Surface Modification for the Hydrophobization of Cellulose Nanocrystals Using Radiation-Induced Grafting.

1H,1H,2H,2H-perfluorodecyl acrylate (PFDA) was grafted using electron beam irradiation to hydrophobize the cellulose nanocrystals' (CNC) surface. FT-IR and XPS measurements showed that PFDA was grafted onto the CNC surface. The results of SEM and EDS showed that PFDA was grafted to the CNC surface in a spherical shape. As a result of the XRD measurement, it was confirmed that the crystallinity of PFDA decreased as it was grafted onto the CNC surface. As a result of the contact angle measurement, it was shown that as the PFDA was grafted on the CNC surface, the contact angle increased, which means that the hydrophobicity increased.

Synthesis and Characterization of Cation-Exchange Fibers with Radiation-Induced Grafting of Glycidyl Methacrylate onto Cotton Cellulose.

Conventional ion exchange beads are used for purification and demineralization of water and for various other applications in the chemical synthesis, hydrometallurgy, and agricultural industries. However, there are some disadvantages associated with ion exchange beads, such as distillation causing porosity during solvent removal, pre-swelling of beads to allow for core functionalization, and pre-swelling of beads overnight prior to end use. Fibrous ion exchange materials have advantages over the conventional ion exchange beads, including simplification of the overall preparation. In this study, a cation-exchange fiber was prepared by a radiation-induced grafting method. Glycidyl methacrylate (GMA) was grafted onto cotton cellulose using a pre-irradiation method by electronbeam irradiation. Sequential treatment with sulfonic acid was performed to react with the cation pollutants. The degree of grafting increased up to 812% with the increase of absorbed dose, reaction time and monomer concentration. It was found that the sulfonation reaction occurred smoothly with 10% sodium sulfite solution, and a high 2.0 meq/g ion exchange capacity was obtained from 140% GMA-grafted non-woven cotton fabric.

Diketopyrrolopyrrole-Based Metallated Polymer for Bulk-Heterojunction Solar Cells and Organic Field-Effect Transistors.

We report the synthesis and optoelectronic properties of novel platinum-based polymers (p-Pt-DPP) incorporating 3,6-di-2-thienyl-2,5-dihydro-2,5-diethylhexylpyrrolo[3,4-c]pyrrole-1,4-dione. The synthesized amorphous metallated polymer exhibited long wavelength absorption in the range of 500­684 nm and a band-gap as low as 1.75 eV. Organic field-effect transistors (OFETs) fabricated from p-Pt-DPP showed hole mobility of 1.6 × 10⁻³ cm² · V⁻¹s⁻¹ and an on/off ratio of 5 × 104. In addition, polymer solar cells (PSCs) based on p-Pt-DPP and PC71BM exhibited a photovoltaic efficiency of 1.22% under AM 1.5 G conditions with an illumination of 100 mW·cm−2 without any annealing process.

Preparation and Study on Nickel Oxide Reduction of Polyacrylonitrile-Based Carbon Nanofibers by Thermal Treatment.

Carbon materials containing magnetic nanopowder have been attractive in technological applications such as electrochemical capacitors and electromagnetic wave shielding. In this study, polyacrylonitrile (PAN) fibers containing nickel nanoparticles were prepared using an electrospinning method and thermal stabilization. The reduction of nickel oxide was investigated under a nitrogen atmosphere within a temperature range of 600 to 1,000 °C. Carbon nanofibers containing nickel nanoparticles were characterized by FE-SEM, EDS, XRD, TGA, and VSM. It was found that nickel nanoparticles were formed by a NiO reduction in PAN as a function of the thermal treatment. These results led to an increase in the coercivity of nanofibers and a decrease in the remanence magnetization.

Effects of surface characteristics of dielectric layers on polymer thin-film transistors obtained by spray methods.

The effect of surface characteristics of dielectric layers on the molecular orientation and device performance of sprayed organic field-effect transistors (OFETs) obtained by a novel solvent-assisted post-treatment, called the solvent-sprayed overlayer (SSO) method, were investigated. The OFETs were fabricated by the spray method using regioregular poly(3-hexylthiophene) (RR-P3HT) as an active material. The SSO treatment was applied on the as-sprayed active layers to arrange the molecular ordering. Bare thin SiO(2) layers and octadecyltrichlorosilane (OTS)-treated SiO(2) (OTS-SiO(2)) were employed as the dielectric materials. The resulting chain orientation, crystallinity, and device performance were correlated as a function of SSO treatment and dielectric layers. The intrinsic limitation of spray methods for polymer film formation was overcome regardless of the type of dielectric layer using the SSO treatment. The orientation direction of RR-P3HT was controlled by SSO treatment to an edge-on dominant orientation that is preferential for charge transport, regardless of the type of dielectric layer. The crystal growth was further enhanced on the OTS-SiO(2) layers because of the reduced nucleation sites. These effects were successfully reflected in the device performance, including an orders-of-magnitude increase in charge mobility. The SSO method is a powerful external treatment method for reorienting the molecular ordering of solidified active films of OFETs to the preferential edge-on packing. The growth of crystals was further optimized by controlling the surface characteristics of the dielectric layers. The purpose of this study was to find the full capabilities of the SSO treatment method that will facilitate the development of high-throughput, large-area organic electronic device manufacturing.

The optical and electrical properties of graphene oxide with water-soluble conjugated polymer composites by radiation.

