Sulfonation Level Research Articles

Preparation and Characterization of Nanocellulose/Sulfonated Poly(Ether Imide) Composite Membrane and Its Application as Proton Exchange Membrane

ABSTRACTThe TEMPO‐oxidized cellulose nanofibril (CNF) membrane is combined with sulfonated poly(ether imide) (SPEI) using the solution impregnation method to enhance its proton exchange membrane properties. SPEI solutions with different sulfonation levels, SPEI1, SPEI2, SPEI4, and SPEI5, are prepared by adjusting the acetyl sulfate to PEI mole ratios from 1:1 to 2:1, 3:1, 4:1, and 5:1, respectively. The CNF membranes are immersed in each SPEI solution for 24 h and hot‐pressed at 100°C for 1 h to form composite membranes. The chemical structure, morphology, wettability, and membrane characteristics are analyzed. The wettability of SPEI on the CNF surface varies with sulfonation degree, and it affects the morphology of each CNF‐SPEI membrane. Consequently, proton conductivity and ion exchange capacity (IEC) increase, while methanol permeability decreases with increasing sulfonation levels. The CNF‐SPEI5 membrane exhibits the highest proton conductivity of 4.23 mS.cm−1 and the lowest methanol permeability at 6.67 × 10−7 cm2.s−1. Additionally, the CNF‐SPEI4 membrane achieves maximum tensile strength and flexibility at 4.91 ± 0.09 MPa and 15.05% ± 0.24%, respectively. While its proton conductivity still faces challenges, the CNF/SPEI membrane demonstrates better methanol permeability suppression than Nafion 117 (1.31 × 10−6 cm2.s−1) and superior dimensional stability compared with the pristine CNF membrane.

Leveraging Tunable Nanoparticle Surface Functionalization to Alter Cellular Migration.

Gold nanoparticles (AuNPs) are a promising platform for biomedical applications including therapeutics, imaging, and drug delivery. While much of the literature surrounding the introduction of AuNPs into cellular systems focuses on uptake and cytotoxicity, less is understood about how AuNPs can indirectly affect cells via interactions with the extracellular environment. Previous work has shown that the monocytic cell line THP-1's ability to undergo chemotaxis in response to a gradient of monocyte chemoattractant protein 1 (MCP-1) was compromised by extracellular polysulfonated AuNPs, presumably by binding to MCP-1 with some preference over other proteins in the media. The hypothesis to be explored in this work is that the degree of sulfonation of the surface would therefore be correlated with the ability of AuNPs to interrupt chemotaxis. Highly sulfonated poly(styrenesulfonate)-coated AuNPs caused strong inhibition of THP-1 chemotaxis; by reducing the degree of sulfonation on the AuNP surface with copolymers [poly(styrenesulfonate-co-maleate) of different compositions], it was found that medium and low sulfonation levels caused weak to no inhibition, respectively. Small, rigid molecular sulfonate surfaces were relatively ineffective at chemotaxis inhibition. Unusually, free poly(styrenesulfonate) caused a dose-dependent reversal of THP-1 cell migration: at low concentrations, free poly(styrenesulfonate) significantly inhibited MCP-1-induced chemotaxis. However, at high concentrations, free poly(styrenesulfonate) acted as a chemorepellent, causing a reversal in the cell migration direction.

Random sulfonated poly(arylene ether sulfone) and sulfonated poly(arylene ether ketone) membranes for fuel cell applications

AbstractIn this study, sulfonated poly(arylene ether sulfone) (SPAES) and sulfonated poly(arylene ether ketone) (SPAEK) were randomly synthesized, employing a presulfonation process. This presulfonation process resulted in a more controlled and reproducible sulfonation level. The respective polymers were prepared using 2,2‐Bis(4‐hydroxyphenyl) propane at 50% molar ratio, which also provided some membrane elasticity. The resulting polymers, each had 25% of the block containing the sulfonic domains (SPAES A 25 and SPAEK A 25). Better conductive membranes were achieved for the random sulfone polymers than for the random ketone polymers, with values, respectively, of 0.24 and 0.07 S cm−1 at 80°C. The lower proton conductivity from the ketone‐based polymer was compensated with very low methanol permeability (0.25 × 10−6 cm2 s−1) and outstanding oxidative stability. The selectivity of both polymer membranes exceeded the reported values for the state‐of‐the‐art Nafion® 117 and other commercially available options. Both polymer membranes, with their unique combination of ionic domains, elastomeric blocks, and resulting morphology, could be viable candidates for fuel cell applications.

