Facile synthesis and responsive behavior of PDMS‐b‐PEG diblock copolymer brushes via photoinitiated “thiol‐ene” click reaction

We present herein a mild and rapid method to create diblock copolymer brushes on a silicon surface via photoinitiated “thiol‐ene” click reaction. The silicon surface was modified with 3‐mercaptopropyltrimethoxysilane (MPTMS) self‐assembled monolayer. Then, a mixture of divinyl‐terminated polydimethylsiloxane (PDMS) and photoinitiator was spin‐coated on the MPTMS surface and exposed to UV‐light. Thereafter, a mixture of thiol‐terminated polyethylene glycol (PEG) and photoinitiator were spin‐coated on the vinyl‐terminated PDMS‐treated surface, and the sequent photopolymerization was carried out under UV‐irradiation. The MPTMS, PDMS, and PEG layers were carefully identified by X‐ray photoelectron spectroscopy, atomic force microscopy, ellipsometry, and water contact angle measurements. The thickness of the polydimethylsiloxane‐block‐poly(ethylene glycol) (PDMS‐b‐PEG) diblock copolymer brush could be controlled by the irradiation time. The responsive behavior of diblock copolymer brushes treated in different solvents was also discussed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Homo‐ and copolymerization of norbornene and 5‐norbornene‐2‐yl acetate with bis‐(β‐ketonaphthylamino)palladium(II)/B(C6F5)3 catalytic system

The polymerization of norbornene with bis(β‐ketonaphthylamino) palladium(II), Pd{CH₃C(O)CHC[N(naphthyl)]CH₃}₂, in combination with tris(pentafluorophenyl)borane (B(C₆F₅)₃), was investigated by varying the B:Pd(II) molar ratio, monomer concentration, reaction temperature, and time. The catalytic activity was found to reach 2.8 × 10⁴ gPolymer/(molPd^?h) and the obtained polynorbornene (PNBE) was confirmed to be vinyl addition polymer and showed good thermo‐stability (T_dec > 350°C), but exhibited poor solubility in organic solvents due to the relative higher stereo regularity. Pd{CH₃C(O)CHC[N(naphthyl)]CH₃}₂/B(C₆F₅)₃ system is also an active catalyst for copolymerization of norbornene and 5‐norbornene‐2‐yl acetate (NBE‐OCOCH₃) in toluene with moderate yields (in 9.2–36.5% yields) and produces the addition‐type copolymer with relatively high molecular weights (0.96 × 10⁴–2.13 × 10⁴ g/mol). The incorporation of functional group in the copolymer can be controlled up to 0.9–23.5 mol% by varying the NBE‐OCOCH₃ monomer feed ratios from 10 to 90%. The copolymers are proved to be noncrystalline and show good solubility in common organic solvents and excellent thermal stability up to 350°C. Copyright © 2011 John Wiley & Sons, Ltd.     

Crystal Structure of Chiral Acetato-bridged Binuclear Cyclopalladated complex[Pd（μ-O2CM3）（S-C6H4CHMeNH2）]2

Reaction of (S)-α-methylbenzylamine with Pd(OAc)2 in anhydrous HOAc produced the chiral complex[Pd(μ-O2CMe)(S-C6H4CHMeNH2)]2.(1).The complex was characterized by 1H NMR spectroscopy,elemental analysis and a single-crystal Xray analysis.The X-ray crystal structure analysis revealed that complex 1 has four isomers:two outer and two inner isomers.     

Synthesis, characteristics and photoluminescent properties of novel Ir-Eu heteronuclear complexes containing 2-carboxyl-pyrimidine as a bridging ligand

Two novel iridium(III) complexes, [Ir(dfppy)(2)(pmc)] and [Ir(ppy)(2)(pmc)] (dfppy = 2-(4',6'-difluoro-phenyl)pyridine, ppy = 1-phenyl-pyridine), were designed and synthesized using 2-carboxyl-pyrimidine (Hpmc) as an ancillary ligand. Single crystals were obtained and characterized by single crystal X-ray diffraction. The tetrametallic complexes {[(C^N)(2)Ir(μ-pmc)](3)EuCl(3)} (C^N = dfppy, ppy) were synthesized using the iridium(III) complexes as "ligands". Photophysical and theoretical studies indicate that [Ir(dfppy)(2)(pmc)] is more suitable for sensitizing the emission of Eu(III) ions than [Ir(ppy)(2)(pmc)].     

Synthetic approach to stop-codon scanning mutagenesis

A general combinatorial mutagenesis strategy using common dimethoxytrityl-protected mononucleotide phosphoramidites and a single orthogonally protected trinucleotide phosphoramidite (Fmoc-TAG; Fmoc = 9-fluorenylmethoxycarbonyl) was developed to scan a gene with the TAG amber stop codon with complete synthetic control. In combination with stop-codon suppressors that insert natural (e.g., alanine) or unnatural (e.g., p-benzoylphenylalanine, Bpa) amino acids, a single DNA library can be used to incorporate different amino acids for diverse purposes. Here, we scanned TAG codons through part of the gene for a model four-helix bundle protein, Rop, which regulates the copy number of ColE1 plasmids. Alanine was incorporated into Rop for mapping its binding site using an in vivo activity screen, and subtle but important differences from in vitro gel-shift studies of Rop function are evident. As a test, Bpa was incorporated using a Phe14 amber mutant isolated from the scanning library. Surprisingly, Phe14Bpa-Rop is weakly active, despite the critical role of Phe14 in Rop activity. Bpa is a photoaffinity label unnatural amino acid that can form covalent bonds with adjacent molecules upon UV irradiation. Irradiation of Phe14Bpa-Rop, which is a dimer in solution like wild-type Rop, results in covalent dimers, trimers, and tetramers. This suggests that Phe14Bpa-Rop weakly associates as a tetramer in solution and highlights the use of Bpa cross-linking as a means of trapping weak and transient interactions.     

