Parallel synthesis of donor-acceptor π-conjugated polymers by post-element transformation of organotitanium polymer.

The donor-acceptor type π-conjugated polymers having heterole units were prepared by the reaction of a regioregular organometallic polymer having both reactive titanacyclopentadiene and electron-donor thiophene-2,5-diyl units in the main chain with electrophiles such as diphenyltin dichloride, dichlorophenylphosphine, and diiodophenylarsine. For example, a polymer having electron-accepting phosphole unit was obtained in 54% yield whose number-average molecular weight (Mn) and molecular weight distribution (Mw/Mn) were estimated as 3,000 and 1.9, respectively. The obtained polymer exhibits a high highest occupied molecular orbital (HOMO) and low lowest unoccupied molecular orbital (LUMO) energy levels (-5.13 eV and -3.25 eV, respectively) due to the electron-donating thiophene and electron-accepting phosphole units. Reflecting upon the alternating structure of thiophene and phosphole, the polymer exhibits a band gap energy level (Eg) of 1.78 eV which is narrower than that of a derivative of poly(thiophene) (Eg = 2.25 eV).

Biodegradable epoxy thermosetting system with high adhesiveness based on glycidate-acid anhydride curing.

Biodegradable epoxy thermosets were developed by curing through copolymerization of a diglycidate monomer, a bifunctional epoxide bearing ester linkages, with cyclic acid anhydrides as a biosafe thermosetting system. The cured products of the glycidate exhibit high adhesiveness, identical to analogous cured products of conventional glycidyl ethers. Even an inert cycloolefin polymer and polyimide can be adhered. The cured products of the glycidate can be hydrolytically and biologically degraded. The biodegradation of the glycidate thermoset in compost completely proceeded within 2 weeks.

Synthesis of Bismuth-Containing Polymer Films with High Refractive Index and X-ray Shielding Property by Radical Polymerization of Styrylbismuthine Derivatives.

Highly refractive and X-ray shielding polymer films were prepared by bulk radical copolymerization of diphenylstyrylbismuthine (MStBi) with tristyrylbismuthine (TStBi). For example, a yellow transparent film was obtained by copolymerization of MStBi and TStBi in a ratio of 70:30 (w/w). The refractive index (nD) and radiopacity of the film of these polymers are 1.72 and 1.60 µm-Al/µm-polymer, respectively. These properties are higher than those of the reported bismuth-containing polymers. The thermal stability and flexural module of the polymer films were controllable by the feed ratio of TStBi. The polymer films also exhibited high surface hardness and solvent resistance due to the rigid and cross-linked structure. The chemical and thermal stability and higher refractive index and radiopacity of the polymers suggest the potential applications for X-ray shielding of optical materials with high refractive indices.

Synthesis and Selective Au(III) Adsorption of Ureido Polymers Containing Large Repeating Rings.

Two polymers (polyBAUEE and polyBAUP) containing 25- and 20-membered rings are synthesized by the cyclopolymerization of bifunctional monomers 1,2-bis(acryloyloxyethyl-ureidoethoxyl)-ethane (BAUEE) and 1,3-bis(acryloyloxyethylureido)propane (BAUP) and studied for the adsorption of precious metal ions. PolyBAUEE and polyBAUP selectively adsorb Au(III) with the adsorption efficiencies above 99.0% after adsorption equilibrium. PolyBAUEE adsorbed faster than polyBAUP, and the Au(III) adsorption is selective in the presence of nine interfering metal ions with similar concentrations (ca. 1 mg/L) in an aqueous solution including Pd(II) and Pt(II). The maximum Au(III) adsorption capacities of polyBAUEE and polyBAUP are 37.6 and 31.8 mg/g, respectively. Au(III) is reduced to Au(0) nanoparticles during the adsorption process. The selective adsorption behavior depends on the controlling regioselective recognition of the ring structure and the ureido groups.

Biogeochemical impacts of flooding discharge with high suspended sediment on coastal seas: a modeling study for a microtidal open bay.

Freshwater, suspended sediment matter (SSM), and nutrients discharged from rivers into the ocean have large impacts on biological production. In particular, during floods, coastal areas are greatly stirred up and large amounts of nutrients are supplied to the sea surface. We investigate the biogeochemical impact of flooding river discharges containing a large amount of SSM by conducting numerical simulations for a specific flooding event of the Yura River, Japan. Parameters are varied over wide ranges of SSM properties and nutrient content in riverine water. Two qualitatively different regimes of the riverine plume, hypopycnal and hyperpycnal, appear within realistic parameter ranges. Compared with the reference case without SSM, the surface salinity (nutrients) within the riverine plume becomes lower (higher) in hypopycnal cases and higher (lower) in hyperpycnal cases within a few days after the flooding discharge. These results suggest the necessity of properly taking into account the effect of SSM in assessing the influence of high river discharges on coastal biogeochemistry. It is the case not only for the specific river and event we are dealing with but also for other flooding events and other rivers and connecting coastal seas.

