Novel segmented copolymers by combination of controlled ionic and radical polymerizations

Transformation of different living and non‐living polymerization mechanisms to controlled/“living” atom transfer radical polymerization (ATRP) in order to prepare block and graft copolymers is described. The synthesis and characterization of macroinitiators and the resulting segmented copolymers is discussed.     

UV-curable poly(ethylene glycol)–based polyurethane acrylate hydrogel

Poly(ethylene glycol) (PEG) with molecular weight (M_n) of 1000, 2000, 3000, and 4000 g/mol, four types of diisocyanate [hexamethylene diisocyanate (HDI), 4,4′-dicyclohexylmethane diisocyanate (H₁₂MDI), isophorone diisocyanate (IPDI), and toluene diisocyanate (TDI)], two types of comonomers [acrylamide (AAm) and acrylic acid (AAc)] that comprised up to 60% of the total solid were used to prepare UV-curable PEG–based polyurethane (PU) acrylate hydrogel. The gels were evaluated in terms of mechanical properties, water content as a function of immersion time and pH, and X-ray diffraction profiles of dry and swollen films. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2703–2709, 1999     

Colorimetric determination of amino acids using genipin from Gardenia jasminoides

Genipin, a hydrolysate of geniposide from gardenia fruits, produces blue pigments on reaction with amino acids. The colorimetric detection of amino acids using this genipin reaction was evaluated and compared with the well-known ninhydrin reaction. The molar absorptivities of the blue pigments, the reaction products of genipin with various amino acids, were greater than those of the respective ninhydrin reaction products. When asparagine was reacted with genipin, the molar absorptivity was about 14 times higher than with ninhydrin. The absorbance of the genipin–amino acids increased linearly with increase of amino acid concentration, indicating that genipin could be a useful reagent for quantitation of amino acids. Thin layer chromatographic analysis showed that the genipin reaction produces clear and stable colored spots. The blue ninhydrin reaction spots were usually bleached in 24 h at room temperature, while the genipin reaction spots remained unchanged for several months. The addition of 0.1 mM Cu²⁺ and Fe³⁺ decreased the absorbance of Gly–ninhydrin pigment by 50% and 98%, respectively, but those metal ions did not affect the absorbance of the Gly–genipin pigment.     

High gas sorption and metal-ion exchange of microporous metal-organic frameworks with incorporated imide groups

Metal-organic frameworks (MOFs), {[Cu(2)(bdcppi)(dmf)(2)]·10DMF·2H(2)O}(n) (SNU-50) and {[Zn(2)(bdcppi)(dmf)(3)]·6DMF·4H(2)O}(n) (SNU-51), have been prepared by the solvothermal reactions of N,N'-bis(3,5-dicarboxyphenyl)pyromellitic diimide (H(4)BDCPPI) with Cu(NO(3))(2) and Zn(NO(3))(2), respectively. Framework SNU-50 has an NbO-type net structure, whereas SNU-51 has a PtS-type net structure. Desolvated solid [Cu(2)(bdcppi)](n) (SNU-50'), which was prepared by guest exchange of SNU-50 with acetone followed by evacuation at 170 °C, adsorbs high amounts of N(2), H(2), O(2), CO(2), and CH(4) gases due to the presence of a vacant coordination site at every metal ion, and to the presence of imide groups in the ligand. The Langmuir surface area is 2450 m(2) g(-1). It adsorbs H(2) gas up to 2.10 wt% at 1 atm and 77 K, with zero coverage isosteric heat of 7.1 kJ mol(-1), up to a total of 7.85 wt% at 77 K and 60 bar. Its CO(2) and CH(4) adsorption capacities at 298 K are 77 wt% at 55 bar and 17 wt% at 60 bar, respectively. Of particular note is the O(2) adsorption capacity of SNU-50' (118 wt% at 77 K and 0.2 atm), which is the highest reported so far for any MOF. By metal-ion exchange of SNU-51 with Cu(II), {[Cu(2)(bdcppi)(dmf)(3)]·7DMF·5H(2)O}(n) (SNU-51-Cu(DMF)) with a PtS-type net was prepared, which could not be synthesized by a direct solvothermal reaction.     

