Radiation grafting of α,β,β-trifluorostyrene onto poly(ethylene–tetrafluoroethylene) film by preirradiation method. III. Properties of anion-exchange membrane obtained by chloromethylation and quaternization of the grafted film

A study was made of certain properties of the anion-exchange membranes obtained by the preirradiation grafting of α,β,β-trifluorostyrene (TFS) onto poly(ethylene–tetrafluoroethylene) (ETFE), followed by chloromethylation and quaternization of the grafted film. Swelling, water uptake, electric conductivity, and transport number of the membranes were measured as a function of ion-exchange capacity. Thermal and chemical stability were also investigated. These properties were found to be mainly dependent on ion-exchange capacity. The stable membrane properties were established due to a homogeneous ion-exchange group distribution in the membrane, as confirmed by X-ray microscopy analysis of the membrane cross sections. In addition, the membranes showed good electrochemical, thermal, and chemical properties, and were found to be acceptable for practical use as anion-exchange membranes.     

Radiation grafting of α,β,β-trifluoroethylenesulfonyl fluoride onto low-density polyethylene film by simultaneous irradiation method. I. Kinetic study of simultaneous-irradiation grafting

α,β,β-Trifluoroethylenesulfonyl fluoride (TFESF) was grafted onto polyethylene (PE) film by a simultaneous-irradiation method. The influences of the grafting conditions were analyzed kinetically. The dependencies of the grafting rate on the dose rates and monomer concentrations ranging from 10 to 75% were found to be of 1 and 0 order, respectively. The overall activation energy for the graft polymerization was 2.05 × 10⁴ J/mol. The grafting rate was found to be independent of the film thicknesses ranging from 25 to 100 μm.     

Correlation between structure and properties of cation-exchange membranes prepared by the paste method

By using cation-exchange membranes prepared by the paste method, a study was made of the influence of the distribution of polyvinyl chloride (PVC) on the electrical conductivity of the membranes and on the structure of the cation-exchange resin component (R-resin). Four kinds of cation-exchange membranes with different PVC contents and degrees of cross-linking were used. The experimental method involved treatment with hydrogen peroxide for selective decomposition of the R-resin. The estimated ratio of the specific electrical conductivity of the R-resin to that of the membrane varied from 2.2 to 4.4, depending upon the volume ratio of PVC in the membrane (0.33–0.45). Each of the membranes had a very high concentration of ion-exchange groups for cross-linking. This could be explained in terms of the mechanical and chemical restraint imposed by the PVC against the swelling of the R-resin. The structure of the R-resin, however, was almost independent of the PVC volume ratio over the range investigated.     

Radiation-induced copolymerization of α,β,β-trifluoroacrylonitrile with α-olefin

Homopolymerization and copolymerization of α,β,β-trifluoroacrylonitrile (FAN) with γ-olefins were carried out in bulk by γ-ray irradiation at 25°C. FAN gives very small quantities of brown and greasy low molecular weight polymer. Cyano groups in FAN polymer were found to be readily hydrolyzed to acid amide groups in the atmosphere. FAN was found to copolymerize with ethylene, propylene, and isobutylene via a radical mechanism to form equimolar copolymers in a wide range of monomer compositions. The polymerization rate increases linearly with FAN fraction in the monomer mixture. These copolymers are also hydrolyzed in the atmosphere, and the hydrolysis proceeds with more difficulty for the copolymer with higher α-olefin. The reactivity ratios r₁ (FAN) and r₂ (α-olefin) were determined to be 0.01 and 0.12 for the FAN/ethylene copolymerization and 0.01 and 0.07 for the FAN/propylene copolymerization. These results confirm that an alternating copolymerization takes place in the FAN/α-olefin system.     

Radiation grafting of α,β,β-trifluorostyrene onto poly(ethylene–tetrafluoroethylene) film by preirradiation method. I. Effects of preirradiation dose,monomer concentration,reaction temperature,and film thickness

Preirradiation grafting of α,β,β-trifluorostyrene onto poly(ethylene–tetrafluoroethylene) film was studied. The trapped radicals formed upon irradiation were able to induce graft polymerization under appropriate conditions. The influences of the grafting conditions were analyzed kinetically. The grafting rate dependency on the preirradiation dose was found to be of order 0.3, and the monomer concentrations, 1.0. The overall activation energies for this grafting were calculated to be 6.2 × 10⁴ and 9.3 × 10³ J/mol below and above 50°C. The grafting rate was found to be independent of the film thickness, which ranged from 25 to 100 μm.     