Electrosyntheses of poly(2,3-benzofuran) films in boron trifluoride diethyl etherate containing poly(ethylene glycol) oligomers

Visible-light transparent high-quality substrate-supported poly(2,3-benzofuran) (PBF) film has been successfully electrosynthesized by direct anodic oxidation of 2,3-benzofuran on stainless steel sheet in boron trifluoride diethyl etherate (BFEE) containing 10% poly(ethylene glycol) (PEG) with molar mass of 400 (by volume). The oxidation potential of 2,3-benzofuran in this medium was measured to be only 1.0 V vs. SCE, which is lower than that determined in acetonitrile + 0.1 M Bu₄NBF₄ (1.2 V vs. SCE). The PBF films obtained in this media showed good electrochemical behaviors and good thermal stability with conductivity of 10⁻² S cm⁻¹, and the doping level of as-prepared PBF films was determined to be only 8.9%. The structure and morphology of the polymer were investigated by UV-vis, infrared spectroscopy and scanning electron microscopy (SEM), respectively. To the best of our knowledge, this is the first case for the syntheses of PBF films.     

Novel poly(1H-benzo[g]indole)/TiO2 nanocomposites for high-performance electrochromic supercapacitor application

Poly(1H-benzo[g]indole) (PBIn)/TiO₂ nanocomposites with core-shell nanorod array morphology are successfully prepared via simply hydrothermal synthesis combined with electrochemical polymerization. The synergistic effect between PBIn and TiO₂ and the matched energy level distribution make PBIn/TiO₂ nanocomposites have a specific capacitance of 29.65 mF cm⁻². At the same time, it can reversibly change between light yellow and light green and show excellent cycling stability (86% retention after 3000 cycles). Thus, the electrochromic supercapacitor device (ESD) is also constructed based on PBIn/TiO₂ nanocomposite and poly(3,4-ethylenedioxythiophene). This ESD shows a good specific capacitance (13.2 mF cm⁻²) and high-coloring efficiency (487 cm² C⁻¹). In the charging and discharging stage, the color of ESD can reversibly change between yellow and dark blue. Thus, the accumulated energy state of the ESD can be simply judged by monitoring the color or transmittance value of the device. To verify the good energy storage and actual application, this ESD can light up the Light Emitting Diode (LED) after charging, which provides new possibilities for the application of intelligent supercapacitors in the future.     

Well-Defined,Versatile and Recyclable Half-Sandwich Nickelacarborane Catalyst for Selective Carbene-Transfer Reactions

Catalytic carbene-transfer reactions constitute a class of highly useful transformations in organic synthesis. Although catalysts based on a range of transition-metals have been reported, the readily accessible nickel(II)-based complexes have been rarely used. Herein, an air-stable nickel(II)-carborane complex is reported as a well-defined, versatile and recyclable catalyst for selective carbene transfer reactions with low catalyst loading under mild conditions. This catalyst is effective for several types of reactions including diastereoselective cyclopropanation, epoxidation, selective X−H insertions (X = C, N, O, S, Si), particularly for the unprotected substrates. This represents a rare example of carborane ligands in base metal catalysis.     

纳米铈-钨发射材料的结构与热发射性能研究

以纳米Ce—W粉末为原料制备了纳米Ce—W发射材料,利用扫描电镜和原位俄歇电子能谱等现代分析技术研究了材料的形貌、铈的分布和高温扩散、以及材料的表面性能,并采用自行研制的微机控制全自动电子发射测量装置测量了材料热发射性能。研究表明,纳米Ce-W材料晶粒细小,稀土元素铈的分布更弥散均匀,铈向表面扩散的能力增强。高温下材料表层形成了含有超额铈的活性层,纳米Ce-W材料的活性层厚度增大,超额铈的含量增多,Ce／O的活性层更厚,因此热发射性能更优异。     

Engineering of Nucleic Acids and Synthetic Cofactors as Holo Sensors for Probing Signaling Molecules in the Cellular Membrane Microenvironment

The comprehensive understanding of the mechanisms underlying the interaction of cells with their membrane microenvironment is of great value for fundamental biological research; however, tracking biomolecules on cell surfaces with high temporal and spatial resolution remains a challenge. Herein, a modular strategy is presented for the construction of cell surface DNA‐based sensors by engineering DNA motifs and synthetic cofactors. In this strategy, a stimuli‐reactive organic molecule is employed as the cofactor for the DNA motif, and the self‐assembly of them forms a FRET‐based holo DNA‐based sensor. With the use of the DNA‐based sensors, the versatility of this modular strategy has been demonstrated in the ratiometric imaging of the cellular extrusion process of endogenous signaling molecules, including sulfur dioxide derivatives and nitric oxide.