XPS studies of radiation grafted PTFE‐g‐polystyrene sulfonic acid membranes

Structural investigations of PTFE‐g‐polystyrene sulfonic acid membranes prepared by radiation grafting of styrene onto PTFE were conducted by X‐ray photoelectron spectroscopy (XPS). The analyzed materials included original PTFE film as a reference material, grafted film, and sulfonated membrane samples having various degrees of grafting. Interest is focused on C1s, F1s, O1s, and S2p of narrow XPS spectra as the basic elemental components of the membrane. The original PTFE film was found to undergo structural changes in terms of chemical composition and shifting in binding energy induced by incorporation of sulfonated polystyrene grafts, and the amount of such changes depends on the degree of grafting. The atomic ratio of F/C was found to decrease with the increase in the degree of grafting, while that for S/C and O/C were found to increase. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 336–349, 2000     

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     

Cation exchange membranes by radiation‐induced graft copolymerization of styrene onto PFA copolymer films. III. Thermal stability of the membranes

Thermal stability of cation exchange, PFA‐g‐polystyrene sulfonic acid membranes prepared by radiation‐induced graft copolymerization of styrene onto PFA films followed by sulfonation was studied by thermal gravimetric analysis (TGA) and oven heat treatment. The tested samples included original and grafted PFA films as reference materials. All the membranes showed multistep decomposition patterns due to dehydration, desulfonation, dearomatization, and decomposition of the PFA matrix. Investigations of the individual decomposition behaviors showed that the weight loss strongly depends upon the degree of grafting. However, the decomposition temperatures were found to be independent of the degree of grafting. The loss in some selected membrane properties such as ion exchange capacity and water uptake was found to be function of the degree of grafting, temperature, and the time of heat treatment. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1877–1885, 2000     

Functionalization of poly(ester‐urethane) surface by radiation‐induced grafting of N‐isopropylacrylamide using conventional and reversible addition–fragmentation chain transfer‐mediated methods

The functionalization of poly(ester‐urethane) (PUR) surface was conducted using radiation‐induced grafting. A thermosensitive layer constructed from N‐isopropylacrylamide (NIPAAm) was introduced onto a polyurethane film and characterized using attenuated total reflection Fourier transform infrared and X‐ray photoelectron spectroscopies and contact angle measurements. Size exclusion chromatography was used to analyse the PUR‐graft‐PNIPAAm copolymers and homopolymers formed in solution. Additionally, reversible addition–fragmentation chain transfer (RAFT) polymerization was performed in order to obtain PNIPAAm‐grafted surfaces with well‐defined properties. Atomic force microscopy was used to evaluate the surfaces synthesized via conventional and RAFT‐mediated grafting methods. The results of various techniques confirmed the successful grafting of NIPAAm from PUR film. © 2015 Society of Chemical Industry     

Preparation and properties of sulfonated ETFE‐g‐polyvinyltoluene membranes for application in fuel cells

A new polymer electrolyte membrane prepared by radiation grafting of vinyltoluene into poly(ethylene‐co‐tetrafluoroethylene) (ETFE) film and subsequent sulfonation was developed for application in fuel cells. The effect of grafting condition on the degree of grafting was investigated in detail. Results indicated that the degree of grafting can be controlled over a wide range. The grafted films were sulfonated in a chlorosulfonic acid solution to obtain the polymer electrolyte membranes, which were characterized with respect to their use in fuel cells. It is concluded that the substituted methyl group on the vinyltoluene can improve the chemical stability of the resulting membranes, and the crosslinked ETFE‐g‐poly(vinyltoluene‐co‐divinylbenzene) membranes can be proposed for the future development of alternative low‐cost and high‐performance membranes for fuel cells. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2661–2667, 2006     

Proton‐exchange membranes via the grafting of styrene and acrylic acid onto fluorinated ethylene propylene copolymer by a preirradiation technique. IV. Dynamic mechanical analysis,X‐ray diffraction,and scanning electron microscopy studies of grafted and sulfonated membranes

