High Degree Of Sulfonation Research Articles

In-situ molecular-level hybridization enabling high-sulfonation-degree sulfonated poly(ether ether ketone) membrane with excellent anti-swelling ability and proton conduction

Sulfonated poly(ether ether ketone) (SPEEK) membrane with high sulfonation degree (SD) is a promising substitute of Nafion as proton exchange membrane (PEM), due to the excellent proton conductivity and low cost. However, its widespread application is limited by the inferior structural stability. Here, we report the fabrication of high SD SPEEK membrane with outstanding structural stability through an in-situ molecular-level hybridization method. Concretely, the ionic nanophase of SPEEK membrane is filled with precursors, which are then in-situ converted into polymer quantum dots (PQDs) by a microwave-assisted polycondensation process. In this manner, the micro-phase separation structure of SPEEK membrane is well maintained. PQDs with abundant hydrophilic functional groups together with the inherent –SO3H groups impart hybrid membrane highly enhanced proton conductivity of 138.2 mS cm−1 at 80 °C, which is comparable to Nafion. This then offers a 116.3% enhancement in device output power. Meanwhile, PQDs act as cross-linkers via generated electrostatic interactions with SPEEK, affording hybrid membrane with SD of 94.1% an ultralow swelling ratio of 1.35% at 25 °C, about 35 times lower than control membrane. More importantly, the in-situ molecular-level hybridization method is versatile, which can also boost the performances of chitosan (CS)-based membranes.

Adsorption of N-heterocyclic compounds from aqueous solutions by sulfonic acid-functionalized hypercrosslinked resins in batch experiments

N-heterocyclic compounds (NHCs) in industrial wastewater, such as pyridine, have potential toxicity to organisms and are difficult to biodegrade, causing great harm to the environment and human health. In this work, four sulfonic acid-functionalized resins (30-R, 40-R, 60-R and 70-R) with different sulfonation degree were prepared on the basis of the conventional hypercrosslinked resin by controlling the reaction temperature with concentrated sulfuric acid. The batch experiments showed that the adsorption capacities of pyridine on the sulfonic resins are pH-dependent, and the optimum pH increases with the increase of sulfonation degree. The adsorption of pyridine on the resin was monolayer, and the maximum adsorption capacity fitted by Langmuir model was positively correlated with sulfonation degree. The fitting results of Weber-Morris model showed that high sulfonation degree meant high intraparticle diffusion rate. The driving forces of adsorption included electrostatic attraction, π-π conjugation and hydrophobic interaction. Although the electrostatic attraction, which played the most important role, significantly improved the adsorption capacity of the sulfonic resin, it weakened the effect of the other two. This phenomenon was caused by the introduction of sulfonic groups significantly promoted the adsorption performance of the resin for single-ring NHCs, but that for fused-ring NHCs with π-electron-rich regions and strong hydrophobicity was unremarkable, or even decreased. Under the synergism of the three driving forces, sulfonic acid-functionalized hypercrosslinked resin exhibited superior adsorption performance for NHCs with easy protonation, high π-electron cloud density and strong hydrophobicity.

Synthesis, characterization, and assessment of novel sulfonated polynorbornene dicarboximides as adsorbents for the removal of heavy metals from water.