Sulfonated polyimide membranes with branched architecture and unique diamine monomer for implementation in vanadium redox flow battery

In this paper, a new functional diamine monomer 2-methyl-1,4-bis(4-amino-2-trifluoromethyl) benzene (FAPOB) is designed and synthesized for further improving the performance of branched sulfonated polyimide (SPI–B) membrane for implementation in vanadium redox flow battery (VRB). At the same time, the sulfonation levels of SPI-B membranes are accurately regulated by modifying the proportion of FAPOB and 4,4′-diaminobiphenyl-2,2′-disulphonic acid. Among them, the SPI-B-50 membrane with 50 % sulfonation degree exhibits a remarkable proton selectivity of 2.31 × 105 S min/cm3, which is 5.5 times higher than the Nafion 212 (NR212) membrane. Moreover, the SPI-B membrane's stability is significantly improved due to its branched structure and the presence of numerous trifluoromethyl groups. Compared to NR212 membrane, SPI-B-50 membrane demonstrates superior coulomb and energy efficiencies at the same current density. Furthermore, the SPI-B-50 membrane exhibits a higher voltage holding capacity compared to the NR212 membrane. Remarkably, the SPI-B-50 membrane maintains stable efficiencies even after undergoing more than 500 charge-discharge cycles. This research not only involves the innovative synthesis of a novel diamine monomer but also the construction of various SPI-B membranes with a unique molecular structure specifically designed for VRB applications.

Response of ionizable block copolymer assemblies to solvent dielectrics: A molecular dynamics study

Ionizable copolymers assembly in solutions is driven by the formation of ionic clusters. Fast clustering of the ionizable blocks often leads to the formation of far-from equilibrium assemblies that ultimately impact the structure of polymer membranes and affect their many applications. Using large-scale atomistic molecular dynamics simulations, we probe the effects of electrostatics on the formation of ionizable copolymer micelles that dominate their solution structure, with the overarching goal of defining the factors that control the assembly of structured ionizable copolymers. A symmetric pentablock ionizable copolymer, with a randomly sulfonated polystyrene center tethered to polyethylene-r-propylene block, terminated by poly(t-butyl styrene), in solvents of varying dielectric constants from 2 to 20, serves as the model system. We find that independent of the solvents, this polymer forms a core–shell micelle with the ionizable segment segregating to the center of the assembly. The specific block conformation, however, strongly depends on the sulfonation levels and the dielectric constant and the polarity of the solvents.

Water solubility, photoluminescence and photocatalytic activity of ZnS quantum dot-sulfonated polystyrene composite

A composite of sulfonated polystyrene with zinc sulfide quantum dot (ZnS QD) was prepared directly in aqueous medium. The partially sulfonated polystyrene (PSS) of sulfonation level, f = 30% hydrogelate in aqueous solution of zinc ions and generate ZnS particles for the formation of PSS-ZnS QD composite. The sulfonated polystyrene (SPS) of sulfonation level, f > 75% behaves as a polyelectrolyte. In aqueous solution, SPS stabilized ZnS particles are synthesized and ultimately form the SPS-ZnS QD composite. PSS-ZnS QD composite is water insoluble and SPS-ZnS QD composite is water soluble. HRTEM images, UV–vis absorption and luminescence of the composites confirm the quantum confinement in ZnS particles. The photoluminescence of the composites predominates in defect state emission relative to band edge emission. Photocatalytic activity of water insoluble PSS-ZnS QD composite in degrading an organic dye is demonstrated. The composite is efficient enough to degrade 84% of methylene blue in 6 h of ultraviolet (UV) illumination. Though water solubility of SPS-ZnS QD limits it use as a photocatalyst, only a limited number of water soluble polymer composites were reported in literature.

