Sep 2009, Volume 4 Issue 3
    

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  • Research articles
    Chip calorimetry for fast cooling and thin films: a review
    Wei CHEN , Dongshan ZHOU , Gi XUE , Christoph SCHICK
    2009, 4(3): 229-248. https://doi.org/10.1007/s11458-009-0090-z
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    Here we review on the thin-film chip calorimeter with controllable cooling as well as heating rates up to 106 K·s−1 developed in the last 5 years at the Institute of Physics, Rostock University. The calorimeter has been successfully used for fast thermal processing and simultaneous calorimetric measurements of many polymer samples, the physical properties of which are generally dependent strongly on their thermal history. Besides, owing to the very small addenda heat capacity, the calorimeter is very sensitive to study samples of only several tenths of nanograms. With differential alternating current (AC) design, the sensitivity of the calorimeter increased to a few tenths of pico-Joules per Kelvin. Therefore, it can be used to study glass transition of polymers confined in ultra-thin films down to several nanometers thickness. After the discussion of the strategy to realize fast cooling, we describe the static and dynamic thermal properties of the sensors used for the setup of the calorimeter. Finally, we present examples to show the performance of the calorimeter in different measurement modes.
  • Research articles
    Oxazine ring construction: methods and applications to natural product synthesis
    Xiaobo WAN , Madeleine M. JOULLIÉ ,
    2009, 4(3): 249-258. https://doi.org/10.1007/s11458-009-0037-4
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    Although natural products containing a 1,2-oxazine ring are rare, more examples in this family of natural products have been discovered since trichodermamides A and B were reported in 2003. In addition to their structural novelty, these natural products possess very interesting bioactivities that are strongly dependent on their structures, making them attractive targets for investigating structure-activity relationships (SAR). In this feature article, we summarized the methodologies developed in recent years for constructing the 1,2-oxazine rings. Racemic and enantioselective total syntheses of trichodermamides A and B, based on these methodologies, are reviewed in detail.
  • Research articles
    Polylactic acid (PLA) synthesis and modifications: a review
    Yanling CHENG , Shaobo DENG , Paul CHEN , Roger RUAN ,
    2009, 4(3): 259-264. https://doi.org/10.1007/s11458-009-0092-x
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    This article reviews various methods of synthesizing polycondensation and ring-opening polymerization and modifying properties of polylactic acid (PLA), which may be used as biomaterials, such as a drug carrier in a drug delivery system, as a cell scaffold and suture in tissue engineering, and as packaging materials in packaging engineering field. Copolymerization of lactide with other monomers or polymers such as malic acid, polyethylene glycol (PEG), polyglycolic acid (PGA), or dextran, as well as blending polylactide with natural derivatives and other methods of modification are discussed. Surface modifications of PLA-type copolymers, such as surface coating, chemical modification, and plasma treatment are described.
  • Research articles
    Probing structural changes of spin-coated polystyrene film after swelling and precipitation by synchrotron GIUSAXS and AFM
    Binbin SUN , Yuqing LAI , Yongfeng MEN , Yoong KIM ,
    2009, 4(3): 265-268. https://doi.org/10.1007/s11458-009-0089-5
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    Polystyrene film of about 50 nm in thickness on silicon wafer was obtained by spin-coating in tetrahydrofuran solution. The film exhibits a rough surface as shown by atomic force microscopy images and ellipsometry data. Furthermore, such surface roughness produced a characteristic lateral correlation peak in an “out-of-plane” scan in the synchrotron grazing incidence ultra-small angle X-ray scattering pattern. The film was treated with liquids of solvent and non-solvent sequentially, resulting in a process of swelling and precipitation of the polystyrene film. Such a solvent/non-solvent treatment completely changed the original surface structure of the film. Aggregates of polystyrene of different sizes were observed both in atomic force microscopy and synchrotron grazing incidence ultra-small angle X-ray scattering measurements. The results demonstrate that synchrotron grazing incidence ultra-small angle X-ray scattering is a unique means to investigate large area micro-structural features of thin films supported on smooth surfaces.
  • Research articles
    Dye-sensitized solar cells based on bisindolylmaleimide derivatives
    Qiong ZHANG , Zhijun NING , Hongcui PEI , Wenjun WU ,
    2009, 4(3): 269-277. https://doi.org/10.1007/s11458-009-0087-7
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    Three organic dyes based on bisindolylmaleimide derivatives (I1, I2 and I3) were synthesized and investigated as sensitizers for the application in nanocrystalline TiO2 solar cells. The indole group, maleimide group and carboxylic group functioned as electron donor, acceptor and anchoring group, respectively. Solar-to-electrical energy conversion efficiencies under simulated amplitude-modulated 1.5 irradiation (100 mW•cm−2) of 2.07% were obtained for solar cells based on I2 and of 1.87 % and 1.50 % for I3 and I1, respectively. The open circuit voltage Voc was demonstrated to be enhanced by the introduction of dodecyl or benzyl moieties on the indole groups. The nonplanar structure of bisindolylmaleimide was proven to be effective in aggregation resistance. This work suggests that organic sensitizers with maleimide as electron acceptor are promising candidates as organic sensitizers in dye-sensitized solar cells.
