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Block Polymer Membranes Functionalized with Nanoconfined Polyelectrolyte Brushes Achieve Sub-Nanometer Selectivity
journal contribution
posted on 2017-06-23, 18:23 authored by Yizhou Zhang, Ryan A. Mulvenna, Siyi Qu, Bryan W. Boudouris, William A. PhillipThe
well-defined nanostructure of membranes manufactured from self-assembled
block polymers enables highly selective separations; however, recent
efforts to push the pore size of block polymer-based membranes to
the lower end of the size spectrum have only been moderately successful
for a variety of reasons. For instance, the conformational changes
of the stimuli-responsive functional groups lining the pore walls
of some block polymer membranes result in varied pore sizes that limit
their operational range. Here, we overcome this challenge through
the directed design of the third moiety of an A-B-C triblock polymer.
The use of this macromolecular design paradigm allows for the preparation
of a 500 nm thick polyisoprene-b-polystyrene-b-poly(2-acrylamido-ethane-1,1-disfulonic acid) (PI-PS-PADSA)
coating atop a hollow fiber membrane support. This nanoporous test
bed, which exhibits an average pore radius of 1 nm, demonstrates an
extremely high solute selectivity by fully gating solutes that have
only an 8 Å size difference, a separation that is based solely
on a sieving mechanism. Furthermore, the nanoscale structural characteristics
of the solvated PADSA pore walls are elucidated by quantifying the
rejection of neutral solutes and calculating the hydraulic permeability
values in solutions of high ionic strength (1 mM ≤ I ≤ 3 M) and over a broad range of solution pH (1
≤ pH ≤ 13). These key results provide a solid foundation
for defining structure–property–performance relationships
in the emerging area of nanoporous triblock polymer thin films. Moreover,
the successful demonstration of the test bed separation device offers
a tangible means by which to manufacture next-generation nanofiltration
membranes that require a robust performance profile over a dynamic
range of conditions.
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test bed separation device8 Å size differencesize spectrumnanoporous test bed1 nmnext-generation nanofiltration membranesA-B-C triblock polymersolutiongating solutespHpermeability valuesnanoporous triblock polymersolute selectivityself-assembled block polymersdesign paradigmblock polymer-based membranesfiber membrane supportblock polymer membranes result500 nmperformance profilepore sizepore wallspore sizesNanoconfined Polyelectrolyte Brushes Achieve Sub-Nanometer Selectivitysieving mechanismblock Polymer Membranes FunctionalizedPI-PS-PADSAsolvated PADSA pore wallspore radius
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