3D Hierarchical α-Calcium Sulfate Hemihydrate Twin-Flowers Composed of Microplates as a Renewable Material for Water Separation from Water-in-Oil Emulsion

Novel three-dimensional hierarchical α-calcium sulfate hemihydrate twin-flowers with a self-symmetrical structure (3D α-HH HTFs) are synthesized successfully assisted by trisodium citrate (TSC). The morphology of α-HH is closely dependent on TSC, and with increasing TSC concentration from 0 to 15 mM, the morphology gradually evolves from a long column to rod, hexagonal plate, twin-flower-like, and eventually microgranule. 3D α-HH HTFs are formed via heterogeneous nucleation coupled with Ostwald ripening. The 3D α-HH HTFs are further used as an immobilized water material to separate water from a surfactant-stabilized water-in-oil emulsion, and exhibit excellent separation performance with a separation efficiency of 99.31 wt % and immobilization efficiency of 93.03 wt %. Impressively, the separated solid after water separation can be regenerated into 3D α-HH HTFs, which retain the high separation performance of the original 3D α-HH HTFs. This work demonstrates that 3D α-HH HTFs are highly promising in purifying oil with undesired water contamination.

Alleviating membrane fouling of modified polysulfone membrane via coagulation pretreatment/ultrafiltration hybrid process

In this study, ultrafiltration membrane fouling was alleviated by hydrophilic modification and coagulation pretreatment. A polydopamine (PDA) layer was used as a bridge to introduce the nano titanium dioxide (TiO₂) onto the polysulfone (PSf) membranes, forming a hydrophilic modified layer. A relationship model was established between the coagulation efficiencies and floc properties and membrane fouling of the modified PSf membranes during the coagulation/ultrafiltration (C-UF) process. The combination styles of flocculants, poly dimethyldiallylammonium chloride (PDMDAAC) and polyaluminum chloride (PAC) were used in C-UF hybrid process. The characterization results indicated that the hydrophilicity was significantly enhanced in the modified PSf membranes. Scanning electron microscopy (SEM) tests proved that the PDA layer could be tightly bound to TiO₂ by coordination bond onto PSf membrane surface. In the acidic conditions, more TiO₂ nano-particles were adhered on the PDA particles surface as the pH of (NH₄)₂TiF₆ solution was increased, which resulted in higher hydrophilicity of membranes. In addition, the C-UF tests exhibited that the coagulation efficiency was greatly improved in the PAC/PDMDAAC system, and the PSf membrane modified by PDA/TiO₂ in UF tests significantly reduced the membrane fouling, this was partially due to the formation of TiO₂ modified coating with higher hydrophilicity.

Bio-inspired robust superhydrophobic-superoleophilic polyphenylene sulfide membrane for efficient oil/water separation under highly acidic or alkaline conditions

The separation of water-in-oil emulsions in harsh environment (strong acid/alkali) is a challenging subject. In this study, we prepared a superhydrophobic-superoleophilic polyphenylene sulfide (PPS) membrane by the mixture of hydrophobic SiO₂ nanoparticles, diphenyl ketone (DPK), benzoin (BZ) and PPS via thermally induced phase separation (TIPS) technology. This superhydrophobic membrane displayed a lotus leaf-like micro-nano structure, and it could be used for oil/water separation in strong acidic or alkaline environment. The hydrophobic SiO₂ nanoparticles played a key role in the membrane structure evolution and its performance. When SiO₂ content was 4 wt%, the pure water contact angle of the prepared superhydrophobic-superoleophilic membrane reached 156.9° and the oil contact angle achieved 0°. The fluxes of water-in-oil emulsions (kerosene, toluene and chloroform) reached 1926, 3150 and 3416 L/(m²·h), respectively. However, the fluxes of their surfactant-stabilized water-in-oil emulsions declined to 531, 685 and 724 L/(m²·h), respectively, due to the great stability of surfactant-stabilized emulsions. Most importantly, all the water rejection rates exceeded 99.9% when the PPS membranes modified with 4 wt% hydrophobic SiO₂ nanoparticles. In addition, the PPS-SiO₂ hybrid membranes exhibited excellent self-cleaning antifouling performance, cycling performance and superior acid/alkali resistance.

