Radiation-induced Graft Polymerization Research Articles

Graft-type polymer electrolyte membranes for fuel cells prepared through radiation-induced graft polymerization into alicyclic polybenzimidazoles

Graft-type sulfonated polybenzimidazole was prepared through radiation-induced graft polymerization of styrenes into an alicyclic polybenzimidazole film and subsequent sulfonation. The alicyclic polybenzimidazole, ChPBI, was prepared from trans-1,4-cyclohexanedicarboxylic acid and 3,3′-diaminobenzidine using typical polycondensation. Anisotropic domains with a size of several tens of micrometers were found in the ChPBI films casted from LiCl-containing N,N-dimethylacetamide. Irradiation of the ChPBI membranes with a 220 kGy dose of γ-rays created radical species with mean lifetimes of two days. The treatment of this membrane with a 50/50 (v/v) mixture of 1-propanol and styrene produced polystyrene graft chains. Sulfonation of the resulting grafted membrane with ClSO3H occurred selectively on the polystyrene grafts. The sulfonated films showed proton conductivity on the order of 10−3–10−2 S/cm with an ion exchange capacity between 2.1 and 2.9 mmol/g. SEM-EDX analysis of the membrane indicated the presence of macrophase separated domains up to 1 μm in diameter. The proton conductivity of the membrane did not decrease for 600 h at 120 °C in liquid water.

Design of modified plastic surfaces for antimicrobial applications: Impact of ionizing radiation on the physical and mechanical properties of polypropylene

Surface modification of polypropylene (PP) sheets was carried out by radiation induced graft polymerization of hydrophilic functional molecules such as N,N-dimethylacrylamide (DMA) and [2-methacryloyloxy)ethyl] trimethylammonium chloride, which is a quaternary ammonium salt (QAS).Polypropylene sheets were activated prior to the grafting reaction by using electron beam radiation. The changes in morphology, crystallinity and tensile parameters like deformation and stress at yield and deformation at break of PP after irradiation were investigated. The results showed that a minor crystalline reorganization takes place during the irradiation of PP at 100kGy.The grafting has been observed to be strongly dependent on the monomer dilution in the reaction medium. After grafting of QAS (40%) and DMA (20%) it was possible to develop highly hydrophilic surfaces (water contact angle comprised between 30 and 41°). The surfaces of virgin, irradiated and grafted PP were studied using polarized optical microscopy (POM) and scanning electron microscopy (SEM). Spherical particles (i.e. polystyrene or silica beads) adhering to the modified samples were studied according to the surface parameters. Adhesion tests confirmed the strong influence of substrate type (mainly hydrophilicity and roughness) and to a lesser extent underlined the role of electrostatic interactions for the design of plastic surfaces for antimicrobial applications.

Preparation of quaternized poly(vinylidene fluoride) membranes by γ-ray irradiation induced graft polymerization and their antibacterial property

PVDF microfiltration membranes were modified by γ-ray irradiation induced grafting polymerization of 4-vinyl pyridine (4-VP) and then quaternization by n-butyl chloride. The effects of grafting method (simultaneous irradiation, pre-irradiation/UV), grafting conditions (absorbed dose, UV irradiation time, and 4-VP concentration) and quaternization conditions (temperature, time, and concentration of n-butyl chloride) were investigated. It was found that, the grafting degree initially increases with the absorbed dose and then reaches a plateau. The optimal concentration of 4-VP is around 15wt.%. The ion exchange capacity increases with quaternization temperature, time, and concentration of n-butyl chloride. After modification, the pores size, permeation flux, as well as elongation at break, of quaternized membrane decreases, while the retention coefficient, tensile strength and Young’s modulus increase apparently. Upon contacting with the membranes, the Escherichia coli concentration decreases gradually. It is the adsorption mechanism for the pristine membranes whereas contact-killing mechanism for the quaternized membranes. Simultaneous irradiation is more effective than pre-irradiation/UV in the improvement of antibacterial property of membranes.

