Sulfonic Acid Functionality Research Articles

Precision Sulfonic Acid Polyolefins via Heterogenous to Homogenous Deprotection

AbstractPolyolefins containing precisely spaced sulfonic acid functionality are made. First, precision ethyl sulfonate ester diene monomers are synthesized, which then are converted to acyclic diene metathesis polymers using Grubbs' catalysis. Subsequently, the poly(ethyl sulfonate esters) are deprotected post‐polymerization via two successful routes, both using a concept of “heterogenous to homogenous deprotection.” The resulting poly(sodium sulfonate) salts are then converted to precise poly(sulfonic acids), where the sulfonic acid functionality is placed either at every ninth or 21st carbon. For comparison, random versions of poly(sulfonates), their salts, and sulfonic acid polymers are synthesized via copolymerization of the “9” sulfonate monomer with 1,9‐decadiene. Precision placement of sulfonic acid functionality could lead to materials of potential utility.

A novel polysulfone-based ternary nanocomposite membrane consisting of metal-organic framework and silica nanoparticles: As proton exchange membrane for polymer electrolyte fuel cells

Abstract In this study, the preparation and characterization of a new ternary nanocomposite polymer electrolyte membrane containing sulfonated PSU, MOF and silica nanoparticles were investigated as a polymer electrolyte membrane. The encapsulation of imidazole in NH2MIL-53(Al) and sulfonic acid functionalization of silica have been developed to produce proton-conducting nanoparticles. In addition, photografting polymerization of AMPS from PSU and sulfonation of PSU backbone was designed to prepare PSU chains bearing sulfonic acid groups. The embedding of MOF/Si nanoparticles resulted in significant improvement of the mechanical and thermal properties of the prepared membranes. According to the result of proton conductivity, proton transport of the prepared nanocomposite membrane increases to 17 mS cm−1 by adding only 5% of sulfonic acid functionalized silica and imidazole-encapsulated MOF nanoparticles (at 70 °C). Also, this nanocomposite membrane showed a power density as high as 40.80 mW cm−2 at peak current density of 100.30 mA cm−2. The thermal and mechanical properties of these nanocomposite membranes were also studied.

PMO-Immobilized AuI -NHC Complexes: Heterogeneous Catalysts for Sustainable Processes.

A stable periodic mesoporous organosilica (PMO) with accessible sulfonic acid functionalities is prepared via a one-pot-synthesis and is used as solid support for highly active catalysts, consisting of gold(I)-N-heterocyclic carbene (NHC) complexes. The gold complexes are successfully immobilized on the nanoporous hybrid material via a straightforward acid-base reaction with the corresponding [Au(OH)(NHC)] synthon. This catalyst design strategy results in a boomerang-type catalyst, allowing the active species to detach from the surface to perform the catalysis and then to recombine with the solid after all the starting material is consumed. This boomerang behavior is assessed in the hydration of alkynes. The tested catalysts were found to be active in the latter reaction, and after an acidic work-up, the IPr*-based gold catalyst can be recovered and then reused several times without any loss in efficiency.

Sulfonic Acid Functionalization of Different Zeolites and Their Use as Catalysts in the Microwave-Assisted Etherification of Glycerol with tert-Butyl Alcohol.

The etherification of glycerol with tert-butyl alcohol in the liquid phase, over different sulfonic acid functionalized zeolites, has been studied. The reaction was carried out using microwaves as a way of heating, measured at autogenous pressure and without any solvent. Dealuminated HY and HZSM-5 zeolites by acid treatment were functionalized with two different organosilica precursors: 3-mercaptopropyltrimethoxysilane (M), which incorporates thiol groups, and 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane (C), which incorporates the sulfonic acid groups directly. The thiol groups were oxidized into sulfonic groups employing hydrogen peroxide. The textural and structural properties of the solids were studied by XRD and N2 adsorption–desorption isotherms, whereas the incorporation of the organosilica in the zeolites was studied by TGA and XPS. The novelty functionalization of M gave rise to solids with the highest acidity, and exhibited the highest yields with more substituted ethers (Yh-GTBE = 13%), at 75 °C and 15 min of reaction time. In addition to the acidity, the textural properties of the zeolites played an important role in their activity; HY, with the largest size of the channels, were more active than the HZSM-5.

