Low Degree Of Sulfonation Research Articles

Polysulfone with Different Degrees of Sulfonation: Simple Method with Acetyl Sulfate

In this work, the authors present as an innovation, the homogeneous sulfonation of Udel® polysulfone (PSU) with acetylsulfate (ACS) under reflux at 45°C in dichloromethane and inert N2 atmosphere (g) for 1.5 h. Different proportions of ACS were used, obtaining sulfonated products with varying degrees of sulfonation (DS). Confirmation of sulfonated polysulfone (PSU-S), denominated as PSU-SA (high degree of sulfonation) and PSU-SB (low degree of sulfonation), was carried out by FTIR and 1H NMR. Determination of DS was carried out through thermogravimetric analysis (TGA/DSC), varying indexes between 0.883 and 3.022, which correspond to a sulfonated polymer with ion exchange capacity (IEC) from 1.720 to 4.400 meq/g. The evolution of DS related to methods used was monitored and confirmed by 1H NRM. Sulfonation is undertaken to enhance the suitability of this polymer for future applications in the production of biofuels, targeting its utilization in catalytic processes for esterification and transesterification mechanisms of oils and fats.

Studying the Effect of Cross-Linking and Sulfonation on the Calcium-Binding Ability of Polystyrene Sulfonate in the Presence of Dodecyl Sulfate

Calcium ions in hard water deteriorate the cleaning performance of detergents by interacting with the anionic surfactants and inducing their precipitation. Polystyrene sulfonate is a common component of cation-exchange resins that adsorb hard ions such as Ca+2 and Mg+2, which adhere to the sulfonate groups. Therefore, understanding the calcium-binding ability of polystyrene sulfonate in the presence of dodecyl sulfate can help in designing novel water-softening agents for applications related to detergency. Studying the association between polystyrene sulfonate and dodecyl sulfate via calcium ion bridges is also important. Since resins contain cross-linked polystyrene sulfonate, degrees of cross-linking and sulfonation are two important parameters. We use molecular dynamics simulations to study the effect of the above parameters on the calcium-binding ability of isotactic polystyrene sulfonate in the presence of dodecyl sulfate. We observe negligible dependence of calcium-ion binding of polystyrene sulfonate on the degrees of cross-linking and sulfonation. The formation of calcium ion bridges between cross-linked polystyrene sulfonate and dodecyl sulfate is strongly affected by the degree of sulfonation. Such bridges are observed more for the intermediate degrees of sulfonation. This is because, at a very low degree of sulfonation, dodecyl sulfate ions align closer to the cross-linking aromatic groups than the sulfonated ones. On the other hand, at high degrees of sulfonation, stronger electrostatic repulsion disfavors the proximity between dodecyl sulfate and polystyrene sulfonate.

Factors affecting mixed-mode retention properties of cation-exchange stationary phases

Cation-exchange stationary phases were characterized in different chromatographic modes (HILIC, RPLC, IC) and applied to the separation of non-charged hydrophobic and hydrophilic analytes. The set of columns under investigation included both commercially available cation-exchangers and self-prepared PS/DVB-based columns, the latter consisting of adjustable amounts of carboxylic and sulfonic acid functional groups. The influence of cation-exchange site and polymer substrate on the multimodal properties of cation-exchangers was identified using selectivity parameters, polymer imaging and excess adsorption isotherms. Introducing weakly acidic cation-exchange functional groups to the unmodified PS/DVB-substrate effectively reduced hydrophobic interactions, whilst a low degree of sulfonation (0.09 to 0.27% w/w sulphur) mainly influenced electrostatic interactions. Silica substrate was found to be another important factor for inducing hydrophilic interactions. The presented results demonstrate that cation-exchange resins are suitable for mixed-mode applications and offer versatile selectivity.

Mesoscale Simulation Based on the Dynamic Mean-Field Density Functional Method on Block-Copolymeric Ionomers for Polymer Electrolyte Membranes.

