Radiation-induced Graft Copolymerization Of Styrene Research Articles

Characterization of polyethyleneterephthalate (PET) based proton exchange membranes prepared by UV-radiation-induced graft copolymerization of styrene

Polymer electrolyte membranes (PEMs) were successfully prepared by simultaneous ultraviolet (UV) radiation-induced graft copolymerization of styrene (35 vol.% concentration) onto poly(ethyleneterephthalate) (PET) film, followed by sulfonation on the styrene monomer units in the grafting chain using 0.05 M chlorosulfonic acid (ClSO 3H). The radiation grafting and the sulfonation have been confirmed by titrimetric and gravimetric analyses as well as Fourier Transform Infrared (FTIR) spectroscopy. The maximum ion-exchange capacity (IEC) of the PEM was measured to be 0.04385 mmol g −1 at its highest level of grafting and sulfonation. They exhibited high thermal and mechanical properties as well as oxidative stability. They are highly stable in H 2SO 4 solutions and can be used in the acidic fuel cells. The membranes showed low water uptake as well as low proton conductivity than Nafion. In this study, the preparation of PEMs from commodity-type polymers is found to be very inexpensive and is a suitable candidate for applications in fuel cells.

Amphoteric ion exchange membrane synthesized by radiation-induced graft copolymerization of styrene and dimethylaminoethyl methacrylate into PVDF film for vanadium redox flow battery applications

Poly(vinylidene difluoride) (PVDF) film was grafted with styrene (St) and dimethylaminoethyl methacrylate (DMAEMA) using γ-irradiation techniques. Through subsequent sulfonation and protonation processes, a new kind of amphoteric ion exchange membrane (AIEM) was synthesized. The grafting yield ( GY) increased with absorbed dose and leveled off at about 60 kGy. The composition of poly(St- co-DMAEMA) grafts was correlated to the ratio of St to DMAEMA monomer in the feed. Micro-FTIR and XPS analyses testified that the grafting and sulfonation of St unit in poly(St- co-DMAEMA) grafts had been carried out as designed. Further characterizations showed that the properties of the AIEM strongly depended on the composition and GY of the film, i.e. higher content of DMAEMA brought lower permeability of vanadium ions and conductivity, while higher GY led to higher water uptake, ion exchange capacity ( IEC) and conductivity. Finally, an AIEM with a GY of 26.1% was assembled and tested in the vanadium redox flow battery (VRFB) system. It was found that the VRFB assembled with the AIEM maintained an open circuit voltage (OCV) higher than 1.2 V after placed for 68 h, which was much longer than that with the Nafion117 membrane. Therefore, this work provides a novel method to develop potential substitute of Nafion membranes to be applied in VRFB system.

EPR investigation on radiation-induced graft copolymerization of styrene onto polyethylene: Energy transfer effects

In this paper, energy transfer phenomena concerning the in-source graft copolymerization of styrene onto LDPE were investigated through the EPR analysis of the radical intermediates. The model solution experiments have shown a substantial deviation of the experimental G (radicals) values with respect to the additivity law, which reflect the negative effect of the styrene monomer concentration on the initiation rate of the graft copolymerization. The EPR measurements performed on polyethylene- co-styrene graft copolymers of various composition following low-temperature vacuum gamma irradiation have confirmed the decrease of the total radical yields with increasing the styrene concentration. The effect was partly attributed to the heterogeneity of the graft copolymer matrix and to the lack of molecular mobility in the solid state at low temperature, which prevents the attainment of the favourable geometrical configurations in intermolecular energy and charge transfer events.