Milling in Seconds Accelerates Acetylation of Cellulose in Hours.

A new sustainable synthetic method for cellulose acetate was developed by a combination of I2-catalyzed solid-liquid acetylation of cellulose and a milling process reducing the crystallinity of cellulose within a few seconds. Milled low-crystalline cellulose was acetylated faster than the original cellulose with higher crystallinity. The plausible factors of acceleration were the conversion of the hydroxy group in hydrogen bonds into reactive ones and the efficient formation of the catalytic species I+ by the enhanced formation of I3 - assisted by the amorphous domain of the milled cellulose, while the morphological and structural changes were ignorable.

Synthesis of Stannole-Containing π-Conjugated Polymers by Post-Element Transformation of Organotitanium Polymer.

The synthesis of stannole-2,5-diyl-containing π-conjugated polymers by the post-element transformation of a regioregular organotitanium polymer is described. For example, a 1,1-diphenylstannole-containing polymer is obtained in 83% yield by the reaction of a regioregular organotitanium polymer, which is prepared from 1,4-bis(2-ethylhexyloxy)-2,5-diethynylbenzene and a low-valent titanium complex with diphenyltin dichloride at -50 °C to ambient temperature. The number-average molecular weight and molecular weight distribution (Mn and Mw /Mn ) of the stannole-containing polymer are estimated as 4800 and 1.8, respectively. The obtained polymer is found to have the extended π-conjugated backbone and relatively low-lying lowest unoccupied molecular orbital (LUMO) energy level (-3.12 eV), which is supported by its UV-vis absorption spectrum and cyclic voltammetric (CV) analysis. In addition, the stannole-containing polymer is found to be applicable to a chemosensor for fluoride anion where the color and photoluminescence intensity of the polymer solution exhibits a distinct change in the presence of a fluoride anion.

pH-Responsive Charge-Conversional and Hemolytic Activities of Magnetic Nanocomposite Particles for Cell-Targeted Hyperthermia.

Magnetic nanocomposite particle (MNP)-induced hyperthermia therapy has been restricted by inefficient cellular targeting. pH-responsive charge-conversional MNPs can enhance selective cellular uptake in acidic cells like tumors by sensing extracellular acidity based on their charge alteration. We have synthesized new, pH-induced charge-conversional, superparamagnetic, and single-cored Fe3O4 nanocomposite particles coated by N-itaconylated chitosan (NICS) cross-linked with ethylene glycol diglycidyl ether (EGDE) (Fe3O4-NICS-EGDE) using a simple, one-step chemical coprecipitation-coating process. The surface of the Fe3O4-NICS-EGDE nanocomposite particles was modified with ethanolamine (EA) via aza-Michael addition to enhance their buffering capacity, aqueous stability, and pH sensitivity. The designed Fe3O4-NICS-EGDE-EA nanocomposite particles showed pH-dependent charge-conversional properties, colloidal stability, and excellent hemocompatibility in physiological media. By contrast, the charge-conversional properties enabled microwave-induced hemolysis only under weakly acidic conditions. Therefore, the composite particles are highly feasible for magnetically induced and targeted cellular thermotherapeutic applications.

Applications of Flow Microreactors in Electrosynthetic Processes.

The fundamental advantages and potential benefits of flow microreactor technology include extremely large surface-to-volume ratios, precise control over temperature and residence time, extremely fast molecular diffusion, and increased safety during reactive processes. These advantages and benefits can be applied to a wide range of electrosynthetic techniques, and so the integration of flow microreactors with electrosynthesis has received significant research interest from both academia and industry. This review presents an up-to-date overview of electrosynthetic processes in continuous-flow microreactors. In addition, the advantages of continuous-flow electrochemistry are discussed, along with a thorough comparison of microreactor-based processes and conventional batch reaction systems.

Cathodic Aromatic C,C Cross-Coupling Reaction via Single Electron Transfer Pathway.

We have successfully developed a novel cathodic cross-coupling reaction of aryl halides with arenes. Utilization of the cathodic single electron transfer (SET) mechanism for activation of aryl halides enables the cross-coupling reaction to proceed without the need for any transition metal catalysts or single electron donors in a mild condition. The SET from a cathode to an aryl halide initiates a radical chain by giving an anion radical of the aryl halide. The following propagation cycle also consists entirely of anion radical intermediates.

