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1.
Seven different fluoropolymer films were used as matrix materials for radiation‐grafted ion‐exchange membranes. The crystallinity and preferred orientation of these membranes were studied with wide‐angle X‐ray scattering, and the lamellar structure of the membranes was examined with small‐angle X‐ray scattering. The crystallinity of poly(vinylidene fluoride) (PVDF)‐based matrix materials varied between 57 and 40%, and the crystallinity of the sulfonated samples varied between 34 and 23%. The lamellar periods of PVDF‐based matrix materials were about 115 Å, and the lamellar periods of poly(ethylene‐alt‐tetrafluoroethylene) and poly(tetrafluoroethylene‐co‐hexafluoropropylene) were 250 and 212 Å, respectively. When the samples were grafted, the lamellar periods increased. Correlation function analysis showed very clearly that the long‐range order decreased because of grafting and sulfonation processes. For those samples that showed good proton conductivity, the lamellar period also increased because of sulfonation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1539–1555, 2002  相似文献   

2.
Salt‐containing membranes based on polymethacrylates having poly(ethylene carbonate‐co‐ethylene oxide) side chains, as well as their blends with poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP), have been studied. Self‐supportive ion conductive membranes were prepared by casting films of methacrylate functional poly(ethylene carbonate‐co‐ethylene oxide) macromonomers containing lithium bis(trifluorosulfonyl)imide (LiTFSI) salt, followed by irradiation with UV‐light to polymerize the methacrylate units in situ. Homogenous electrolyte membranes based on the polymerized macromonomers showed a conductivity of 6.3 × 10?6 S cm?1 at 20 °C. The preparation of polymer blends, by the addition of PVDF‐HFP to the electrolytes, was found to greatly improve the mechanical properties. However, the addition led to an increase of the glass transition temperature (Tg) of the ion conductive phase by ~5 °C. The conductivity of the blend membranes was thus lower in relation to the corresponding homogeneous polymer electrolytes, and 2.5 × 10?6 S cm?1 was recorded for a membrane containing 10 wt % PVDF‐HFP at 20 °C. Increasing the salt concentration in the blend membranes was found to increase the Tg of the ion conductive component and decrease the propensity for the crystallization of the PVDF‐HFP component. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 79–90, 2007  相似文献   

3.
On purpose to develop a polymer actuator with high stability in air‐operation as well as large bending displacement, a series of ionic polymer–metal composites (IPMC) was constructed with poly(styrene sulfonate)‐grafted fluoropolymers as ionomeric matrix and immidazolium‐based ionic liquids (IL) as inner solvent. The prepared IPMC actuators exhibited greatly enhanced bending displacement compared to Nafion‐based actuators. The actuators were stable in air‐operation, maintaining initial displacement for up to 104 cycles or 24 h. Investigating the material parameters and morphology of the IPMCs, high ion exchange capacity of the ionomers resulted in high ion conductivity and robust electrode of IPMC, which synergistically contributed to the high bending performance.

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4.
In this study, a novel polymer electrolyte membrane, poly(vinylbenzyl sulfonic acid)‐grafted poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP‐g‐PVBSA), has been successfully prepared by simultaneous irradiation grafting of vinylbenzyl chloride (VBC) monomer onto a FEP film and taking subsequent chemical modification steps to modify the benzyl chloride moiety to the benzyl sulfonic acid moiety. The chemical reactions for the sulfonation were carried out via the formation of thiouronium salt with thiourea, base‐catalyzed hydrolysis for the formation of thiol, and oxidation with hydrogen peroxide. Each chemical conversion process was confirmed by FTIR, elemental analysis, and SEM‐EDX. A chemical stability study performed with Fenton's reagent (3% H2O2 solution containing 4 ppm of Fe2+) at 70 °C revealed that FEP‐g‐PVBSA has a higher chemical stability than the poly(styrene sulfonic acid)‐grafted membranes (FEP‐g‐PSSA). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 563–569, 2010  相似文献   

