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Journal Articles

Ion-track grafting of vinylbenzyl chloride into poly(ethylene-$$co$$-tetrafluoroethylene) films using different media

Nuryanthi, N.*; Yamaki, Tetsuya; Kitamura, Akane; Koshikawa, Hiroshi; Yoshimura, Kimio; Sawada, Shinichi; Hasegawa, Shin; Asano, Masaharu; Maekawa, Yasunari; Suzuki, Akihiro*; et al.

Transactions of the Materials Research Society of Japan, 40(4), p.359 - 362, 2015/12

http://doi.org/10.14723/tmrsj.40.359

The ion-track grafting of a vinylbenzyl chloride (VBC) into a poly(ethylene-co-tetrafluoroethylene) (ETFE) film is necessary for preparing nanostructured hydroxide-ion-conductive electrolyte membranes. A key for success here is to obtain as high graft levels as possible (for higher conductivity) in a smaller number of tracks (for improving the other membrane properties). To this end, therefore, the effect of the medium for the VBC grafting was investigated as part of our continuing effort to optimize the experimental conditions. A 25 $$mu$$m-thick ETFE film was irradiated in a vacuum chamber with 560 MeV $$^{129}$$Xe at different fluences, and then the grafting was performed by immersing the irradiated films in a 20vol% VBC monomer at 60$$^{circ}$$C. A medium was a mixture of water (H$$_{2}$$O) and isopropyl alcohol (iPrOH) at different volume ratios. The degree of grafting increased as the H$$_{2}$$O content became higher, and reached a maximum in pure H$$_{2}$$O. These results can be explained by considering the well-known Trommsdorff effect, in which poor solubility of the grafted polymer in polar media leads to an increased polymerization rate probably due to a lower termination rate.

Journal Articles

Effect of $$gamma$$-irradiation on latent tracks of polyethylene terephthalate (PET) film

Hiroki, Akihiro; Asano, Masaharu; Yamaki, Tetsuya; Yoshida, Masaru

Chemical Physics Letters, 406(1-3), p.188 - 191, 2005/04

https://doi.org/10.1016/j.cplett.2005.02.115
 Times Cited Count：10 Percentile：32.95(Chemistry, Physical)

The pre-treatment effect of $$gamma$$-irradiation on latent tracks of polyethylene terephthalate (PET) films bombarded with swift heavy ions was investigated by electric conductometry and scanning electron microscopy (SEM) observation. The Xe-ion bombarded PET films were etched for 6 hours in 0.2 M NaOH aqueous solution at 70$$^{circ}$$C to prepare track-etched membranes. As $$gamma$$-irradiation doses increased in the range of 0-160 kGy, the pore diameter obtained by SEM observation decreased while that obtained by conductometry became large. This inconsistent result between the two methods was due to an increase in the crosslinked region in the latent tracks caused by $$gamma$$-irradiation.

Oral presentation

Ion-track grafting of vinylbenzyl chloride into poly(ethylene-co-tetrafluoroethylene) films using different media; Comparison with $$gamma$$-ray-induced grafting

Nuryanthi, N.*; Yamaki, Tetsuya; Kitamura, Akane; Koshikawa, Hiroshi; Yoshimura, Kimio; Sawada, Shinichi; Hasegawa, Shin; Asano, Masaharu; Maekawa, Yasunari; Suzuki, Akihiro*; et al.

no journal, , 

The ion-track grafting of a vinylbenzyl chloride (VBC) into a poly(ethylene-co-tetrafluoroethylene) (ETFE) film is necessary for preparing nanostructured hydroxide-ion conductive electrolyte membranes. A key for success here is to obtain as high graft levels as possible (for higher conductivity) in a smaller number of tracks (for improving the other membrane properties). To this end, therefore, the effect of the medium for the VBC grafting was investigated as part of our continuing effort to optimize the experimental conditions. A 25 $$mu$$m-thick ETFE film was irradiated in a vacuum chamber with 560 MeV $$^{129}$$Xe at different fluences, and then the grafting was performed by immersing the irradiated films in a 20vol% VBC monomer at 60$$^{circ}$$C. A medium was a mixture of water (H$$_{2}$$O) and isopropyl alcohol (iPrOH) at different volume ratios. The degree of grafting increased as the H$$_{2}$$O content became higher, and reached a maximum in pure H$$_{2}$$O.

Oral presentation

Creation of fluoropolymer-based nanostructures by swift-heavy-ion irradiation

Yamaki, Tetsuya

no journal, , 

My talk is devoted to the following two topics, both of which include the creation of fluoropolymer-based nanostructures with swift heavy ions mainly from the cyclotron of the Takasaki Ion Accelerators for Advanced Radiation Application. (1) We have prepared the ion-track membranes of poly(vinylidene fluoride) (PVDF), a type of fluoropolymer, by etching out latent tracks of MeV-GeV heavy ions in an alkaline solution. (2) The electrolyte membranes for fuel cell applications have been prepared by the direct grafting of a styrene monomer into the ion tracks in a fluoropolymer substrate, poly(ethylene-co-tetrafluoroethylene) (ETFE) film.

