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Abstract Highly permeable and cost-affordable membranes are highly desired in separation processes. Herein, such membranes are produced by designing gradient phenolics inside the macropores of polyvinylidene fluoride (PVDF) substrates. Solutions consisting of resol, poly(ethylene oxide)/poly(propylene oxide) copolymer and ZnCl 2 are infiltrated into the macropores of PVDF. Phenolic nanoparticles and nanopores with increasing sizes are formed across the membrane thickness after fast solvent evaporation, ZnCl 2 -facilitated resol polymerization and acid soaking. The prepared gradient phenolic@PVDF membranes exhibit a permeance up to 1315 L/(m2 h bar), which is several times higher than that of other membranes with similar rejections to bovine serum albumin (91%) and lysozyme (71%). Moreover, the membranes are robust enough to withstand a pressure of at least 12.0 bar due to the interlaced structures of phenolics and PVDF. We demonstrate that thus-produced membranes can efficiently separate and concentrate gold nanoparticles with sizes down to 5 nm. This work suggests a new strategy for rational design of gradient porosities in macroporous substrates to produce robust membranes with high permeances and tight rejections. Graphical abstract fx1 Highlights • Gradient nanoporous phenolics are filled into the macropores of PVDF substrates. • Sizes of pores and phenolic nanoparticles are increased along membrane profiles. • Membranes exhibit high permeances several times higher than other membranes. • Separation performances can be tuned by adjusting dosages of phenolics. • Tight size-sieving capabilities to 5 nm-nanoparticles are achieved. [ABSTRACT FROM AUTHOR]

Mesoporous polymers derived from supramolecules of phenolic resins (PRs) and block copolymers (BCPs) containing highly uniform pores with sizes down to a few nanometers, are expected to deliver promising membrane separation performances. Here we report on the preparation of mesoporous phenolic membranes exhibiting tight ultrafiltration properties through a pore-filling strategy. Solutions of PR/BCP supramolecules are filled into the macropores of polyvinylidene fluoride (PVDF) microfiltration membranes (substrates), followed by thermopolymerization to solidify the solution in the pores. Subsequently, the filled PVDF substrates are treated in hot H 2 SO 4 to remove the BCP components, thus producing mesopores in the PR framework. The produced composite membranes are mechanical robust and ductile as mesoporous phenolic resins are tightly embedded in the pores of the PVDF matrix. The mesoscale porosity in the PR phases endow the composite membrane a tight ultrafiltration performance with the molecular-weight-cut-off (MWCO) down to 2350 Da. The separation properties can be tuned simply by adjusting the dosage of supramolecule solutions used to fill the macroporous substrates. Considering the tight and uniform pore sizes and the robustness of phenolic resins, this strategy opens a new avenue to ultrafiltration membranes with low MWCOs or even nanofiltration membranes. [ABSTRACT FROM AUTHOR]

Membranes with sub-10-nm pores are receiving growing interest in recognizing and separating nanocolloids, biomolecules, and soluble salts from water, but suffer from difficulty of optimizing pore structures and inferior stability. Herein, we report an efficient method for the preparation of robust nanoporous phenolic membranes with widely tunable pore sizes in the range of nanofiltration and tight-ultrafiltration. Solutions of resol precursors and poly(ethylene glycol)s (PEGs) are spin-coated to form thin films and then heated to thermopolymerize resols into phenolics. Subsequently, the films are treated in H 2 SO 4 solution to degrade PEGs, producing nanoporous phenolic membranes. Thus-prepared phenolic membranes exhibit adjustable effective pore sizes and tunable separation performances from nanofiltration to tight-ultrafiltration, which is otherwise inaccessible. Due to the thin thicknesses and rich water channels, the membranes exhibit higher permeances than other tight-ultrafiltration membranes and commercial ultrafiltration membranes with similar rejections. Furthermore, thanks to the robust frameworks and good chemical resistance of phenolics, the membranes deliver stable performances in long-term operations, elevated pressures, and acidic conditions. This work provides a facile and universal strategy for the synthesis of membranes with sub-10-nm pores for nanofiltration and tight-ultrafiltration. [Display omitted] • Nanoporous phenolic membranes are prepared using PEG as the template. • Pore structures can be simply tuned by changing the proportion of PEG. • Tunable nanofiltration and tight-ultrafiltration performances are achieved. • Membranes exhibit good mechanical and chemical stabilities. [ABSTRACT FROM AUTHOR]