Block copolymers generally have peculiar morphological characteristics, such as strong phase separation. They have been actively applied to polymer electrolyte membranes for proton exchange membrane fuel cells (PEMFCs) to obtain well-defined hydrophilic regions and water channels as a proton pathway. Although molecular simulation tools are advantageous to investigate the mechanism of water channel formation based on the chemical structure and property relationships, classical molecular dynamics simulation has limitations regarding the model size and time scale, and these issues need to be addressed. In this study, we investigated the morphology of sulfonated block copolymers synthesized for PEM applications using a mesoscale simulation based on the dynamic mean-field density functional method, widely applied to investigate macroscopic systems such as polymer blends, micelles, and multi-block/grafting copolymers. Despite the similar solubility parameters of the monomers in our block-copolymer models, very different morphologies in our 3D mesoscale models were obtained. The model with sulfonated monomers, in which the number of sulfonic acid groups is twice that of the other model, showed better phase separation and water channel formation, despite the short length of its hydrophilic block. In conclusion, this unexpected behavior indicates that the role of water molecules is important in making PEM mesoscale models well-equilibrated in the mesoscale simulation, which results in the strong phase separation between hydrophilic and hydrophobic regions and the ensuing well-defined water channel. PEM synthesis supports the conclusion that using the sulfonated monomers with a high sulfonation degree (32.5 mS/cm) will be more effective than using the long hydrophilic block with a low sulfonation degree (25.2 mS/cm).

Constructing a long-range proton conduction bridge in sulfonated polyetheretherketone membranes with low DS by incorporating acid-base bi-functionalized metal organic frameworks

Functionalized metal-organic frameworks (MOFs) are being extensively developed as viable fillers to enhance the proton conductivity of proton exchange membranes. Herein, an amino-pendant sulfonic acid bi-functionalized MOFs material (UNCS)-doped SPEEK membrane with low degree of sulfonation (DS) can improve the proton conductivity as well as maintain the membrane dimensional stability. UNCS can act as bridges of proton donors and acceptors to reduce the activation energy barrier and shorten the distance of long-range proton conduction. Among all as-prepared membranes, SPEEK/UNCS-3 exhibited the highest proton conductivity of 186.4 mS·cm−1 at 75 °C and 100% relative humidity (RH), which is much greater than that of pristine SPEEK and Nafion 117. Benefiting from the acid-base pair interaction between the amino groups of UNCS and the sulfonic acid groups of SPEEK, the dimensional stability and mechanical properties of the composite membranes were enhanced. More interestingly, STEM-HAADF and SAXS characterization consistently revealed that UNCS served as bridges among proton channels in the composite membranes for continuous proton transport.

Functionalized carbon black modified sulfonated polyether ether ketone membrane for highly stable vanadium redox flow battery

Sulfonated polyether ether ketone (SPEEK) membranes have attracted much attention as ion exchange membranes for vanadium redox flow batteries (VRFBs) owing to their affordability and low vanadium permeability. It's noted that they suffer from poor proton conductivity at low degree of sulfonation (DS) while poor mechanical stability at high DS. Therefore, it is a challenge to balance their performance and DS. In this work, functionalized carbon black (FCB) particles with sulfonic acid substituents were prepared and used as fillers to obtain advanced SPEEK composite membranes. This kind of SPEEK/FCB composite membranes show outstanding ion selectivity, low vanadium permeability, high proton conductivity and excellent stability. The VRFB cell with the optimized SPEEK/FCB composite membrane shows high energy efficiency (94.26%, at 50 mA cm−2), low-capacity fade rate (0.052% per cycle, at 120 mA cm−2) and long cycle life.

A review of alternative polymer electrolyte membrane for fuel cell application based on sulfonated poly(ether ether ketone)

A proton exchange membrane (PEM) is a crucial component in a fuel cell application as a proton carrier and separator for the anode and cathode. Sulfonated poly(ether ketone ether) (SPEEK) has been recognized as one of the promising alternatives PEM in fuel cell application due to the advantagious properties of SPEEK, including the high thermal stability, proton conductivity, mechanical strength, low fuel crossover, and easy to operate. The proton conductivity properties of SPEEK are influenced by the degree of sulfonation (DS). In practical, high DS of SPEEK-based membrane will produce high proton conductivity and a high density of sulfonic acid functional groups grafted into the polymer backbone. However, the excessive production of DS will have side effects on the stability of membrane dimensional and chemical properties. Meanwhile, the low DS of SPEEK has reduced the ability to diffuse the proton within the polymeric matrix. Therefore, getting the optimal DS SPEEK is very important to fabricate the alternative of PEM. But this process is hard. Thus, the researchers have modified the SPEEK membrane with various types of nanoparticles as a filler. This is one of the promising efforts to improve the SPEEK membrane properties and fuel cell application performance. This review aimed to discuss eight conductive materials such as silica, clay, metal oxide, heteropolyacids, carbon, graphene, metal organic framework, and zeolite used as fillers to develop the PEM component based on SPEEK for fuel cell applications. This review also comprehensively discusses the characterization of SPEEK-based membrane modification, including mechanical properties, water intake, proton conductivity, thermal properties, fuel permeability, crystal and structural analysis, chemical oxidation stability, and single-cell performance. Thus, this article can serve as a reference for researchers to planning the best strategies to optimize the properties and performance of the SPEEK-based membrane for fuel cell application.