Oral presentation

Nanostructure-controlled anion exchange membranes for fuel cell applications by high-energy heavy-ion irradiation; Preparation and characterization of anion exchange membranes

Yamaki, Tetsuya; Nuryanthi, N.*; Kitamura, Akane; Koshikawa, Hiroshi; Yoshimura, Kimio; Sawada, Shinichi; Asano, Masaharu; Maekawa, Yasunari; Suzuki, Akihiro*; Terai, Takayuki*

no journal, , 

Heavy ions at kinetic energies typically from several hundreds of MeV to a few GeV passing through a polymer substrate induce a continuous trail of excitations and ionizations called latent tracks. We used a direct ion-track grafting method for preparation of anion exchange membranes for fuel cells. The functional anion exchange groups were introduced inside the latent tracks, thereby achieving OH$$^{-}$$-conductive channels through the thickness. These straight channels increased conductivities, while the isolated cylindrical structure of tracks restricted the water uptake.

Oral presentation

Ion-track grafting of vinylbenzyl chloride into poly(ethylene-co-tetrafluoroethylene) films; Kinetic analysis of reaction-medium effects

Yamaki, Tetsuya; Nuryanthi, N.*; Kitamura, Akane; Koshikawa, Hiroshi; Yoshimura, Kimio; Sawada, Shinichi; Asano, Masaharu*; Maekawa, Yasunari; Suzuki, Akihiro*; Terai, Takayuki*

no journal, , 

We investigated the ion-track grafting of vinylbenzyl chloride (VBC) into a poly(ethylene-${it co}$-tetrafluoroethylene) (ETFE) film using different grafting media for applications as anion exchange membranes for fuel cells. In an attempt to increase the grafting yield, we applied a poor solvent system as the grafting medium, ${it i.e.}$, a mixture of water and isopropyl alcohol (H$$_{2}$$O-${it i}$PrOH mixture). The optimum H$$_{2}$$O-${it i}$PrOH composition was identified by the kinetic parameters including the initial polymerization rate (r$$_{p0}$$), the radical recombination rate ($$gamma$$) and the grafting efficiency (r$$_{p0}$$/$$gamma$$). These parameters changed depending on the VBC-grafting/chain-transfer reaction competition for the radicals on ETFE and the Trommsdorff effect; the swelling of the grafting substrate gave an additional effect.

Oral presentation

Ion-track grafting of vinyl benzyl chloride into poly(ethylene-co-tetrafluoroethylene) film by different ion beams

Nuryanthi, N.*; Yamaki, Tetsuya; Kitamura, Akane; Koshikawa, Hiroshi; Yoshimura, Kimio; Sawada, Shinichi; Asano, Masaharu*; Maekawa, Yasunari; Suzuki, Akihiro*; Terai, Takayuki*

no journal, , 

We have used the ion-track grafting technique for developing an anion exchange membrane for fuel cell applications. In order to obtain the membrane, a vinyl benzyl chloride (VBC) was grafted into an ion-irradiated poly(ethylene-${it co}$-tetrafluoroethylene) film. This study deals with investigation of the radicals remaining in each track and the VBC grafting with a variety of ion beams from the TIARA cyclotron. The accelerated ions with different masses and energies enabled us to clarify the effect of the LET and radial dose distribution in the track on the VBC grafting. Such extensive research will bring us interesting knowledge relating the track structures to the resulting membrane properties.

Oral presentation

Heavy ion tracks in fluoropolymer film; Recent developments and future prospects

Yamaki, Tetsuya; Nuryanthi, N.*; Koshikawa, Hiroshi; Asano, Masaharu*; Sawada, Shinichi; Kitamura, Akane; Maekawa, Yasunari; Kay-Obbe, V.*; Severin, D.*; Seidl, T.*; et al.

no journal, , 

Practically, polyvinylidene fluoride (PVDF) has been said to be the only fluoropolymer in which ion tracks can be developed by chemical etching. We thus investigated the possibility of varying the beam parameters and applying the effect of a pre-etching treatment for PVDF ion-track membranes with the goal of achieving enhanced track etching for effective control of the pore size and shape. Our activities also cover all types of fluoropolymers including PVDF. Compared to PVDF, poly(ethylene-${it co}$-tetrafluoroethylene) and a series of perfluoropolymers are known to be very stable in highly-concentrated acid or alkaline solutions or at higher temperatures. Although this property might make their ion-track etching very challenging, the ongoing research is expected to allow one to accumulate know-how on methods of chemical etching, which can be generalized for the chemical structures. These will give feedback to a guiding principle for effective ion-track etching in fluoropolymers.

Oral presentation

Characterization of ion-exchange membranes prepared by ion irradiation graft polymerization method and $$gamma$$-ray irradiation graft polymerization method

Goto, Mitsuaki*; Omori, Masayuki*; Yamaki, Tetsuya; Sawada, Shinichi; Koshikawa, Hiroshi; Kitamura, Akane; Higa, Mitsuru*

no journal, , 

We have prepared cation exchange membranes for applications to electrochemical energy-conversion devices by swift-heavy-ion irradiation, and then investigated their charge density, ${it i.e.}$, a concentration of fixed charge groups, in comparison with that of the conventional $$gamma$$-ray-grafted membranes. Poly(ethylene-${it co}$-tetrafluoroethylene) films with a 25 $$mu$$m thickness were irradiated in a vacuum chamber with 560 MeV $$^{129}$$Xe and subsequently immersed in a grafting solution containing sodium ${it p}$-styrenesulfonate at 60$$^{circ}$$C. The charge density was estimated through the measurement of the membrane potential in an aqueous solution of potassium chloride. Our membranes exhibited higher charge density (reaching 2.40 mol/dm$$^{3}$$ at maximum) than the $$gamma$$-ray-grafted samples probably due to track structures characteristic of the bombarding heavy ions.

Oral presentation

Track structure effect on the ion-track grafting of vinylbenzyl chloride into poly(ethylene-${it co}$-tetrafluoroethylene) films

Nuryanthi, N.*; Yamaki, Tetsuya; Saiki, Seiichi; Kitamura, Akane; Koshikawa, Hiroshi; Yoshimura, Kimio; Sawada, Shinichi; Terai, Takayuki*

no journal, , 

This study deals with the ion-track grafting of vinylbenzyl chloride (VBC) into poly(ethylene-${it co}$-tetrafluoroethylene) (ETFE) film irradiated with 560 MeV $$^{129}$$Xe and 330 MeV $$^{40}$$Ar for the application to anion exchange membrane fuel cells (AEMFC). The accelerated ions with different masses and energies enabled us to clarify the effect of the LET and radial dose distribution in the track on the ETFE film. The lower-LET Ar ion gave the higher degree of VBC grafting than the higher-LET Xe ion although its radial dose distribution showed smaller track size. This study gave an insight of the importance to study the track structure in relation with the final membrane properties of the AEMFC.

Oral presentation

Characterization of ion-exchange membranes prepared by ion irradiation graft polymerization method

Goto, Mitsuaki*; Yamaki, Tetsuya; Koshikawa, Hiroshi; Sawada, Shinichi; Kitamura, Akane; Higa, Mitsuru*

no journal, , 

We have exploited a grafting technique with heavy-ion beams to create ion exchange membranes for various practical applications such as fuel cells and water desalination systems. In this study, instead of styrene that is a common monomer, sodium styrene sulfonate (SSS) was for the first time employed for this so-called ion-track grafting. A 25 $$mu$$m-thick poly(vinylidene fluoride) film was bombarded with 560 MeV $$^{129}$$Xe at a fluence of 3.0$$times$$10$$^{8}$$ or 1.0$$times$$10$$^{9}$$ ions/cm$$^{2}$$, and subsequently immersed in a SSS grafting solution at 60$$^{circ}$$C. The charge density was estimated through the measurement of the membrane potential in an aqueous solution of potassium chloride. Our membranes exhibited higher charge density than the conventional or commercially-available samples probably due to track structures characteristic of the bombarding heavy ions.

Oral presentation

Preparation and characterization of anion exchange membranes for fuel cell applications by ion-track grafting polymerization

Nuryanthi, N.*; Yamaki, Tetsuya; Kitamura, Akane; Koshikawa, Hiroshi; Sawada, Shinichi; Yoshimura, Kimio; Terai, Takayuki*

no journal, , 

Swift heavy ions with kinetic energies of MeV to GeV will create cylindrical tracks along their trajectories in a polymer film. These tracks of tens to hundreds nanometers in diameter contain free radicals; they can be used as initiators for graft polymerization. The so-called ion-track grafting technique was used for the development of anion exchange membranes (AEMs). The OH$$^{-}$$ conductivities at 60$$^{circ}$$C in the fully-hydrated state were higher for ion-track-grafted membranes than for the conventional $$gamma$$-ray-grafted ones at the certain same IEC. Due to a lower diffusion coefficient of OH$$^{-}$$, improving the conductivity has been one of the most challenging problems in AEM studies. In this sense, we found the ion-track grafting to be very promising.

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