Preparation of Highly Stable Ion Exchange Membranes by Radiation-Induced Graft Copolymerization of Styrene and Bis(vinyl phenyl)ethane Into Crosslinked Polytetrafluoroethylene Films

We prepared novel ion exchange membranes for possible use in polymer electrolyte fuel cells (PEFCs) by the radiation-induced graft copolymerization of styrene and new crosslinker bis(vinyl phenyl)ethane (BVPE) into crosslinked polytetrafluoroethylene (cPTFE) films and subsequent sulfonation and then investigated their water uptake, proton conductivity, and stability in an oxidizing environment. In contrast to the conventional crosslinker, divinylbenzene (DVB), the degree of grafting of styrene∕BVPE increased in spite of high crosslinker concentrations in the reacting solution (up to 70mol%). Quantitative sulfonation of the aromatic rings in the crosslinked graft chains resulted in the preparation of membranes with a high ion exchange capacity that reached 2.9meq∕g. The bulk properties of the membranes were found to exceed those of Nafion membranes except for chemical stability. The emphasis was on the fact that the BVPE-crosslinked membranes exhibited the higher stability in the H2O2 solution at 60°C compared to the noncrosslinked and DVB-crosslinked ones, as well as decreased water uptake and reasonable proton conductivity. These results are rationalized by considering the reactivity between styrene and the crosslinker, which is an important factor determining the distribution of the crosslinks in the graft component. In the case of BVPE, the crosslinks at a high density were homogeneously incorporated even into the interior of the membrane because of its compatibility with styrene while the far too reactive DVB led to a crosslink formation only near the surface. The combination of both the cPTFE main chain and BVPE-based grafts, i.e., a perfect “double” crosslinking structure, is likely to effectively improve the membrane performances for PEFC applications.

Surface studies of radiation grafted sulfonic acid membranes: XPS and SEM analysis

PTFE-g-polystyrene sulfonic acid membranes prepared by radiation-induced graft copolymerization of styrene onto poly(tetrafluoroethylene) (PTFE) films followed by sulfonation reactions were investigated with respect to their morphology and surface chemical properties. The chemical composition of the membranes surfaces was monitored at various degrees of grafting using X-ray photoelectron spectroscopy (XPS). Considerable differences in the concentration of the chemical components of the surfaces were observed despite the predominance of all membranes surfaces by a hydrocarbon fraction originated from the incorporated sulfonated polystyrene grafts. The distribution of the sulfonated polystyrene grafts in membranes having various degrees of grafting was investigated by scanning electron microscopy (SEM). The membranes achieved a homogenous distribution at degrees of grafting of 24% and above. The results of this work suggest that the membranes have a chemically sensitive surfaces and this is most likely to have an impact on their interfacial properties and chemical stability.

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 physicochemical 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.

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

Cation exchange membranes by radiation-induced graft copolymerization of styrene onto PFA copolymer films. IV. Morphological investigations using X-ray photoelectron spectroscopy

Morphological investigations of poly(tetrafluoroethylene-co-perfluorovinyl ether) (PFA)-g-polystyrene sulfonic acid membranes prepared by radiation-induced graft copolymerization of styrene onto PFA films followed by sulfonation were performed by X-ray photoelectron spectroscopy. The analyzed materials included grafted film and sulfonated membrane samples having various degrees of grafting. Original PFA film was used as a reference material. The results of the X-ray photoelectron spectral analysis show that PFA film undergoes changes in terms of chemical compositions and binding energies of its basic elemental components under the influence of membrane preparation procedure, i.e., grafting and sulfonation. The chemical compositions of the surfaces of the membranes were found to be dependent on the degree of grafting unlike the binding energies of their elemental components (C, F, O, and S), which were found to be independent of the degree of grafting. The atomic ratio of F/C was found to decrease drastically with the increase in the degree of grafting and the membranes were found to have almost pure hydrocarbon structure at the layers close to their surfaces where degradation is suggested to be concentrated. The results of these investigations suggest that the morphology of the membranes plays an important role in the chemical degradation of the membranes.