Robust Ion‐Selective Membrane for Redox Flow Batteries Based on Ultralow Sulfonation Degree Poly(Ether Sulfone)

AbstractLow‐cost and high‐performance ion‐conducting membranes are of urgent need for the large‐scale launch of vanadium redox flow batteries. In this work, sulfonated poly(ether sulfone) (SPES) with extremely low sulfonation degree of 5% is utilized to prepare ion‐selective membranes, which possess significantly enhanced chemical stability as compared with the high sulfonation degree SPES. High ion‐selectivity of the membrane is achieved via a novel solvent‐controlled swelling method invented by the group, with which the proton conductivity and vanadium permeability of the membrane can be precisely adjusted at molecular level. The influence of sulfonation degree on the chemical stability of SPES is revealed. The characteristics of the membrane, including water uptake, proton conductivity, VO2+ permeability, and tensile strength are comprehensively studied. At 100 mA cm–2, the energy efficiency of the vanadium redox flow battery (VRFB) cell equipped with the low sulfonation degree SPES membrane reaches 81.1% and shows excellent cycling stability over 150 charge–discharge cycles.

Defining sulfonation limits of poly(ether-ether-ketone) for energy-efficient dehumidification

Unprecedented water vapor uptake of 320% was demonstrated with SPEEK at an unexpectedly low degree of sulfonation of 19% due to the high S–S distance.

Incorporating of layered double hydroxide/sepiolite to improve the performance of sulfonated poly(ether ether ketone) composite membranes for proton exchange membrane fuel cells

AbstractSulfonated poly(ether ether ketone) (SPEEK) with a low sulfonation degree was blended using nanofiller layered double hydroxide (LDH, Mg2AlCl)/sepiolite nanostructured material as additive to use as an electrolyte membrane for fuel cell application. Characterization assessments, that is, mechanical stability, thermal gravimetric analysis, ion exchange capability, swelling properties, water uptake capacities, electrochemical impedance spectroscopy analysis, and Fourier transform infrared spectroscopy of the composite membranes were conducted. The presence of LDH/sepiolite nanoarchitectured material within SPEEK was found to have the highest water retention and proton conductivity value at high temperature rather than LDH/SPEEK and pristine SPEEK membranes.

Preparation and Application of Aromatic Polymer Proton Exchange Membrane with Low-Sulfonation Degree

4,4′-Dichlorodiphenylsulfone-3,3′-disulfonic acid (disodium) salt and 4,4′-difluorodiphenylsulfone were used as sulfonated monomer. 4,4′-Fluorophenyl sulfones were used as the nonsulfonated monomer. 4,4′-Dihydroxy diphenyl ether or 4,4′-thiodibenzenethiol was used as the comonomer. The sulfonated poly (aryl ether sulfone) (SPES) and sulfonated poly (arylene thioether sulfone) (SPTES) with sulfonation degree of 30% and 50% were successfully prepared by nucleophilic polycondensation. Two kinds of aromatic polymer proton exchange membranes were prepared by using sulfonated poly phthalazinone ether ketone (SPPEK) material and fluidization method. The performance of the prepared aromatic polymer proton exchange membrane was researched by the micromorphology, ion exchange capacity, water absorption and swelling rate, oxidation stability, tensile properties, and proton conductivity. Experimental results show that there is no agglomeration in the prepared aromatic polymer proton exchange membrane. The ion exchange capacity is 0.76–1.15 mmol/g. The water absorption and swelling rate increase with the increase of sulfonation degree. The sulfonated poly (aryl ether sulfone) membrane shows better oxidation stability than sulfonated poly (aryl sulfide sulfone). They have good mechanical stability. The prepared aromatic polymer proton exchange membrane with low sulfonation degree has good performance, which can be widely used in portable power equipment, electric vehicles, fixed power stations, and other new energy fields.