Cesium removal in freshwater using potassium cobalt hexacyanoferrate-impregnated fibers

Potassium cobalt hexacyanoferrate compounds (KCo-HCFe's) were impregnated onto a 6-nylon fiber by radiation-induced graft polymerization and subsequent chemical modifications. First, dimethylaminoethyl methacrylate was graft-polymerized onto the nylon fiber. Second, hexacyanoferrate ions were bound to graft chains via an anion-exchange interaction. Third, KCo-HCFe's were formed on the nylon fiber via the precipitation reaction of hexacyanoferrate ions with cobalt ions in the presence of potassium chloride. The resulting KCo-HCFe-impregnated fiber had an impregnation percentage of the fiber for KCo-HCFe's of 7%. The cesium concentration in 10ppm cesium chloride solution with the immersion of this fiber decreased to 0.6ppm within 60min at a ratio of liquid volume (10mL) to fiber mass (0.1g). The fiber was fabricated into a braid with a length of 100cm and a diameter of 8cm for practical use at sites contaminated with cesium.

Crystal morphology-dependent graft polymerization in poly(ether ether ketone) films

The effect of crystal morphology, such as the crystallinity and lamellar structure, on the radiation-induced graft polymerization of styrenesulfonate ethyl ester (E4S) onto poly(ether ether ketone) PEEK films was evaluated. The PEEK films possessing crystallinities ranging from 11 to 32% were irradiated with 30–150 kGy, and the graft polymerization was performed in an E4S/1,4-dioxane solution at 80 °C. For the PEEK films with crystallinities between 11 and 26%, the graft polymerization proceeded and reached grafting degrees of up to 70%, whereas for those having crystallinities higher than 26%, the reaction barely proceeded. The concentration of phenoxy radicals that initiated the graft polymerization in the irradiated PEEK films was constant over the entire range of crystallinity (11–32%). On the other hand, in the small-angle X-ray scattering (SAXS) profiles, a discontinuous change in the peak intensity at Q = 0.44 nm−1, which corresponds to a lamellar spacing of 14 nm, was observed at a crystallinity of approximately 26%; namely, the PEEK films with a crystallinities greater than 26% exhibited prominent anisotropic scattering in the drawing direction. Judging from the above results, it can be concluded that the graft polymerization of styrene derivatives onto the PEEK films was affected by the formation of oriented lamellar structures that inhibited monomer diffusion into the films.

Selective Immobilization of Silver Nanoparticles onto Poly(acrylic acid)-Patterned Poly(tetrafluoroethylene) Surface Prepared by Using Radiation-Induced Graft Polymerization

Chan-Hee Jung1, In-Tae Hwang1, In-Seol Kuk1, Oh-Sun Kwon2, Kwanwoo Shin2, and Jae-Hak Choi1 3 ∗ 1Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup-si, Jeollabuk-do 580-185, Republic of Korea 2Department of Chemistry and Institute of Biological Interfaces, Sogang University, Seoul 121-742, Republic of Korea 3Department of Polymer Science and Engineering, Chungnam National University, Yusong-gu, Daejeon 305-764, Republic of Korea

Polymerization mechanism for radiation-induced grafting of styrene into alicyclic polyimide films for preparation of polymer electrolyte membranes

Alicyclic polyimides (APIs) derived from 1, 2, 4, 5-pyromellitic dianhydride (PMDA) bis(4-aminocyclohexyl)methane (DCHM) were successfully applied to radiation-induced graft polymerization for developing polymer electrolyte membranes for fuel cells. Pyromellitic-type CoPIs were prepared from PMDA and a mixture of aromatic and alicyclic diamines with certain molar ratios, and the radiation-induced grafting of styrene was then examined using pre-irradiation with a dose of 220kGy, followed by graft polymerization in a bulk styrene solution at 60°C. The grafting into fully aromatized polyimide barely proceeded (degree of grafting (DG) of less than 5%), whereas that of styrene into the API films proceeded with styrene DGs of up to 70%.Electron spin resonance measurements clearly showed that the irradiated API with the highest alicyclic component possessed the largest amount of radicals (up to 1.13 × 1018spins/g). Furthermore, in combination with ultraviolet–visible (UV–vis) spectroscopy, the radical species was identified as a long-lived intermediate with a spectrum containing λmax = 420 and 600nm, and 10% of the radicals were consumed as grafting initiators. Note that the alicyclic structure of the API films is advantageous for radiation-induced graft polymerization because of the generation of high-concentration initiation radicals.The moderate reaction conditions allowed for selective sulfonation on the polystyrene grafts, and not on the API substrates, to give API-based polymer electrolyte membranes (PEMs) with ion exchange capacities (IECs) of 1.7–2.8mmol/g. The PEMs exhibited appropriate proton conductivity (0.06 ≤ σ ≤ 0.34S/cm) and low water uptake (≤100%), together with excellent mechanical properties (tensile strength, 90MPa), compared with conventional PEMs such as Nafion®.

