Teruaki Hayakawa

One-Step Direct-Patterning Template Utilizing Self-Assembly of POSS-Containing Block Copolymers.

We report the self-assembly of organic-inorganic block copolymers (BCP) in thin-films by simple solvent annealing on unmodified substrates. The resulting vertically oriented lamellae and cylinders are converted to a hard silica mask by a single step highly selective oxygen plasma etching. The size of the resulting nanostructures in the case of cylinders is less than 10 nm.

Selective Aerobic Oxidation of Benzylic Alcohols Catalyzed by Carbon‐Based Catalysts: A Nonmetallic Oxidation System

Selective oxidation is of great importance in organic synthesis, and green, efficient, selective oxidation techniques are highly sought after in the chemical industry. In particular, selective oxidation of alcohols is a fundamental transformation in the synthesis of fine chemicals. Recently, aerobic oxidation processes have received increasing attention, as oxygen or air are used as the terminal oxidant to replace the stoichiometric metal oxides such as chromates and manganese oxides. The use of oxygen has great benefits from both economic and green chemistry viewpoints, because oxygen is relatively cheap and produces water as the only byproduct. Accordingly, varied heterogeneous and homogenous catalysts derived from precious metals have been developed for this purpose, for example, Pt, Ru, Pd, Au, and Ag. However, because of their rarity and high price, precious metals are impractical for industrial use. Despite this, few efforts have been made to seek out nonprecious metal catalysts. One example is the 2,2,6,6-tetramethylpiperidine1-oxyl (TEMPO)/Br2/NaNO2 aerobic oxidation system reported by Liu et al. , in which TEMPO was used as a homogeneous catalyst, and the in situ generated NO played a crucial role in the activation of O2. Our interests are in the exploration of the potential of carbon-based materials to be applied as metal-free catalysts for selective aerobic oxidation of alcohols. Several studies of carbon catalyst materials have already revealed the ability to replace metal-based catalysts in several important transformations, such as the Friedel–Crafts reaction and the oxidative dehydrogenation of aromatic hydrocarbons and alkanes. Interestingly, carbon catalysts with an ordered nanoshell structure or doped with heteroatoms have been reported to possess surprisingly high oxygen reduction reaction (ORR) activities. However, to date there is no report on the selective aerobic oxidation of alcohols using the same catalyst. Herein, we present a novel protocol: nitric acid assisted carbon-catalyzed oxidation System (NACOS), by which benzyl alcohol and its substituted derivatives can be smoothly oxidized by oxygen under mild reaction conditions, affording high conversions and good selectivities into the corresponding aldehydes. The nanoshell carbon (NSC) used in this investigation was prepared by pyrolization of a blend of phenol resin and iron phthalocyanine, similar to methods reported by Ozaki et al. , and subsequent acid washes using concentrated HCl. The iron metal on the carbon surface can be thoroughly removed by acid washes, and the metal-free surface was characterized by energy dispersive X-ray spectroscopy (EDS) (Figure 1a) and X-ray photoelectron spectroscopy (XPS; Table 4). The specific surface area of NSC was 330 m g , determined by N2 adsorption. Initial experiments with benzyl alcohol showed that the NSC alone could not activate oxygen and no alcohol conversion was observed. It was postulated that the catalyst might take effect in the presence of an additive, so several acid and base additives were tested. Among all the tested additives, concentrated nitric acid

Head‐to‐tail regioregularity of poly(3‐hexylthiophene) in oxidative coupling polymerization with FeCl3

We investigated a head-to-tail regioregularity of poly(3-alkylthiophenes) from 3-alkylthiophene by an oxidative coupling polymerization, which is the simplest and easiest way for the synthesis of polythiophenes. The polymerizations were conducted using ferric chloride (III) as an oxidant in chloroform. Investigating the polymerization conditions, a lower temperature and a lower concentration were effective for increasing the head-to-tail (HT) content. The best HT content of 88% was obtained when the temperature was -45°C and the initial monomer concentration was 0.02 mol L -1 . Washing the resulting polymer by n-hexane further increased the content to 91%. Thus, it was found that the high regioselectivity can be achieved by the simple polymerization and the simple operation such as washing. The polymerization mechanism causing the regularity is also discussed.

Novel Bipolar Bathophenanthroline Containing Hosts for Highly Efficient Phosphorescent OLEDs

The electronic structures of eight bathophenanthroline derivatives were elucidated by DFT calculations, and four representatives of which CZBP, m-CZBP, m-TPAP, and BPABP were synthesized and employed as the hosts to afford highly efficient phosphorescent OLEDs. The calculated molecular orbital energies agree well with the experimental results, which further demonstrates that the localization of HOMO and LUMO at the respective hole- and electron-transporting moieties is desirable in bipolar molecular designs.

