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Table of Content

    10 February 2017, Volume 38 Issue 2
    Content
    Cover and Content of Chemical Journal of Chinese Universities Vol.38 No.2(2017)
    2017, 38(2):  0-0. 
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    Articles: Inorganic Chemistry
    Adsorption of Cr(Ⅵ) from Aqueous Solutions on Organic Modified Laponite
    CAO Xiaoqiang, YAN Bingqi, WANG Qian, WANG Yaping, QIU Jun, HUANG Yongqing, LI Lin, ZHANG Yan, HU Shugang, KANG Ling, LÜ Xianjun
    2017, 38(2):  173-181.  doi:10.7503/cjcu20160462
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    Laponite was synthesized by hydrothermal method and modified by cetyltrimethyl ammonium bromide(CTMAB). The adsorption of Cr(Ⅵ) on modified laponite(CTMABL) as a function of pH, CTMABL dosage, ionic strength, contact time, and temperature was studied via batch technique. The results showed that the specific surface area and pore volume of modified samples were decreased, while the average pore size was increased. The d(001) value of CTMABL raised from 1.23 nm to 1.79 nm after the modification, which indicated that the CTMAB had entered into the interlayer of laponite. The removal of Cr(Ⅵ) from solution increased with the increase of solution pH value. At pH<8.5, the surface Zeta potential of CTMABL particles is positive, and thus the adsorption efficiency can be promoted by the electrostatic attraction between CTMABL particles and Cr(Ⅵ) anions. The adsorption of Cr(Ⅵ) on CTMABL increased with the increase of adsorbent dosage, maintaining a removal efficiency of >99% at the dosage of 4 g/L. The effect of ionic strength on the adsorption of Cr(Ⅵ) was not obvious. The adsorption kinetic data of Cr(Ⅵ) on CTMABL were well described by the pseudo-second-order kinetics model, and the adsorption rate was influenced by the membrane diffusion and intra-particle diffusion. The adsorption isotherms of Cr(Ⅵ) on CTMABL can be described well by the Langmuir model. The thermodynamic parameters of Cr(Ⅵ) adsorption on CTMABL at different temperatures indicated that the adsorption was endothermic and spontaneous. The adsorption of Cr(Ⅵ) was dominated by surface complexation, whereas electrostatic attraction could also promote the Cr(Ⅵ) adsorption on CTMABL.

    Analytical Chemistry
    Colloidal Magnetically Assembled Molecularly Imprinted Photonic Crystals and L-Phenylalanine Sensing
    YOU Aimei, NI Xinjiong, CAO Yuhua, CAO Guangqun
    2017, 38(2):  182-186.  doi:10.7503/cjcu20160861
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    A colloidal magnetically assembled molecularly imprinted photonic crystals(CMA-MIPCs) with high sensitivity, strong specificity and rapid responsiveness for L-phenylalanine(L-Phe) was developed by combing a molecular imprinting technique with colloidal magnetically assembled photonic crystals. The magnetic assembly process was rapid and reversible. L-Phe magnetic molecularly imprinted nanoparticles(MMIPs) that prepared by miniemulsion polymerization were with a uniform spherical morphology and distinct core/shell structure, the average particle size of MMIPs was 104.3 nm. The CMA-MIPCs could directly transmitted the stimuli from the adsorption of different concentrations L-Phe into visual readable optical signals. The diffraction color changed from purple to orange as increasing the L-Phe concentration from 6.0×10-7 mol/L to 6.0×10-4 mol/L. The largest Bragg diffraction wavelength redshift range could reach 181 nm and the sensing time was 1 min. In addition, CMA-MIPCs showed no response to the structural analogues L-Tyr and L-Trp, which indicated that CMA-MIPCs possessed a good selectivity.

    Aptamer-capped Mesoporous Silica Nanoparticles for Myoglobin Detection
    GAO Lei, WANG Qing, YANG Xiaohai, WANG Kemin, DENG Peng, ZHANG Hua, LI Zhiping
    2017, 38(2):  187-192.  doi:10.7503/cjcu20160721
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    A novel, simple and label free method was constructed for the quantitative detection of myoglobin based on the aptamer-capped mesoporous silica nanoparticles. Rhodamine 6G, a kind of small fluorescent molecules, was blocked in the aptamer-capped mesoporous silica particles. In the presence of myoglobin, the aptamer left from the mesoporous surface and the fluorescence intensity was significantly enhanced after releasing rhodamine 6G to the solution. The result showed that the concentration of myoglobin was positively associated with the fluorescence intensity of the solution. Therefore, the quantitative detection of myoglobin was achieved by monitoring the change of fluorescence intensity. Through this strategy, the limit of detection(LOD) of myoglobin was proved to be 1.1 nmol/L with excellent selectivity. It was suggested that the method could satisfactorily meet the detection requirement of myoglobin in clinical medicine.