Simultaneous radiation induced graft polymerization of N-vinyl-2-pyrrolidone onto polypropylene non-woven fabric for improvement of blood compatibility

In this study, N-vinyl-2-pyrrolidone (NVP) was grafted onto polypropylene non-woven fabric (PPNWF) through a simultaneous irradiation induced graft polymerization technique. Effect of the parameters of graft polymerization, i.e., monomer concentration, absorbed dose and dose rate, on the degree of grafting (DG) was investigated. The graft polymerization of NVP was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). A contact angle goniometry was used to test water contact angle (WCA) of original PPNWF and modified samples. The in vitro blood compatibility, including hemolysis, protein adsorption, platelet adhesion and activated partial thromboplastin time (APTT) of tested specimens, was evaluated. The results demonstrated that the hemocompatibility of PPNWF was improved via graft polymerization of NVP.

Alkaline Durable Anion Exchange Membranes Based on Graft-Type Fluoropolymer Films for Hydrazine Hydrate Fuel Cell

Anion exchange membranes (AEMs) having polyvinylimidazolium grafts were synthesized by radiation-induced graft polymerization of N-vinylimidazole (NVIm) or the coplymerizaiton with styrene onto poly(ethylene-co-tetrafluoro-ethylene) (ETFE) film, followed by N-alkylation and ion exchange reactions. The alkaline durability of the membranes was evaluated in 1M KOH at 60 and 80{degree sign}C. The AEM consisting of the homopolymer and copolymer (1:1 molar ratio) grafts (AEM2 and AEM3) with the ion exchange capacity (IEC) of 0.86 and 1.18 mmol g-1 exhibited ionic conductivity of 23 and 63 mS cm-1, respectively. The homopolymer-type AEM2 showed alkaline stability at 60 {degree sign}C for 270 hours, but degraded at 80 {degree sign}C for ca. 150 hours. In contrast, the copolymer-type AEM3 kept its ion conductivity above 10 mS cm-1 in 1M KOH at 80 {degree sign}C for 250 h. The alkylimidazolium group in the copolymer grafts is a promising anion exchange group in AEMs for highly alkaline durable fuel cells.

Dependence of protein binding capacity of dimethylamino-γ-butyric-acid (DMGABA)-immobilized porous membrane on composition of solvent used for DMGABA immobilization

Dimethylamino-γ-butyric acid (DMGABA) as an ampholite was reacted with the epoxy group of the poly-glycidyl methacrylate chain grafted onto the pore surface of a porous hollow-fiber polyethylene membrane by radiation-induced graft polymerization. DMGABA was dissolved in a mixture of dioxane and water at various dioxane volume fractions, defined by dividing the dioxane volume by the total volume. The equilibrium binding capacity (EBC) of the DMGABA-immobilized porous hollow-fiber membrane for lysozyme was evaluated in the permeation mode. The EBC was varied from a 1/50-fold monolayer binding capacity to a 10-fold monolayer binding capacity by controlling the composition of the solvent used for DMGABA immobilization and the molar conversion of the epoxy group into the DMGABA group.

Location and size of nanoscale free-volume holes in crosslinked- polytetrafluoroethylene-based graft-type polymer electrolyte membranes determined by positron annihilation lifetime spectroscopy

The location and size of nanoscale free-volume holes (nanoholes) in graft-type polymer electrolyte membranes (PEMs), which were prepared by radiation-induced graft polymerization (grafting) of styrene into crosslinked-polytetrafluoroethylene (cPTFE) films and subsequent sulfonation, were investigated using positron annihilation lifetime (PAL) spectroscopy. The PAL spectra of the PEMs indicated the existence of two types of ortho-positronium (o-Ps) species, corresponding to nanoholes with volumes of 0.11 and 0.38nm3. A comparison of the PAL data of the PEMs with that of the precursor original cPTFE and polystyrene-grafted films demonstrated the probability that the smaller holes were located in both the PTFE crystalline phases and the poly(styrene sulfonic acid) graft regions, whereas the larger holes are potentially localized in the PTFE amorphous phases. Taking into account both the size and the location of the nanoholes, it was concluded that gas transport through the larger holes in the amorphous PTFE phases was dominant over permeation through the smaller holes in the PTFE crystals and grafted regions.