The grafting of styrene and acrylic acid onto fluorinated ethylene propylene copolymer was carried out by a preirradiation technique. The resulting membranes were sulfonated with concentrated sulfuric acid. The effects of the degree of grafting and sulfonation on the structure of the membranes were studied by X‐ray diffraction and scanning electron microscopy. The crystallinity percentage decreased with increasing grafting. Scanning electron microscopy studies confirmed that grafting took place by a front mechanism, by which grafting started at the surface and slowly proceeded inwards. The dynamic mechanical properties of the membranes and their sulfonated derivatives were also investigated. The storage modulus at room temperature increased with grafting and increased further with sulfonation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1426–1431, 2005     

An investigation of the friction and wear behaviors of micrometer copper particle‐ and nanometer copper particle‐filled polyoxymethylene composites

Micrometer and nanometer copper particle‐filled polyoxymethylene composites (coded as POM‐micro Cu and POM‐nano Cu, respectively) were prepared by compression molding. The compression strength and tensile strength of the composites were evaluated with a DY35 universal materials tester. An RFT‐III reciprocating friction and wear tester was used to examine the tribological properties of the composites. The elemental compositions in the transfer films and the chemical states of the elements in the composite‐worn surfaces were analyzed with electron probe microanalysis and X‐ray photoelectron spectroscopy, while the surface morphologies were observed with scanning electron microscopy. It was found that Cu( CH₂ O )_n was produced in sliding of a POM‐nano Cu pin against an AISI 1045 steel block and Cu₂O was produced in sliding of a POM‐micro Cu pin against the same counterface. POM‐micro Cu exhibited higher copper concentration in the transfer film compared with POM‐nano Cu, and the transfer film of the former was thick and patchy compared with that of the latter. It was also found that micrometer and nanometer copper particles as fillers in POM exhibit a distinctive size effect in modifying the wear mechanisms of the composites. In other words, the wear mechanism of POM‐micro Cu is mainly scuffing and adhesion, while that of POM‐nano Cu is mainly plastic deformation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2404–2410, 2000     

Preparation and characterization of phosphoric acid composite membrane by radiation induced grafting of 4‐vinylpyridine onto poly(ethylene‐co‐tetrafluoroethylene) followed by phosphoric acid doping

Preparation of phosphoric acid composite membranes by radiation induced grafting of 4‐vinylpyridine (4‐VP) onto electron beam irradiated poly(ethylene‐co‐tetrafluoroethylene) film followed by phosphoric acid doping was investigated. The effect of grafting parameters (monomer concentration, absorbed dose, reaction time, and temperature) on the degree of grafting (G%) in the membrane precursor and its relation with the amount of acid doped was studied. The proton conductivity of the obtained membranes was evaluated in correlation with G% and temperature using ac impedance. Fourier transform infrared, thermal gravimetric analysis, X‐ray diffraction, and universal mechanical tester were used to investigate chemical composition, thermal resistance, structure, and mechanical properties of the membranes, respectively. The membranes of 34 and 49% recorded high proton conductivity in the magnitude of 10^‐2 S cm^‐1 without humidification. The membranes were also found to have reasonable mechanical integrity together with thermal stability up to 160°C. The obtained membranes are suggested to be less‐water dependent and have potential for testing in high temperature polymer electrolyte membrane fuel cell. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Proton‐exchange membranes via the grafting of styrene and acrylic acid onto fluorinated ethylene propylene copolymer by a preirradiation technique. III. Thermal and mechanical properties of the membranes and their sulfonated derivatives