In order to overcome the difficulty of dispersion and low conductivity in composite containing graphene, graphene oxide (GO) has been used instead of neat graphene. And the GO treated by radiation, could give improved conductivity of the GO-containing polymer composite. In this study, fluorene based water-soluble conjugated polymer (WPF-6-oxy-F) was introduced in GO solution to investigate the change of optical and electrical properties through radiation process. UV-Vis absorption of irradiated WPF-6-oxy-F-GO composite was red shifted and I(D)/I(G) ratio of Raman spectra decreased. XPS analysis showed that C-N bonds was formed after the irradiation and confirmed the increased bonds between the GO and the water-soluble conjugated polymer matrix. From the AFM and XPS analysis, it was found that the water-soluble conjugated polymer matrix was stacked between the modified GO in the morphology of irradiated WPF-6-oxy-F-GO composite was increased after gamma ray irradiation up to 10(-2) S/cm.

Characterization of polyacrylonitrile based carbon nanofiber mats via electron beam processing.

The aim of this study was to evaluate the ability of electron beam irradiation to drive stabilization reactions within PAN nanofiber mats to obtain carbon nanofiber mats. PAN nanofiber mats with fiber diameters of 300-400 nm were prepared via an electrospinning method. Electrospun PAN nanofiber mats were stabilized by electron beam irradiation with various doses up to 5,000 kGy. Using the irradiation-stabilized PAN nanofiber mats, carbon nanofibers were obtained by pyrolysis in a tube furnace for 1 h at 1,000 degrees C under an N2 atmosphere. FT-IR analysis indicated that the transformation of C[triple bond]N groups to C==N groups was accelerated by electron beam stabilization. The thermal behavior of the PAN nanofiber mats was studied using DSC and TGA. DSC thermograms showed that the peak temperatures of the exothermic reactions were found to decrease with increasing electron beam irradiation doses. Irradiation-stabilized PAN nanofiber mats were not observed to dramatically decrease in weight between 290 degrees C and 320 degrees C, an observation presumed to be related to cyclization. The char yields of PAN were found to increase with increasing irradiation doses.

Effect of electromagnetic shielding on electron beam-cured multi-walled carbon nanotubes/epoxy composites.

In this study, the electromagnetic interference shielding properties of multi-walled carbon nanotubes/epoxy composites were investigated in the frequency region from 1 approximately 8 GHz (L, S and C bands). Electromagnetic shielding samples were fabricated using an electron beam. The electromagnetic shielding properties of these absorber specimens were measured by a network analyzer (Agilent, 4901A), and their fracture behavior was analyzed by scanning electron microscopy. It was found that the saturation conductance depends on the fraction of the multi-walled carbon nanotubes in the composite, which affects the initial permittivity. These results show that the dielectric loss is a dominant factor in the L, S, and C bands, and the resonance frequency of the composite increased with the increasing fraction of multi-walled carbon nanotubes. Finally, the reflection loss was calculated from the permeability and permittivity of these composites. Composite with 10 wt% multi-walled carbon nanotubes and 1.5 mm thickness showed a reflection loss below -20 dB in the L, S, and C bands. Therefore, it is believed that thin multi-walled carbon nanotubes/epoxy composites may be good candidates for microwave absorption applications.

High frequency properties of Fe-Si nano-powder/epoxy films.

Composites of Fe93.5Si6.5 powder and epoxy (diglycidyl ether of bisphenol A type) were prepared using an electron beam irradiation process. Scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and network analyzer were used to analyze the structure, electromagnetic properties and micro wave absorption of the composites. Results show that the saturation magnetization depends on the fraction of the Fe93.5Si6.5 powder in the composite, which affects initial permeability. It is believed that the eddy current loss is a dominant factor over 1 GHz and that the resonance frequency of the composite decreases with increasing fractions of Fe93.5Si6.5 powder. Finally, reflection loss was calculated from the permeability and permittivity of these composites. Composite with 50 wt% Fe93.5Si6.5 powder fractions and 5 mm thickness showed reflection loss below -20 dB from 3.66 GHz to 4.16 GHz. Therefore, it is believed that thin Fe-Si/epoxy composites may be a good candidate for microwave absorption application.

Effects of Electron Beam Irradiation on the Electrospinning of Polyacrylonitrile.

Electron beam (e-beam) irradiation of polyacrylonitrile (PAN) was performed to investigate the effects of radiation on the electrospinning process. For this study, polyacrylonitrile powder was subjected to e-beam irradiation with different doses of up to 100 kGy under an N2 atmosphere. Polymer solutions were prepared by dissolving PAN in N,N-dimethyl-formamide (DMF) at a 1:9 ratio by weight. The prepared PAN/DMF solutions showed different colors with different e-beam doses. The resulting structures in solutions contained conjugated C=N bonds, which caused the observed color formation. In addition, the conductivity of the PAN/DMF solution increased with an increase in e-beam irradiation dose. In the DSC spectra of electrospun PAN fibers, the peak temperature of the exothermic reactions was observed to decrease with an increase in the e-beam irradiation strength.

Improved pretreatment process using an electron beam for optimization of glucose yield with high selectivity.

In this study, electron beam irradiation (EBI) assisted by a dilute acid pretreatment process was investigated to improve the glucose yield and show high selectivity in the enzymatic hydrolysis of rice straw. In the first step, EBI of rice straw was performed at various doses ranging from 50 to 500 kGy. The electron beam-irradiated rice straw was then autoclaved with 3 % dilute acid at 120 °C for 1 h. The pretreated rice straw was finally subjected to enzymatic hydrolysis at 50 °C for 24, 48, and 72 h by 70 filter paper units (FPU)/mL cellulase and 40 cellobiose units (CbU)/mL glucosidase. Glucose was obtained with a very high selectivity of 92.7 % and a total sugar yield of 80 % from pretreated rice straw after 72 h of enzymatic hydrolysis.