5.
Nanometer thick films of sputtered and evaporated Cu were deposited on the surfaces of the fluoropolymers poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP) and poly(tetrafluoroethylene‐co‐perfluoropropyl vinyl ether) (PFA) and studied by both angle‐resolved XPS at takeoff angles of 10°, 45° and 80° and in situ argon ion etching. Higher yields of the fluoride ion to fluoropolymer ratio were detected for sputtered than evaporated Cu. PFA and FEP show enhanced interaction with sputtered Cu to produce fluoride ions relative to the more polycrystalline PTFE. At intermediate depths (takeoff angle of 45°), PFA and FEP exhibit the strongest fluoride F 1s signals compared with the fluoropolymer peaks. The amount of fluoride ion detected reaches a maximum after brief Ar ion etching and then decreases with prolonged etching. Compared with untreated fluoropolymers, improved adhesion of evaporated Cu was observed on the fluoropolymer surfaces that were argon ion etched to expose fluoride ions. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

6.
Pre‐irradiation grafting of styrene/divinylbenzene (DVB) onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP) films was studied with respect to the influence of solvent. Particularly favorable grafting conditions with long radical lifetimes and reasonably high polymerization rates were achieved with solvents that are precipitants for the newly formed polystyrene, e.g., low‐molecular‐mass alcohols like iPrOH, AcOH, their mixtures with H2O, and H2O/surfactant systems. Using one of these solvents significantly extended the range of accessible graft levels, and a specific degree of grafting was obtained at a much lower monomer concentration and irradiation dose than with grafting in a good solvent such as toluene. As practical consequences, the monomer was used more efficiently, and the radiation damage of the perfluorinated base material was reduced with the result of improved mechanical properties of the grafted films.  相似文献   

7.
Graft copolymers comprising poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) backbone and poly(styrene sulfonic acid) side chains, i.e. P(VDF‐co‐CTFE)‐g‐PSSA were synthesized using atom transfer radical polymerization (ATRP) for composite nanofiltration (NF) membranes. Direct initiation of the secondary chlorinated site of CTFE units facilitates grafting of PSSA, as revealed by FT‐IR spectroscopy. The successful “grafting from” method and the microphase‐separated structure of the graft copolymer were confirmed by transmission electron microscopy (TEM). Wide angle X‐ray scattering (WAXS) also showed the decrease in the crystallinity of P(VDF‐co‐CTFE) upon graft copolymerization. Composite NF membranes were prepared from P(VDF‐co‐CTFE)‐g‐PSSA as a top layer coated onto P(VDF‐co‐CTFE) ultrafiltration support membrane. Both the rejections and the flux of composite membranes increased with increasing PSSA concentration due to the increase in SO3H groups and membrane hydrophilicity, as supported by contact angle measurement. The rejections of NF membranes containing 47 wt% of PSSA were 83% for Na2SO4 and 28% for NaCl, and the solution flux were 18 and 32 L/m2 hr, respectively, at 0.3 MPa pressure. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

8.
The synthesis of a novel aromatic sulfonic acid bearing an amino function H2N? C2H4? S? C2H4? C6H4? SO3Na ( 1 ) from the radical addition of mercaptoethylamine hydrochloride onto styrene sodium sulfonate, and its subsequent grafting onto poly(vinylidene fluoride‐co‐hexafluoropropylene), poly(VDF‐co‐HFP), copolymer are presented. First, the radical telomerization, carried out under radical conditions and in water, led to various products [monoadduct ( 1 ), multiadducts, and polymers], the amounts of which depend on the experimental conditions and [mercaptan]0/[monomer]0 initial molar ratio (R0). An R0 ≥ 1 led to the monoadduct ( 1 ) only and achieved in ~85% yield. The zwitterionic isomer was obtained mainly and its chemical modification was possible to get an original aromatic sodium sulfonate containing an amino end group. A kinetic study of the telomerization was presented for R0 < 1. Thermogravimetric analysis of the telomer showed that this compound was stable up to 200 °C. Second, the grafting of ( 1 ) onto poly(VDF‐co‐HFP) copolymer was also investigated. Such a grafting proceeded as expected by a classic mechanism of grafting of amines. Molar percentages of grafted telomer were assessed by 1H NMR spectroscopy and by elemental analysis. Ion exchange capacity (IEC) values of the membranes were deduced from the mol % grafted telomer. Scanning electron microscopy pictures showed a good homogeneity in the cross‐section of membranes, and energy dispersive X‐ray evidenced that all SO3Na groups of the grafted amine were changed into SO3H after treatment with concentrated HCl. Method involving an impedance analyzer, working at increasing high frequencies was used to assess the protonic conductivities, σ. These values were lower than that of Nafion117®, but σ increased with the IEC to 0.4 mS/cm at room temperature and 95% relative humidity. Water and methanol uptakes were also assessed, and it was shown that σ increased when water uptakes increased. Membranes started to decompose from 170 °C under air. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 121–136, 2009  相似文献   