Synthesis of polystyrene-grafted-graphene hybrid and its application in electrochemical sensor of dopamine

Polystyrene-grafted-graphene oxide hybrid was prepared via γ-ray irradiation-induced graft polymerization and then reduced to polystyrene-grafted-graphene hybrid by the solvothermal reduction method. The structure, thermal stability and morphology of polystyrene-grafted-graphene hybrid were investigated by Fourier transform infrared spectroscopy, X-ray diffractometer, thermogravimetric analysis and scanning electron microscopy. It reveals that γ-ray irradiation is expected to be an effective and facile technique for scale-up preparation of polymer functionalized graphene. The hybrid modified glassy carbon electrodes were applied to the electrochemical sensor of dopamine and a good linearity with the concentration in the range of 5–100μM was obtained. The excellent behavior as electrochemical sensor of the polymer functionalized hybrid may lead to new applications in electrochemical analysis.

One-pot, Radiation-induced Graft Polymerization of Vinylsulfonic Acid onto Poly(ether ether ketone) and High Proton Conductivity of Its Membrane

Abstract A poly(vinylsulfonic acid) (PVSA)-grafted poly(ether ether ketone) (PEEK) was simply prepared by one-pot, γ-ray radiation-induced graft polymerization of the vinylsulfonic acid (VSA) solution dissolving PEEK. The VSA-highly-grafted PEEK membrane possessed high ion exchange capacity (e.g., 7.2 mequiv g−1) and showed proton conductivity in the order of 10−1 and 10−3–10−6 S cm−1 under hydrated and nonhumidified conditions, respectively.

Removal of Urea from Water Using Urease-Immobilized Fibers

Dimethylaminoethyl methacrylate (DMAEMA) was graft-polymerized at a density of 1.7 mmol/g onto a 6-nylon fiber by radiation-induced graft polymerization. Urease was bound to the resultant anion-exchange fiber by electrostatic interaction. After crosslinking with transglutaminase, 80% of the bound urease was immobilized at a density of 41 mg/g of the fiber. Urea in water was quantitatively hydrolyzed during the permeation of a 0.20 mg/L urea solution through the urease-immobilized-fiber-packed bed with a diameter of 5.5 mm and a height of 27 mm in the residence time range of 12–180 s. The activity of immobilized urease did not deteriorate after repeated use of the fiber, i.e., during reaction and storage.

Protein-Binding Characteristics of Anion-Exchange Particles Prepared by Radiation-Induced Graft Polymerization at Low Temperatures

Protein-Binding Characteristics of Anion-Exchange Particles Prepared by Radiation-Induced Graft Polymerization at Low Temperatures

放射線グラフト重合法による高機能イオン交換高分子材料の開発<br/>―グラフト鎖の伸縮の検出と活用―

放射線グラフト重合法による高機能イオン交換高分子材料の開発<br/>―グラフト鎖の伸縮の検出と活用―

Nanoscale structures of radiation-grafted polymer electrolyte membranes investigated via a small-angle neutron scattering technique