Arsole-Containing π-Conjugated Polymer by the Post-Element-Transformation Technique.

A synthetic method to obtain an arsole-containing π-conjugated polymer by the post-transformation of the organotitanium polymer titanacyclopentadiene-2,5-diyl unit with an arsenic-containing building block is described. The UV/Vis absorption maximum and onset of the polymer were observed at 517 nm and 612 nm, respectively. The polymer exhibits orange photoluminescence with an emission maximum (Emax ) of 600 nm and the quantum yield (Φ) of 0.05. The polymer proved to exhibit a quasi-reversible redox behavior in its cyclic voltammetric (CV) analysis. The energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were estimated to be -5.43 and -3.24 eV, respectively, from the onsets for oxidation and reduction signals in the CV analysis. Further chemical modification of the arsole unit in the π-conjugated polymer by complexation of gold(I) chloride occurred smoothly resulting in the bathochromic shift of the UV/Vis absorption and lowering of the LUMO energy level.

Electroresponsive Structurally Colored Materials: A Combination of Structural and Electrochromic Effects.

Electroresponsive structurally colored materials composed of ordered arrays of polyaniline@poly(methyl methacrylate) (PANI@PMMA) core-shell nanoparticles have been successfully prepared. The core-shell nanoparticles were synthesized by deposition of PANI shells on the surfaces of the PMMA cores by the oxidative polymerization of anilinium chloride. Ordered arrays were then fabricated by using the fluidic cell method. Because the ordered arrays and the PANI shells generate structural and electrochromic colors, respectively, these core-shell colloidal crystals exhibited colors resulting from the combined effects of these materials. The crystal colors depended greatly on the size of PANI@PMMA particles and could also be varied by the application of a voltage. The electrochromic colors of these arrays were found to be quite different from those exhibited by pure PANI films prepared by electrochemical oxidation.

Practical Synthesis and Properties of 2,5-Diarylarsoles.

2,5-Diarylarsoles were easily synthesized from nonvolatile arsenic precursors. Diiodoarsine was generated in situ and reacted with titanacyclopentadienes to give 2,5-diarylarsoles. The structures and optical properties were studied in comparison with those of 2,5-diarylphosphole. It was found that the arsoles were much more stable in the air than the phosphole. Single crystal X-ray diffraction revealed the arsenic atoms adopted a trigonal pyramidal structure, reflecting on the s-character of the lone pair. The obtained 2,5-diarylarsoles and 2,5-diarylphosphole showed intense emission in solutions and solid state. In addition, the optical properties were controlled by transition-metal coordination.

Parallel Synthesis of photoluminescent π-conjugated polymers by polymer reactions of an organotitanium polymer with a titanacyclopentadiene unit.

A regioregular organometallic polymer with titanacyclopentadiene unit, obtained by the reaction of a 2,7-diethynylfluorene derivative and a low-valent titanium complex, is subjected to the reaction with three kinds of electrophiles (i.e., sulfur monochloride, hydrochloric acid, and dichlorophenylphosphine) to give π-conjugated polymers possessing both fluorene and building blocks originated from the transformation of the titanacycles in the main chain. For example, a phosphole-containing polymer whose number-average molecular weight is estimated as 5000 is obtained in 50% yield. The obtained thiophene, butadiene, and phosphole-containing polymers exhibit efficient photoluminescence (PL) with emission colors of blue, green, and yellow, respectively. For example, the phosphole-containing polymer exhibits yellow PL with an emission maximum (Emax ) of 533 nm and a quantum yield (Φ) of 0.37.

Synthesis of π-Conjugated Polymers Containing Phosphole Units in the Main Chain by Reaction of an Organometallic Polymer Having a Titanacyclopentadiene Unit.

A regioregular organometallic polymer possessing titanacyclopentadiene units in the main chain, which was obtained by the reaction of terminal diyne and a low-valent titanium complex, was subjected to the reaction with dichlorophosphines to give π-conjugated polymers with phosphole or phosphole oxide units in the main chain. For example, a phenylphosphole-containing polymer was obtained in 76% yield by the reaction with dichlorophenylphosphine, whose number-average molecular weight (Mn) and molecular weight distribution (Mw/Mn) were estimated to be 6100 and 1.9, respectively, by GPC. The polymer was found to have an extended π-conjugated system, and its lowest unoccupied molecular orbital (LUMO) energy level was remarkably low (-3.28 eV) as supported by its UV-vis absorption spectrum and cyclic voltammetric (CV) analysis. Also, the polymer exhibits orange photoluminescence with an emission maximum (Emax) of 595 nm and a quantum yield (Φ) of 0.10.