The occurrence of heavy metals in the natural aquatic systems arising from anthropogenic sources is an issue of global and environmental concern because of their extremely harmful effects to living beings even in rather low concentrations. The synthesis and ring-opening metathesis polymerization (ROMP) of novel norbornene dicarboximides bearing highly aromatic pendant groups, specifically, N-4-tritylphenyl-norbornene-5,6-dicarboximide (2a) and N-2,4,6-(triphenyl)phenyl-norbornene-5,6-dicarboximide (2b), their hydrogenation and further polymer sulfonation to render them adsorbents for the uptake of heavy metal ions from water is reported in this study. The macromolecules were characterized by means of FT-IR, 1H NMR, and thermal analysis, among others. A thoroughly kinetic and isothermal study of adsorption in single and ternary aqueous solutions of Pb2+, Cd2+, and Ni2+ was performed considering several experimental variables for instance initial metal concentration, contact time and solution pH. In general, the experimental data were adjusted more efficiently to the pseudo-second order kinetic model and to the Freundlich isotherm model, respectively. The maximum removal amounts were found to be 55.7 mg/g for Pb2+, 33.9 mg/g for Cd2+, and 10.2 mg/g for Ni2+ in the sulfonated trityl-bearing polymer 5a while those found for the sulfonated triphenyl-bearing polymer 5b were 31.5 mg/g for Pb2+, 26.6 mg/g for Cd2+, and 7.0 mg/g for Ni2+, respectively. The higher heavy metal removal capacity of polymer 5a was attributed to its also higher degree of sulfonation. The outcomes indicate that these novel sulfonic acid containing polymer-based adsorbents are effective for the uptake of heavy metallic elements from water.

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.

NH2-UiO-66 coated fibers to balance the excellent proton conduction efficiency and significant dimensional stability of proton exchange membrane

The proton exchange membrane (PEM) with high sulfonation degree (DS) exhibits high proton conductivity but poor dimensional stability and mechanical properties. In order to improve dimensional stability and strength of PEM as well as maintaining excellent proton conductivity, we proposed to modify pre-oxidized polyacrylonitrile nanofibers (PPNF) through amino functionalization with NH2-UiO-66 (NU6). Compared with primary sulfonated poly (ether ether ketone) (SPEEK), the dimensional stability of 1.3% NU6 @PPNF-SPEEK composite membrane increase 30% due to the chemical crosslinking structure of PPNF. The acid-enriched layers, which provide an efficient proton transport channel, form along the fibers because of interaction between NU6 and -SO3H, since then composite membranes exhibit higher proton conductivity. Most importantly, this study firstly revealed the mechanism of formation process of sulfuric acid-rich layer through FTIR and EDS, which could provide a strategy for constructing and adjusting the proton transport channel efficiently. In summary, NU6@PPNF-SPEEK with excellent proton conductivity, outstanding dimensional stability and great mechanical properties in hydrated condition has been successfully fabricated.

Role of Doping Agent Degree of Sulfonation and Casting Solvent on the Electrical Conductivity and Morphology of PEDOT:SPAES Thin Films.

Poly(3,4-ethylenedioxythiophene) (PEDOT) plays a key role in the field of electrically conducting materials, despite its poor solubility and processability. Various molecules and polymers carrying sulfonic groups can be used to enhance PEDOT’s electrical conductivity. Among all, sulfonated polyarylether sulfone (SPAES), prepared via homogenous synthesis with controlled degree of sulfonation (DS), is a very promising PEDOT doping agent. In this work, PEDOT was synthesized via high-concentration solvent-based emulsion polymerization using 1% w/w of SPAES with different DS as dopant. It was found that the PEDOT:SPAESs obtained have improved solubility in the chosen reaction solvents, i.e., N, N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone and, for the first time, the role of doping agent, DS and polymerization solvents were investigated analyzing the electrical properties of SPAESs and PEDOT:SPAES samples and studying the different morphology of PEDOT-based thin films. High DS of SPAES, i.e., 2.4 meq R-SO3− g−1 of polymer, proved crucial in enhancing PEDOT’s electrical conductivity. Furthermore, the DMSO capability to favor PEDOT and SPAES chains rearrangement and interaction results in the formation of a polymer film with more homogenous morphology and higher conductivity than the ones prepared from DMAc, DMF, and NMP.