Gamma radiation-induced graft copolymerization of styrene onto poly(ethyleneterephthalate) films

Gamma radiation-induced graft copolymerization of styrene onto poly(eth- ylene terephthalate) (PET) films was studied using simultaneous irradiation technique. The effects of grafting conditions on the degree of grafting were investigated. The grafting conditions include monomer concentration, irradiation dose, dose rate, and the type of solvent. Moreover, the effect of the addition of crosslinking agents (i.e., divinyl- benzene (DVB) and triallyl cyanurate (TAC)) having various concentrations were also investigated. The degree of grafting was found to be greatly dependent on the grafting conditions. Of the three diluents employed, methylene chloride was found to drastically enhance the degree of grafting. The order of dependence of the initial rate of grafting on the monomer concentration was found to be 2.2. The grafted PET films were identified by FTIR spectroscopy and characterized by X-ray diffraction (XRD). © 2000 John Wiley &

Cation exchange membranes by radiation-induced graft copolymerization of styrene onto PFA copolymer films. I. Preparation and characterization of the graft copolymer

PFA-g-polystyrene graft copolymers were prepared by simultaneous radiation-induced graft copolymerization of styrene onto poly(tetrafluoroethylene-co-perfluorovinyl ether) (PFA) films. The effects of grafting conditions such as monomer concentration, dose, and dose rate were investigated. Three solvents, i.e., methanol, benzene, and dichloromethane, were used as diluents in this grafting system. Of the three solvents employed, dichloromethane was found to greatly enhance the grafting process, and the degree of grafting increased with the increase of monomer concentration until it reached its highest value at a styrene concentration of 60 (vol %). The dependence of the initial rate of grafting on the monomer concentration was found to be of the order of 1.2. The degree of grafting was found to increase with the increase in irradiation dose, while it considerably decreased with the increase in dose rate. The formation of graft copolymers was confirmed by FTIR analysis. The structural investigation by X-ray diffraction (XRD) shows that the degree of crystallinity content of such graft copolymers decreases with the increase in grafting, and consequently, the mechanical properties of the graft copolymers were influenced to some extent. Both tensile strength and elongation percent decreased with the increase in the degree of grafting. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2095–2102, 1999

Proton Exchange Membranes by Radiation-Induced Graft Copolymerization of Monomers into Teflon-FEP Films

A state-of-the-art in radiation-induced graft copolymerization of styrene and acrylic acid monomers into Teflon-FEP films is presented with a view to develop proton exchange membranes for various applications. This process offers an easy control over the composition of a membrane by careful variation in radiation dose, dose rate, monomer concentration, and temperature of the grafting reaction. By varying the nature and the amount of the grafted content, it is possible to achieve a membrane with desired physico-chemical properties. In this paper, a correlation among the degree of grafting, structural changes, and properties of graft copolymer membranes is discussed.

Radiation-induced graft copolymerization of styrene with vinylic monomers at high dose rates

Radiation-induced graft copolymerization of the following monomer pairs: styrene-acrylonitrile (AN), styrene-methyl methacrylate (MMA), styrene-2-methyl-5-vinylpyridine (MVP) and styrene- acrylic acid (AA) onto polyethylene film was studied at room temperature in the range of dose rates 8.10 −2–6.10 3 Gy/s. The grafted copolymer compositions were determined and copolymerization reactivity ratios were calculated. At high dose rates the contribution of the ionic mechanism is proved by the change of the copolymer compositions obtained at essential different dose rates and by different influence of the donor and acceptor solvents on this process. It is established that transition from radical mechanism to ionic one begins in the interval of dose rates 10 2–10 3 Gy/s for styrene-AN, styrene-MMA, styrene-MVP systems but occurs in the interval of dose rates 10 3–6.10 3 Gy/s for styrene-AA system. The formation of the grafted polymer compositions, obtained at high dose rates, must be described by the kinetics which takes into account the presence of ionic process.

Property Modifications of Cotton Fabric After Radiation-Induced Grafting of Vinyl Monomers

The samples obtained by radiation-induced graft copolymerization of styrene and divinyllbenzene (DVB) onto cotton cellulose fabric were examined for modified physical and textile properties. After grafting with styrene or with DVB, cotton fabric showed considerably better water repellence and abrasion resistance, while breaking strength was not impaired. Air permeability and moisture regain decreased. Copolymerization with DVB improved the crease resistance. The presence of vinyl homopolymer in quantities over 5% affect the properties of the sample in an unfavorable way and should be removed.

