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Asymmetric ultrafiltration membranes derived from block copolymer self-assembly have seen growing attention as a result of their ordered pore structures and scalable fabrication process. One route to extend their utility is to provide, through the molecular architecture of the block copolymer, covalent binding sites for facile attachment of foreign functional molecules. Here, we report the synthesis of triblock terpolymer poly(styrene)-block-poly(4-vinylpyridine)-block-poly(propylene sulfide) (SVPS) and its fabrication into isoporous ultrafiltration membranes. Final SVPS membrane top surfaces exhibit narrowly dispersed mesopores with 6-fold symmetry. Membranes show a switchable response to pH changes demonstrating the potential as a chemical gate. Membrane pore surfaces are decorated with thiol groups providing active covalent binding sites via versatile thiol-ene click chemistry. The work may open pathways to produce high-performance multifunctional membranes for chem- and bio-sensing and for separation and as membrane reactors. [ABSTRACT FROM AUTHOR]

Evaporation-induced asymmetric triblock terpolymer membrane formation from polyisoprene-block-polystyrene-block-poly(4-vinylpyridine) (ISV) that relies on self-assembly of doctor bladed solutions was studied using in situ grazing incidence small-angle X-ray scattering (GISAXS). Transient ordered structures were observed for two ISV terpolymers at intermediate evaporation times in the top surface layers of the films as a function of molar mass and solution concentration. Analysis of the GISAXS patterns revealed the evolution from disordered to ordered structures including a transition from body-centered cubic (BCC) to simple cubic (SC) lattices and finally to an amorphous mesoscale structure. The BCC to SC transition solves an apparent structural puzzle resulting from comparisons of, on one side, earlier quiescent solution SAXS studies suggesting BCC terpolymer micelle structures at higher concentrations and, on the other side, electron microscopy studies consistent with SC lattices originating from polymer micelles in the top separation layer of asymmetric ISV membranes. Gaining insights into the structural evolution of asymmetric triblock terpolymer film formation may enable further optimization of self-assembly plus non-solvent-induced phase separation (SNIPS) based high performance isoporous asymmetric block copolymer ultrafiltration membranes. [ABSTRACT FROM AUTHOR]

Tailoring pore size of ultrafiltrationmembranes all the way downtoward the nanofiltration regime in a predictable manner from moleculardesign principles is highly desirable. Here we present a way to achievethis in surface separation layers of nonsolvent induced phase separation(NIPS) derived graded block copolymer (BCP) membranes by means ofan organic additive. Glycerol, a nontoxic organic molecule, is incorporatedat varying amounts into poly(isoprene-b-styrene-b-4-vinylpyridine) (ISV) triblock terpolymer casting solutions.Employing scanning electron microscopy image analysis and solute rejectiontests on resulting membranes, the relationship between the amountof additives and membrane performance (permeability, selectivity)is established. Pore size increases from 23 to 48 nm are achievedby moving from membranes cast from pure ISV solutions to those castfrom up to 40% weight (relative to ISV) glycerol containing solutions.It is then demonstrated how a combination of additive driven poreexpansion in conjunction with P4VP chain stretching via charge repulsioncan be used to reduce pore sizes down to 5 nm under acidic (pH 3.6)conditions. This provides a path to move from ultrafiltration towardnanofiltration applications for asymmetric BCP membranes without compromisingmembrane mechanical properties. It also enables production of advancedmembranes with wide tunability, low cost, and high performance. [ABSTRACT FROM AUTHOR]

Selective degradation of block copolymer templates and backfilling the open mesopores is an effective strategy for the synthesis of nanostructured hybrid and inorganic materials. Incorporation of more than one type of inorganic material in orthogonal ways enables the synthesis of multicomponent nanomaterials with complex yet well-controlled architectures; however, developments in this field have been limited by the availability of appropriate orthogonally degradable block copolymers for use as templates. We report the synthesis and self-assembly into co-continuous network structures of polyisoprene-Wodc-polystyrene-Mock-poly(propylene carbonate) where the polyisoprene and polypropylene carbonate) blocks can be orthogonally removed from the polymer film. Through sequential block etching and backfilling the resulting mesopores with different metals, we demonstrate first steps toward the preparation of three-component polymer--inorganic hybrid materials with two distinct metal networks. Multiblock copolymers in which two blocks can be degraded and backfilled independently of each other, without interference from the other, may be used in a wide range of applications requiring periodically ordered complex multicomponent nanoarchitectures. [ABSTRACT FROM AUTHOR]