Ageing of ion-exchange membranes in oxidant solutions

In electrodialysis processes, membranes tend to loose some transport properties after a certain period of utilization. Two ion-exchange membranes, namely a homogeneous anion-exchange membrane (MX) and a heterogeneous cation-exchange membrane (MK-40), were used to investigate the ageing phenomenon and to highlight the characteristic parameters of these membranes which evolve most quickly with ageing. An artificial ageing was carried out under oxidizing conditions (i.e. peracetic acid, and P3 Active Oxonia^® solutions) on both membranes. It was found that an increase in conductivity and swelling rate, implying a modification of the polymer chain structure with time, but without a significant deterioration of the functional groups since the exchange capacity remained almost constant.     

Cr(VI) transport through ceramic ion-exchange membranes for treatment of industrial wastewaters

This work is devoted to assessment of the possibility of using ceramic membranes, which contain an ion-exchange component, such as hydrated zirconium dioxide (HZD), for Cr(VI) removal from dilute solutions by electrodialysis. Transport properties of the membranes were investigated. HZD-containing membranes were found to be permeable to anions in acidic media while they demonstrate cation-exchange properties in alkaline media. Cr(VI) anion transport through HZD membranes was studied. It was shown that an increase in the amount of ion-exchanger in the membrane results in a rise in electrodialysis efficiency. The transport number of Cr(VI) species was found to range from 0.33 to 0.63 for currents below the limiting current. It was also shown that increasing the concentration of H⁺ or Cr(VI) ions in the solution to be purified allows higher rate of Cr(VI) ion transport through the membrane.     

Cation exchange membranes by radiation‐induced graft copolymerization of styrene onto PFA copolymer films. II. Characterization of sulfonated graft copolymer membranes

PFA‐g‐polystyrene sulfonic acid membranes were prepared by simultaneous radiation‐induced graft copolymerization of styrene onto poly(tetrafluoroethylene‐co‐perfluorovinyl ether) (PFA) film followed by sulfonation. The membrane physico‐chemical properties such as swelling behavior, ion exchange capacity, hydration number, and ionic conductivity were studied as a function of the degree of grafting. Thermal as well as chemical stability of the membranes was also investigated. The membrane properties were found to be mainly dependent upon the degree of grafting. The water uptake, ion exchange capacity, hydration number, and ionic conductivity of the membranes were increased, whereas the chemical stability decreased as the degree of grafting increased. The membranes showed reasonable physico‐chemical properties compared to Nafion 117 membranes. However, their chemical stability has to be further improved to make them acceptable for practical use in electrochemical applications. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1–11, 2000     

Intermediates of Prostanoid Synthesis. Stereospecific conversion of (+)-5β-hydroxycyclopenten-2-yl-1β-acetic acid γ-lactone into (+)-1β-methoxycarbonylmethyl-2β,3β-(p-nitrobenzylidene)-dioxycyclopentan-5-one

Starting from (+)-5β-hydroxycyclopenten-2-yl-1β-acetic acid γ-lactone ( 1 ), (+)-1β-methoxycarbonylmethyl-2β, 3β-(p-nitrobenzylidene)-dioxycyclopentan-5-one ( 7 ) was prepared within 4 steps. Subsequent cleavage of the latter gives (−)-3β-hydroxy-1-methoxy-carbonylmethylcyclopent-1-en-5-one ( 8a ). Hydroxylation of the lactone ( 1 ) was found to give (+)-2β,3β,5β-trihydroxycyclopentyl-1β-acetic acid γ-lactone ( 2a ) with cis-oriented hydroxy groups in respect to the lactone ring. No formation of the trans-isomer, as has been reported earlier [4], was observed.     

Separation of bovine serum albumin (BSA) using γ‐Al2O3–clay composite ultrafiltration membrane

BACKGROUND: Ceramic membranes have received more attention than polymeric membranes for the separation and purification of bio‐products owing to their superior chemical, mechanical and thermal properties. Commercially available ceramic membranes are too expensive. This could be overcome by fabricating membranes using low‐cost raw materials. The aim of this work is to fabricate a low‐cost γ‐Al₂O₃–clay composite membrane and evaluate its potential for the separation of bovine serum albumin (BSA) as a function of pH, feed concentration and applied pressure. To achieve this, the membrane support is prepared using low‐cost clay mixtures instead of very expensive alumina, zirconia and titania materials. The cost of the membrane can be further reduced by preparing a γ‐alumina surface layer on the clay support using boehmite sol synthesized from inexpensive aluminium chloride instead of expensive aluminium alkoxide using a dip‐coating technique. RESULTS: The pore size distribution of the γ‐Al₂O₃‐clay composite membrane varied from 5.4–13.6 nm. The membrane was prepared using stable boehmite sol of narrow particle size distribution and mean particle size 30.9 nm. Scanning electron microscopy confirmed that the surface of the γ‐Al₂O₃–clay composite membrane is defect‐free. The pure water permeability of the support and the composite membrane were found to be 4.838 × 10^?6 and 2.357 × 10^?7 m³ m^?2 s^?1 kPa^?1, respectively. The maximum rejection of BSA protein was found to be 95%. It was observed that the separation performance of the membrane in terms of flux and rejection strongly depends on the electrostatic interaction between the protein and charged membrane. CONCLUSION: The successively prepared γ‐Al₂O₃‐clay composite membrane proved to possess good potential for the separation of BSA with high yield and could be employed as a low cost alternate to expensive ceramic membranes. Copyright © 2009 Society of Chemical Industry     