Calcium Sulfate Hemihydrate Nanowires: One Robust Material in Separation of Water from Water-in-Oil Emulsion

Here we report a facile and cost-effective wet-chemical approach to the synthesis of calcium sulfate hemihydrate nanowires (HH NWs, CaSO₄·0.5H₂O), and their robust performance in immobilizing water molecules to the crystal lattice of CaSO₄ and then separating them from a surfactant-stabilized water-in-oil emulsion (mean droplet size of around 1.2 μm). Every gram of HH NWs are capable of treating 20 mL emulsion (water content: 10.00 mg mL^-1) with a separation efficiency of 99.23% at room temperature, and this efficiency can be further improved by tuning the surface charge density of HH. Along with the water immobilization, HH NWs are converted to large cubic-like calcium sulfate dihydrate microparticles (DH, CaSO₄·2H₂O, mean size: 50 μm), and the accompanied size increment enables efficient collection of the solid phase from oil. DH microparticles can be regenerated into HH NWs, which retain the high performance of the original NWs. Such a unique renewable feature improves the economics of our method and simultaneously prevents the secondary pollution. Further economic evaluation finds that purification of every cubic meters of emulsion (water content: 10.00 mg mL^-1) will cost about $34.18 for HH NWs, much lower than the $490.78 for the previously reported HH NPs, and $11 052.05-$23 420.32 Fe₃O₄ NP-based adsorbents, respectively. With the high efficiency, easy collection, low cost, and renewable feature, HH NWs show highly promising applications in the field of oil purification and recycle.

Antibacterial and biocompatible ABA-triblock copolymers containing perfluoropolyether and plant-based cardanol for versatile coating applications

ABA-triblock copolymers were prepared via ATRP, using modified perfluoropolyether (PFPE) as a macroinitiator (Br–PFPE–Br) to form the B block, and 2-hydroxy-3-cardanylpropyl methacrylate (HCPM) as a monomer to form the A blocks.

Mimicking the cell membrane: bio-inspired simultaneous functions with monovalent anion selectivity and antifouling properties of anion exchange membrane

A new bio-inspired method was applied in this study to simultaneously improve the monovalent anion selectivity and antifouling properties of anion exchange membranes (AEMs). Three-layer architecture was developed by deposition of polydopamine (PDA) and electro-deposition of N-O-sulfonic acid benzyl chitosan (NSBC). The innermost and outermost layers were PDA with different deposition time. The middle layer was prepared by NSBC. Fourier transform infrared spectroscopy and scanning electron microscopy confirmed that PDA and NSBC were successfully modified on the surfaces of AEMs. The contact angle of the membranes indicated an improved hydrophilicity of the modified membranes. A series of electrodialysis experiments in which Cl⁻/SO₄²⁻ separation was studied, demonstrating the monovalent anion selectivity of the samples. The Cl⁻/SO₄²⁻ permselectivity of the modified membranes can reach up to 2.20, higher than that of the commercial membrane (only 0.78) during 90 minutes in electrodialysis (ED). The increase value of the resistance of the membranes was also measured to evaluate the antifouling properties. Sodium dodecyl benzene sulfonate (SDBS) was used as the fouling material in the ED process and the membrane area resistance of modified membrane increase value of was only 0.08 Ωcm² 30 minutes later.

A Carbonaceous Membrane based on a Polymer of Intrinsic Microporosity (PIM-1) for Water Treatment

As insufficient access to clean water is expected to become worse in the near future, water purification is becoming increasingly important. Membrane filtration is the most promising technologies to produce clean water from contaminated water. Although there have been many studies to prepare highly water-permeable carbon-based membranes by utilizing frictionless water flow inside the carbonaceous pores, the carbon-based membranes still suffer from several issues, such as high cost and complicated fabrication as well as relatively low salt rejection. Here, we report for the first time the use of microporous carbonaceous membranes via controlled carbonization of polymer membranes with uniform microporosity for high-flux nanofiltration. Further enhancement of membrane performance is observed by O₂ plasma treatment. The optimized membrane exhibits high water flux (13.30 LMH Bar⁻¹) and good MgSO₄ rejection (77.38%) as well as antifouling properties. This study provides insight into the design of microporous carbonaceous membranes for water purification.

Star Polymers

Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

Preparation and Anti-Fouling Property of Acryloylmorpholine-Grafted PVDF Membrane: The Effect of Cross-Linking Agent

Inspired by the hydration capability of hydrogel materials, cross-linked poly(N-acryloylmorpholine) (PACMO) chains were designed into poly(vinylidene fluoride) (PVDF) backbones to synthesize the copolymers (PVDF-g-PACMO) using the radical polymerization method. These copolymers were then cast into the porous membranes via immersion phase inversion. The effects of N,N′-methylenebisacrylamide (MBAA) in the reaction solution on the structure and performance of as-prepared copolymer membranes were evaluated by elemental analysis, X-ray photoelectronic spectroscopy, field emission scanning electron microscopy, water contact angle measurement, protein adsorption and filtration experiment. The grafting degree of PACMO increases with the increase of MBAA amount in the reaction solution, which endows the copolymer membrane with a good hydrophilicity. The protein adsorption and irreversible membrane fouling decrease and then further increase with the elevated grafting degree of PACMO. This result indicates that the anti-fouling property of membrane not only depends on the surface hydrophilicity and but also associates with the grafting structures of PACMO. This work provides a fundamental understanding of various grafting structures governing the performance of anti-fouling properties.