Production of furan based biofuel with an environmental benign carbon catalyst

A sulfonated carbon material was developed and investigated as an environmentally benign catalyst for furfural production. The sulfonic acid functionality was introduced by sequential hydrothermal carbonization and sulfonation of xylose. The morphology and textural properties were examined by scanning electron microscopy and N2 sorption measurements, respectively. The presence of sulfonic acid on the surface was proven by both Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy analysis. Meanwhile, the acid properties were studied using an NH3‐TPD profile. Two different sulfonated carbons that was activated with KOH before sulfonation and one that was compared. The KOH‐activated sulfonated carbon contained both a porous structure and a high sulfonic acid content that improved the furfural yield and selectivity by more than 50% compared to the nonactivated sulfonated carbon. The reusability of the catalyst was investigated by monitoring the furfural selectivity over several reaction cycles, and after the 3rd cycle, a reduction in the selectivity from 72 to 30% was observed. However, the acid‐functionalized carbon could still be useful for furfural production due to its low environmental impact in both the preparation and disposal steps. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1455–1461, 2018

Novel Corrosion Inhibitor Pigments Based on Benzotriazolium Cation Exchanged Resin

A novel corrosion-inhibitor pigment is described which is prepared by the reaction of benzotriazole (BTA) with a crosslinked polystyrene sulfonic acid resin (Amberlite 120H). This pigment is completely insoluble in water and may readily be ground to sub-micron particle size. The formation reaction relies on the resin sulfonic acid functions (pKa -2.8) being significantly more acidic than BTA (pKa 1.1) so that proton transfer produces the benzotriazolium cation ( BTAH+) in an exchangeable form. The kinetics of BTA uptake from aqueous solution at 60oC are followed spectrophotometrically. It is thus shown that uptake is rapid (complete in minutes) and results in a BTAH+ exchange capacity of 143 milli-equivalents per100g. The BTAH+ pigment is evaluated as a corrosion inhibitor by dispersion in an ethanolic solution of polyvinylbutyral (PVB) which is then coated onto the cleaned surface of zinc-coated (hot dip galvanized) steel to produce a dry film thickness of ca. 30 microns. The BTAH+ pigmented PVB coatings thus prepared had BTAH+ pigment volume fractions of between zero and 0.2. A corrosive electrolyte solution (5% w/w aqueous NaCl) was introduced into a penetrative defect in the organic coating and the subsequent process corrosion-driven cathodic coating disbondment was followed using a scanning Kelvin probe (SKP) instrument in a “Stratmann type”experiment at 96% R.H. The SKP data show that increasing BTAH+ pigment volume fraction produces two well defined effects. First the potential of the intact (undisbonded) coated surface becomes depressed by up to 0.3 V versus the unpigmented case. Second the kinetics of cathodic disbondment are profoundly inhibited, becoming immeasurably slow for pigment volume fractions greater than 0.1. These results are interpreted in terms of two phenomena. First the “etching” of the zinc surface by the acidic resin with a consequent release of Zn2+ cations and neutral BTA. Second the inhibition of underfilm cathodic O2 reduction(COR) by surface adsorbed BTA or BTA-zinc complex. The inhibition of COR by BTA in solution is systematically investigated using a zinc rotating disk electrode (RDE) in conjunction with potentiodynamic polarization. The polarization data show that, although BTA profoundly inhibits COR on zinc, BTA is actually a mixed inhibitor and inhibits both anodic zinc dissolution and the COR.