Concentration of Sodium Hydroxide Solutions by Electrodialysis

Several commercial ion-exchange membranes (FumaTech, DuPont) were tested in the electrodialytic oncentration of NaOH solutions in the range 1–5 M. It was found that the FumaTech cation-exchange membrane showed better performance than the bilayer Nafion membranes (DuPont) because of lower diluting effect caused by the electro-osmotic flow. However, neither of the tested membranes showed high enough efficiency for a practical application. The experimental results were modeled using the extended Nernst-Planck and Donnan equations. It was found that the derived model with two fitted parameters (effective fixed-charge concentration, tortuosity-porosity factor) satisfactorily describes the investigated process in the concentration range 1–4 M.     

Controlling the oxidation of organic brightener during electroplating using an ion-exchange membrane

The effect of an ion-exchange membrane combined with a dimensionally stable anode on the oxidation rate of organic brightener and electroplating performance was investigated. The oxidation rate of the brightener was measured by analyzing the total organic carbon content in the plating solution. The oxidation rate increased rapidly as the current density increased when there was no ion-exchange membrane. However, when an ion-exchange membrane was present, the oxidation rate of the brightener was significantly reduced by Neosepta CMX and CMS cation-exchange membranes. The CMS monovalent selective cation-exchange membrane in particular was the most effective in reducing organic brightener oxidation, regardless of the current density. Through-hole printed circuit board electroplating was more precise with an ion-exchange membrane than with no membrane. These results confirmed that the electroplating performance was improved by the presence of an ion-exchange membrane on the anode, effectively inhibiting the oxidation of organic brightener.     

β-Ketoester — a Rearranged Product of Epoxidation of α, β-Unsaturated Methyl Ester

Attempted epoxidation of long-chain α,β-unsaturated esters resulted in the formation of the rearranged products of the corresponding epoxyesters. It was observed that reaction of peracids with esters of C₁₆, C₁₈ and C₂₂ trans-2-enoic acids, instead of yielding the expected epoxides, gave the isomerized products characterized as β-ketoesters. The structure of β-ketoester as saturated 3-oxoester was unambiguously established by chemical methods as well as by IR, NMR and Mass spectrometry. The selectivity of this rearrangement provides a useful synthetic pathway for the preparation of β-ketoesters.     

Surface modification of polyethersulfone hollow-fiber membranes by γ-ray irradiation

The fouling of ultrafiltration membrane is often caused by gel formation on the membrane surface. This gel layer arises due to concentration polarization or macromolecular adsorption on the membrane surface. The gel layer affects both the hydraulic permeability and the rejection properties of the membrane. In this report, the adsorption of porcine albumin and the concentration polarization effect on modified and unmodified polyethersulfone (PES) hollow-fiber membrane is studied. PES ultrafiltration hollow-fiber membranes were modified by the grafting of polyethylene glycol (PEG) polymer on the internal surface using γ-ray irradiation method. The modified hollow fibers were less susceptible to fouling than were the unmodified fiber. The performance of both modified and unmodified hollow fibers was tested as a function of feed flow rates and protein concentrations. © 1994 John Wiley & Sons, Inc.     

Preparation and characterization of P2FAn/PVDF composite cation-exchange membranes for the removal of Cr(III) and Cu(II) by Donnan dialysis

In this work, poly(2-fluoroaniline) (P2FAn) was chemically synthesized with different dopant anions such as p-toluenesulfonate (PTS), 1,3 (6 or 7)-naphthalene trisulfonic acid (NSA), o-aminobenzen sulfonic acid (ABS), sodium dodecyl sulfate (SDS). The P2FAn/PVDF composite cation-exchange membranes were obtained from prepared poly(2-fluoroaniline) by casting method. These membranes were used for the removal of chromium (III) and copper (II) ions from aqueous solution with Donnan dialysis (DD) experiments. The change of surface morphologies of the P2FAn/PVDF composite cation-exchange membranes were investigated by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The membrane thickness and their ion-exchange capacities were also measured. The flux values (J) and recovery factor (RF) of chromium (III) and copper (II) were obtained. The flux value of Cu(II) ion was higher than Cr(III) for all of composite membranes because of the hydration volume.     

