Ultrathin and Switchable Nanoporous Catalytic Membranes of Polystyrene‐b‐poly‐4‐Vinyl Pyridine Block Copolymer Spherical Micelles

Abstract

membranes with a thick separation layer have broad pore size distribution, and this result in poor cutoff properties, fi ltrate loss within the membranes, and low permeation rates. The challenge is to control the pore size precisely at a few nanometers. For increased nanofi ltration performance with higher throughput at lower applied pressure, reduction of the fi lter thickness is benefi cial. [4][5][6][7] However, reaching the limit of a few nanometers is diffi cult when mechanical robustness and tightly controlled pore size are also required. Even though many methods have been developed, the fabrication of porous membranes that have well-defi ned structures and controlled pore sizes precisely at a few nanometers is still missing. For this purpose, a number of researchers have examined various methods to form molecular-scale porous membranes, which include phase separation of block copolymers, [8][9][10][11][12] self-assembled gold nanocrystal membrane, [ 7 ] supported lyotropic liquid crystals, [ 13 ] aligned carbon nanotubes, [ 4,14 ] ultrathin carbon nanosheets, [ 15 ] ultrathin protein layers, [ 5 ] and ultrathin silicon membranes with average pore sizes of 5 to 25 nm. [ 6,16 ] Several reports are available where nanoparticles have been used for thin fi lm construction. [ 17 ] Block copolymers are promising materials for fabricating high throughput and improved amphiphilic fi ltration membranes. [ 9,10,12 ] Block copolymers are composed of two or more chemically distinct, and usually immiscible, polymer chains, which are covalently bound together. Due to these two immiscible blocks, phase separation occurs in ordered microstructures with length scales of the order of ten to hundred nano meters. [ 18 ] The ordered phase separation leads to the formation of thin nanoporous membranes. Although nanoporous membranes based on block copolymers offer great chemical tunability, limitations in thermal stability, mechanical performance, and solvent resistance can thwart even broader applications. [ 19 ] Different strategies have been used to prepare isoporous block copolymer membranes such as supramolecular self-assembly, self-assembly in combination with nonsolvent phase inversion, selective etching of blocks, magnetic alignment, etc. [ 20,21 ] In all above cases, membranes were prepared in the order of 150-200 µm thick on highly porous support layers.An easy fabrication of close-packed and block copolymer micelles-based ultrathin membranes for water purifi cation, separation, catalytic, and dye degradation applications is reported. Nanoporous membranes based on the self-assembly of 2-(4′-hydroxybenzeneazo) benzoic acid (HABA)-polystyreneb -poly(4-vinylpyridine) (PS-b -P4VP) diblock copolymers supramolecular complexes are prepared by simple spin coating on pore-fi lled polyethylene terephthalate (PET) track-etched membranes. The prepared membranes are characterized by scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and water permeation studies. The separation performance is stu...

Self-assembled membrane composed of amyloid-like proteins for efficient size-selective molecular separation and dialysis

“…For 50-nm-thick nanomembrane, the surface porosity is also useful that was further estimated as 3.2% by using the Hagen-Poiseuille equation (Equation 4 in Methods), since this equation has been widely applied to the filtration membranes with flow channels larger than 2 nm in diameter 22 . An interfacial channel surrounded by three such oligomers with a diameter ~20 nm could be geometrically calculated to have a size of 3.1 nm 31 (Fig. 1e).…”

Poly (ionic liquid)-Based Breath Figure Films: A New Kind of Honeycomb Porous Films with Great Extendable Capability

“…Due to common commercial use of Congo red as a colorant in dyeing industry, the research of its degradation is necessary 37 , 38 . Herein honeycomb films decorated with Au nanoparticles were used to photocatalytic degradation of Congo red dye.…”

Polydopamine modified membranes with in situ synthesized gold nanoparticles for catalytic and environmental applications

“…Pienamann et al reported that gold nanoparticle immobilized in polystyrene-b-poly vinyl pyridine (PS-P4VP) block copolymer hollow fiber membrane could reduce $80% of PNP feed containing a 100 mL portion of a solution containing 1.39 mg PNP and 37.83 mg NaBH 4 at 0.003 mL/(cm 2 s) flux [28]. In a similar approach we also reported PS-P4VP micelle membranes with gold nanoparticles, which can reduce more than 95% PNP (1.7 mL of water, 0.3 mL of 2 mM solution of PNP, and 1 mL of 0.03 M NaBH4 solution at $200 L m À2 h À1 flux) and 98% Congo red (40 ppm feed at 589.3 L m À2 h À1 flux) in flow reactor [29]. Bruening et al…”