Fluorescent 3-methylene-2,3-dihydrochalcogenophenes incorporated in a rigid dibenzobarrelene skeleton

The fluorescent 3-methylene-2,3-dihydroselenophene derivative (Φ(F) = 0.86 in CH(2)Cl(2)) incorporated in a dibenzobarrelene skeleton was synthesized by the reaction of a four-membered selenaplatinacycle with dimethyl acetylenedicarboxylate (DMAD) or reaction of bis(dibenzobarrelenyl) diselenide with DMAD in the presence of Pd(PPh(3))(4) and PPh(3). A fluorescent sulfur homologue (Φ(F) = 1.0 in CH(2)Cl(2)) was also synthesized by the reaction of bis(dibenzobarrelenyl) disulfide with DMAD in the presence of Pd(PPh(3))(4). Selected chemical transformations of these diesters were also investigated.     

Auger recombination dynamics in hybrid silica-coated CdTe nanocrystals

CdTe quantum dots coated with a silica layer containing CdS-like clusters exhibit intense photoluminescence and a spectral red-shift. Biexciton Auger recombination of these particles is examined by transient absorption spectroscopy. A lengthening of the Auger recombination lifetime by a factor of ～3.5 in the presence of the CdS-like clusters is observed and may contribute to the good PL properties of these nanostructures.     

Graphene and carbon nanotube composite electrodes for supercapacitors with ultra-high energy density

We describe a graphene and single-walled carbon nanotube (SWCNT) composite film prepared by a blending process for use as electrodes in high energy density supercapacitors. Specific capacitances of 290.6 F g(-1) and 201.0 F g(-1) have been obtained for a single electrode in aqueous and organic electrolytes, respectively, using a more practical two-electrode testing system. In the organic electrolyte the energy density reached 62.8 Wh kg(-1) and the power density reached 58.5 kW kg(-1). The addition of single-walled carbon nanotubes raised the energy density by 23% and power density by 31% more than the graphene electrodes. The graphene/CNT electrodes exhibited an ultra-high energy density of 155.6 Wh kg(-1) in ionic liquid at room temperature. In addition, the specific capacitance increased by 29% after 1000 cycles in ionic liquid, indicating their excellent cyclicity. The SWCNTs acted as a conductive additive, spacer, and binder in the graphene/CNT supercapacitors. This work suggests that our graphene/CNT supercapacitors can be comparable to NiMH batteries in performance and are promising for applications in hybrid vehicles and electric vehicles.     

Study of the surface and interfacial tensions in systems containing a low molar mass liquid crystal

The surface tension of a low molar mass liquid crystal (LMMLC), 4-cyano-4'-n-heptyloxybiphenyl (70CB), was measured as a function of temperature using the pendant drop method, forming drops of different volumes ranging from 5 to 11 mm³. Contact angles formed by drops of 70CB in the nematic and isotropic phases on plates of polystyrene (PS) and of a liquid crystal polymer (LCP), VECTRA A910, were also measured. Only large drops could be used for surface tension analysis. It was shown that in the nematic phase the surface tension of 70CB decreases with increasing temperature, and that in the isotropic phase the surface tension increases with increasing temperature. Using the values of contact angle and of surface tension of 7OCB it was possible to evaluate the interfacial energy between 7OCB and PS and between 7OCB and VECTRA. The interfacial energy between 7OCB and PS, and between 7OCB and VECTRA, decreased with increasing temperature for ranges of temperatures corresponding to both phases of 70CB.     

Polymer particles having molecule-imprinted skin layer

We developed a novel type of protein molecule-imprinted particles. Bovine hemoglobin (BHb) and submicron-sized polymer particles were used in this study as a template and a substrate, respectively. BHb molecules were softly and sparsely adsorbed on the particle surface. Then skin layer was formed with a thickness of BHb molecule size by living radical graft polymerization of moderately hydrophilic monomers. After that, BHb molecules were removed from their embedded spaces. The ability of vacant spaces on the surface layer of particles to take BHb molecules selectively was examined. Successful results were obtained not only in single protein adsorption system but also in the competitive adsorption system of several proteins and BHb, that is, the imprinted space was reserved for BHb even if other proteins coexisted, although their nonspecific adsorption on non-imprinted surface was not avoided.     

