Ring-opening polymerization of 2-oxazolines initiated by chloromethyl groups introduced onto carbon black surface

Summary The ring-opening polymerization of 2-oxazolines (OXZs) was found to be initiated by chloromethyl groups introduced onto carbon black surface. The introduction of chloromethyl groups onto the surface was achieved by the reaction of carbon black with 3,3-bischloromethylbenzoyl peroxide in carbon tetrachloride. During the polymerization, poly-OXZs were grafted from carbon black based on the propagation of the polymers from the surface: percentage of grafting increased with an increase of conversion and reached 40–60%. The polymerization was accelerated by the addition of potassium iodide. Poly-OXZ-grafted carbon black produced stable colloidal dispersions in both hydrophobic and hydrophilic solvents.     

Grafting of poly(ethylene-block-ethylene oxide) onto a vapor grown carbon fiber surface by γ-ray radiation grafting

To modify the surface of vapor grown carbon fiber (VGCF), poly(ethylene-block-ethylene oxide) (PE-b-PEO, M_n=1400, PEO content=50 wt%) was successfully grafted onto the surface by using γ-ray irradiation of the PE-b-PEO-adsorbed VGCF in solvent-free system. It is found that the percentage of polymer grafting reached 15.0% when the PE-b-PEO-adsorbed VGCF was irradiated by γ-ray over 40 kGy dose at 110 °C, but at the lower irradiation temperature of 75 °C, the grafting reaction scarcely proceeded. This indicates that polymer radicals formed by γ-ray irradiation were successfully trapped by VGCF surface above melting point of PE-b-PEO. On the other hand, when the dispersion of VGCF in THF solution of PE-b-PEO was irradiated, the percentage of PE-b-PEO grafting was less than 4.0%. It was confirmed by a field-emission scanning electron microscope (FE-SEM) that the surface of the VGCF was uniformly covered by grafted PE-b-PEO. In addition, the surface free energy of ungrafted and PE-b-PEO-grafted VGCF was determined.     

Grafting of poly(ethylene oxide) onto C60 fullerene using macroazo initiators

In order to improve the solubility of C₆₀ fullerene in conventional solvents, grafting of hydrophilic poly(ethylene oxide) (PEO) by utilizing the radical-trapping nature of C₆₀ fullerene was investigated. Macroazo initiators containing a poly(ethylene oxide) unit, known as Azo-PEO, were prepared at various molecular weights by the reaction of 4,4′-azobis(4-cyanopentanoyl chloride) with poly(ethylene glycol) methyl ether. PEO radicals formed by thermal decomposition of Azo-PEO were successfully trapped by C₆₀ fullerene to give PEO-grafted C₆₀ fullerene. Their structures were confirmed by FT-IR spectroscopy, size exclusion chromatography, UV-vis spectroscopy, and differential scanning calorimetry. When Azo-PEO with low-molecular weight was reacted with C₆₀ fullerene, a bis-adduct, C₆₀-(PEO)₂, and a tetrakis-adduct, C₆₀-(PEO)₄, were formed. In contrast, in reactions with Azo-PEO of higher molecular weight, only the bis-adduct was formed, and no formation of the tetrakis-adduct was observed. The structure of bis-adduct was found to be 1,4-type. The solubility of C₆₀ fullerene in water, THF, methanol, and other conventional organic solvents was remarkably improved by grafting of PEO. In addition, the thermal stability of PEO was dramatically increased by grafting onto C₆₀ fullerene.     

Responsiveness of electric resistance of polymer-grafted carbon black/alumina gel composite against solvent vapor and solute in solution

The carbon black/alumina gel composites were prepared by sol-gel reaction of aluminum isopropoxide in the presence of polymer-grafted carbon black. The electric resistance of the alumina gel composite from polymer-grafted carbon black was very sensitive to vapor of good solvent for grafted polymer on carbon black: the electric resistance of the alumina gel composite suddenly decreased in solvent vapor and returned to initial resistance when it was transferred into dry air. The effect of surface area and particle size of carbon black on the responsiveness was also investigated. In addition, the electric resistance of the alumina gel composite was found to respond to water and methanol in n-hexane and diethyl ether.     

Beat Noise Mitigation of Spectral Amplitude Coding OCDMA Using Heterodyne Detection

In order to relax the limitation of the number of multiplexed signal lights caused by beat noise between signal lights, we investigate the applicability of a heterodyne detection technique to a spectral amplitude coding optical code division multiple access scheme. In this investigation, for the first time, we found analytically that the optical frequency chips that form parts of the signal and local lights require uniform phase differences even for envelope detection. We also confirm this requirement and our theoretical analysis experimentally.     

Optimum parameter design of Er/sup 3+/-doped fiber for optical amplifiers

The parameters of Er/sup 3+/-doped fiber which optimize the signal gain of a fiber amplifier pumped by a 1.48- mu m laser diode are theoretically determined using the rate equation for a three-level laser system. The basic parameters specified are the relative-index difference and the cutoff wavelength. The optimum cutoff wavelength of a completely Er/sup 3+/-doped core fiber with a step-index profile is 0.8 mu m regardless of the value of the relative-index difference. The optimum cutoff wavelength depends on the Er/sup 3+/-doped area radius.<>     

Chromatic dispersion measurement of a single-mode fibre by improved optical heterodyne interferometry

The chromatic dispersion of a single-mode fibre is successfully measured by means of an optical heterodyne detection method with temporal resolution of 0.01 ps. The heterodyne signal is detected at the near end of the fibre of length approximately 1 m using laser diodes operating in the 1.19?1.51 ?m wavelength region.     

Reactive carbon black having isocyanate or acyl azide group

Summary Introduction of isocyanate (NCO) group onto carbon black surface was achieved by the treatment of carbon black with toluene-2,4-diisocyanate. In addition, carbon black having acyl azide (CON₃) group, a precursor of NCO group, was prepared by the reaction of COCl or COOCOOC₂H₅ group on carbon black with NaN₃. The CON₃ group on carbon black was relatively stable at below 20°C but readily decomposed to NCO group by heating (Curtius rearrangement). By the reation of NCO group on carbon black with hydroxyl group of polymers, such as polypropylene glycol, polyethylene glycol, and polyvinyl alcohol, these polymers were found to be grafted onto carbon black.     

Effect of initiating groups introduced onto ultrafine silica on the molecular weight polystyrene grafted onto the surface

Summary The effect of initiating groups introduced onto silica surface on the molecular weight of grafted polystyrene chain was investigated. By the treatment of polystyrene-grafted silica with aqueous solution of alkali, surface grafted polystyrene was isolated from the surface. The molecular weight of polystyrene grafted onto the silica obtained from the radical graft polymerization initiated by peroxyester groups introduced onto the surface was found to be much larger than that from the cationic polymerization initiated by acylium perchlorate groups. The number of grafted polystyrene in the radical polymerization, however, was much less than that in the cationic polymerization. Furthermore, the effect of molecular weight of grafted polystyrene on the dispersibility of silica in tetrahydrofuran was examined.