Tight ultrafiltration (UF) membranes with high permeances have gained growing attention in the separation of biomacromolecules. Herein, we report the preparation of gradient carbonaceous structures filled in macroporous polyvinylidene fluoride (PVDF) substrates and their efficient separation of polypeptides. Gradient phenolics composed of nanoparticles with sizes increasing from top side to bottom side are firstly synthesized inside PVDF substrates. When soaked in concentrated H 2 SO 4 , phenolic nanoparticles are partially carbonized and foamed to form micropores while the PVDF substrate maintains intact. Thus-produced carbonaceous membranes are mechanical robust and exhibit narrowed pore sizes and enhanced hydrophilicity. Their permselectivity can be adjusted simply by changing the dosages of phenolic precursors filling into the PVDF substrates. Low dosages lead to remarkably high water permeances up to 1721 L/(m2·h·bar). At higher dosages, the membrane is tightened to show a molecular-weight-cut-off (MWCO) down to 3.7 kg/mol and high permeances several times larger than other membranes with similar MWCOs. We demonstrate that such a tight UF membrane efficiently separates polypeptides with molecular weights of only a few kg/mol (angiotensin Ⅱ and thymosin β4). Our work opens a new avenue for the synthesis of high-flux tight UF membranes with narrowed pores, enabling the precise separation and fractionation of biomacromolecules. Image 1 • Gradient structures are synthesized inside macroporous PVDF substrates. • Phenolics are carbonized by concentrated H 2 SO 4 while PVDF maintains intact. • The obtained carbonaceous membranes exhibit narrowed pore sizes. • Membranes exhibit tight selectivity with high permeances than other membranes. • Membranes can efficiently separate polypeptides with similar molecular weights. [ABSTRACT FROM AUTHOR]

High permeability is one of the most important pursuits of separation membranes. In this work, high-performance ultrafiltration membranes are prepared by synergetically coupling nonsolvent-induced phase separation (NIPS) and selective swelling of a block copolymer, polysulfone- block -poly (ethylene glycol) (PSF- b -PEG). NIPS is used to prepare PSF- b -PEG membranes with a thin skin layer and a fingerlike sublayer. Subsequent selective swelling generates mesopores in the skin layer and enriches PEG blocks on the surface. Compared to the membranes without swelling, the swelling-treated membranes exhibit simultaneously upgraded permeability, hydrophilicity, and fouling resistance. For instance, the permeability of the membrane swollen in 50% acetic acid at 65 °C for 1 h is doubled compared to the pristine one while the rejection is only modestly reduced. Fouling resistance of the swelling-treated membranes is also improved, which is ascribed to the enrichment of PEG on the membrane surface. We demonstrate that the performances of the membranes can be tuned in a relatively wide range by tailoring the swelling conditions, such as swelling reagents, durations and temperatures. Because of the extreme simplicity and high efficiency, this selective swelling strategy is expected to be applicable in tuning the surface properties and improving performances of many other membranes. [ABSTRACT FROM AUTHOR]

Ultrafiltration (UF) membranes with high permeability and good fouling resistance hold great promise in water treatment and many industry sectors. Herein, antifouling UF composite membranes with mesoporous films of polystyrene (PS)/poly(ethylene oxide) (PEO) block copolymer as the selective layers were produced by the process of selective-swelling-induced pore generation. We spin-coated thin layers of block copolymer onto macroporous supports, and activated the copolymer layers by soaking them in hot ethanol to induce the selective swelling of the PEO microdomains. The porous structures of the block copolymer selective layers can be continuously modulated simply by varying the swelling durations, resulting in UF membranes with water permeabilities adjustable in the range of ~ 100 to 600 L m -2 h -1 bar -1 . Interestingly, the hydrophilic PEO blocks were enriched on the pore walls after swelling, rendering an inherent fouling resistance to the membranes. Protein fouling tests demonstrated that the membrane exhibited exceptional fouling resistance with a recover ratio in water flux of nearly 100%. This fouling resistance is expected to be long-standing as the PEO chains are covalently bonded to the membrane matrix. [ABSTRACT FROM AUTHOR]