Surface-anchored counterions on weak chiral anion-exchangers accelerate separations and improve their compatibility for mass-spectrometry-hyphenation

In the present work we propose new variants of chiral stationary phases (CSP) with tert-butylcarbamoylquinine (tBuCQN) as chiral selector molecule. Four tBuCQN-CSPs with distinct bonding chemistries are compared in terms of their pH-dependent surface charge by ζ-potential determinations, by achiral and chiral liquid chromatographic tests and LC–ESI–MS hyphenation. In one embodiment tBuCQN was immobilized on 3-mercaptopropylmethylsilyl-modified silica by thiol-ene click reaction (brush type CSP with selector coverage of 0.38mmol/g). In another embodiment, poly-(3-mercaptopropyl)-methylsiloxane was coated onto vinylized silica particles in presence of tBuCQN and radical initiator. The tBuCQN selector was then immobilized onto the polysiloxane film which in turn was crosslinked to the vinyl-surface in a simultaneous double click reaction leading to a CSP with enhanced stability due to multiple linkages (0.29mmol/g tBuCQN). Aliquots of each of the two CSPs were further modified by oxidation of free residual thiol groups to sulfonic acid functionalities to obtain strongly acidic endcapping groups which act as immobilized counterions of the chiral WAX CSPs (0.2mmol/g sulfonic acid co-ligands for brush type CSP). This caused secondary repulsive interactions, hence balanced interactions of the target analytes (chiral acids) at the WAX site and decreased non-specific interactions. Furthermore, this rendered possible the use of milder elution conditions, i.e. lower ionic strength, for acidic compounds. Separation performance was maintained and slightly improved, respectively, when using polar organic or reversed-phase type elution mode in chiral separations which were significantly accelerated (isoeluotropic conditions could be achieved with ca. factor 40 lower counterion concentration in the mobile phase). Thus, LC–ESI–MS enantiomer separations could be readily performed at very low ionic strength conditions (10mM acetate) which is favorable due to less ion suppression. In addition to this the newly developed stationary phases showed complementary retention profiles in RP- and HILIC-mode which make these type of stationary phases also promising tools for achiral applications in pharmaceutical analysis, especially as orthogonal separation principle e.g. in 2D-LC and impurity profiling.

Expeditious Synthesis of Dianionic-Headed 4-Sulfoalkanoic Acid Surfactants.

4-Sulfoalkanoic acids are a class of important dianionic-headed surfactants. Various 4-sulfoalkanoic acids with straight C8, C10, C12, C14, C16, and C18 chains were synthesized expeditiously through the radical addition of methyl 2-((ethoxycarbonothioyl)thio)acetate to linear terminal olefins and subsequent oxidation with peroxyformic acid. This is a useful and convenient strategy for the synthesis of dianionic-headed surfactants with a carboxylic acid and sulfonic acid functionalities in the head group region.

Highly porous polytriazole ion exchange membranes cast from solutions in non-toxic cosolvents

The development of highly functionalized porous materials for protein separation is important for biotech processes. We report the preparation of highly porous polytriazole with sulfonic acid functionalization. The resulting ion exchange membranes are selective for protein adsorption. The starting material was a hydroxyl-functionalized polytriazole, which is an advantageous platform for further modification. The polymer was dissolved in a mixture of 1-ethyl-3-methylimidazolium acetate ([C2mim]OAc) and dimethyl carbonate (DMC), which can be both considered green solvents. The polymer solubilization was only possible due to an interesting effect of cosolvency, which is discussed, based in phase diagrams. Membranes were prepared by solution casting, followed by immersion in a non-solvent bath. We then grafted sulfone groups on the membranes, by reacting the hydroxyl groups with 1,3-propane sultone and 1,4-butane sultone. Lysozyme adsorption was successfully evaluated. Membranes modified with 1,4-butane sultone adsorbed more protein than those with 1,3-propane sultone.