Molecular weight controlled sulfonated Poly(Arylene Ether)s and sulfonated Poly(Ether Ether ketone) polymer blends for fuel cell applications

We synthesized molecular weight-controlled and fluorine-containing PAEs (MWCPAEs) using decafluorobiphenyl (DFBP), 2-bis (4-hydroxyphenyl) propane (Bis A), and 2,2-Bis (4-hydroxyphenyl) hexafluoropropane (Bis AF). Later, commercially available PEEK and the MWCPAEs were sulfonated (SPEEK and SMWCPAE) and blended to fabricate blend membranes (BMs). All BMs have been prepared by solution casting method in 5 wt%-20 wt% concentrations using N,N-dimethylacetamide. The effects of chemical structures, sulfonation levels, MW and compositions on the membrane properties are discussed. We obtained miscible and mechanically compatible BMs. The highest proton conductivity (238.9 mS/cm) was determined for SPEEK70/S-DFBP-Bis-A based blend membrane (Mw: 48.355, 5wt. %). All chemical, mechanical, thermal, and hydrolytic properties of the BMs are comparable with, or better than, that of Nafion. We suggest that designing polymeric structures with desired MWs and sulfonation levels may enable enhanced properties and can help to design materials with on demand properties.

Sulfonated Cellulose Membranes: Physicochemical Properties and Ionic Transport versus Degree of Sulfonation

AbstractThe next generation of green ion selective membranes is foreseen to be based on cellulosic nanomaterials with controllable properties. The introduction of ionic groups into the cellulose structure via chemical modification is one strategy to obtain desired functionalities. In this work, bleached softwood fibers are oxidatively sulfonated and thereafter homogenized to liberate the cellulose nanofibrils (CNFs) from the fiber walls. The liberated CNFs are subsequently used to prepare and characterize novel cellulose membranes. It is found that the degree of sulfonation collectively affects several important properties of the membranes via the density of fixed charged groups on the surfaces of the CNFs, in particular the membrane morphology, water uptake and swelling, and correspondingly the ionic transport. Both ionic conductivity and cation transport increase with the increased level of sulfonation of the starting material. Thus, it is shown that the chemical modification of the CNFs can be used as a tool for precise and rational design of green ion selective membranes that can replace expensive conventional fluorinated ionomer membranes.

Ion channels in sulfonated copolymer-grafted nanoparticles in ionic liquids.

The use of ionic liquids as solvents for polymers or polymer-grafted nanoparticles provides an exciting feature to explore electrolyte-polymer interactions. 1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIm-TFSI) can have specific interactions with the polymer through ion-dipole forces or hydrogen bonding. In this work, poly(methyl methacrylate)-b-poly(styrene sulfonate) (PMMA-b-PSS) copolymer-grafted Fe3O4 nanoparticles with different sulfonation levels (∼4.9 to 10.9 mol% SS) were synthesized, and their concentration dependent ionic conductivities were reported in acetonitrile and HMIm-TFSI/acetonitrile mixtures. We found that conductivity enhancement with the particle concentration in acetonitrile was due to the aggregation of grafted particles, resulting in sulfonic domain connectivity. The ionic conductivity was found to be related to the effective hopping transfer within ionic channels. On the contrary, the conductivity decreased or remained constant with increasing particle concentration in HMIm-TFSI/acetonitrile. This result was attributed to the ion coupling between ionic liquids and copolymer domains.