Dynamic properties of an omni-directional piezoelectric motor for precision position control

A piezoelectric motor capable of omni-directional movements has been developed to apply for robot joints, eyes, and precision positioning stage. The piezoelectric actuator has a simple structure of a cone type consisting of two piezoelectric ring-typed ceramics with electrodes divided into four segments and stainless steel elastic bodies. Before manufacturing the piezoelectric motor, the admittance characteristics and displacements of the actuator as a function of frequency were simulated. Elliptical motions of the actuator were created at several frequencies between the longitudinal and transverse resonance frequencies. The actual motor with alumina ball exhibited nice performance using a driving circuit with two rotary encoders and a PID controller. The moving element was omni-directionally operated at a driving frequency of 53.8 kHz and an output voltage of 280 V_p-p. The developed motor enables the moving element to move to a desired position with a resolution of 1.2°/pulse, an angular velocity of 4 rad/s, and a thrust force of 200 g.     

The effect of nitrogen incorporation on surface properties of silicon oxynitride films

In order to investigate the surface heterogeneity of silicon oxynitride films, we observed the nanoscale variation of the surface potential by Kelvin probe force microscopy (KFM), the molecular bonding characteristics by Fourier transform infrared spectrometry (FTIR), and the wetting behavior by contact angle measurement. Nitrogen incorporation into silicon oxynitride films influenced the decrease in the surface potential and the polar component of the surface free energy. We present the first correlation between the nanoscale measurement of the surface potential and the macroscopic measurement of the surface free energy in silicon oxynitride films grown by a standard plasma‐enhanced chemical vapor deposition (PECVD) technique. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Simultaneous analysis of seven 2‐hydroxy fatty acids as tert‐butyldimethylsilyl derivatives in plasma by gas chromatography–mass spectrometry

An efficient method for the simultaneous analysis of seven 2‐hydroxy fatty acids (2‐HFAs) as tert‐butyldimethylsilyl (TBDMS) derivative was developed by gas chromatography–mass spectrometry in selected ion monitoring mode. New mass spectral data on 2‐hydroxycapric, 2‐hydroxypalmitic, 2‐hydroxystearic and 2‐hydroxybehenic acids as di‐TBDMS derivatives for hydroxyl and carboxyl groups were built. Under the optimal conditions, the present method showed a good correlation coefficient (r ≥ 0.999) in the range of 0.01–0.5 µg. The precision showed low relative standard deviation of <10%, and the accuracy (percentage relative error) varied from ?5.2 to 0.3 for the seven 2‐HFAs studied. Recovery rates of all 2‐HFAs were ≥ 93.2% with good precision. When applied to normal human plasma, seven 2‐HFAs were positively identified. Therefore, the present efficient method will be useful for simultaneous analysis of 2‐HFAs in plasma. Copyright © 2014 John Wiley & Sons, Ltd.     

Li2MnSiO4/carbon nanofiber cathodes for Li-ion batteries

Pure single-phase Li₂MnSiO₄ nanoparticle-embedded carbon nanofibers have been prepared for the first time via a simple sol-gel and electrospinning technique. They exhibit an improved electrochemical performance over conventional carbon-coated Li₂MnSiO₄ nanoparticle electrodes, including a high discharge capacity of ～200 mAh g^?1, at a C/20 rate, with the retention of 77 % over 20 cycles and a 1.6-fold higher discharge capacity at a 1 C rate.     

A Facile Method for the Preparation of Monodisperse Beads with Uniform Pore Sizes for Cell Culture

This paper describes a facile method for the preparation of porous gelatin beads with uniform pore sizes using a simple fluidic device and their application as supporting materials for cell culture. An aqueous gelatin droplet containing many uniform toluene droplets, produced in the fluidic device, is dropped into liquid nitrogen for instant freezing and the small toluene droplets evolve into pores in the gelatin beads after removal of toluene and then freeze‐drying. The porous gelatin beads exhibit a uniform pore size and monodisperse diameter as well as large open pores at the surface. Fluorescence microscopy images of fibroblast‐loaded gelatin beads confirm the attachment and proliferation of the cells throughout the porous gelatin beads.