Removal of calcium and magnesium using polyaniline and derivatives modified PVDF cation-exchange membranes by Donnan dialysis

In this work, polyaniline (PAni), poly-n-ethylaniline, poly-n-methylaniline and poly-o-anisidine were prepared by chemical polymerization. 1,3 (6 or 7)-napthalenetrisulfonic acid was used for the first time in the literature as a dopant to increase the solubility of the polymers in methanol solution. The structure and properties of these conducting polymers were characterized by FTIR, UV–Vis, elemental analysis and conductivity measurements. Poly(vinylidene fluoride) (PVDF) membranes were modified by PAni and its derivatives and used as cation-exchange membranes. Poly-n-ethylaniline, poly-n-methylaniline and poly-o-anisidine were also used for the first time for this purpose in the literature. Ion-exchange capacity, water uptake and fixed group concentration of the polymer modified PVDF membranes were investigated. The changes in the surface morphologies of non-modified and polymer modified PVDF membrane was investigated by AFM and SEM. The polymer modified membranes were used for the removal of calcium (II) and magnesium (II) ions from water samples with Donnan dialysis (DD) experiments. The modified membranes show excellent stability during 120 days.     

Enhancement in Performance of Sulfonated PES Cation-Exchange Membrane by Introducing Pristine and Sulfonated Graphene Oxide Nanosheets Synthesized through Hummers and Staudenmaier Methods

Sulfonated polyether sulfone-based cation-exchange membranes are prepared by incorporating different amounts of graphene oxide and sulfonated graphene oxide nanosheets. The graphene oxide nanosheets are synthesized according to Staudenmaier and Hummer methods and functionalized using 3-mercaptopropyl trimethoxysilane. Transport properties of nanocomposite membranes including ion-exchange capacity, transport number, and conductivity as well as their thermal stabilities are enhanced by incorporating sulfonated graphene oxide rather than graphene oxide. Also, the enhancement is more significant for the nanocomposites having functionalized graphene oxide synthesized by Staudenmaier method than those by Hummers method due to higher density of active sites in the Staudenmier graphene oxides for functionalization.     

Polymerization of α,β-unsaturated carbonyl monomers initiated by 9-borabicyclo [3.3.1] nonane

9-Borabicyclo[3.3.1]nonane (9-BBN) initiated the polymerization of α,β-unsaturated carbonyl monomers such as ethyl acrylate (EA) without an oxidant at low temperatures (to −90°C) under argon. Hydroquinone and 2,6-di-tert-butyl-p-cresol had little effect on the polymerization, indicating that the propagating chain end is not a free radical. The rate of polymerization was found to be proportional to [9-BBN]^1.0 and [EA]^1.5. Electron spin resonance measurements using 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap showed the absence of any radical species under polymerization conditions. No copolymerization of EA with styrene occurred. On the basis of the results obtained, this polymerization was assumed to proceed via a non-radical mechanism.     

Polymerization of α, α-disubstituted-β-propiolactones and lactams. 9. ABA block copolymers of α-methyl-α-butyl-β-propiolactone and pivalolactone

ABA block copolymers were prepared by the anionic polymerization of α-methyl-α-butyl-β-propiolactone, MBPL (B block), and pivalolactone, PL (A blocks). The MBPL block had a very low decree of crystallinity and a glass temperature of ? 13°C, so phase separation with extensive crystallization of the PL blocks gave thermoplastic elastomers when the MBPL block constituted the principal and continuous phase. The observed crystallinity and melting point of 40–45°C in the MBPL homopolymer have not been previously reported. Measurements were obtained by electron microscopy of the initial size distribution of the PL domains as a function of copolymer composition and degree of polymerization, and on the effect of annealing on this parameter. Tensile strengths and elongations at break were both less than those previously observed for equivalent ABA block copolymers of PL and α-methyl-α-propyl-β-propiolactone.     

Chemoselective Reduction of α,β‐Unsaturated Carbonyls over Novel Mesoporous CoHMA Molecular Sieves under Hydrogen Transfer Conditions

Chemoselective reduction of α,β‐unsaturated carbonyls to the corresponding alcohols was achieved by a catalytic transfer hydrogenation (CTH) method using cobalt(II)‐substituted hexagonal mesoporous aluminophosphate (CoHMA) molecular sieve catalyst. Further, the catalyst was found to be promising as a heterogeneous catalyst as the yield was practically unchanged after up to six cycles.