Fabrication of hydrophilic cation exchange membrane with improved stability for electrodialysis: An excellent anti-scaling performance

A novel preparation method of cation exchange membranes (CEM), based on sulfonated materials with low sulfonation degree (DS), has been proposed in previous studies. For the preparation of CEMs, these studies have provided an approach with low cost, environment-friendly technology, and ideal properties, and proved the value and feasibility of the new method. Based on this, more work remained to be done to further modify the properties of CEMs prepared with this method. One purpose of this study, which was for the basic needs of good CEM practicability, was to improve CEM stability based on sulfonated polyether sulfone (SPES). This purpose was achieved satisfactorily by the proper design, and proved forcefully by stability testing, including thermostability, mechanical stability, and resistance to acid and base, etc. The other purpose, which was designed due to the special membrane surfaces, was to investigate CEM anti-scaling properties during electrodialysis (ED) processes. Compared with commercial CEMs, one clear different characteristic of CEM prepared by this method was flatter and smoother membrane surfaces, which should be an advantage for anti-scaling of salts during an ED process. From this, experiment of the second part was designed to specifically explore anti-scaling factors, but an unexpected result obtained. It was the higher hydrophilicity of these CEMs rather than their smoother surface that played an important role in anti-scaling behavior. The obtained result should be an innovative and significant discovery of this work. It will directly impact on anti-scaling research of both CEM and anion exchange membranes (AEMs). Hence, this work was a meaningful bridge for expanding previous research of CEM preparation into anti-scaling applications of ion exchange membranes.

Fabrication of cation exchange membrane with excellent stabilities for electrodialysis: A study of effective sulfonation degree in ion transport mechanism

Composite cation exchange membranes (CEMs) based on sulfonated polyether sulfone (SPES) with low sulfonation degree (DS) have been prepared in our previous studies. The results provided an approach for the preparation of CEM with low cost, environment-friendly technology, and ideal properties. On the basis of the previous research, the first purpose of this study was aimed to explore more suitable hydrophilic additives to further improve CEM properties. Hydrophilic polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) with different molecular weight (Mw) were used as hydrophilic additives, while SPES was still used as the matrix material. The results showed that PEG was not a suitable additive for CEMs due to the low MW, while stability was clearly improved with increased PVP MW. Hence, for researchers, there is no need to waste time on PEG as a hydrophilic agent of CEM prepared with this method in the future. The second purpose of this study, which was the further optimization of the CEM performance, was achieved in the research of suitable hydrophilic additives. The results of stability and electrodialysis showed that SPES blended with PVP K90 was the best prepared CEM. The third purpose was the investigation of mechanism of synergistic effects between sulfonated groups and hydrophilicity on membrane properties. In this part, an innovative concept of effective DS was put forward. This innovative concept will directly impact on ion transport mechanism, and have a very important influence on the preparation idea of CEM. In conclusion, this study is of great significance for selection of CEM materials, improvement of membrane stability and further study of ion transport mechanism.

Physicochemical characterization of low sulfonated polyether ether ketone/Smectite clay composite for proton exchange membrane fuel cells

AbstractPolyether ether ketone (PEEK) with a low sulfonation degree was blended using different proportions of sodium rich Smectite clay (3 and 6 wt%) to use as an electrolyte membrane for fuel cell application. The structural functionalities, surface morphologies, and the thermal stability of the resultant composite membranes were characterized using Fourier‐transform infrared spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy, atom force microscopy, and thermo‐gravimetric analysis. FT‐IR showed that no chemical reactions take place between the sulfonated polyether ether ketone (SPEEK) and the clay with different ratios. XRD diffractograms illustrated a lower degree of crystallinity of the blended SPEEK than pristine SPEEK. The elaborated composite membranes proved to have a higher thermal stability than SPEEK. Furthermore, the SPEEK/clay composite membranes with 3 and 6 wt% in clay loading had higher water uptake and lower methanol uptake than those in pristine SPEEK It was also shown that, the incorporation of sodium ions rich Smectite clay layers between the clusters in SPEEK improved the conductivity to 2 × 10−2 S/cm at 140°C (for 6 wt% in clay) without compromising the dimensional stability of the composite membranes. These results propose the composite membranes as a potential candidate for methanol fuel cells at temperatures above 120°C making SPEEK composite membrane competitive to that of Nafion membrane.