Performance of the sulfonated poly ether ether ketone proton exchange membrane modified with sulfonated polystyrene and phosphotungstic acid for microbial fuel cell applications

AbstractIn this research, the preparation of low cost proton exchange membranes (PEMs) based on sulfonated poly ether ether ketone (SPEEK) for application in the microbial fuel cells (MFCs) is studied. Sulfonated polystyrene (SPS) and phosphotungstic acid (PWA) were employed to improve the performance of PEM through the creation of more proton pathways. At first, the sulfonation of PEEK and polystyrene were performed through two modified methods to obtain uniform and high degree of sulfonation (DS) of the polymers and then, the PEMs were prepared through the solution casting method. Accordingly, the formation of uniform skin layer was confirmed by the SEM micrographs. Blending the aforementioned additives to the SPEEK polymer solution significantly enhanced the proton conductivity, water uptake and durability of the modified membranes. The proton conductivities of SPEEK/SPS and SPEEK/PWA membranes at additive/SPEEK weight ratio of 0.15 were 45.3% and 26.2% higher than that of the commercial Nafion117 membrane, respectively. Moreover, the degradation times for the abovementioned modified membranes were 140 and 350 min which indicated satisfactory oxidation stability. Besides, the aforementioned membranes exhibited two times more water uptake compared to the neat SPEEK membrane. Finally, SPEEK/SPS and SPEEK/PWA membranes produced 68% and 36% higher maximum power in the MFC, compared to the commercial Nafion117 membrane. Therefore, the fabricated PEMs are potentially suitable alternatives to be used in the fuel cell applications.

Preparation, structures and properties of Phosphate/S-PEEK hybrid composites utilized sintering Al(OH)3 particles as curing agents

In order to improve interface effect, PEEK was successfully modified by a direct sulfonation method. As a result, PEEK ultilized 80 wt% H2SO4 solution as sulfonation would display much higher degree of sulfonation, which was increased with the reaction time. Al2O3 particles with different crystal forms were prepared by sintering Al(OH)3 particles as curing agents for phosphates. The influence of sintering temperature on structures of Al2O3 particles was evaluated by XRD and shear strength testing. Furthermore, Al2O3-phosphate/sulfonated PEEK (S-PEEK) hybrid composites were prepared by ultrasonic dispersion and molding at 360 °C. Mechanical properties were also measured by the shear, flexural and compressive strength testing. The phosphate ultilized α-Al2O3 particles as the curing agent could perform much better mechanical properties. In paticular, the compressive strength of α-Al2O3 phosphate/S-PEEK hybrid composites would reach 334.58 MPa. These composites would have many potential applications in aerospace, mechanics and medicines.

Characterization of Sulfonylated Poly(styrene) Based Proton Exchange Membranes for Fuel Cells

The change from an energy industry based on fossil fuels to an energy industry based on renewable energy sources is a global challenge. For this reason, dynamic storage systems are needed to be developed for fluctuating wind and solar energy. Water electrolysis and fuel cells are important energy converters that offer the possibility of using hydrogen as an energy carrier. Generally, good thermal-oxidative stability and high proton conductivity are expected for membranes in fuel cells [1].As an alternative to perfluorosulfonic acid based membranes, hydro-carbon based proton exchange membranes may reduce stack costs. This assumption motivates us to synthesize and investigate polymer membranes whose proton conductor is cross-linked sulfonated sulfonylated poly(styrene) (ssPS). The advantage of ssPS in contrast to sulfonated polystyrene is the stability of the sulfonic acid group at temperatures around 100°C [2]. Disadvantages of ssPS are the water solubility at high degrees of sulfonation (ion exchange capacity of about 3,5 mmol/g) and poor film formation properties.According to this, the proton conductor must be cross-linked during synthesis and embedded in a nonpolar polymer matrix during the membrane production.Our investigations show that ssPS (non-cross-linked) has a similar thermal-oxidative stability as Nafion® (examined by thermal analysis/oxidative induced temperature (OIT)) [3]. The cross-linking of ssPS with divinylbenzene mixtures leads to a less good thermal-oxidative stability. Furthermore, our results show that the water uptake can be adjusted by varying the amount of cross-linker. In addition, the proton exchange membranes show conductivities in the range of Nafion® 117 at room temperature.The presentation will show the development of a new proton exchange membrane and its characterization. To discuss the membranes quality, the focus is on ion exchange capacity (stability at 90°C), thermal-oxidative stability (differential scanning calorimetry), water uptake and electrical resistance as a function of temperature up to 90°C.This work is supported by the Federal Ministry of Education and Research (BMBF).[1] J.A.Kerres, A.Katzfuß, A.Chromik, V.Atanasov, J. Appl. Polym. Sci. 2014 , 131 , 39889.[2] H.Widdecke, M.Dettmer, W.Reith, Patent DE4425216C2, 2003.[3] G.W.Ehrenstein, G.Riedel, P.Trawiel, Thermal analysis of plastics, Hanser Verlag, 2004.

