Living cationic polymerization of an azide‐containing vinyl ether toward addressable functionalization of polymers

We first achieved the living cationic polymerization of azide‐containing monomer, 2‐azidoethyl vinyl ether (AzVE), with SnCl₄ as a catalyst (activator) in conjunction with the HCl adduct of a vinyl ether [H‐CH₂CH(OR)‐Cl; R ? CH₂CH₂Cl, CH₂CH(CH₃)₂]. Despite the potentially poisoning azide group, the produced polymers possessed controlled molecular weights and fairly narrow distributions (M_w/M_n ～ 1.2) and gave block polymers with 2‐chloroethyl vinyl ether. The pendent azide groups are easily converted into various functional groups via mild and selective reactions, such as the Staudinger reduction and copper‐catalyzed azide‐alkyne 1,3‐cycloaddition (CuAAC; a “click” reaction). These reactions led to quantitative pendent functionalization into primary amine (? NH₂), hydroxy (? OH), and carboxyl (? COOH) groups, at room temperature and without any acidic or basic treatment. Thus, poly(AzVE) is a versatile precursor for a wide variety of functional vinyl ether polymers with well‐defined structures and molecular weights. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1449–1455, 2010     

Use of silk protein, sericin, as a sustained-release material in the form of a gel, sponge and film

To evaluate the usability of silk protein (sericin, SC) as a sustained-release material, the physicochemical properties of SC and the release profiles of model drugs from SC gel, sponge and film were studied. Heat aids the dissolution of SC. The molecular weight of SC tended to decrease as the heating temperature and heating time increased. The gel and sponge formed by SC were moldable and consisted of high molecular weight SC polymers (250 kDa and about 400 kDa). SC film was easily broken and exhibited elastic distortion. The addition of moisture-retaining plasticizer (glycerin and sorbitol) improved the film-forming characteristics of SC. The results suggested that SC is practical as a moldable gel and sponge, and as a tensible film. To evaluate the release profiles of small molecules, fluorescein isothiocyanate-dextran ((1) FD4, 4 kDa and (2) FD70, 70 kDa) were used as two model drugs with significantly different molecular weights, and fluorescein isothiocyanate-albumin ((3) FA, 66 kDa) was used as a charged drug. Each was formulated in SC gel, sponge and film. In each preparation, the release rate of the model drugs tended to be FA相似文献   

Fabrication of core-shell structured nanoparticle layer substrate for excitation of localized surface plasmon resonance and its optical response for DNA in aqueous conditions

LSPR from nanostructured noble metals such as gold and silver offers great potential for biosensing applications. In this study, a core-shell structured nanoparticle layer substrate was fabricated and the localized surface plasmon resonance (LSPR) optical characteristics were investigated for DNA in aqueous conditions. Factors such as DNA length dependence, concentration dependence, and the monitoring of DNA aspects (ssDNA or dsDNA) were measured. Different lengths and concentrations of DNA solutions were introduced onto the surface of the substrate and the changes in the LSPR optical characteristics were measured. In addition, to monitor the changes in LSPR optical characteristics for different DNA aspects, a DNA solutions denatured by means of heat or alkali were introduced onto the surface, after which optical characterization of the core-shell structured nanoparticle substrate was carried out. With this core-shell structured nanoparticle layer for the excitation of LSPR, the dependence upon specific DNA conditions (length, concentration, and aspect) could be monitored. In particular, the core-shell structured nanoparticle layer substrate could detect DNA of length 100-5000 bp and 400-bp DNA at a concentration of 4.08 ng mL⁻¹ (1 × 10⁷ DNA molecules mL⁻¹). Furthermore, the changes in LSPR optical characteristics with DNA aspect could be monitored. Thus, LSPR-based optical detection using a core-shell structured nanoparticle layer substrate can be used to determine the kinetics of biomolecular interactions in a wide range of practical applications such as medicine, drug delivery, and food control.     

Double layer structure and adsorption/desorption hysteresis of neat ionic liquid on Pt electrode surface — an in-situ IR-visible sum-frequency generation spectroscopic study

The electrochemical interface between a polycrystalline Pt electrode and the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim][OTf]) has been studied by in-situ IR-visible sum-frequency generation (SFG) spectroscopy. Potential dependent adsorption/desorption processes of OTf anions has been monitored within the electrochemical window. SFG results indicate that the ions form a double layer structure at the interface. Significant adsorption/desorption hysteresis has been observed for the anions on the Pt surface.     