Coaxial electrospun sulfonated poly (ether ether ketone) proton exchange membrane for conductivity-strength balance

Coaxial electrospun strategy is proposed to resolve the typical conductivity-strength dilemma of proton exchange membrane and then improve performance of fuel cell. The advantages of co-electrospinning and effects of coaxial components are demonstrated through a simple design of co-electrospun nanofibers, i.e. sulfonated poly(ether ether ketone) with different degree of sulfonation for the core and shell components. The inner nozzle-wall provides extra electrostatic force and enhances microphase separation, as evidenced by the larger ionic clusters and ordered hydrophilic-hydrophobic domains through TEM and SAXS. As a result, the co-electrospun membranes even with the same degree of sulfonation as both the core and shell components exhibit 15.5% increase in proton conductivity and 8.3% decrease in swelling ratio at 80 oC as compared with the uni-electrospun membranes. The low degree of sulfonation core@high degree of sulfonation shell design endows the co-electrospun membranes with relatively high abilities of reinforce (about 51.6 MPa) and proton conduction (about 222.7 mS cm−1 at 80 °C), which indicates the core layer control of strength and shell layer control of proton conduction in the co-electrospun membranes. The H2/O2 cell assembled with the coaxial electrospun membrane exhibits a power density of about 1.3 times that assembled with the commercial benchmark Nafion115.

Novel pore-filling membrane based on block sulfonated poly (ether sulphone) with enhanced proton conductivity and methanol resistance for direct methanol fuel cells

The problem remains unsolved in DMFCs applications that the increase in proton conductivity is usually caused the permeation of methanol. Herein, a novel kind of pore-filling membrane is investigated to meet this challenge. The porous substrate is fabricated from block poly (ether sulphone) with low degree of sulfonation, which form well-developed conductive channels owing to an aggregation of sulfonic acid groups, ensuring low methonal crossover and swelling ratio. The pore structures are achieved by a solution casting method which introduces alpha-cyclodextrin as the porogen. The resulting porous substrate possesses homogeneous opening pore structures. Then, the filling electrolyte, an organic-soluble tetrabutylammonium 4-vinylbenzene sulfonate, is used to fill the substrate and form a crosslinked network inside the pores to ensure high proton conductivity. The pore-filling membrane with block polymers shows higher proton conductivity (0.083 S cm−1 at 80 °C) than that prepared by random polymers (0.072 S cm−1 at 80 °C). Compared with Nafion 117, the composite membrane exhibits higher dimensional stability (6.6%) and methanol resistance (4.0 × 10−7 cm2 s−1). Furthermore, the pore-filling membrane outperforms Nafion 117 with an open circuit voltage of 0.61 V as well as a maximum power density of 46.8 mW/cm2 under 10 M methanol condition.

A morphology strategy to disentangle conductivity–selectivity dilemma in proton exchange membranes for vanadium flow batteries

A novel integrally thin skinned asymmetric proton exchange membrane (ITSA-PEM) is proposed to disentangle the typical conductivity–selectivity dilemma in PEMs for vanadium flow batteries (VFBs). The membrane is successfully fabricated by a porogen-leaching-out method. It consists of a porous sublayer and an ultrathin skin layer, which is defect-free verified by the high H2/N2 separation factor of 64.9. The degree of sulfonation (DS) of PEM is reduced to extremely low (DS = 36.3%) to suppress swelling, and numerous interconnected pores are introduced to facilitate proton transfer. Low swelling ratio and defect-free skin layer lead to undetectable vanadium permeation. Meanwhile, the area resistance of ITSA-PEM is dramatically lowered to 2.1 Ω cm2 from 5.4 Ω cm2 of the dense PEM. Therefore a membrane with both improved proton conductivity and ion selectivity is obtained. Low DS also equips the membrane with sufficient mechanical strength and enhanced thermal stability. The VFB assembled with ITSA-PEM displays high energy efficiencies (EE: 75.6–90.2%) over a current density of 20–80 mA cm−2, much superior to those of Nafion 211 (EE: 55.9–73.4%). It also shows favorable stability and slow capacity decay rate during cycling test over 50 cycles.

Lignosulfonate Improves Photostability and Bioactivity of Abscisic Acid under Ultraviolet Radiation.