Polymer electrolyte membranes were prepared via the grafting of styrene and acrylic acid onto fluorinated ethylene propylene copolymer with a preirradiation technique and subsequent sulfonation. The thermal and mechanical properties of the grafted membranes and their sulfonated derivatives were dependent on the degree of grafting. The grafted membranes showed a two‐step degradation pattern, whereas their sulfonated derivatives showed a three‐step degradation pattern. The glass‐transition temperature and crystallinity percentage of the membranes were determined with differential scanning calorimetry. With an increase in the degree of grafting and sulfonation, the glass‐transition temperature increased, whereas the crystallinity percentage decreased. The tensile strength and elongation decreased with the degree of grafting and sulfonation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1418–1425, 2005     

Influence of the radiation grafting conditions on the cross‐sectional distribution of poly(vinylbenzyl chloride) grafted polymer onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) films

Poly(vinylbenzyl chloride) (PVBC)‐grafted poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP) films were prepared as precursors for ion‐exchange membranes with a radiation grafting technique. A scanning electron microscopy–energy dispersive X‐ray spectroscopy (SEM‐EDX) instrument was used to investigate the effects of the radiation grafting conditions on the distribution profiles of the grafts in the FEP‐g‐PVBC films because the properties of the ion‐exchange membranes were largely affected not only by the degree of grafting (DOG) but also by the distribution of the graft chain. These results indicate that the distribution profile of the grafts largely depended on the grafting parameters, such as the solvent, monomer concentration, film thickness, and irradiation dose. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polyphosphazene membranes. III. Solid‐state characterization and properties of sulfonated poly[bis(3‐methylphenoxy)phosphazene]

Poly[bis(3‐methylphenoxy)phosphazene] was sulfonated in a solution with SO₃ and solution‐cast into 100–200‐μm‐thick membranes from N,N‐dimethylacetamide. The degree of polymer sulfonation was easily controlled and water‐insoluble membranes were fabricated with an ion‐exchange capacity (IEC) as high as 2.1 mmol/g. For water‐insoluble polymers, there was no evidence of polyphosphazene degradation during sulfonation. The glass transition temperature varied from −28°C for the base polymer to −10°C for a sulfonated polymer with an IEC of 2.1 mmol/g. The equilibrium water swelling of membranes at 25°C increased from near zero for a 0.04‐mmol/g IEC membrane to 900 % when the IEC was 2.1 mmol/g. When the IEC was < 1.0 mmol/g, SO₃ attacked the methylphenoxy side chains at the para position, whereas sulfonation occurred at all available aromatic carbons for higher ion‐exchange capacities. Differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized microscopy showed that the base polymer, poly[bis(3‐methylphenoxy)phosphazene], was semicrystalline. For sulfonated polymers with a measurable IEC, the 3‐dimensional crystal structure vanished but a 2‐dimensional ordered phase was retained. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 387–399, 1999     

Surface modification of low‐density polyethylene films by UV‐induced graft copolymerization with a fluorescent monomer

Surface modification of argon plasma–pretreated low‐density polyethylene (LDPE) film via UV‐induced graft copolymerization with a fluorescent monomer, (pyrenyl)methyl methacrylate (Py)MMA, was carried out. The chemical composition and morphology of the (Py)MMA‐graft‐copolymerized LDPE [(Py)MMA‐g‐LDPE] surfaces were characterized, respectively, by X‐ray photoelectron spectroscopy (XPS) and by atomic force microscopy (AFM). The concentration of the surface‐grafted (Py)MMA polymer increased with Ar plasma pretreatment time and UV graft copolymerization time. The photophysical properties of the (Py)MMA‐g‐LDPE surfaces were measured by fluorescence spectroscopy. After graft copolymerization with the fluorescent monomer, the surface of the LDPE film was found to have incorporated new and unique functionalities. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1526–1534, 2001     

Surface‐initiated atom transfer radical polymerization of regenerated cellulose membranes with thermo‐responsive properties