High‐performance blended membranes based on poly(arylene ether sulfone) and sulfonated poly(styrene‐isobutylene‐styrene) for direct methanol fuel cell applications

AbstractIn this study, two series of poly(arylene ether sulfone)s (PAES) with hydrophobic blocks made of 4,4′‐dihydroxyphenyl (BP) and 2,2‐bis(4‐hydroxyphenyl) propane (BPA) were synthesized. The copolymers were prepared by a coupling reaction between decafluorobiphenyl (DFBP) end‐capped nonsulfonated block (PAES A or B) and sulfonated block (SPAES B). The reactive behavior of DFBP facilitates the low‐temperature coupling reaction (below 105°C). The final copolymers were blended at distinct weight percent ratios (0, 20, 30, and 40) with poly(styrene‐b‐isobutylene‐b‐styrene) (SIBS) at a sulfonation level of 88% to obtain strong and flexible membranes. Morphological, thermal stability, and conduction properties of the resulting membranes were measured and reported here. Results suggest that phase segregation between hydrophobic and hydrophilic domains occurs below 1 meq. g−1 ion exchange capacity. These membranes have low water absorption and high thermal stability. Incorporating SIBS 88 into the blend added elastomeric behavior enhancing transport properties and additional ionic domains, achieving proton conductivities of 0.21 S cm−1 for BPA‐based membranes at 50°C (40% SIBS 88). The selectivity of the studied membranes surpasses Nafion® 117, making them strong candidates for proton exchange membranes in direct methanol fuel cell applications.

Sulfonated poly(styrene‐isobutylene‐styrene) grafted with hexyl‐ and butyl‐imidazolium chloride ionic liquids

AbstractIn this work, novel sulfonated poly(ionic liquid)s block‐copolymers based on poly(styrene–isobutylene–styrene) (SIBS) are synthesized for chemical protective clothing (CPC) applications. The synthesis consists of the chloromethylation of SIBS, followed by the incorporation of N‐alkylimidazole through chemical grafting, and concluding with sulfonation of the resulting compound. Properties of the membranes are determined as a function of different N‐alkylimidazoles (butylimidazole and hexylimidazole) and sulfonation levels (7–23 mol%). Results show that the incorporation of imidazole and sulfonic groups increases the thermal stability of SIBS as well as its water absorption capabilities. The interaction between the ionic moieties in the polymeric matrix allows the formation of hydrophilic nanochannels, which promote the transport of permeants through the membrane. The high water vapor transmission rate (above 2000 g m−2 day−1) and values of selectivity (~50) demonstrate that the breathability of the synthesized membrane is improved while blocking the passage of dimethyl methylphosphonate (simulant of agent Sarin). The above mentioned observations suggest that sulfonated SIBS‐PIL's membranes are potential materials for CPC applications.

Influences of sulfonation level on the nanofiltration performance of sulfonated graphene oxide polyamide nanocomposite membranes

In this study, thin-film nanocomposite (TFN) membranes containing sulfonated graphene oxide (SGO) were prepared and used for water desalination. SGO sulfonation level influences on the physicochemical and separation performance of the prepared TFNs were studied. The TFN membranes were synthesized by interfacial polymerization of 1,3-Phenylene diamine (MPD),1,3,5-benzenetricarbonyl trichloride, and sodium dodecyl sulfate as an additive on polyethersulfone support, while GO and SGOs were dispersed in an aqueous solution of MPD. The physicochemical characterization of GO and SGO samples revealed that the sulfonation level of GO greatly influences the interlayer d-spacing, ion exchange capacity, and zeta potential of GO. Morphology analysis confirmed that GO and SGO were incorporated into the polyimide layer and that the SGO sulfonation level greatly influences the surface morphologies of TFN membranes. Generally, SGO incorporated TFN membranes provided higher hydrophilicity, water uptake, and more desirable surface morphologies for the desalination processes. Increasing the sulfonation level from 25 to 50% wt of sulfanilic acid to GO led to a notable improvement in the salt rejection of SGO-incorporated TFNs, and it reached to about 97% for Na2SO4. This was also accompanied by a considerable increase in these membranes' pure water flux, compared to the GO-containing TFN membranes (~ 42%) and the TFC membranes (~ 4 times). Furthermore, the flux recovery ratio of this membrane was about 24% higher compared to the unmodified membranes, indicating the promising influences of the sulfonated groups on the compatibility, recovery and the reuse of TFN membranes.