Organic Macromolecular High Dielectric Constant Materials: Synthesis, Characterization, and Applications

Hyperbranched and dendritic architectures have been targeted for various applications such as sensing, drug delivery, optical limiting, and light harvesting. One interesting development in this area has focused on utilizing the existence of long-range delocalization in hyperbranched structures to achieve high dielectric constants. In this Feature Article, we will review the creation and development of this concept, and we highlight our recent research progress in this aspect. In particular, we discuss (1) synthetic methods for a particular group of hyperbranched polymers; (2) detailed optical and electronic characterization of this group of hyperbranched polymers, revealing the design criteria for achieving a good combination of high dielectric constant and minimum loss in such materials; and (3) the importance and potential applications of these materials.

Fe-containing polyimide-based high-performance ORR catalysts in acidic medium: a kinetic approach to study the durability of catalysts

The ORR activity and durability of Fe-containing non-precious N-doped carbon catalysts in acidic medium were studied using a rotating ring-disk electrode voltammetry and XPS technique. The catalysts (Fe/PI) were synthesised from the pyrolysis of the Fe(acac)3 and polyimide nanoparticle (PI) mixture. The catalytic activity and durability of Fe/PI are superior to that of the conventional phthalocyanine-based catalyst. The onset potential of ORR was 0.915 V vs. RHE in 0.5 M H2SO4 which is very close to that of a commercially available Pt/C catalyst. The Fe/PI catalyst sustains its activity and stability even after 11 110 repeating potential steps between 0.6 and 1.0 V vs. RHE in O2-saturated 0.5 M H2SO4 and 1110 potential cycles between 1.0 and 1.5 V vs. RHE in argon-saturated 0.5 M H2SO4, respectively. The kinetic and mechanistic analyses of the ORR on this catalyst indicate that the ORR, as a whole, follows a 4-electron (parallel) pathway. The N 1s XPS spectra before and after the durability test indicate that pyridinic and graphite-like nitrogens take part in improving the ORR activity, whereas nitrogen oxides have a negative role in the ORR. The loss of ORR activity was observed after the acid washing of the catalysts, which suggests the role of Fe in the overall 4-electron reduction of O2.

High performance Pt-free cathode catalysts for polymer electrolyte membrane fuel cells prepared from widely available chemicals

A high performance Pt-free cathode catalyst for polymer electrolyte fuel cells has been synthesized by the multi-step pyrolysis of polyimide fine particles with a diameter of about 100 nm. This cathode catalyst exhibits good fuel cell performance (1.0 A cm−2 at 0.6 V and 80 °C) along with promising durability.

Cracking of n-Butane Over Alkaline Earth-Containing HZSM-5 Catalysts

The effect of alkaline earth modification on HZSM-5 was investigated by catalytic cracking of n-butane under non-oxidative and oxidative conditions. The yields of aromatic products were low compared with that obtained using the non-modified HZSM-5, and higher yields of ethylene and propylene were observed with Mg-, Ca-, and Ba-ZSM-5. The NH3-TPD spectra of these catalysts show that the strong acid sites were transformed to weak acid sites. The dehydrogenation cracking was considered to occur at the acid sites modified with the alkaline earth elements because the ethylene/ethane ratio and the C2/other products ratio were high using the alkaline earth-containing HZSM-5. It is suggested that the suppression of hydrogen transfer reaction and the stimulation of dehydrogenation cracking were the major cause of the improvement of olefin yield in the cracking.

Hyperbranched polysiloxysilane nanoparticles: surface charge control of nonviral gene delivery vectors and nanoprobes.

New hyperbranched polysiloxysilane (HBPS) materials containing terminal carboxylic acid and quaternary ammonium groups were designed and synthesized to obtain fluorescent-dye-encapsulated nanoparticles. These polymers exhibited desirable characteristics, including amphiphilicity for nanoparticle formation, and contained various terminal groups for surface-charge control on the nanoparticles or for further bioconjugation for targeted imaging. Nanoprobes composed of polysiloxysilane nanoparticles encapsulating two-photon dyes were also prepared for optical bioimaging with controlled surface charge density (zeta potential) for modulation of cellular uptake. Intracellular delivery of these structurally similar polysiloxysilane nanoparticles, with substantially different surface charges, was investigated using confocal and two-photon fluorescence microscopy as well as flow cytometry. Finally, the use of these nanoparticles as efficient gene delivery vectors was demonstrated by means of in vitro transfection study using beta-galactosidase plasmid and pEGFP-N1 plasmid and the most efficient combination was obtained using HBPS-CN30:70.

Synthesis of a regioregular head-to-tail poly(3-alkylphenylthiophene) by oxidative coupling using VO(acac)2

Abstract Regiocontrolled poly(3-(4-dodecylphenyl)thiophene) was prepared by oxidative coupling polymerization of 3-(4-dodecylphenyl)thiophene using an oxovanadium complex as an oxidation catalyst. Polymerizations were conducted in the presence of vanadium acetylacetonate, trifluoromethanesulfonic acid and trifluoroacetic anhydride under oxygen atmosphere in 1,2-dichloroethane at room temperature. The structure of the resulting polymer was characterized by means of 1 H- and 13 C-NMR spectroscopies, and consisted of head-to-tail linkage. Degenerate four-wave mixing (DFWM) measurements of this polymer yielded the third-order susceptibility as high as 5.1 × 10 −10 esu.