Using atom transfer radical polymerization (ATRP), thermo‐responsive regenerated cellulose membranes were synthesized. Regenerated cellulose membranes were firstly modified by reacting the hydroxyl groups on the surface with 2‐bromoisobutyryl bromide, followed by grafting with poly(N‐isopropylacrylamide). The membranes had obvious thermally modulated permeability properties. Analysis was carried out by means of X‐ray photoelectron spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis. The results showed that N‐isopropylacrylamide had been grafted successfully on the surface of the regenerated cellulose membranes. The thermally modulated permeability properties of the grafted membranes were studied using water flux measurements. It was found that the thermally modulated permeability properties of a cellulose surface can be tailored by the use of the ATRP method. Copyright © 2010 Society of Chemical Industry     

Synthesis and characteristics of radiation‐grafted membranes for fuel cell electrolytes

Proton exchange membranes were prepared by simultaneous radiation grafting of styrene onto polytetrafluoroethylene (PTFE) films at room temperature and subsequent sulfonation by chlorosulfonic acid. A series of grafted films with degree of grafting ranging from 0.947% to 35.4% were obtained. The effect of styrene concentration on the grafting yield was investigated and the maximum value was obtained at a monomer concentration of 70‐vol%. The structure of PTFE‐graft‐polystyrene sulfonic acid membranes was studied by infrared spectroscopy. The membrane properties, such as water uptake, ion exchange capacity, swelling performance and ionic resistance, were studied as functions of the degree of grafting. The thermal and chemical stability of the sulfonic acid membranes was also investigated. The membrane properties were found to depend on the degree of grafting and the amorphous character of the membrane structure, and the better membrane properties were obtained at a degree of grafting in the range 12–21%. Copyright © 2003 Society of Chemical Industry     

Synthesis and surface characterization of poly(methyl methacrylate)‐block‐polydimethylsiloxane copolymers from macroazoinitiator

Poly(methyl methyacrylate)‐block‐polydimethylsiloxane (PMMA‐b‐PDMS) copolymers with various compositions were synthesized with PDMS‐containing macroazoinitiator (MAI), which was first prepared by a facile one‐step method in our lab. Results from the characterizations of X‐ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM) showed that the copolymer films took on a gradient of composition and more PDMS segments enriched at the film surfaces, which then resulted in the low surface free energy and little microphase separation at the film surfaces. By contrast, transmission electron microscopy (TEM) analysis demonstrated that distinct microphase separation occurred in bulk. Slight crosslinking of the block copolymers led to much steady morphology and more distinct microphase separation, in particularly for copolymers with low content of PDMS. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Proton exchange membranes prepared by simultaneous radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) films. I. Effect of grafting conditions

The simultaneous radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP) films was studied at room temperature. The effects of grafting conditions (type of solvent, irradiation dose, dose rate, and monomer concentration) were investigated. The degree of grafting was found to be dependent on the investigated grafting conditions. The dependence of the initial rate of grafting on the dose rate and the monomer concentration was found to be of 0.5 and 1.3 orders, respectively. The results suggest that grafting proceeds by the so‐called front mechanism in which the grafting front starts at the surface of the film and moves internally toward the middle of the film by successive diffusion of styrene through the grafted layers. Some selected properties of the grafted films were evaluated in correlation with the degree of grafting. We found that the grafted FEP films possess good mechanical stability, which encourages their use for the preparation of proton exchange membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 220–227, 2000     

Liquid/solid two‐phase carbonization of low‐molecular‐weight chloro‐/bromo‐hydrocarbons

A novel liquid/solid two‐phase reaction has been discovered that enables destruction of a series of low‐molecular‐weight chloro‐/bromo‐hydrocarbons to carbon‐based materials. The solid phase is anhydrous potassium hydroxide and the liquid phase is a benzene or tetrahydrofuran solution of halide and contains a certain amount of tetrabutyl ammonium bromide (TBAB) as phase transfer catalyst. The structure of the carbon‐based materials have been characterized by elemental analysis, Fourier transform infrared (FT‐IR), FT‐Raman, and X‐ray photoelectron spectroscopies, and their morphologies have been examined by wide‐angle X‐ray diffraction and transmission electron microscopy. The results indicate that the products are amorphous nanoparticles and contain mainly elemental carbon. They consist of sp, sp², and sp³ carbon atoms simultaneously and can be regarded as carbyne analogues. This work provides a convenient method for synthesizing new carbon‐based materials in relatively high yields. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1510–1515, 2000     