    Organic Chemistry
    Synthesis, Structures and Electrochemical Properties of Pyridine-based Tetrathiafulvalene Derivatives
    ZHAO Bangtun, MA Shuxiu, TAO Jingjing, ZHU Weimin
    2017, 38(2):  193-199.  doi:10.7503/cjcu20160625
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    Using the ethyl acetoacetate/Cu2O system, 4,5-bis(pyridin-2-ylthio)-1,3-dithiole-2-thione(2a), 4,5-bis(pyridin-3-ylthio)-1,3-dithiole-2-thione(2b) and 4,5-bis(pyridin-4-ylthio)-1,3-dithiole-2-thione(2c) were prepared by the reaction of di(tetraehylammonium)-bis(1,3-dithiol-2-thione-4,5-dithiocate) zincate with 2-iodopyridine(1a), 3-iodopyridine(1b) and 4-iodopyridine(1c) with the yields of 88%, 55% and 60%, respectively. Thiones 2a, 2b and 2c were conversed to 4,5-bis(pyridin-2-ylthio)-1,3-dithiole-2-one(3a), 4,5-bis(pyridin-3-ylthio)-1,3-dithiole-2-one(3b) and 4,5-bis(pyridin-4-ylthio)-1,3-dithiole-2-one(3c) under the presence of Hg(OAc)2 in almost quantitative yields. Consequently, the pyridine-tetrathiafulvalene compounds 2,3,6,7-tetrakis(pyridine-2-ylthio) tetrathiafulvalene(4a), 2,3,6,7-tetrakis(pyridine-3-ylthio) tetrathiafulvalene(4b) and 2,3,6,7-tetrakis(pyridine-4-ylthio) tetrathiafulvalene(4c) were obtained correspondingly through triethylphosphite-mediated self-coupling reactions of 3a, 3b and 3c with the yields of 80%, 74% and 69%. All novel compounds were characterized by proton and carbon nuclear magnetic resonance spectroscopy(1H NMR and 13C NMR), fourier transform infrared spectroscopy(FTIR) and mass spectroscopy(MS) methods. Meanwhile, the structures of 4b and 4c was identified by X-ray diffraction analysis. The cyclic voltammograms showed that the pyridine-tetrathiafulvalene 4a, 4b and 4c displayed two-electron quasi-reversible redox processes. Combined with quantum chemical calculations, the effects of the different pyridyl substituted tetrathiafulvalenes 4a, 4b and 4c on electrochemical potentials were analysised.

    Synthesis Process Research of γ-Secretase Inhibitors(LY411575)
    GUO Hongyao, LI Dong, LEI Xiong, ZHANG Xu, XU Renjun, WANG Feng, LI Wenhong
    2017, 38(2):  200-205.  doi:10.7503/cjcu20160742
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    The original synthetic route of gamma secretase inhibitors(LY411575) was improved, the yield of 35% was achieved which increased by 16% compared with the traditional process. Meanwhile, key interme-diates were resolved by chiral acid in advance so that the consumption of raw materials in latter three steps of synthetic process was decreased by 50%. The method contributed to decrease the reaction cost and the difficulty of product purification. In addition, the single-factor experiment was conducted for main factors affected the resolving process to study the influence of various factors on the e.e. value and the yield of products. The optimal reaction condition was obtained as follows: D-(+)-2 methyl benzoyl tartaric acid as the resolution agent, methanol as the solvent, heated to reflux for dissolution, the solvent of 12 mL per gram substrate, the time from the initial temperature of reflux to room temperature controlled in 120 min, the resolution yield of 40% and the e.e. value of 99%.

    Production and Characterization of Phenylalanine Aminomutase from Streptomyces Maritimus and Synthesis of β-Arylalanine
    ZHU Longbao, TAO Yugui, GE Fei, LI Wanzhen, LIU Yi, DU Guocheng
    2017, 38(2):  206-211.  doi:10.7503/cjcu20160624
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    The gene of phenylalanine aminomutase was cloned from Streptomyces maritimus. The corresponding enzyme(SmPAM) was expressed to synthesize the β-arylalanine in E. coli. A pair of primers was designed to amplify the gene pam of SmPAM, and the pamof 1569 bp was cloned into pET28a to construct pET28a-pam which was transferred into E. coli BL21 to express the recombinant SmPAM. The pam of SmPAM was cloned and expressed in E. coli. The activity was 2.5 U/mg at optimum condition of 30 ℃ and pH=9. Moreover, the enzyme exhibited excellent thermostablity and pH stability, no activity decrease was observed at 60—70 ℃ even incubated for 3 h, and about 98% of activity remained after incubation at pH=9—11 for 24 h. The enzyme displayed broad substrate spectrum, and could be used to synthesize the β-arylalanine with different groups at benzene ring, among these β-arylalanines, the yield of 2-nitro-β-phenylalanine was the maximum and reached 93%. The SmPAM displayed excellent stability and broad substrate spectrum with potential prospectin industrial application.