End‐group cross‐linked membranes based on highly sulfonated poly(arylene ether sulfone) with vinyl functionalized graphene oxide as a cross‐linker and a filler for proton exchange membrane fuel cell application

AbstractHigh‐performance end‐group cross‐linked sulfonated poly(arylene ether sulfone) (SPAES) membranes are developed using thiolate‐terminated SPAES with very high degree of sulfonation (DS) such as 90 mol% (SK‐SPAES90) and vinyl functionalized graphene oxide (VGO) as a cross‐linker and a filler through the thiol‐Michael addition reaction. Since free‐standing membranes for fuel cell application could not be prepared using the water soluble and highly proton conductive SPAES with high DS of 90 mol%, cross‐linked SPAES90 membranes are intentionally prepared. The cross‐linked membranes are found to have good physicochemical properties with excellent proton conductivity that can be applied for the proton exchange membrane. In particular, the cross‐linked SPAES90 membrane prepared using 1.0 wt% of VGO exhibits better dimensional stability than a SPAES70 membrane from the linear SPAES with DS of 70 mol% and the proton conductivities of this membrane are larger than those of Nafion 211 at 80 °C under different relative humidity conditions (40%‐95%).

Investigation of thermo-mechanical behavior, proton transfer and methanol permeation of polymer electrolyte membrane in low sulfonated state modified with thermally stable surface functionalized graphene oxide nanosheets

Sulfonated polyether ether ketone is currently under investigation to replace the expensive Nafion® as polymer electrolyte membrane. Sulfonic acid group is hydrophilic in nature and plays a key role in proton transfer in polymer electrolyte membranes. The higher the degree of sulfonation the higher proton conductivity in sPEEK based polymer exchange membrane is achieved; however, high degree of sulfonation causes severe dimensional instability due to higher water uptake which in turn affects membrane fuel retention capabilities as well as thermo-mechanical strength. Graphene oxide nanosheets were functionalized with aryl dizonium salt of p-Aminobenzene sulfonic acid for modification of sPEEK in low sulfonated state (DS = 53%) to improve its proton conductivity and suppress fuel crossover. The functionalization was carried out to compensate for the possible dilution of proton exchangeable sites by fillers. The resulting membranes were characterized in terms of morphology, thermo-mechanical behavior, methanol permeability, water uptake, and proton conductivities. The results proved that sulfonated GO not only improved thermo-mechanical behavior of the membrane but also dramatically increased proton conductivity (47 mS cm−1) than pristine sPEEK (25 mS cm−1). The composite membranes showed highly reduced methanol crossover compared with pristine sPEEK. The electrochemical selectivity increased from 9.5 × 104 Scm−3s (pristine sPEEK) to 26.9 × 104 Scm−3s.

Hyperbranch-Crosslinked S-SEBS Block Copolymer Membranes for Desalination by Pervaporation.