Hierarchical Porous Interlocked Polymeric Microcapsules: Sulfonic Acid Functionalization as Acid Catalysts

Owing to their unique structural and surface properties, mesoporous microspheres are widely applied in the catalytic field. Generally, increasing the surface area of the specific active phase of the catalyst is a good method, which can achieve a higher catalytic activity through the fabrication of the corresponding catalytic microspheres with the smaller size and hollow structure. However, one of the major challenges in the use of hollow microspheres (microcapsules) as catalysts is their chemical and structural stability. Herein, the grape-like hypercrosslinked polystyrene hierarchical porous interlocked microcapsule (HPIM-HCL-PS) is fabricated by SiO2 colloidal crystals templates, whose structure is the combination of open mouthed structure, mesoporous nanostructure and interlocked architecture. Numerous microcapsules assembling together and forming the roughly grape-like microcapsule aggregates can enhance the structural stability and recyclability of these microcapsules. After undergoing the sulfonation, the sulfonated HPIM-HCL-PS is served as recyclable acid catalyst for condensation reaction between benzaldehyde and ethylene glycol (TOF = 793 h−1), moreover, exhibits superior activity, selectivity and recyclability.

Functionalized Metal-Organic Framework as a Biomimetic Heterogeneous Catalyst for Transfer Hydrogenation of Imines.

Mimicking a biocatalytic system has been one of the prevalent strategies for the design of novel and efficient chemical transformations. Among the enzyme-catalyzed reactions, the cooperative interplay of Lewis- and Brønsted-acidic functionalities at active sites represents a common feature in activating reactants. Employing MIL-101(Cr) as a biomimetic platform, we customize a sulfonic group (SO3H) into its hierarchical pores to generate a heterogeneous catalyst for transfer hydrogenation of imines by using Hantzsch ester as the reductant. Both aldimines and ketimines were efficiently converted to their hydrogenated counterparts in a manner similar to metal enzymes. The Cr3+ node and sulfonic acid functionality encapsulated in MOF cages worked cooperatively in promoting this transformation, resulting in an enhanced reactivity as compared to its homogeneous analogue. Furthermore, MIL-101(Cr)-SO3H could be recycled for many times without considerable loss in reactivity.

States of water in proton exchange membranes: Part A - Influence of chemical structure and composition

Disulfonated poly(arylene ether) and polyimide copolymers can phase separate to form nanoscale hydrophilic and hydrophobic domain morphology. Water in these domains has been assigned to three different states, tightly bound, loosely bound and free water. The states of water were characterized using DSC, NMR relaxation and TGA. The chemical structures of the proton exchange membranes were varied in chemical composition, microstructure (random and block) and also regarding functional sulfonic acid groups fixed to the polymer backbones. A strong dependence of the types of water on the ion content and morphology was observed. For the random copolymers, the formation of free water in the system occurs after reaching a certain ion content. For the multi-blocks, in addition to the ion content, free water also develops with increasing block lengths. The formation of continuous morphology in the copolymers was correlated to the onset of free water. Influences of the states of water on PEM transport properties will be reported separately.

Optimizing side chains for crystal growth from water: a case study of aromatic amide foldamers.

The growth of crystals of aromatic compounds from water much depends on the nature of the water solubilizing functions that they carry. Rationalizing crystallization from water, and structure elucidation, of aromatic molecular and supramolecular systems is of general value across various fields of chemistry. Taking helical aromatic foldamers as a test case, we have validated several short polar side chains as efficient substituents to provide both solubility in, and crystal growth ability from, water. New 8-amino-2-quinolinecarboxylic acids bearing charged or neutral aminomethyl, carboxymethyl, sulfonic acid, or bis(hydroxymethyl)-methoxy side chains in position 4 or 5, were prepared on a multi gram scale. Fmoc protection of the main chain amine and suitable protections of the side chains ensured compatibility with solid phase synthesis. One tetrameric and five octameric oligoamides displaying these side chains were synthesized and shown to be soluble in water. In all cases but one, crystals were obtained using the hanging drop method, thus validating the initial design principle to combine polarity and rigidity. The only case that resisted crystallization appeared to be due to exceedingly high water solubility endowed by eight sulfonic acid functions. The neutral side chain did provide crystal growth ability from water but contributed poorly to solubility.