수소-산소 연료 전지용 나노물질 첨가 고분자 전해질 막

The solid electrolyte membrane for a hydrogen-oxygen fuel cell was prepared and investigated from the potential of sulfonated poly(ether ether ketone) (SPEEK) embedded together with montmorillonite (MMT). Acid hydrophilized poly(ether ether ketone) (PEEK) and MMT with varying sulfonation levels of 25-70% prepared through solvent casting were investigated for their performance. The nuclear magnetic resonance (1H NMR) spectra at 7.5 ppm affirmed the occurrence of sulfonation reaction, and its degree was studied by both 1H NMR and titration method. The reaction time was varied to achieve sulfonation levels from 25 to 70%. The effect of incorporation of pristine and sulfonated MMT into SPEEK was examined. The membranes, prepared using solvent casting technique, were involved for water uptake over the wide range of temperature, thermal stability, and proton conductivity measurements. The cross-sectional surface arrangement of the membrane and clay dispersion was deliberated using SEM. The proton exchange membrane fuel cell (PEMFC) single cell’s tests revealed that sulfonated PEEK membrane demonstrated service performance comparable to that of Nafion, as validated using MATLAB software.

Fabrication of membrane electrode assembly based on nafion/sulfonated graphene oxide nanocomposite by electroless deposition for proton exchange membrane fuel cells

This report describes a fabrication route for membrane electrode assembly (MEA) with low Pt loading based on Nafion/sulfonated graphene oxide (SGO) nanocomposite membrane. The Pt catalyst was directly electroless deposited on both sides of Nafion/SGO membranes and electrochemical performance of the fabricated MEAs toward hydrogen adsorption/desorption reactions were studied. The effects of Nafion SGO content, Pt salt concentration, and SGO sulfonation level on the physicochemical and electrochemical characteristics of MEAs were investigated. The physicochemical properties of MEAs were studied by field emission scanning electron microscopy, water uptake (WU) measurements, and x-ray diffraction technique. Cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy techniques were applied to compare the electrochemical behavior of the prepared MEAs. WU of the best Nafion/SGO MEA appeared to be significantly higher than that of pure Nafion MEA (~ 2.5 times) and Nafion/GO MEA (~1.7 times). The electrochemical evaluation revealed the best Nafion/SGO MEA possessed a high electrochemical surface area of 67.4 m2 g−1, which was about 24 times and 50 % higher than those obtained for MEAs based on Nafion and Nafion/GO membranes. The best MEA showed high durability and retained about 93% of initial ECSA after 1000 cycles in an acidic solution. A high proton conductivity of 39.9 mS cm−1 was achieved for this MEA in which it was about 2.5 times and 1.9 times higher compared to those of MEAs prepared based on Nafion (15.9 mS cm−1) and Nafion/GO (20.7 mS cm−1).

Chemical and morphological effects of blended sulfonated poly(styrene‐isobutylene‐styrene) and isopentylamine for direct methanol fuel cell applications

AbstractIn this study, blend membranes based on a combination of sulfonated poly (styrene‐isobutylene‐styrene) (SIBS) with isopentylamine (IPA) were synthetized as potential candidates for direct methanol fuel cell (DMFC) applications. The impact of sulfonation level (57–93 mol%) and percentage of IPA incorporation (1, 3, and 5 wt%) were analyzed via different properties of the resulting membrane. FTIR analysis showed that IPA was successfully incorporated into the sulfonated polymer matrix and also confirmed the interaction between the sulfonic and amine groups. This interaction generates significant morphological changes in the nanostructure of the membranes that are evident through results of small angle x‐ray scattering and atomic force microscopy analysis. Proton conductivity and methanol permeability of the membranes were also analyzed. Proton conductivity was significantly enhanced with the incorporation of IPA at an optimum loading, creating additional paths for the conduction of protons through the membrane. It was also sensitive to the morphological changes produced after the IPA incorporation and the interconnection between the ionic domains. Methanol permeability increased slightly due to the additional water domains and the inability of the isopentyl groups of IPA to block the free‐volume in the membrane. Despite this, the selectivity (proton conductivity over methanol permeability) of the membranes was comparable to the state‐of‐the‐art Nafion®, especially at an optimum IPA incorporation of 3 wt%.