INTRODUCTION OF CATIONIC GROUPS ONTO CARBON BLACK SURFACE AND THEIR DISPERSIBILITY IN WATER

Imidazoline hydrochlonde groups were successfully introduced onto carbon black surface by the treatment of imidazoline groups, which were introduced by the trapping of 2-(2-imidazolin-2-yl)propane radicals formed by the thermal decomposition of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] (AJP) with hydrochloric acid. In addition, arrridine hydrochlonde groups were introduced onto carbon black surface by the radical trapping of 2-methylpropionamidine dihydrochloride radicals formed by the thermal decomposition of 22'-azobis(2-methylpropionamidine) dihydrochloride (AMPAD). The content of imidazoline hydrochlonde and amidine hydrochlonde groups introduced onto carbon black was determined to be 0.6 mmol/g and 0,7 mmol/g, respectively. The mean particle size of AIP/HCl-lreated and AMPAD-treated carbon black was determined to be 31 nm and 16 nm, respectively, by dynamic light scattering method. It was found that the surface of carbon black turned from hydraphobic to hydrophilic by the introduction of cationic moieties and gave a very stable colloidal dispersion in neutral and acidic water at room temperature.     

Radical Graft Polymerization of Vinyl Monomers Initiated by A20 Groups Introduced Onto a Carbon Black Surface: Effect of azo Groups on Graft Polymerization

The radical graft polymerization of vinyl monomers from carbon black initiated by azo groups introduced onto the surface was investigated. The introduction of azo groups onto carbon black surface was achieved by three methods: the reaction of 2,2′-azobis[2-(2-imidazolin-2-yl)propane] (AIP) with (1) epoxide groups, which were introduced by the reaction of carbon black with chlorometh-yloxirane; (2) acyl chloride groups, which were introduced by the reaction of carboxyl groups on the surface with thionyl chloride; and (3) 3-chloroformyl-1-cyano-1-methylpropyl groups, which were introduced by the reaction of carbon black with 4,4′-azobis(4-cyanovaleric acid) and then thionyl chloride. The amount of azo groups introduced onto the surface by the above methods was determined to be 0.07-0.19 mmol/g. The graft polymerization of methyl methacrylate was found to be initiated by azo groups introduced onto the carbon black surface. During the polymerization, poly(methyl methacrylate) was effectively grafted onto carbon black through propagation of the polymer from the radical produced on the surface by the decomposition of the azo groups. The percentage of grafting using carbon black having azo groups introduced by method 1 increased to 40%. It was also found that the graft polymerization of several vinyl monomers such as styrene, acrylonitrile, and acrylic acid was initiated by the azo groups introduced onto the surface and the corresponding polymer was effectively grafted onto the surface. Furthermore, the effect of the amount of carbon black having azo groups on the graft polymerization was investigated.     

Grafting of Polymers onto Activated Carbon Surface: Graft Polymerization of Vinyl Monomers Initiated by Azo Groups That Were Introduced onto the Surface

Abstract

We examined the grafting of polymers onto an activated carbon powder surface by polymerization that was initiated by azo groups that were introduced onto the surface as well as the effects of grafted polymers on the adsorption of acetic acid. The introduction of azo groups onto the surface was achieved by the following methods: (1) a reaction of 4,4′-azobis(4-cyano-pentanoic acid) (ACPA) with surface isocyanate groups that were introduced beforehand by treatment with tolylene 2,4-diisocyanate (AC-Azo 1) and (2) the direct condensation of ACPA with surface phenolic hydroxyl groups by using N,N'-dicyclohexylcarbodiimide (AC-Azo 2). The radical polymerizations of styrene, methyl methacrylate, N,N-diethylacrylamide (DEAM), and N-isopropylacrylamide (NIPAM), were successfully initiated by the azo groups on the surface and the corresponding polymers were grafted onto the surface. There was a significant decrease in the adsorption of the acetic acid of the activated carbons when polymers were grafted onto them, particularly in regards to the grafting of hydrophobic polymers. On the other hand, a decrease in the adsorbability of the polyDEAM-grafted and polyNIPAM-grafted activated carbon was barely observed. In addition, polyDEAM-grafted and polyNIPAM-grafted activated carbons showed temperature-dependent adsorption of acetic acid: the adsorbability of these activated carbon decreased above lower critical solution temperature of these polymers, which is about 32°C.