  • Research articles
    Address-crossing digital information processing on a self-aggregatable cyclodextrin derivative based nanosystem
    Liangliang ZHU , Fengyuan JI , Qiaochun WANG , Xiang MA , Zhaofei CHEN , He TIAN ,
    2009, 4(3): 278-291. https://doi.org/10.1007/s11458-009-0088-6
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    A novel pH-responsive and photo-isomerizing β-cyclodextrin (β-CD) derivative DACD was synthesized and fully characterized by 1H-NMR, 13C-NMR, and HRMS. At room temperature, this compound would self-assemble to layer aggregations in an aqueous environment. The aggregated state can reversibly switch to a monomeric solution state attributed to the hydrophobic competition of an additional substance to the β-CD cavity. This self-aggregatable cyclodextrin derivative based nanosystem functioned by switching between the aggregated and monomeric state. An effective address-crossing digital information system, in response to pH and UV stimuli, was demonstrated based on such mechanism. This chemical system, capable of data memories and logic functions in nanoscale, can mimic the functions of pointer-based data processing.
  • Research articles
    Unimolecular half-adders and half-subtractors based on acid-base reaction
    Wei JIANG , Hengyi ZHANG , Yu LIU ,
    2009, 4(3): 292-298. https://doi.org/10.1007/s11458-009-0091-y
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    According to the structural analysis of reported molecular processors with acids and bases as inputs, we proposed a general method for constructing molecular half-adders and/or half-subtractors based on acid-base reaction. The method is preliminarily supported by four molecular processors (8-hydroxyquinoline, 4-hydroxypyridine, 4-aminophenol and 5-amino-1-naphthol) capable of the elementary addition and/or subtraction algebraic operations. Noticeably, 8-hydroxyquinoline can mimic the functions of three logic devices, i.e. half-adder, half-subtractor and digital comparator, by the use of superposition and reconfiguration. The method described in this paper may be useful not only for designing new unimolecular arithmetical processors with the same inputs and outputs as standard devices for the construction of future molecular computers, but it can also help us disclose the simplest molecules and biomolecules with computational properties concealed around us.
  • Research articles
    Chiral ruthenium-SDPs/diamine complexes-catalyzed enantioselective hydrogenation of -alkyl arylacetones via dynamic kinetic resolution
    Jianhua XIE , Weiling KONG , Xiaocheng WANG , Wenju BAI , Lixin WANG , Qilin ZHOU ,
    2009, 4(3): 299-306. https://doi.org/10.1007/s11458-009-0093-9
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    The asymmetric hydrogenation of the conformationally flexible racemic α-substituted acyclic dialkyl ketones via dynamic kinetic resolution (DKR) has been developed by using Ru-SDPs/diamine catalysts. Chiral alcohols were produced in high yields with good to excellent enantioselectivities (85%―97% ee) and diastereoselectivities (up to 97:3). This hydrogenation reaction provided a new approach to the synthesis of the key intermediate of J-104118.
  • Research articles
    Recognition of Anions by Protonated Methylazacalixpyridines
    Hanyuan GONG , Dexian WANG , Zhitang HUANG , Meixiang WANG ,
    2009, 4(3): 307-312. https://doi.org/10.1007/s11458-009-0094-8
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    Methylazacalixpyridines are a unique kind of macrocyclic molecules that are able to self-regulate their conformations to best fit the guests. They had shown good recognition to both neutral molecules such as diols and fullerenes and cations. After protonation, the conformation of methylazacalixpyridines became more flexible and could serve as receptors for anions. In the solution, the protonated methylazacalix[2]pyridine[2]arene formed complexes with halides yielding biding constants of 79 (mol/L)−1 for chloride, 10 (mol/L)−1 for bromide, and 79 (mol/L)−1 for iodide, respectively. The crystal structures of the complexes between protonated methylazacalix[4]pyridine (MACP-4), methylazacalix[2]pyridine[2]arene (MACP-2-A-2), and iodide anion showed a multiple interaction mode including electrostatic attraction, hydrogen bonding, and anion-p interactions.
  • Research articles
    Investigation into hemp fiber- and whisker-reinforced soy protein composites
    Linxiang WANG , Rakesh KUMAR , Lina ZHANG ,
    2009, 4(3): 313-320. https://doi.org/10.1007/s11458-009-0085-9
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    Whiskers, designated as W, were prepared from hemp fibers. Both fibers and whiskers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis. Scanning electron microscopy and transmission electron microscopy were used to evaluate the dimensions of the fibers and whiskers, respectively. By incorporating different weight fraction of the fibers and whiskers into soy protein isolate, we prepared two different composites designated as SC and SC-W, respectively. Thiodiglycol was used as a plasticizer for the preparation of composites. The SC and SC-W composites were characterized and compared in terms of mechanical properties, volume fraction of porosity, and water uptake. The results indicated that there was not much significant difference in the properties of the composites. In fact, mechanical properties of fiber-reinforced composites were higher than whisker-reinforced composites at optimum weight fractions. This study can give us the idea about the judicious use of fibers or whiskers as reinforcement materials.
  • Research articles
    Researches towards advanced materials in the Institute of Chemistry, Chinese Academy of Sciences (ICCAS)
    Lin TIAN ,
    2009, 4(3): 321-323. https://doi.org/10.1007/s11458-009-0097-5
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