Cross-linking/sulfonation to improve paste stability, adhesion and film properties of corn starch for warp sizing

To investigate the influence of cross-linking/sulfonation on the viscosity stability, adhesion, film properties and desizability of corn starch for ameliorating its end-use ability in application of warp sizing, a series of itaconic acid cross-linked and sulfonated starch (IACLSS) samples with different levels of cross-linking (LCL) and degrees of substitution (DS) were synthesized by the cross-linking of acid-converted starch (ACS) with itaconic acid (IA) and subsequent sulfonation with NaHSO3. The apparent viscosity and viscosity stability were determined and adhesion was evaluated using a standardized method (FZ/T 15,001–2008). Film properties were also estimated in terms of tensile strength, breaking elongation, bending endurance, and moisture regain and the desizability of the IACLSS samples was investigated by measuring the time required to break the films in hot water. The experimental results showed that cross-linking/sulfonation was capable of improving the viscosity stability of cooked starch paste, enhancing the adhesion of starch to cotton and polyester fibers, increasing breaking elongation, bending endurance and moisture regain of starch film as well as decreasing its tensile strength, thereby stabilizing paste viscosity, ameliorating the adhesion to fibers and diminishing film brittleness. In addition, modification could reduce the time required to break the films in 80 °C water, indicating that modification favored the desizing of starch in hot water. Increasing sulfonation levels whilst decreasing the LCL values favored improvement in stability and desizability, enhancement in the adhesion to cotton and polyester fibers, and decrease in brittleness. The IACLSS showed potential in the applications of cotton and polyester sizing.

Incorporation of sulfonated silica nano particles into polymer blend membrane for PEM fuel cell applications

In the present work sulfonated poly (ether ether ketone) (SPEEK)/poly (amide imide) (PAI or Torlon) was successfully prepared for various conditions such as percentage compositions of the SPEEK/PAI blended with sulfonated silica (S-SiO2). The Nuclear Magnetic Resonance spectroscopy (NMR), Ion Exchange Capacity (IEC) analyses confirm the degree of sulfonation level as 65%. The as-prepared composite membranes were subjected to characterize using Fourier Transform Infrared spectroscopy (FTIR). Surface morphology of the acid-base composite membranes was analyzed by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Other physical properties related to conductivities, ion exchange capacity and proton conductivity were also evaluated for the prepared composite membranes. The 90 wt% SPEEK- 10 wt% PAI- 3 wt% S-SiO2 membrane had (0.75 V) open-circuit voltage (OCV), (350 mA cm−2) current density and (120 mW cm−2) power density. 90 wt% SPEEK- 10 wt% PAI- 3 wt% S-SiO2 composite showed good proton conductivities, durability and expected for developing of Proton Exchange Membrane Fuel Cell (PEMFC) applications.

Morphology and proton diffusion in a coarse-grained model of sulfonated poly(phenylenes).

A coarse-grained model previously used to simulate Nafion using dissipative particle dynamics (DPD) is modified to describe sulfonated Diels-Alder poly(phenylene) (SDAPP) polymers. The model includes a proton-hopping mechanism similar to the Grotthuss mechanism. The intramolecular parameters for SDAPP are derived from atomistic molecular dynamics (MD) simulation using the iterative Boltzmann inversion. The polymer radii of gyration, domain morphologies, and cluster distributions obtained from our DPD model are in good agreement with previous atomistic MD simulations. As found in the atomistic simulations, the DPD simulations predict that the SDAPP nanophase separates into hydrophobic polymer domains and hydrophilic domains that percolate through the system at sufficiently high sulfonation and hydration levels. Increasing sulfonation and/or hydration leads to larger proton and water diffusion constants, in agreement with experimental measurements in SDAPP. In the DPD simulations, the proton hopping (Grotthuss) mechanism becomes important as sulfonation and hydration increase, in qualitative agreement with experiment. The turning on of the hopping mechanism also roughly correlates with the point at which the DPD simulations exhibit clear percolated, hydrophilic domains, demonstrating the important effects of morphology on proton transport.