9.
In the present article, we investigate by differential scanning calorimetry (DSC) the thermal behavior (melting, crystallization, and crystal–crystal transitions) far from equilibrium of blends constituted of two crystalline polymers. In particular, the following blends are examined: PTFE–PFMVE, PTFE–FEP, and FEP–PFMVE where PTFE is poly(tetrafluoroethylene), PFMVE is poly(tetrafluoroethylene‐co‐perfluoromethylvinylether), and FEP is poly(tetrafluoroethylene‐co‐hexafluoropropylene). The two last ones are random tetrafluoroethylene copolymers with small amounts of comonomer. Our results indicate that, under the experimental investigated conditions, the blends containing PTFE do not give cocrystallization on cooling from the melt, although under very rapid crystallization conditions, quenching, the presence of the copolymer would seem to slightly influence PTFE crystallization (lower peak temperatures are observed for the crystalline transitions and the melting with respect to those of the neat homopolymer). The behavior of the FEP–PFMVE blend is completely different; in fact, our results indicate the occurrence of cocrystallization, then miscibility in the crystalline phase, for almost all compositions and all investigated experimental conditions. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 679–689, 1999  相似文献   

10.
Pre‐irradiation grafting of styrene/divinylbenzene (DVB) onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP) films from isopropanol (iPrOH) solution was investigated with respect to the effect of irradiation dose, film thickness, cross‐linker concentration, and reaction temperature. A mathematical model was applied to the kinetic curves to extract information on the polymerization rate, the radical‐recombination rate, and the grafting through time. It turned out that the two closely correlated reaction rates for polymerization and radical recombination can be varied over a wide range by changing the irradiation dose, the cross‐linker concentration, and the reaction temperature. On the other hand, the time until the grafting front has progressed to the center of the film is mainly affected by the film thickness and the reaction temperature. The formation of homopolymer in the grafting solution increases steeply with temperature and cross‐linker concentration.  相似文献   

11.
Novel, well‐defined fluorinated polystyrene was synthesized for the first time via the controlled radical polymerization of styrene through a relatively simple process and was characterized with 1H NMR, 19F NMR, and gel permeation chromatography. The surface properties of polystyrene and poly(acrylonitrile‐co‐butadiene‐co‐styrene) films were modified with the obtained polymers. X‐ray photoelectron spectroscopy measurements of the air‐side surface composition of the modified poly(acrylonitrile‐co‐butadiene‐co‐styrene) films showed that fluorine enriched the outermost surface, resulting in fantastic surface properties that came close to those of poly(tetrafluoroethylene). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3853–3858, 2006  相似文献   

12.
In this contribution a series of novel multiblock‐co‐ionomers consisting of hydrophobic (partially fluorinated) and hydrophilic (sulfonated) domains has been prepared and characterised in terms of their applicability as fuel cell membranes. The synthesis of these multiblock‐co‐ionomers is a four‐step procedure including (1) the sulfonation of the monomer 4,4′‐difluorodiphenylsulfone, (2) the preparation of hydrophilic telechelic macromonomers by molecular‐weight controlled step‐growth polycondensation of the sulfonated monomer with various bis(thio)phenols, (3) the preparation of a hydrophobic telechelic macromonomer and (4) the coupling of both telechelic macromonomers to yield microphase‐separated block‐co‐ionomers. This study focuses on the investigation of the influence of various linkage groups and atoms within the hydrophilic domains of the multiblock‐co‐ionomers. Both the telechelic macromonomers and the multiblock‐co‐ionomers were structurally investigated by 1H‐ and 19F‐NMR spectroscopy and gel permeation chromatography (GPC). All multiblock‐co‐ionomers of this series could be cast into membranes and their membrane properties (ion‐exchange capacity, specific resistance, swelling ratio, water uptake, thermal and oxidative stability) were measured and discussed in dependence of the various linkage groups within the hydrophilic domains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5237–5255, 2007  相似文献   