Magnetic nanoparticles functionalized ethane sulfonic acid (MNESA): as an efficient catalyst in the synthesis of coumarin derivatives using Pechmann condensation under mild condition

This paper reports an efficient heterogeneous catalyst based on sulfonic acid functionalization of magnetic nanoparticles. This new catalyst was prepared using the reaction between magnetic nanoparticles and sodium 2-bromoethane-1-sulfonate. Magnetic nanoparticles functionalized ethane sulfonic acid (MNESA) was found as efficient catalyst for the synthesis of coumarin derivatives using Pechmann condensation under mild condition. This reaction was catalyzed by MNESA under solvent-free condition at 90 °C, to give the corresponding products in excellent yields. The catalyst is easily separated from the reaction condition and can be reused for several times with consistence in the activity.

Catalytic etherification of glycerol to tert-butyl glycerol ethers using tert-butanol over sulfonic acid functionalized mesoporous polymer

Mesoporous polymers (MP) were synthesized by free radical polymerization of divinylbenzene by a solvothermal method followed by sulfonic acid functionalization by a post synthetic modification with conc.

Immobilized transition metal-based radical scavengers and their effect on durability of Aquivion® perfluorosulfonic acid membranes

A simple and broadly applicable preparation procedure to obtain silica-supported transition metal (namely Cr, Co and Mn)-based radical scavengers, containing sulfonic acid functionalities, is reported. These systems are widely characterised in terms of structure, bulk and surface composition and morphology by X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), X-Ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The scavenger material is loaded in ePTFE reinforced membranes prepared from Aquivion® perfluorosulfonic acid (PFSA) dispersions. All these composite membranes show longer lifetime in Accelerated Stress Tests (AST) and reduced fluoride release in Fenton's tests than the scavenger-free membranes without any loss in electrochemical performance. The Cr-scavenger-based polymer electrolyte shows a three-time larger stability than the pristine membrane.

PVDF-HFP/silica-SH nanocomposite synthesis for PEMFC membranes through simultaneous one-step sol–gel reaction and reactive extrusion

In this study, synthesis of thiol-functionalized silica/PVDF-HFP [poly(vinylidene fluoride-hexafluoropropylene)] nanocomposite materials was carried out by reactive extrusion through in situ sol–gel reactions of an alkoxysilane inorganic precursor solution composed of polydimethoxysiloxane (PDMOS) and mercaptopropyltriethoxysilane (MPTES). Successful introduction of the functional MPTES and structural PDMOS alkoxysilanes, and subsequent condensation reactions in the PVDF-HFP, were obtained through pre-hydrolysis reactions of the precursors. 29Si-Nuclear magnetic resonance was used to assess the hydrolysis level of the inorganic precursor solution and condensation state in the resulting PVDF-HFP/functionalized silica nanocomposites, while the morphology was observed using scanning electron microscopy (SEM). The hydrolysis-condensation reactions resulting in the inorganic phase were optimized by setting an appropriate R0 molar ratio (H2O/alkoxy function), R1 molar ratio (MPTES/PDMOS) and pH of the solution. Increasing the R0 ratio barely affected the hydrolysis kinetics. However, a higher R1 ratio led to a decrease in the inorganic precursors condensation state and consequently to an increase in the reaction time in the extruder to reach the subsequent condensation state. Hence the morphology of the obtained nanocomposites was finer for the highest R1 ratio and in agreement with the evolution of the solubility parameters. Promising ionic exchange capacity (IEC) and conductivity values were obtained for these innovative nanocomposite materials thanks to a controlled oxidation reaction of the thiol groups into sulfonic acid functions. This original approach demonstrated the possibility of incorporating in situ functionalized silica into a molten fluorinated polymer matrix in a unique reactive extrusion procedure.

