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Block copolymer (BCP) ultrafiltration (UF) membranes derived from a hybrid process of BCP self-assembly and non-solvent induced phase separation (SNIPS) exhibit an asymmetric structure consisting of ordered pores in a selective skin layer above a highly permeable substructure. In this work, we investigate relative humidity (RH) as a casting condition that influences poly(isoprene- b -styrene- b -4-vinylpyridine) (ISV) membrane surface structure in terms of order and uniformity. An optimum RH of 40–45% is determined to produce membranes characterized by a high density of square packed pores with a narrow pore size distribution. Membranes cast at lower and higher RH show a drop off in order and uniformity. The RH dependent structural changes correlate well with small molar mass dye solute (methyl orange; molar mass of 327 g/mol) diffusion rates. Membranes cast at 40% RH reveal higher diffusivity than when cast at 75% RH. The rate of permeation is further controlled via pH dependent pore closure as well as through ISV terpolymer molecular architecture with increasing solute diffusivity observed in membranes cast from increasing terpolymer molar mass. Experimental findings on small molar mass solute permeability can only be accounted for when compared with theoretical predictions from a hydrodynamic theory combined with the effects of tortuosity when a simplified membrane structure is assumed. Results suggest that SNIPS derived BCP membranes may have potential for applications in drug delivery.

Asymmetric poly(isoprene-b-styrene-b-4-vinylpyridine) (ISV) block copolymer membranes fabricated via self-assembly and non-solvent induced phase separation (SNIPS) process have drawn significant attention due to the simple processing method and the generation of high-quality isoporous ultrafiltration membranes. With the present study on SNIPS membrane substructure, we systematically varied membrane casting parameters to tune the cross-sectional morphologies of SNIPS membranes while simultaneously preserving top surface structure. Parameters such as polymer concentration, evaporation time, solvent ratio, and coagulation bath temperature were investigated to control transformation of commonly produced sponge-like cross-sectional morphologies into more open and permeable finger-like substructures. Membranes with sponge-like and finger-like substructures were then integrated onto nylon supports for enhanced mechanical properties. Hydraulic permeability tests at various pH conditions gave distinct open-state flux values for SNIPS membranes with different sublayer morphologies, while maintaining pH responsive functionality resulting from the poly(4-vinylpyridine) block.

© 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Optical metamaterials offer the tantalizing possibility of creating extraordinary optical properties through the careful design and arrangement of subwavelength structural units. Gyroid-structured optical metamaterials possess a chiral, cubic, and triply periodic bulk morphology that exhibits a redshifted effective plasma frequency. They also exhibit a strong linear dichroism, the origin of which is not yet understood. Here, the interaction of light with gold gyroid optical metamaterials is studied and a strong correlation between the surface morphology and its linear dichroism is found. The termination of the gyroid surface breaks the cubic symmetry of the bulk lattice and gives rise to the observed wavelength- and polarization-dependent reflection. The results show that light couples into both localized and propagating plasmon modes associated with anisotropic surface protrusions and the gaps between such protrusions. The localized surface modes give rise to the anisotropic optical response, creating the linear dichroism. Simulated reflection spectra are highly sensitive to minute details of these surface terminations, down to the nanometer level, and can be understood with analogy to the optical properties of a 2D anisotropic metasurface atop a 3D isotropic metamaterial. This pronounced sensitivity to the subwavelength surface morphology has significant consequences for both the design and application of optical metamaterials.

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 polyme...

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 ...

Prussian blue analogues (PBAs) have been recently investigated as promising electrode materials for battery and supercapacitor applications. While most explorations have focused on PBA nanoparticles, very little attention has been focused on PBA films deposited on a metallic support. In this work, we have examined electrogenerating hexacyanoferrate (HCF) and hexacyanoruthenate (HCR) films on nickel surfaces via cyclic voltammetry. We found that the total material deposited was influenced by the metal cation present in the electrolyte solution and that, on average, the rate of deposition of the surface adsorbed/immobilized species was dependent on the species in solution. In particular, films electrogenerated in the presence of Na+ and K+ had the highest deposition rates. The cyclic voltammetric profiles exhibited dramatic differences depending on the cation present in the electrolyte solution. In addition, we found that all films were electrochemically irreversible in the presence of Li+ and Mg2+ containing electrolyte solutions. Further, and as a proof of concept, we modified high surface area nickel electrodes with HCF in sodium-based electrolytes, finding that these electrodes could operate reversibly at equivalent C-rates as high as 1667C.

Block copolymer (BCP) self-assembly is a promising route to manufacture functional nanomaterials for applications from nanolithography to optical metamaterials. Self-assembled cubic morphologies cannot, however, be conveniently optically characterized in the lab due to their structural isotropy. Here, the aligned crystallization behavior of a semicrystalline-amorphous polyisoprene-b-polystyrene-b-poly(ethylene oxide) (ISO) triblock terpolymer was utilized to visualize the grain structure of the cubic microphase-separated morphology. Upon quenching from a solvent swollen state, ISO first self-assembles into an alternating gyroid morphology, in the confinement of which the PEO crystallizes preferentially along the least tortuous pathways of the single gyroid morphology with grain sizes of hundreds of micrometers. Strikingly, the resulting anisotropic alignment of PEO crystallites gives rise to a unique optical birefringence of the alternating gyroid domains, which allows imaging of the self-assembled grain structure by optical microscopy alone. This study provides insight into polymer crystallization within a tortuous three-dimensional network and establishes a useful method for the optical visualization of cubic BCP morphologies that serve as functional nanomaterial templates.

International audience; Nanostructured silver stands out among other plasmonic materials because its optical losses are the lowest of all metals. However, nanostructured silver rapidly degrades under ambient conditions, preventing its direct use in most plasmonic applications. Here, a facile and robust method for the preparation of highly stable nanostructured silver morphologies is introduced. 3D nanostructured gyroid networks are fabricated through electrodeposition into voided, self-assembled triblock terpolymer scaffolds. Exposure to an argon plasma degraded the polymer and stabilized the silver nanostructure for many weeks, even in high humidity and under high-dose UV irradiation. This stabilization protocol enables the robust manufacture of low-loss silver nanostructures for a wide range of plasmonic applications.