Improvement of magnetic intergranular isolation and evaluation of read/write characteristics on SmCo5 perpendicular magnetic thin films

SmCo₅ alloy is a promising candidate for ultra-high-density perpendicular magnetic recording (PMR) media because of its high uniaxial magnetocrystalline anisotropy K_u of more than 1.1×10⁸ erg/cm³. Previously, we successfully achieved high K_u in a sputter-deposited SmCo₅ thin film by introducing a Cu/Ti dual underlayer. However, in order to apply the SmCo₅ films to practical PMR media, it is necessary to decrease medium noise. A granulated magnetic film comprising of small and magnetically decoupled grains is effective in reducing the medium noise. In this paper, we have proposed a new granular film that is fabricated by partial thermodiffusion of Cu between the Sm-Co continuous layer and the Cu underlayer, which is granulated using compositional segregation caused by the addition of Ta₂O₅. We have analyzed the magnetic properties, magnetic domain size, and magnetization reversal process of the proposed SmCo₅ film. The magnetic domain size decreased and the magnetization reversal process changed from the magnetic-wall-motion mode to a coherent rotation mode to some extent on isolation of magnetic grains. The read/write characteristics of granulated SmCo₅ double-layered media were also evaluated. The medium noise decreased and the signal-to-noise ratio increased for the granulated double-layered (PMR) medium.     

Interactive Radical Dimers in Photoconductive Organic Thin Films

Fully interactive : Overlap between extended unoccupied molecular orbitals leads to the high photoconductivity of interactive radical dimers. Sandwich‐type cells (see picture; ITO=indium tin oxide) comprising highly oriented thin films of a disjoint diradical, 4,4′‐bis(1,2,3,5‐dithiadiazolyl) (BDTDA) exhibit a photocurrent with a high on/off ratio at reverse bias voltages and photovoltaic behavior at zero bias voltage.

     

Thermo-responsive extraction of cadmium(II) ion with TPEN-NIPA gel. Effect of the number of polymerizable double bond toward gel formation and the extracting behavior

N,N,N′,N′-(Tetrakis-2-pyridylmethyl)ethylenediamine (TPEN) derivatives bearing the different number (1-4) of a double bond moiety on the pyridine ring are synthesized and subjected to copolymerization with N-isopropylacrylamide in the presence of AIBN. The obtained poly(TPEN-NIPA) gels show thermo-responsive swelling/shrinking behaviors and are employed for the extraction of cadmium(II) ion from the aqueous solution to examine the relationship of the gel characteristics and the extraction performance. The polymer gels composed of the TPEN derivative bearing three or four double bonds exhibit temperature-dependent change of swelling and shrinking in water. These gels extract Cd^II ion efficiently from the aqueous solution in the swelling state at 5 °C, while little extraction was observed at 45 °C with shrinking.     

A photoluminescent six-coordinated zinc(II) complex with hydroxides as axial ligands, [Zn(Hhpa)2(OH)2] (Hhpa = 3-hydroxypicolinamide)

A highly luminescent zinc(II) complex has been prepared using 3-hydroxypicolinamide; it has a six-coordinated octahedral structure with hydroxides as axial ligands in solution.     

Ruthenium-catalyzed carbon-carbon formation to synthesize tetraarylethanes and tetraarylxylylene through dechlorinative dimeric reaction

Dechlorinative coupling-dimerization reaction is studied to synthesize alkanes by using tris-triphenylphosphine ruthenium (II) in the presence of hydrogen atmosphere. Two types of halides (α-chlorodiarylmethanes 1a-d and bis(chlorophenylmethyl)-1,3-phenylene 6) are employed as substrates to form radical species and then dimerized to generate alkanes in high yields. To our knowledge, it is the first time that the formation of 1,1,2,2-tetraarylethanes and 1,2,9,10-tetraphenyl-di-m-xylylene over typical ruthenium-catalyzed dehalogenative coupling-dimerization conditions is reported.     

Photosensitized oxygenation of diaryl tellurides to telluroxides and their oxidizing properties

Photosensitized oxidation of tellurides carrying bulky aromatic substituents afforded the corresponding telluroxides which were found to react with simple alcohols to give the corresponding carbonyl compounds in excellent yields along with the starting tellurides.