New route to functional polyolefins: sulfonation of poly[ethylene‐co‐(5,7‐dimethylocta‐1,6‐diene)] and evaluation of properties

An ethylene/5,7‐dimethylocta‐1,6‐diene copolymer was sulfonated using two different approaches, solution and surface modification, varying parameters such as reaction time, temperature and concentration of the sulfonation reagent. Techniques such as attenuated total reflectance Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy and elemental analysis confirmed the successful sulfonation of the copolymer by both methods. Water uptake studies showed that the polarity of the initial copolymer was markedly changed upon functionalization and that the sulfonation by the in‐solution method produced more hydrophilic polymers compared to the surface procedure. Moreover, differential scanning calorimetry and thermogravimetric analysis pointed out additional changes to the thermal properties of the sulfonated polymers relative to the copolymer precursor. This study showed that the sulfonation process of the non‐polar ethylene–diene copolymer led to a new hydrophilic material with a potential wide range of applications. © 2017 Society of Chemical Industry     

Sulfonated polysulfone as promising membranes for polymer electrolyte fuel cells

A new, milder sulfonation process was used to produce ion‐exchange polymers from a commercial polysulfone (PSU). Membranes obtained from the sulfonated polysulfone are potential substitutes for perfluorosulfonic acid membranes used now in polymer electrolyte fuel cells. Sulfonation levels from 20 to 50% were easily achieved by varying the content of the sulfonating agent and the reaction time. Ion‐exchange capacities from 0.5 to 1.2 mmol SO₃H/g polymer were found via elemental analysis and titration. Proton conductivities between 10⁻⁶ and 10⁻² S cm⁻¹ were measured at room temperature. An increase in intrinsic viscosity with increasing sulfonation degree confirms that the sulfonation process helps to preserve the polymer chain from degradation. Thermal analysis of the sulfonated polysulfone (SPSU) samples reveals higher glass transition temperatures and lower decomposition temperatures with respect to the unsulfonated sample (PSU). Amorphous structures for both PSU and SPSU membranes were detected by X‐ray diffraction analysis and differential scanning calorimetry. Preliminary tests in fuel cells have shown encouraging results in terms of cell performance. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1250–1257, 2000     

Photografting polymerization of polyacrylamide on poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) films. II. Wettability and crystallization behaviors of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)‐graft‐polyacrylamide films

The wettability and crystallization behaviors of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV)‐graft‐polyacrylamide (PAM) films were studied. X‐ray photoelectron spectroscopy analyses illustrated that about 62 atom % of the total polar functionalities on the grafted film with 17% grafting percentage (GP) was amide groups. Wide‐angle X‐ray diffraction results suggest that grafted PAM induced defects in PHBV crystals and influenced their crystal structure. Differential scanning calorimetry (DSC) spectra showed the two melting regions, 60–90 and 145–170°C, of the imperfect PHBV crystals of the grafted films. Grafted PAM could suppress the recrystallization of PHBV, which was consistent with the polarizing optical microscopy results, in which the maximum PHBV spherulite diameter decreased from 350 μm for the PHBV film to 50 μm for the film with 53% GP. In addition, DSC studies revealed that the crystallinity of the grafted films decreased with increasing GP, which facilitated the diffusion of water into the films. The water contact angle of grafted films decreased and the water‐swelling percentage increased as GP went up. These results demonstrate the potential of PHBV‐g‐PAM for wettable surface constructs in tissue engineering applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008