A Scalable Method toward Superhydrophilic and Underwater Superoleophobic PVDF Membranes for Effective Oil/Water Emulsion Separation

A superhydrophilic and underwater superoleophobic PVDF membrane (PVDFAH) has been prepared by surface-coating of a hydrogel onto the membrane surface, and its superior performance for oil/water emulsion separation has been demonstrated. The coated hydrogel was constructed by an interfacial polymerization based on the thiol-epoxy reaction of pentaerythritol tetrakis (3-mercaptopropionate) (PETMP) with diethylene glycol diglycidyl ether (PEGDGE) and simultaneously tethered on an alkaline-treated commercial PVDF membrane surface via the thio-ene reaction. The PVDFAH membranes can be fabricated in a few minutes under mild conditions and show superhydrophilic and underwater superoleophobic properties for a series of organic solvents. Energy dispersive X-ray (EDX) analysis shows that the hydrogel coating was efficient throughout the pore lumen. The membrane shows superior oil/water emulsion separation performance, including high water permeation, quantitative oil rejection, and robust antifouling performance in a series oil/water emulsions, including that prepared from crude oil. In addition, a 24 h Soxhlet-extraction experiment with ethanol/water solution (50:50, v/v) was conducted to test the tethered hydrogel stability. We see that the membrane maintained the water contact angle below 5°, indicating the covalent tethering stability. This technique shows great promise for scalable fabrication of membrane materials for handling practical oil emulsion purification.

Mussel-inspired dopamine- and plant-based cardanol-containing polymer coatings for multifunctional filtration membranes

A series of copolymers [PCD#s, where # is the weight percentage of dopamine methacrylamide (DMA) in polymers] containing mussel-inspired hydrophilic dopamine and plant-based hydrophobic cardanol moieties was prepared via radical polymerization using DMA and 2-hydroxy-3-cardanylpropyl methacrylate (HCPM) as the monomers. PCD#s were used as coating materials to prevent flux decline of the membranes caused by the adhesion of biofoulants and oil-foulants. Polysulfone (PSf) ultrafiltration membranes coated with PCD#s showed higher biofouling resistance than the bare PSf membrane, and the bactericidal properties of the membranes increased upon increasing the content of HCPM units in the PCD#s. Serendipitously, the PSf membranes coated with the more or less amphiphilic PCD54 and PCD74, having the optimum amount of both hydrophilic DMA and hydrophobic HCPM moieties, showed noticeably higher oil-fouling resistance than the more hydrophilic PCD91-coated membrane, the more hydrophobic PCD0-coated membrane, and the bare PSf membrane. Therefore, multifunctional coating materials having biofouling- and oil-fouling-resistant and bactericidal properties could be prepared from the monomers containing mussel-inspired dopamine and plant-based cardanol groups.

Synthesis of High Molecular Weight Polymethacrylates with Polyhedral Oligomeric Silsesquioxane Moieties by Atom Transfer Radical Polymerization

A new polyhedral oligomeric silsesquioxane (POSS) methacrylate monomer, 1-(3-(methacryloyloxy)propyl)dimethylsiloxy-3,5,7,9,11,13,15-hepta(isobutyl)pentacyclo-[9.5.1.1^3,9.1^5,15.1^7,13]octasiloxane ((i-Bu)₇POSS-OSiMe₂-MA, 1), with a flexible spacer between the cubic POSS cage and methacrylate group was synthesized to reduce steric strain and thus achieve polymethacrylates (poly(POSS-MA)s) with high molecular weight (MW). Atom transfer radical polymerization (ATRP) of 1 at high monomer concentration (1 M, corresponding to ca. 85 wt % of 1) led to polymers with the absolute number-average MW, determined by multiangle laser light scattering, M_n,_MALLS = 2 350 000 (and apparent MW, measured by gel permeation chromatography with linear poly(methyl methacrylate) (PMMA) standards, M_n,GPC = 550 000). Optimization of the reaction conditions, including the ATRP catalyst, targeted degrees of polymerization, monomer concentrations, as well as a monomer feeding, resulting in the first well-defined high MW polymers with POSS moieties.

Organic-Inorganic Hybrid Polymers as Adsorbents for Removal of Heavy Metal Ions from Solutions: A Review

Over the past decades, organic-inorganic hybrid polymers have been applied in different fields, including the adsorption of pollutants from wastewater and solid-state separations. In this review, firstly, these compounds are classified. These compounds are prepared by sol-gel method, self-assembly process (mesopores), assembling of nanobuilding blocks (e.g., layered or core-shell compounds) and as interpenetrating networks and hierarchically structures. Lastly, the adsorption characteristics of heavy metals of these materials, including different kinds of functional groups, selectivity of them for heavy metals, effect of pH and synthesis conditions on adsorption capacity, are studied.

Star-shaped POSS diblock copolymers and their self-assembled films

This first example of 16-arm, star-shaped diblock copolymers s-POSS-PMMA_277.3-b-P(MA-POSS)_{5.8,16.4,25.4} can be used as solvent-dependent coatings.