Abscisic acid (ABA), as a commonly used plant growth regulator, is easy to be degraded and lose its bioactivity under sunshine. To select an eco-friendly and efficient photoprotectant for the improvement of photostability and bioactivity of ABA when exposed to ultraviolet (UV) light, we tested the effects of three biodegradable natural-derived high polymers, sodium lignosulfonates 3A [molecular weight (MW) > 50000, with degree of sulfonation (DS) of 0.48] and NA (20000 < MW < 50000, with DS of 0.7) and calcium lignosulfonate CASA (MW < 20000, with DS of 0.7), on the photodegradation of ABA. Lignosulfonates 3A, NA, and CASA showed significant photostabilizing capability on ABA. Lignosulfonate 3A showed preferable photostabilizing effects on ABA compared to CASA, while NA showed an intermediate effect. That indicated that lignosulfonate with a high MW and low DS had a stronger UV absorption and the hollow aggregate micelles formatted by lignosulfonate protect ABA from UV damage. Approximately 50% more ABA was kept when 280 mg/L ABA aqueous solution was irradiated by UV light for 2 h in the presence of 2000 mg/L lignosulfonate 3A. The bioactivity on wheat (JIMAI 22) seed germination was greatly kept by 3A in comparison to that of ABA alone. The 300 times diluent of 280 mg/L ABA plus 2000 mg/L 3A after 2 h of irradiation showed 20.8, 19.3, and 9.3% more inhibition on shoot growth, root growth, and root numbers of wheat seed, separately, in comparison to ABA diluent alone. We conclude that lignosulfonate 3A was an eco-friendly and efficient agent to keep ABA activity under UV radiation. This research could be used in UV-sensitive and water-soluble agrichemicals and to optimize the application times and dosages of ABA products.

Catalytic fructose dehydration to 5-hydroxymethylfurfural over sulfonated carbons with hierarchically ordered pores

Sulfonated carbons with hierarchically ordered pores (SCHOP) were prepared by means of dual template self-assembly, carbonization, HF etching, and sulfonation. The effect of carbonization temperature on microstructure of the prepared carbons as well as the SCHOPs were surveyed at 500–700°C. Using fructose dehydration to 5-hydroxymethylfurfural as a probe reaction, catalytic performance of SCHOPs was examined. The results show that SCHOP-500 carbonized at 500°C exhibits the highest catalytic activity. SEM and TEM characterization as well as N2 adsorption desorption show that all of the SCHOPs possess hierarchically ordered macropores and mesopores, but high carbonization temperature damages the regularity of carbon materials slightly. FT-IR, EDS and –SO3H determination confirm that sulfonic acid group could be successfully introduced to carbon materials by sulfonation. However, high carbonization temperature lowers aromaticity of the carbon materials, and as a result leading to low sulfonation degree. Under the catalysis of SCHOP-500, as high as 93.4% of 5-HMF yield with 96.1% fructose conversion rate is achieved after reacting at 130°C for 20 min, indicating that SCHOP-500 is a highly effective and efficient solid acid catalyst.

Homogeneous synthesis and characterization of sulfonated polyarylethersulfones having low degree of sulfonation and highly hydrophilic behavior

In the present paper, the wettability of polyarylethersulfones (PESs) was promoted through the controlled introduction of sulfonic groups in PES polymeric chain. Homogeneous synthesis using a sulfonated comonomer introduced sulfonic groups while exerting a tight control over the degree of sulfonation (DS) and avoiding the undesired side reactions brought about by heterogeneous sulfonation reactions. A series of sulfonated polyarylethersulfones (SPESs) with very low amounts of sulfonic groups - 0.5, 0.75, and 1 meq SO 3 -* g-1 of polymer - was synthesized via polycondensation using 4,4’-difluorodiphenylsulfone, 4,4’-dihydroxydiphenyl and a sulfonated comonomer, 2,5-dihydroxybenzene-1-sulfonate potassium salt. The presence of sulfonic groups was confirmed by Fourier transform infrared (FTIR) spectra; the macromolecular structure and the real DS of SPESs were determined by 1H NMR; the molecular weights were investigated by size exclusion chromatography (SEC); ion exchange capacity (IEC) values, measured by potentiometric titration, are in good agreement with the experimental DS. The polyelectrolyte effect was studied on intrinsic viscosity (IV) measurements. The effect of DS on the thermal properties of SPES membranes was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC); wetting properties were characterized by static water contact angle (SWCA) measurements on membranes obtained via solution casting. The results showed that an increased DS results in higher glass transition temperatures (T g ) and lower water contact angles, the latter dropping from $$\overline {91} ^\circ $$ to $$\overline {43} ^\circ $$ as DS was raised from 0 to 1.0 meq SO 3 -* g-1. This work demonstrates that homogeneous synthesis of SPES is an efficient way to prepare SPES membranes with tightly controlled DS and enhanced hydrophilic properties, in particular, an excellent hydrophilic SWCA even at very low amounts of sulfonic moieties.