Preparation and Characterization of Sulfonic Acid Functionalized Silica and Its Application for the Esterification of Ethanol and Maleic Acid

The surface of commercially available silica gel, 60–200 mesh size, was modified with sulfonic acid through surface activation, grafting of 3-Mercaptopropyltrimethoxysilane, oxidation and acidification of 3-Mercaptopropylsilica. Sulfonic Acid Functionalization of Silica (SAFS) was confirmed by Fourier Transform Infra-red (FTIR) spectroscopy and thermal gravimetric analysis. Acid–base titration was used to estimate the cation exchange capacity of the SAFS. Catalytic activity of SAFS was judged for the esterification of ethanol with maleic acid. An effect of different process parameters viz. molar ratio, catalyst loading, speed of agitation and temperature were studied and optimized by Box Behnken Design (BBD) of Response Surface Methodology (RSM). Quadratic model developed by BBD–RSM reasonably satisfied an experimental and predicted values with correlation coefficient value R2 = 0.9504.

Hypercrosslinked organic polymer based carbonaceous catalytic materials: Sulfonic acid functionality and nano-confinement effect

Porous hypercrosslinked polymers (HCPs) based novel metal-free heterogeneous solid acid catalysts were synthesized via Friedel–Crafts alkylation by self-condensation of bischloromethyl monomers such as α,α′-dichloro-p-xylene and 4,4′-bis(chloromethyl)-1,1′-biphenyl, followed by post-sulfonation process to generate acidic sites. The obtained HCP-based solid acids possessed large amounts of acidic sites homogeneous dispersed over the large surface area of more than 1000m2g−1, and narrow dispersed pores mostly centered at about 2nm, the junction region of micro and mesopores. Assessed in Friedel–Crafts alkylation and Beckmann rearrangement reactions, the obtained HCP-based porous solid acid catalysts demonstrated superior performance and special nano-confinement effect in the reactions. These were due to their acidic property and unique pore structure, thus providing an efficient metal-free carbonaceous catalyst for eco-friendly “carbocatalysis” process and some clues to prepare multi-functional catalysts from HCP-based materials.

32.Sulfonic acid functionalization of 2-aminoterephthalate metal−organic framework and silica nanoparticles by surface initiated radical polymerization: as proton-conducting solid electrolytes

A post-polymerization method for metal–organic frameworks (MOFs) and silica nanoparticles have been developed to produce super-acidic solid nanoparticle. Thus, silica and amino-functionalized metal−organic framework [NH2-MIL-101(Al)] were functionalized with 4.4′-Azobis(4-cyanovaleric acid) (ACVA) from hydroxyl and amine groups to yield initiator anchored silica and MOF nanoparticles. Then, sulfonated polymer/MOF and sulfonated polymer/silica hybrid nanoparticles were prepared by free radical polymerization of 2-acrylamido-2-methyl-1-propane sulfonic acid [(MOF-g-PAMPS) and (Si-g-PAMPS)], initiated onto the surfaces of initiator functionalized nanoparticles. Synthesis and modification of nanoparticles were characterized by fourier transform infrared (FTIR), thermogravimetric analysis (TGA). Also, the attachment of ACVA modifier agent on the surface of silica nanoparticles was studied using X-ray photoelectron spectroscopy (XPS). FTIR and TGA results indicated that AMPS monomer was successfully grafted onto the MOF and silica nanoparticles. The grafting efficiency of PAMPS polymer onto the silica and MOF nanoparticles were estimated from TGA thermograms to be 17 and 35 % for silica and MOF nanoparticles, respectively. Morphology of MOF and silica nanoparticles before and after modification processes were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively.