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Changes in the free volume of poly(tetrafluoroethylene-co-hexafluoropropylene) proton exchange membrane caused by the grafting of styrene and incorporation of a sulfonic acid group (-SO 3 H) was investigated by using a positron annihilation lifetime measurement. The free volume size of the film decreases because of not only the incorporation of -SO 3 H but also structural changes in hydrogen bonds during proton transportation. The decrease of free volume size leads to the close distribution of -SO 3 H; therefore, the performance of the proton exchange membrane increases with the increase of the degree of grafting. • Proton exchange membrane was fabricated from fluorinated polymer. • Free volume change was investigated by positron annihilation lifetime measurement. • Longest ortho -positronium (o -Ps) lifetime was shortened by the grafting and sulfonating. • Fraction of positrons annihilate as o -Ps was decreased by changes in the chemical structure of the membrane. [ABSTRACT FROM AUTHOR]

Ionic polymer-metal composites (IPMC) actuators were fabricated by applying ionic exchange groups such as sulfonic acids and carboxylic acids using EB graft-polymerization to two types of fluorine-based copolymers (Poly (tetrafluoroethylene-co-hexafluoropropylene): FEP and Poly (ethylene-co-tetrafluoroethylene): ETFE) as base materials, and then forming electrodes with Pt-Pd by sputtering. The physical properties of the obtained graft membrane and the evaluation as an actuator were performed. It was suggested that the acrylic acid graft membrane is preferable for PEM as components of IPMC actuator, because the ion conduction mechanism is a vehicle mechanism in which oxonium ions pass through formed hydrated clusters in PEM. In the case of operation at 10 V, IPMC actuator based on the acrylic acid-grafted FEP and ETFE showed similar or larger displacement than that based on conventional membrane. The grafted ETFE, which has high mechanical properties, is superior to the grafted FEP used in the actuators. Therefore, it was found that the ETFE grafted with acrylic acid is preferable for the IPMC actuator. • Ionic polymer-metal composites (IPMC) actuators were fabricated by applying ionic exchange groups using EB graft polymerization. • Physical properties of the obtained graft membrane and the evaluation as an actuator were performed. • Acrylic acid graft membrane was preferable for PEM as components of IPMC actuator. • Grafted ETFE, which has high mechanical properties, is superior to the grafted FEP used in the actuators. • ETFE grafted with acrylic acid is preferable for the IPMC actuator. [ABSTRACT FROM AUTHOR]

Thermo-responsive templates for the cell cultivation based on Poly(tetrafluoroethylene- co -ethylene) (ETFE) were fabricated by pre-irradiation grafting of N -isoproplyacrylamide (NIPAAm) monomer by electron beam (EB) irradiation under nitrogen gas atmosphere at room temperature, and their characteristic properties were studied. The detachment of cultured HeLa cells from fabricated thermo-responsive templates were attempted. Furthermore, the reaction mechanism is proposed using ESR spectroscopy and FT-IR spectroscopy. It is confirmed that the cultured HeLa cells were detached from fabricated thermo-responsive templates at 20 °C. Water contact angle analysis indicated that obtained templates had thermo-response around 30 °C. It is suggested that the grafted polymer chains would mainly react with peroxy radicals (–CF 2 –CF(OO･)–) on tetrafluoroethylene unit in ETFE. [ABSTRACT FROM AUTHOR]

Because of their different charge states, positrons and positronium (Ps) behave quite differently in macromolecules. The behavior of positively charged positrons is strongly influenced by electrostatic interactions. In nonpolar macromolecules such as polyethylene, energetic positrons, if not incorporated into Ps, fall into a delocalized state. These positrons are sensitively trapped by polar groups, if any. On the other hand, charge-neutral Ps is localized in a free volume regardless of the macromolecule's chemical structure. In this study, we discuss the behavior and annihilation characteristics of positrons and Ps in various macromolecules, emphasizing their differences. • Positrons fall into a delocalized mobile state in nonpolar macromolecules. • Positively charged positrons are sensitively trapped by polar groups. • Charge-neutral positronium is trapped by free volume. • Chemical structure has different effects for positron and positronium. [ABSTRACT FROM AUTHOR]

Micro-fabrication of poly(tetrafluoroethylene) (PTFE) was carried out using a high-energy heavy ion beam in the MeV region. PTFE was irradiated with various ions (6MeV/u) under vacuum (<1.0×10−4 Pa) at room temperature (298K). The surface of the irradiated PTFE was observed by laser microscopy and a scanning electron microscope (SEM). Micro-scale fabrications of PTFE were successfully performed by direct ion beam etching. Under our experimental conditions the etching proceeded more effectively by heavy ion beams (larger than N7+), compared with lower-energy ion beams (keV region). A larger atomic number (Z) of the irradiating ion induced higher etching rates in PTFE; the etching rate for Ne10+ and Xe54+ changed from 6.5×10−13 to 2.0×10−11 μm/(ioncm−2), respectively. As a result we suggest that due to their high electronic stopping powers, etching could be efficiently achieved using high-energy ion beams. [ABSTRACT FROM AUTHOR]

Abstract: Supercontinuum (SC) with photonic crystal fiber (PCF) is a new technique of pulsed white light generation. The pump beam and the white probe light are necessary for pump–probe pulse radiolysis. The improvement of pulse radiolysis system can be expected by using PCF based SC as probe light. The source size of white light that depends on core size of PCF will be improved. Nanosecond time resolution pulse radiolysis with SC probe was successfully conducted about pure water sample. The absorption decay and spectrum of hydrated electron was obtained. As SC is a short pulse, it would be applicable for picosecond time resolution pulse radiolysis based on the stroboscopic method. [Copyright &y& Elsevier]

Abstract: Trapped radicals induced in poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP) were observed by X-band electron spin resonance (ESR) spectroscopy at room temperature (RT) under atmospheric field after an irradiation with various kinds of high energy ion beams (6MeV/u). The irradiation was carried out to a stacked FEP films under vacuum (<4E−4Pa) at RT with various fluences from 1.0×109 to 1.0×1011 ions/cm2. All ESR spectra indicated an existence of peroxy radicals in each of the FEP films without any relation to a kind of ion and a penetration depth. Obtained depth profiles of radical concentrations induced with each ion beam almost correspond to those of stopping power. The trapped radical concentrations were strongly dependent on stopping power. It was found that G-value of trapped radicals by ion beam irradiation was decreased with increasing a stopping power, and was less than the case of gamma-rays irradiation. [Copyright &y& Elsevier]

Abstract: Micro- and nano-fabrications of polystyrene (PS) having the atactic and syndiotactic structures were carried out with direct maskless etching using focused ion beam (FIB). Micro- and nano-scale structures were obtained with selective beam and material conditions avoiding the beam-heating and charge-up effects. The etching rates were different between atactic and syndiotactic PS. The rate of fabrication for syndiotactic PS shows higher than that of atactic one. Moreover, the direct etching was influenced by the molecular weight. The etching rate for the lower molecular weight became the faster. The FIB direct etching proceeds through the two steps (decomposition and desorption (outgas)). Both decomposition and desorption are influenced by both conformation (morphology) and configuration (stereoregularity). Furthermore, the beam profiles and fluence play the important roles to perform the nano-fabrication of PS. [Copyright &y& Elsevier]

Abstract: High linear energy transfer (LET) heavy ion beams were used to irradiate poly(tetrafluoroethylene-co-ethylene) (ETFE) under vacuum and in air. The irradiation effects in ETFE as a function of the depth were precisely evaluated by analyzing each of the films of the irradiated samples, which were made of stacked ETFE films. It was indicated that conjugated double bonds were generated by heavy ion beam irradiation, and their amounts showed the Bragg-curve-like distributions. Also, it was suggested that higher LET beams would induce radical formation in high density and longer conjugated C=C double bonds could be generated by the second-order reactions. Moreover, for samples irradiated in air, C=O was produced correlating to the yield of oxygen molecules diffusing from the sample surface. [ABSTRACT FROM AUTHOR]

Abstract: Polytetrafluoroethylene (PTFE) was exposed to Ar, CF4, N2 and O2 plasmas using a reactive ion etching facility. After the exposure, the change in the surface morphology of PTFE was examined and characterization studies were performed for the etching rate, surface roughness, radical yields, chemical structures, water repellency and so on. The etching rates of Ar, CF4, N2 and O2 plasmas were 0.58, 7.2, 4.4 and 17μm/h, respectively. It was observed that needle-like nano-fiber structures on the surface were irregularly fabricated by the CF4 plasma. In addition, when the water repellency of exposed samples was evaluated by contact angle, they showed super-hydrophobic properties: contact angle over 150°. [ABSTRACT FROM AUTHOR]

Abstract: The sensitivities of deep-UV resist TDUR-P722 (Tokyo Ohka Kogyo Co., Ltd.) and two types of electron beam (EB) resists ZEP520A and ZEP7000 (ZEON Co.) to soft X-rays in the water window region (284–532eV) were investigated for the nano-scale imaging of the contact X-ray microscopy. At the periphery of the water window, there are absorption edges of main constituent elements of the resist materials, namely carbon and oxygen. It was found that the sensitivities varied widely along the range of X-ray energies used, which correlated with the X-ray absorption of the resists. Moreover for the first time, it was confirmed that K- and L-edge absorptions have a strong influence on the resist sensitivity. Among these resists, ZEP7000 had the highest sensitivity. It was suggested that water window X-ray imaging with nano-scale resolution would be possible with about 1/500 of the fluence, which has the same units (mJ/cm2 or J/cm2) as that of so-called dose/sensitivity in the field of resist research, compared with the previously reported method of using polymethylmethacrylate (PMMA). The details of the reaction mechanisms of the resists will be published elsewhere. [ABSTRACT FROM AUTHOR]

Abstract: Micro- and nano-fabrication researches of various perfluorinated polymers carried out recently both by synchrotron radiation (SR) direct photo-etching and by focused ion beam (FIB) direct mask less etching are reviewed. After the irradiation, the etching depth of the fabricated samples has been evaluated by optical microscope and scanning electron microscope. SR-induced surface modifications were studied by solid-state 19F nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimeter (DSC) analysis. It was found that the etching rate of FEP at 140°C was highest and that of PTFE and PFA at 140°C was lower in the SR etching. It was found that crosslinking reactions were induced by SR irradiation at the region within about 50μm from the irradiated surface. FIB mask less etching showed very attractive features for nano-scale fabrications. The aspect ratio for crosslinked PTFE (RX-PTFE) reached 390. In addition, the nano-scale controlled structures with high aspect and quality of RX-PTFE were obtained without solid debris. [ABSTRACT FROM AUTHOR]

Abstract: The performance of a polymer electrolyte fuel cell (PEFC) is affected by the interfacial property between the proton exchange membrane (PEM) and the electrodes. Thus, development of well-laminated membrane electrode assemblies (MEAs) has been carried out. The hybrid PEM, consisting of perfluoro-sulfonic acid (PFSA) ionomer and sulfonated polystyrene grafted tetrafluoroethylene-co-hexafluoropropylene (sulfonated PS-g-FEP) synthesized by the soft electron beam (soft-EB) induced grafting method, was fabricated by mixing sulfonated PS-g-FEP with PFSA ionomer, which is coated on the interface of the PEM and the electrodes. The obtained hybrid PEM was characterized in terms of water uptake, ion exchange capacity, polarization performance and electrochemical impedance. The ion exchange capacity (IEC) of the hybrid PEM was 1.0–1.2meq/g. The polarization curve and electrochemical impedance of the hybrid PEM was analyzed. As a result, the ionic conductivity was 0.16S/cm and is the highest in the tested PEMs. The maximum power density is about 1.0W/cm2 with low humidity (relative humidity RH: 16%), which is 1.5 times higher than that of commercially available Nafion® 112. [ABSTRACT FROM AUTHOR]

Abstract: An ultra low energy electron beam (UL-EB) was used to irradiate various polymeric materials such as fluorinated polymers and a polyimide under an oxygen-free atmosphere. After the irradiation of the polyimide, the change in the thermal properties was measured by DSC and TGA. The surface modification of fluorinated polymers was demonstrated by use of styrene grafting by the preirradiation grafting method. By the use of UL-EB irradiation it was possible to facilitate styrene monomer grafting onto the surface of fluorinated polymers without losing their material characteristics. Moreover, in the case of the polyimide (Kapton™), which has excellent radiation resistance, the glass transition temperature was improved by about 20°C by irradiation up to 40MGy within 1h. [ABSTRACT FROM AUTHOR]

Abstract: At Waseda University, we are developing a table-top size soft X-ray source based on inverse Compton scattering between a high quality electron beam and a high power laser. Using 1047nm laser beam (Nd:YLF) and 4.6MeV electron beam generated from a photo-cathode rf-gun, we had already succeeded in generating inverse Compton X-rays. The energies are within the “water window” region (250–500eV) which can be applied to biological studies. For good signal to noise ratio (S/N) and a larger number of photons, we remodeled our collision chamber and laser amplifier system. S/N is defined by the X-ray photon signal over all other noises and backgrounds such as a bremsstrahlung X-rays from a lost electron beam and an electric noises caused by a radiation and rf power source. With these modifications, the X-ray photons detected by a micro channel plate (MCP) have increased 10-fold to reach 312ph/pulse. Total generated photons were estimated to be 3.3×104. Further, we succeeded in generating stable soft X-rays for more than 12h. Good S/N ratio, stable X-rays have made it possible to observe the beam–laser interaction very precisely. By using this technique, we have measured the electron beam size at the collision point as 251μm (σx )×56μm (σy ). [Copyright &y& Elsevier]

Cell-sheet engineering aims to generate tissues and organs through lamination and transplantation of acquired cell sheets. The technique has become used in the field of regenerative medicine, and the development of cell-culture plates equipped with a switching function for cell adhesion/cell-sheet detachment has been in progress. Our research group has produced thermo-responsive cell-culture membranes by grafting poly(N -isopropylacrylamide) (PNIPAAm) onto an ethylene-tetrafluoroethylene copolymer (ETFE). Grafting is achieved via electron beam (EB) pre-irradiation grafting methods. The high biocompatibility of ETFE is well known, and high yields of trapped radicals can be obtained through the use of ionizing radiation. Increased thermo-responsivity of the cell-culture membranes can be achieved by increasing the amount of grafted PNIPAAm. In the present study, we fabricated grafted membranes with different grafting yields (GY), and evaluated the thermo-responsivity and cell-adhesion/cell-sheet-detachment abilities. First, C2C12 cells were cultured at 37°C for 2 days on the grafted samples, then the cell sheet was detached by reducing the temperature to 20°C after cell proliferation. In the fabricated samples with the GY of 14.9% ± 1.0%, cells reached confluence in 2 days, and the resulting cell sheet was detached within 15 min without any damage. • Thermo-responsive cell-culture membranes were created by grafting PNIPAAm onto ETFE. • Graft polymerization mechanism of ETFE and PNIPAAm was indicated by 13C-NMR results. • C2C12 cells proliferated on membranes and detached at low temperature. • Cell adhesion/cell-sheet detachment abilities were related to grafting yield. • Cell sheets without any damages were obtained from the membrane with GY 14.9 ± 1.0%. [ABSTRACT FROM AUTHOR]