The nanoscale structures of graft-type polymer electrolyte membranes (PEMs), prepared by radiation-induced graft polymerization (grafting) of styrene onto poly(ethylene-co-tetrafluoroethylene) (ETFE) films followed by sulfonation, were investigated using a small-angle neutron scattering (SANS) technique. For comparison, SANS measurements were also performed on two precursor materials, the original ETFE film and polystyrene (PS)-grafted films. The SANS profiles of the grafted films showed shoulder peaks at a d-spacing of ∼30 nm, which were attributed to the PS grafts introduced into the amorphous phases between the ETFE lamellar crystals. This grafting would result in the construction of a stack structure with alternating ETFE crystalline and PS-grafted layers as a repeating unit. In the ETFE PEMs, the spacing of the PS sulfonic acid (PSSA) grafts and ETFE crystals increased because the graft regions were enlarged by the volume of the attached sulfonic acid groups. Interestingly, the graft/crystal stack spacing in the PEMs did not increase from the dry- to fully-hydrated states. This finding implies restricted water absorption in the PSSA grafts between the ETFE lamellar crystals. In other words, most of the PSSA grafts introduced outside of the lamellae were considered to be hydrated and to act as proton conduction pathways. The nanoscale structures of graft-type PEMs, prepared by radiation-induced graft polymerization of styrene onto poly(ethylene-co-tetrafluoroethylene) (ETFE) films followed by sulfonation, were investigated using a small-angle neutron scattering (SANS) technique. The SANS profiles of the grafted films showed shoulder peaks at a d-spacing of ∼30 nm, which were attributed to the polystyrene grafts introduced into the amorphous phases between the ETFE lamellar crystals. In the ETFE PEMs, this d-spacing increased to 34 nm because the graft regions were enlarged by the volume of the attached sulfonic acid groups.

Gamma radiation-induced grafting of glycidyl methacrylate (GMA) onto water hyacinth fibers

Water hyacinth fibers (Eichhornia crassipes) were functionalized using radiation-induced graft polymerization of glycidyl methacrylate by γ-rays from 60Co source. The simultaneous grafting technique was employed wherein the water hyacinth fibers were irradiated in nitrogen atmosphere in the presence of glycidyl methacrylate dissolved in water/methanol solvent. The effects of different grafting parameters to the grafting yield were evaluated. The optimal values of solvent, absorbed dose, dose rate, and concentration of monomer were found to be 1:3 (volume/volume) water–methanol solvent, 10kGy, 8kGyh−1 dose rate and 5% volume/volume glycidyl methacrylate, respectively. Using the optimum conditions, degree of grafting of approximately 58% was achieved. The grafted water hyacinth fibers were characterized using Attenuated Total Reflectance-Fourier Transformed Infrared Spectroscopy (ATR-FTIR), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). The results of these tests confirmed the successful grafting of glycidyl methacrylate onto water hyacinth fibers.

Crosslinking induced by irradiation raises selectivity of polymeric adsorbent

Amine-type adsorbents were prepared by radiation-induced graft polymerization. The sorption behaviors for an individual metal ion of Cu2+ and Pb2+ separately, as well as with mixed Cu2+/Pb2+, were studied in both column and batch mode. Ethylenediamine-type adsorbent exhibited a high capacity for Cu2+ and Pb2+ at a high flow rate of 1000 h−1, but low selectivity in the mixed Cu2+/Pb2+ solutions. Radiation-induced crosslinking of the amine-type adsorbent was performed in water to improve selectivity. Crosslinking of the material was demonstrated by gel fraction, water content, and scanning electron microscopy image. Compared with the results from the noncrosslinked adsorbents, the breakthrough curve of Cu2+ right shifted, whereas the breakthrough curve of Pb2+ left shifted, indicating the higher adsorption capacity of Cu2+ and the lower adsorption capacity of Pb2+ from the crosslinked adsorbent. After 300 kGy irradiation, the crosslinked adsorbent was found to selectively adsorb Cu2+ from the mixed Cu2+/Pb2+ solution. The results revealed that crosslinking raised the selectivity of the adsorbents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Microfiltration membranes prepared from poly(N-vinyl-2-pyrrolidone) grafted poly(vinylidene fluoride) synthesized by simultaneous irradiation

Poly(N-vinyl-2-pyrrolidone) grafted poly(vinylidene fluoride) (PVDF-g-PVP) copolymers were synthesized by a simultaneous irradiation induced graft polymerization technique in a homogeneous system. The kinetics of the radiation induced graft polymerization was studied. Evidence for the existence of the graft chains in grafted PVDF was characterized by FT-IR spectroscopy in ATR mode. Then, membranes were cast from pristine PVDF and PVDF-g-PVP of different degree of grafting (DG) under phase inversion method. The contact angle, water uptake, water filtration and antifouling property of membranes were measured. The morphology was also studied with the use of AFM and SEM. The results showed that with the increasing DG, the contact angle became smaller, the water uptake, RMS roughness, water flux and pore size and amount of the membrane surface increased. The water flux recovery showed that membranes cast from PVDF-g-PVP also possessed an effective antifouling performance.