13.
The possibility of the cocrystallization of random fluorinated tetrafluoroethylene copolymers was investigated with differential scanning calorimetry and wide‐angle X‐ray scattering. In particular, mixtures composed of poly(tetrafluoroethylene)‐co‐(hexafluoropropylene) containing 8 or 1 mol % comonomer or poly(tetrafluoroethylene)‐co‐perfluoromethylvinylether (2–10 mol % comonomer) were examined. The extent of cocrystallization was determined by the difference in the comonomer content, being higher when the difference was lower, and it was favored when quenching from the melt state was adopted. Nevertheless, a key to determining the extent of cocrystallization was the behavior of counits with respect to inclusion or exclusion from the crystal lattice: when the components were different with respect to this behavior, they were not likely to be miscible in the crystal state even if the difference in the comonomer content was low. Moreover, the similarity in the crystallization rates between the components played an important role: the cocrystallization decreased as the difference in the crystallization rate increased until, when the difference became high enough, the blend became immiscible. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1477–1489, 2002  相似文献   

14.
In this study, we proposed an innovative and versatile method for preparation of highly stable and conductive supported ionic liquid (IL) membranes for proton exchange fuel cell applications. Novel covalently supported dual acidic IL membranes were prepared by radiation induced grafting of 4-vinyl pyridine (4-VP) onto poly(ethylene-co-tetrafluoroethylene) (ETFE) film followed by post-functionalization via sequential treatments with 1,4-butane sultone and sulfuric acid to introduce pyridinium alkyl sulfonate/hydrogen sulfate moieties. The advantage of our approach lies in grafting polymers with highly reactive functional groups suitable for efficient post-sulfonation. The membranes displayed better swelling and mechanical properties compared to Nafion 112 despite having more than 3 times higher ion exchange capacity (IEC). The proton conductivity reached superior values to Nafion above 80 °C. Particularly, the membrane with ion exchange capacity of 3.41 displayed a proton conductivity of 259 mScm−1 at 95 °C. This desired conductivity value is attributed to the high IEC of the membranes as well as dissociation of the hydrophobic ETFE polymer and hydrophilic pyridinium alkyl sulfonate groups. Such appealing properties make the supported IL membranes promising for proton exchange membrane fuel cells (PEMFC).  相似文献   

15.
To prepare a crosslinked hybrid polymer electrolyte membrane (PEM) with high chemical stability, a silane monomer, namely p‐styryltrimethoxysilane (StSi), was first grafted to poly(ethylene‐co‐tetrafluoroethylene) (ETFE) film by γ‐ray preirradiation. Hydrolysis‐condensation and sulfonation were then performed on the StSi‐grafted ETFE (StSi‐g‐ETFE) films to give them crosslinks and proton conductibility, respectively. Thus, a crosslinked proton‐conducting hybrid PEM was obtained. The crosslinks introduced by the silane‐condensation have an inorganic ? Si? O? Si? structure, which enhance the chemical and thermal stabilities of the PEM. The effect of the timing of the hydrolysis‐condensation (before or after sulfonation) and the sulfonation method (by chlorosulfonic acid or H2SO4) on the properties of the resulting hybrid PEMs such as ion‐exchange capacity, proton conductivity, water uptake, chemical stability, and methanol permeability were investigated to confirm their applicability in fuel cells. We conclude that the properties of the new crosslinked hybrid StSi‐grafted PEMs are superior to divinylbenzene (DVB)‐crosslinked styrene‐grafted membranes. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5559–5567, 2008  相似文献   

16.
A Novel solid polymer electrolyte (SPE) membrane containing both ? COOH and ? SO3H group has been prepared by simultaneous method of radiation grafting of acrylic acid onto FEP followed by sulfonation. The presence of weakly acidic acrylic acid controls the swelling in water while ? SO3H group provides conductivity due to its strongly ionic characteristic. FEP‐g‐acrylic acid and its sulfonated derivatives were characterized by their properties. While the mechanical properties decreased, other properties such as ion exchange capacity (IEC), water uptake and ionic conductivity increased with increase in graft content. These properties further changed on sulfonation. Acrylic acid being weakly acidic in nature, conductivity values of the grafted membrane were quite low. However, introduction of strong ? SO3H group resulted in conductivity closer to Nafion 117. Few sulfonated membranes have been tested with respect to H2/O2 fuel cell performance. Short‐term fuel cell test for 100 hr gave a stable performance. These membranes are less expensive compared to Nafion. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

