Dual-spacing-channel graphene oxide membranes with multiple hydrophilic domains give high permeance and high rejection in organic solvent nanofiltration.

CitationDesign of block copolymer membranes using segregation strength trend lines 2016 Mol. Syst. Des. Eng. Block copolymer self--assembly and non--solvent induced phase separation are now being combined to fabricate membranes with narrow pore size distribution, and high porosity. The method has the potential to be used with a broad range of tailor made block copolymers to control functionality and selectivity for specific separations. However, the extension of this process to any new copolymer is challenging and time consuming, due to the complex interplay of influencing parameters, such as solvent composition, polymer molecular weights, casting solution concentration, and evaporation time. We propose here an effective method for designing new block copolymer membranes. The method consists of predetermining a trend line for preparation of isoporous membranes, obtained by computing solvent properties, interactions and copolymer block sizes for a set of successful systems and using it as a guide to select the preparation conditions for new membranes. We applied the method to membranes based on poly(styrene--b--ethylene oxide) diblocks and extended it to newly synthesized poly(styrene--b--2--vinyl pyridine--b--ethylene oxide) (PS--b--P2VP--b--PEO) terpolymers. The trend line method can be generally applied to other new systems and is expected to dramatically shorten the path of isoporous membrane manufacture. The PS--b--P2VP--b--PEO membrane formation was investigated by in situ Grazing Incident Small Angle X--ray Scattering (GISAXS), which revealed a hexagonal micelle order with domains spacing clearly correlated to the membrane interpore distances. Eprint version

CitationSutisna B, Polymeropoulos G, Mygiakis E, Musteata V, Peinemann K-V, et al. (2016) Our results demonstrate that artificial channels can be designed for protein transport via block copolymer self--assembly using classical methods of membranes preparation. text goes here.

Membranes are prepared by self-assembly and casting of 5 and 13 wt% poly(styrene-b-butadiene-b-styrene) (PS-b-PB-b-PS) copolymers solutions in different solvents, followed by immersion in water or ethanol. By controlling the solution-casting gap, porous films of 50 and 1 µm thickness are obtained. A gradient of increasing pore size is generated as the distance from the surface increased. An ordered porous surface layer with continuous nanochannels can be observed. Its formation is investigated, by using time-resolved grazing incident small angle X-ray scattering, electron microscopy, and rheology, suggesting a strong effect of the air-solution interface on the morphology formation. The thin PS-b-PB-b-PS ordered films are modified, by promoting the photolytic addition of thioglycolic acid to the polybutadiene groups, adding chemical functionality and specific transport characteristics on the preformed nanochannels, without sacrificing the membrane morphology. Photomodification increases fivefold the water permeance to around 2 L m h bar , compared to that of the unmodified one. A rejection of 74% is measured for methyl orange in water. The membranes fabrication with tailored nanochannels and chemical functionalities can be demonstrated using relatively lower cost block copolymers. Casting on porous polyacrylonitrile supports makes the membranes even more scalable and competitive in large scale.

Biological systems are the ultimate model for an effective selective permeation device. Biomimetic artificial channels based on the assembly of peptides have been previously integrated in vesicles and lipid layers with the expectation of leading in the future to a more efficient water purification and biological separation. We demonstrate here the design of scalable membranes constituted by synthesized copolymers with α-helical polypeptide blocks. They have unique feather-like and lamellar structures and were obtained from poly(styrene-b-γ-benzyl-L-glutamate) copolymers via phase inversion or spin-coating. The membranes were then hydrolyzed using acid vapor annealing, which preserved the helical morphology after hydrolysis. Water permeation up to 3.5 L m-2 h-1 bar-1 was obtained. Dialysis experiments with membranes prepared via phase inversion had high retention of cytochrome-c. High rejection of cytochrome-c and the negatively charged dye Brilliant Blue was demonstrated for the spin-coated membranes. The bioinspired membranes are developed for effective molecular separation, aiming at applications in the biotech industry.

Polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-b-P2VP-b-PEO)terpolymer is a versatile polymer to form isoporous films and membranes, due to the possibility of self-assembly control and the properties of the different blocks, such as the P2VP ability of complexation, and H-bond formation, and the PEO biocompatibility.Copolymers with different block ratios and sizes were synthesized. The correlation between their equilibrium bulk morphology, the self-assembly in dilute and semi-dilute solutions and the non-equilibrium porous structures of membranes, obtained by nonsolvent induced phase separation, was investigated and discussed in detail. The characterization was performed by small-angle X-ray scattering (SAXS), scanning (SEM)and transmission electron microscopy (TEM). Hexagonal, cubic and lamellar arrangements were observed. The preparation conditions were optimized and a regular, isoporous morphology, suitable for membrane application, was successfully obtained with PS 80.5k -b-P2VP 64.4k -b-PEO 16.1k .

CitationMadhavan P, Sutisna B, Sougrat R, Nunes SP (2016

We combine self-assembly in solution, complexation with metallic salts and phase separation induced by solvent-non-solvent exchange to prepare nanostructured membranes for separation in the nanofiltration range. This method was applied to prepare membranes from newly synthesized poly(acrylic acid)-b-polysulfone-b-poly(acrylic acid) copolymers dissolved in a selective solvent mixture and immersed in aqueous Cu or Ag solutions.