(Invited) Structure and Dynamics in Ion-Conducting Polymers from MD Simulations

Simulations of ion transport in ion-conducting polymers such as ionomers are challenging because dynamical processes relevant to the ion transport occur across many orders of magnitude in time. Additionally, designing improved ionomers requires an understanding of how both polymer architecture and ionomer morphology affect ion dynamics. To build a better understanding of the relationships among ionomer chemistry, morphology, and ion transport, we have performed a series of molecular dynamics simulations and connected aspects of these simulations with experiment. In this talk I will describe our recent results on two different ionic polymers. The first is a series of precise poly(ethylene-co-acrylic acid) ionomers, which have acid groups precisely spaced along the polymer backbone. These ionomers form nanoscale ionic aggregates with morphologies dependent on the spacer length between acid groups on the polymer backbone and on mobile ion concentration. Recent atomistic MD simulations of these ionomers are in good agreement with quasi-elastic neutron scattering data at short time scales. The comparison with experiment validates the dynamics in the simulations, which we then use to probe ion dynamics at longer time scales. We also performed coarse-grained simulations to provide insight into ion transport mechanisms at longer times. The second system is a sulfonated poly(phenylene), which conducts protons when hydrated. Atomistic simulations of the structure are in good agreement with NMR spin diffusion measurements of domain sizes and with X-ray scattering. At low sulfonation and hydration levels, clusters are more elongated in shape and poorly connected throughout the system. As the degree of sulfonation and water content are increased, the clusters became more spherical, and a fully percolated ionic domain is formed. I will discuss the connections among the hydrophilic domain morphology, the state of the hydrogen bonding network, and the conductivity in these polymers. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. Figure 1

Fabrication of high-performance nanofiber-based FO membranes

Being partially commercialized and has specific application areas, where the reverse osmosis technology cannot serve, forward osmosis (FO) technology is continually receiving extensive research to promote its performance. In this study, high-performance FO nanofiber-based substrate membrane was fabricated for potential application of saline water desalination. Sulfonated polysulfone (sPSU) with definite sulfonation level was used to fabricate support layer. Tubular beadless fiber network owning scaffold-like structure with a fiber diameter of 247 nm was formed. Polysulfone was sulfonated by heterogeneous method using chlorosulfonic acid as a sulfonation agent. The substrate and FO membranes were characterized mainly by means of scanning electron microscopy (SEM), water permeation flux, porometry, contact angle, Fourier transform infrared (FTIR), as well as other tests, while the characterization of thin-film composite separation layer was restricted to SEM and FTIR. The characterization illustrates that the sPSU support layer is highly porous with a narrow pore size distribution. FO performance evaluation of two commercial and newly developed membranes was probed using FO and pressure-retarded osmosis (PRO) modes with cocurrent and counter-current flow scheme. The active layer presents excellent intrinsic properties with A/B of 17.31 and a high salt separation ratio of 99.54%. The newly developed membrane can achieve a high FO and PRO water flux of 65.7 and 313 L m(-2) h(-1), respectively, using a 1 M NaCl draw solution and deionized water feed solution. The corresponding salt flux is only 2.5 and 5.3 g m(-2 )h(-1). The reverse flux selectivity represented by the ratio of water flux to reverse salt flux (J(w)/J(s)) was kept as high as 26.3 and 58.8 L g(-1) for FO and PRO modes. To the best of our knowledge, the performance of the current work-developed membrane is superior to all FO membranes previously reported in the literature.