Sulfonated aromatic polymer (SAP) featuring hydrophilic nanochannels for water transport is a promising membrane material for desalination. SAPs with a high sulfonation degree favor water transport but suffer from reduced mechanical strength and membrane swelling. In this work, a hyperbranched polyester, H302, was introduced to crosslink a sulfonated styrene-ethylene/butylene-styrene (S-SEBS) copolymer membrane. The effects of crosslinking temperature and amount of H302 on the microstructure, and the pervaporation desalination performance of the membrane, were investigated. H302/S-SEBS copolymer membranes with different crosslinking conditions were characterized by various techniques including FTIR, DSC, EA, SEM, TEM and SAXS, and tensile strength, water sorption and contact angle measurements. The results indicate that the introduction of hyperbranched polyester enlarged the hydrophilic microdomain of the S-SEBS membrane. Crosslinking with hyperbranched polyester with heat treatment effectively enhanced the mechanical strength of the S-SEBS membrane, with the tensile strength being increased by 140–200% and the swelling ratio reduced by 45–70%, while reasonable water flux was maintained. When treating 5 wt% hypersaline water at 65 °C, the optimized crosslinked membrane containing 15 wt% H302 and heated at 100 °C reached a water flux of 9.3 kg·m−2·h−1 and a salt rejection of 99.9%. The results indicate that the hyperbranched-S-SEBS membrane is promising for use in PV desalination.

Preparation and properties of sulfonated poly (2, 6-dimethyl-1, 4- phenylene oxide) / ionic liquid /phosphoric acid high temperature proton exchange composite membrane

ABSTRACT A SPPO/IL composite membrane was obtained by self-assembly using the SPPO with the highest degree of sulfonation and the prepared ionic liquid (1-methyl-3-methylimidazolium). SPPO/IL composite membrane is doped with phosphoric acid to form SPPO/IL/PA composite membrane. The SPPO/IL composite membrane is immersed in PA for 24 h, the ion conductivity reaches 36.1 mS/cm. The mechanical stability (350°C), swelling (area 2.26%, volume 2.58%), and oxidation stability (4.2 h) are all acceptable. SPPO/IL/PA composite membranes have application potential as HTPEM materials. A sulfonated poly(2,6-dimethyl-1,4-phenylene oxide)/ionic liquid (SPPO/IL) composite membrane was obtained by self-assembly using the SPPO with the highest degree of sulfonation and the prepared ionic liquid (1-methyl-3-methylimidazolium). SPPO/IL composite membrane is doped with phosphoric acid to form SPPO/IL/PA composite membrane.

Attapulgite solvent-free nanofluids modified SPEEK proton exchange membranes for direct methanol fuel cells

Sulfonated poly(ether ether ketone) (SPEEK) is currently considered to be one of the most potential candidates of commercial perfluorinated sulfonic acid proton exchange membranes. Although SPEEK with high sulfonation degree exhibits high proton conductivity, over high content of polar sulfonic groups will lead to over-swelling of membranes, which in turn result in degraded mechanical properties and alcohol resistance. Herein, to balance the overall performance of SPEEK, attapulgite solvent-free nanofluids (ATP-IL) with special flow behavior were prepared for the first time, and then a series of SPEEK/ATP-IL composite membranes were successfully fabricated and evaluated. The grafted organic long-chain ions on the surface of ATP can not only promote the dispersion of ATP in SPEEK matrix, but also endow ATP with proton conduction ability and thus form channel-like proton transport pathway in the composite with the aid of one-dimension shape of ATP. As a result, the composite membranes demonstrated simultaneously improved strength and toughness. Moreover, the maximum conductivity was 50.7 mS cm−1 for the composite membrane with 5 wt% of ATP-IL at 25 °C and 100% R.H., which was 40% higher than that of SPEEK membrane (only 36.4 mS cm−1).

Gaseous sulfur trioxide induced controllable sulfonation promoting biomineralization and osseointegration of polyetheretherketone implants

Fabricating a desired porous structure on the surface of biomedical polyetheretherketone (PEEK) implants for enhancing biological functions is crucial and difficult due to its inherent chemical inertness. In this study, a porous surface of PEEK implants was fabricated by controllable sulfonation using gaseous sulfur trioxide (SO3) for different time (5, 15, 30, 60 and 90 min). Micro-topological structure was generated on the surface of sulfonated PEEK implants preserving original mechanical properties. The protein absorption capacity and apatite forming ability was thus improved by the morphological and elemental change with higher degree of sulfonation. In combination of the appropriate micromorphology and bioactive sulfonate components, the cell adhesion, migration, proliferation and extracellular matrix secretion were obviously enhanced by the SPEEK-15 samples which were sulfonated for 15 min. Finding from this study revealed that controllable sulfonation by gaseous SO3 would be an extraordinarily strategy for improving osseointegration of PEEK implants by adjusting the microstructure and chemical composition while maintaining excellent mechanical properties.