Radiation-Induced Graft Copolymerization of Styrene to Polyvinyl Chloride) Latex in a Pilot Plant System

Abstract A pilot plant study of the radiation grafting of styrene to polyvinyl chloride) (PVC) latex is described. When correct extraction conditions are used less than 3% grafting took place. This is shown to be due to the low total radiation doses needed to polymerize the styrene in an emulsion system. A parallel study with PVC film did, however, lead to substantial true grafting. The G (radical) value for PVC film as determined by ESR was found to be 4.6.

Radiation-induced grafting onto wool. A kinetic analysis

The radiation-induced graft copolymerization of styrene onto wool in aqueous methanol was studied over a temperature range of 0°C to 45°C and a radiation dose-rate range of 0.05 to 2.0 Mrad/hr. The rate of grafting was found to obey the classical polymerization equation. Chain transfer to wool was found to play an important role in the grafting process, and the molecular weight of the resulting graft copolymer was found to be independent of the irradiation dose. The activation energy of the graft process changed from a value of 4.7 kcal/mole below 19°C to a value of 18.7 kcal/mole above this temperature. This phenomenon is ascribed to the formation of hydrogen-bonded systems between the protic solvent molecules and the protein chain in the wool.

Radiation-induced graft copolymerization of styrene on to nylon-6 via various routes

Radiation-induced graft copolymerization of styrene on to nylon-6 was performed by various methods. viz. liquid phase mutual irradiation, vapour phase mutual irradiation, and grafting on peroxidized polymer. Liquid phase mutual irradiation grafting was carried out in air either in the presence or in the absence of a redox salt. The use of a redox salt led to a considerable increase in the grafting yield. The effects of total dose, solvent type and composition, and monomer concentration on the direct grafting in the liquid and vapour phases were investigated. The results indicate that, if all the conditions were fixed, the vapour phase technique gave rise to higher grafting yields than the liquid phase method. Grafting yields obtained via the pre-irradiation method were considerably lower than those obtained under the same conditions of direct grafting either in the vapour or in the liquid phase.

Radiation‐induced graft copolymerization of styrene to cellulose

AbstractThe radiation‐induced graft copolymerization of styrene to cellulose has been studied in vacuo at 30°C and at dose rates from (0.37 to 8.73) × 10−2 W/kg. Dioxan was used as solvent for monomer and polystyrene homopolymer, and water (2% total volume) was incorporated as swelling agent for cellulose. The concentration of styrene in the bulk medium was varied from 0.432 to 3.46 moles/l., and the rates of both grafting and homopolymerization were shown to be proportional to [monomer] · [intensity]1/2. The value of 3.3 × 10−4 l. mole−1 sec−1 derived for kp2/kt in homopolymerization is similar to that for normal free‐radical polymerization of styrene. However, reduced termination during grafting yielded a much higher value (58 l. moles−1 sec−1). Degradation of cellulose in the absence of monomer was followed viscometrically, and values of 13.5 and 24.6 were derived for G (scission) in vacuo and in air, respectively.

The graft copolymerization of styrene and lignin. II. Kraft softwood lignin

AbstractThe radiation‐induced graft copolymerization of styrene and various kraft softwood lignins was studied. Expression of the results as the usual “per cent graft” was impossible, because grafting caused the lignin to become extractable in solvents for the styrene homopolymer. However, evaluation of the effects of various solvents on the degree of reaction was made through an indirect, and possibly more characteristic, measure. Grafting was least pronounced under conditions of low lignin accessibility (e.g., when less than 10% methanol was present), but increased with the addition of better lignin solvents or with higher methanol concentrations. The precipitating nature of the latter conditions was also found to contribute to an accelerated rate of grafting. Surprisingly, the graft copolymer was found to degrade at higher doses. Proof of grafting is offered in a fractionation scheme. Measurement of the molecular weight of the polystyrene separated from the lignin backbone allows the estimation of approximately one polystyrene graft per lignin molecule in benzene‐extractable copolymers. Two glass transition temperatures could be detected in several fractionated copolymers.