17.
Amphoteric polymers have been studied for various applications such as separation of low molecular weight organic molecules from inorganic salt mixtures, selective ion transport, drug delivery through membranes of biological interest, separation of ionic drugs and proteins, and separation of alcohol and water. Typical amphoteric polymers consist of weak base and weak acid groups. In present study, the copolymerization of 5‐vinyltetrazole (VT) and diisopropyl‐p‐vinylbenzyl phosphate (DIPVBP) via free radical polymerization is studied. The reactivity ratio of VT and DIPVBP, which is calculated from Kelen‐Tudos plot, is 0.251 and 0.345, respectively. The amphoteric copolymer of VT and diisopropyl‐p‐vinylbenzyl phosphonic acid (poly(VT‐co‐VBPA)) is obtained from hydrolysis of the copolymer of VT and DIPVBP (poly(VT‐co‐DIPVBP)). Poly(VT‐co‐VBPA) is thermally stable under 190 °C. The anhydrous proton conductivity of amphoteric poly(VT‐co‐VBPA) can reach 1.54 × 10‐4 S cm?1 at 170 °C with an activation energy of 114.7 kJ mol?1. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3486–3493  相似文献   

18.
Hybrid organic–inorganic approaches are used for the synthesis of bifunctional proton exchange membrane fuel cell (PEMFC) membranes owing to their ability to combine the properties of a functionalized inorganic network and an organic thermostable polymer. We report the synthesis of both sulfonic and phosphonic acid functionalized mesostructured silica networks into a poly(vinylidenefluoride‐co‐hexafluoropropylene) (poly(VDF‐co‐HFP) copolymer. These membranes, containing different amounts of phosphonic acid and sulfonic acid groups, have been characterized using FTIR and NMR spectroscopy, SA‐XRD, SAXS, and electrochemical techniques. The proton conductivity of the bifunctional hybrid membranes depends strongly on hydration, increasing by two orders of magnitude over the relative humidity (RH) range of 20 to 100 %, up to a maximum of 0.031 S cm−1 at 60 °C and 100 % RH. This value is interesting as only half of the membrane conducts protons. This approach allows the synthesis of a porous SiO2 network with two different functions, having  SO3H and  PO3H2 embedded in a thermostable polymer matrix.  相似文献   

19.
A series of temperature‐sensitive poly(CSA‐co‐NIPAAm) membranes that were suitable for cell culture and confluent cell sheets detachment were prepared. The membranes with thermo‐responsive surface properties were synthesized by the copolymerization of acrylic acid‐derivatized chitosan (CSA) and N‐isopropylacrylamide (NIPAAm) in aqueous solution. Characterization of the membranes were carried out by means of the Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and water contact‐angle (WCA) measurements. The adhesion and detachment of mouse fibroblast (L929) cells on these membranes have been investigated. The study showed that poly(CSA‐co‐NIPAAm) membranes could not only enhance fibroblasts attachment but also harvest confluent cell sheets by simply lowering the temperature. Furthermore, the detached cells retained high viability and could proliferate again after transferred to a new culture surface. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

20.
A series of amphiphilic graft copolymers of poly (vinylidene fluoride‐co‐chlorotrifluoroethylene)‐g‐poly(2‐vinyl pyridine), P (VDF‐co‐CTFE)‐g‐P2VP, with different degrees of P2VP grafting (from 26.3 to 45.6 wt%) was synthesized via one‐pot atom transfer radical polymerization (ATRP). The amphiphilic properties of P (VDF‐co‐CTFE)‐g‐P2VP graft copolymers allowed itself to self‐assemble into nanoscale structures. P (VDF‐co‐CTFE)‐g‐P2VP graft copolymers were introduced into neat P (VDF‐co‐CTFE) as additives to form blending membranes. When two different solvents, N‐methyl‐2‐pyrrolidone (NMP) and dimethylformamide (DMF), were used, specific organized crystalline structures were observed only in the NMP systems. P (VDF‐co‐CTFE)‐g‐P2VP played a pivotal role in controlling the morphology and pore structure of membranes. The water flux of the membranes increased from 57.2 to 310.1 L m?2 h?1 bar?1 with an increase in the PVDF‐co‐CTFE‐g‐P2VP loading (from 0 to 30 wt%) due to increased porosity and hydrophilicity. The flux recovery ratio (FRR) increased from 67.03% to 87.18%, and the irreversible fouling (Rir) decreased from 32.97% to 12.82%. Moreover, the pure gas permeance of the membranes with respect to N2 was as high as 6.2 × 104 GPU (1 GPU = 10–6 cm3[STP]/[s cm2 cmHg]), indicating their possible use as a porous polymer support for gas separation applications.  相似文献   

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