Friedel-Crafts self-crosslinking of sulfonated poly(etheretherketone) composite proton exchange membrane doped with phosphotungstic acid and carbon-based nanomaterials for fuel cell applications

In this work, self-crosslinked sulfonated polyether etherketone membrane (C-SPEEK) was synthesized by Friedel-Crafts alkylation at 130 °C with chloromethylated sulfonated polyether etherketone (SPEEK-Cl). The water uptake (WU) of the C-SPEEK was 47.75% with a 8.69% swelling rate (SR) at 60 °C, compared with the sulfonated polyether etherketone membrane (SPEEK) with WU of 110.60% and SR of 57.99%. The contradiction between dimensional stability and proton conductivity under high sulfonation degree was overcome. The self-crosslinking composite membranes were prepared by doping with carbon nanomaterials (Graphite oxide, GO; reduced graphene oxide, rGO and carbon nanotubes, CNTs) and phosphotungstic acid (HPW). Since HPW and carbon nanomaterials incorporated in membrane facilitate protons conduction via both Grotthuss and Vehicle mechanisms, the hybrid membranes demonstrated the improved conductivities. At 80 °C, C-SPEEK/HPW/GO showed proton conductivity as high as 119.04 mS/cm, which was 2.4 folds higher than that of the C-SPEEK. Furthermore, the superior performance of C-SPEEK/HPW/GO was further validated through H2/O2 single cell test. The C-SPEEK/HPW/GO produced a higher power output of 876.80 mW/cm2, whereas only 776.72 mW/cm2 for C-SPEEK was recorded. Thus, C-SPEEK/HPW/GO and C-SPEEK may be promising membrane materials for potential applications in fuel cells.

Highly selective SPEEK/ENR blended polymer electrolyte membranes for direct methanol fuel cell

Sulfonated poly (ether ether ketone) (SPEEK) at higher degrees of sulfonation (DS) produced high proton conductivity, but it is impractical for DMFC application due to excessive swelling and severe methanol crossover. In this study, a novel blended membrane based on SPEEK at higher degrees of sulfonation (DS) of 80% and epoxidized natural rubber (ENR-50) are prepared at different mass ratio of SPEEK to ENR-50 (9.5:0.5, 9.0:1.0, 8.5:1.5, 8.0:2.0, and 7.5:2.5) via solution intercalation method. The influence of ENR-50 loading on the physical properties of SPEEK blends membranes was investigated and compared with the pristine SPEEK and Nafion117 membranes. The blended membranes were characterized by FTIR, which showed a successful chemical interaction between ENR-50 and SPEEK matrix. SEM images revealed a uniform dispersion of ENR-50 droplets in the polymer structure. The water uptake and methanol permeability of SPE50 membrane were found to be decreased with increasing of ENR-50 content. The highest proton conductivity of SPE50 membrane obtained was 47% higher than pure SPEEK, whereas the lowest permeability value obtained was 21 times lower than Nafion117 membrane. Consequently, incorporation of ENR-50 into SPEEK matrix has substantially enhanced the selectivity of the membrane by five folds. Apparently, this newly developed SPE blend membrane can be listed as one of the potential proton electrolyte membranes for the usage in DMFCs.

Preparation of Ascidian-Inspired Hydrogel Thin Films to Selectively Induce Vascular Endothelial Cell and Smooth Muscle Cell Growth.

Hydrogel thin films (HTFs), which have multiple functions including hemocompatibility and ability of enhancing growth of endothelia cells (ECs) while suppressing proliferation of smooth muscle cells (SMCs), have garnered intense scientific interest due to their potential applications in the field of blood-contact materials. In the present study, we developed stable, multifunctional HTFs containing multiple functional groups (-SO3Na, -COONa, -OH, and -NH2) by layer-by-layer (LbL) self-assembly of a modified sulfonated sodium alginate (SSA) and chitosan (CS), followed by ascidian-inspired post-cross-linking. The prepared HTFs with a 3D porous structure, as revealed by scanning electron microscopy (SEM), maintained outstanding long-term stability. The results of protein adsorption, platelet adhesion and activation, and clotting time confirmed that the hemocompatibility of the HTFs was significantly enhanced compared with the matrix. From the cytocompatibility test, the multiple functional groups at the HTF surface led to remarkable enhancement in human umbilical vein endothelial cell (HUVEC) growth and significant inhibition effects on human umbilical artery smooth muscle cell (HUASMC) proliferation. The ratio of HUVEC to HUASMC increased from 0.25 on the Ti surface to 2.87 on the surface of the HTF with the highest degree of sulfonation (DS). The improved blood compatibility was ascribed to the introduction of the multiple functional groups, and the strongly selective effects on vascular cells were attributed to the synergistic effect of the high degree of sulfonation and the existence of phenolic hydroxyl groups. The unique HTFs prepared in this study, demonstrating excellent hemocompatibility and high selectivity toward vascular cells, may help guide the design of cardiovascular biomaterials for endothelialization.

Preparation and Properties of Covalently Crosslinked Polybenzimidazole High Temperature Proton Exchange Membranes Doped with High Sulfonated Polyphosphazene

An insoluble sulfonated polyphosphazene (SPOP) with high degree of sulfonation is synthesized and used as the proton conductor in polybenzimidazole (PBI) high-temperature proton exchange membrane. Polyfunctional triglycidyl isocyanurate (TGIC) is used as covalent cross-linking agent to obtain a high proton conductivity at low cross-linking degrees. The composite membrane is characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). SPOP has good compatibility with mPBI-TGIC, leading to uniform dispersion in the obtained membranes with neither phase separation nor agglomeration. As a highly efficient cross-linking agent, TGIC not only makes the composite membrane have good mechanical properties, thermal stability, anti-swelling and anti-oxidation properties at low cross-linking degrees, but also leads to high doping amount of SPOP, thus making the composite the membrane have a high proton conductivity. The conductivity of mPBI-TGIC(5%)/SPOP(50%) at 100% RH, 50% RH and 0 RH is 0.143, 0.076 and 0.044 S cm−1 at 180 °C, respectively. In addition, the composite membranes has good methanol resistance and selectivity, so the composite membrane can be applied in the direct methanol fuel cell.

Synthesis and structural characterization of lignin/silica hybrid nanoparticles functionalized with sulfonic acid-terminated polyamidoamine

Lignin nanoparticles (LNPs) with an average diameter ($$\overline{d}_{n}$$) of 78.2 nm were prepared via rapid pH decrease of alkaline solution to acidic state. Two lignin/silica hybrid (LSH) nanoparticles, i.e., LSH1 ($$\overline{d}_{n}$$ = 80.9 nm) and LSH2 ($$\overline{d}_{n}$$ = 83.0 nm), with different lignin contents were synthesized using LNP via sol–gel method and then aminated using 3-aminopropyltriethoxysilane. Polyamidoamine (PAMAM) was then grafted onto the aminated LSHs, resulting in LSHx-PAMAM G1.0 (x = 1 or 2). Firstly, methyl acrylate was reacted with aminated LSHs. Then, methyl ester groups in the 0.5th generation were reacted with ethylenediamine (EDA), resulting in the LSHx-PAMAM G1.0. Structure and functional groups of the bio-based nanoparticles were characterized quantitatively using adequate techniques. In addition, LSH1-PAMAM G1.0 was kept for a long time in EDA (pH 13), so that the physically bonded LNP was dissolved and S-PAMAM G1.0 was obtained. LSH1-PAMAM G1.0 and S-PAMAM G1.0 were sulfonated using 1,3-propanesultone and a high degree of sulfonation, i.e., 99.93% and 99.34%, respectively, was obtained.