    Interaction of Inverted Cucurbit[7]uril with N,N'-dibenzyl -4,4'-pyridine Chloride
    GAO Zhongzheng, YANG Liguo, BAI Dong, CHEN Lixia, TAO Zhu, XIAO Xin
    2017, 38(2):  212-216.  doi:10.7503/cjcu20160458
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    An inclusion complex formed on self-assembly of the inverted cucurbit[7]uril(iQ[7]) host with N,N'-dibenzyl-4,4'-pyridine chloride(G1) guest was investigated by 1H NMR technique, electronic absorption and fluorescence spectroscopies, isothermal titration calorimetry(ITC) experiments and MALDI-TOF mass spectrometry. The experimental results showed that iQ[7] can encapsulate the benzyl moiety of the guest in its hydrophobic cavity to form dumbbell-type host-guest supramolecular assembly, and the inclusion ratio is 2:1. While a part of 4,4'-bipyridine is located inside the cavity of the iQ[7] host, the other part remains outside of the portal of the iQ[7] host.

    Physical Chemistry
    Fast Removal of Aqueous Mn(Ⅱ) Using Partially Reduced Graphene Oxide-Fe3O4
    BULIN Chaoke, GUO Ting, ZHANG Bangwen, DAI Zhian, YU Huitao, XING Ruiguang, ZI Luxiong
    2017, 38(2):  217-224.  doi:10.7503/cjcu20160664
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    Partially reduced graphene oxide-Fe3O4 composite(PRGO-Fe3O4) was prepared by one step co-precipitation onto graphene oxide(GO) synthesized by modified Hummers method. The as obtained composite was characterized by XRD, FESEM, EDX, HRTEM, SAED, XPS and FTIR. The impact of pH, contact time, dosage, foreign substances, reduction of GO and cycle times on the adsorption performance of the composite towards Mn(Ⅱ) were investigated and the dsorption isotherm, thermodynamics and kinetics were analyzed. The results indicate that Fe3O4 distribute evenly and uniformly in the as-obtained composite, with a fine particle size of 15—20 nm, resulting in a low remanence and coercivity. The composite shows efficient adsorption property and good recycability towards aqueous Mn(Ⅱ) owing to the thin GO sheets in its structure caused by the anchoring effect of Fe3O4. Adsorption equilibrium was reached within 3 min with the adsorption percent and capacity of 99.35% and 404.49 mg/g, respectively, under the conditions of pH=7, dosage 500 mg/L, and initial concentration of Mn(Ⅱ) of 201.32 mg/L, with the subsequent magnetic separation taking only 10 s. After five consecutive cycles, the adsorption capacity of the composite remians 78% that of the first cycle. Analyses on the mechanism and thermodynamics show that the adsorption is an endothermic, sponta-neous and monolayer chemical adsorption step.

    Adsorption Property of Mg-MOF-74 for CO2/H2O
    DU Tao, LONG Yuan, TANG Qi, LI Shenglu, LIU Liying
    2017, 38(2):  225-230.  doi:10.7503/cjcu20160584
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    Mg-MOF-74 was synthesized through a solvothermal method using Mg(NO3)2·6H2O and 2,5-dihydroxyterephthalic acid as raw materials. The product was then characterized via X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy, scanning electron microscopy(SEM) and breakthrough experiments. The results show that pure Mg-MOF-74 with complete structure, regular morphology and excellent CO2 adsorption properties was prepared. It is confirmed in breakthrough experiments that the as-synthesized Mg-MOF-74 maintains a high CO2 adsorption properties in the presence of H2O. Therefore, the prepared Mg-MOF-74 is a suitable candidate for capturing CO2 from wet flue gas stream.

    Synthesis of Nano ZSM-23 Zeolites with Low L/D Value Morphology and Their Hydroisomerization Performance
    ZHANG Yujian, ZHAI Xuli, FU Kaimei, JIANG Tao
    2017, 38(2):  231-237.  doi:10.7503/cjcu20160577
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    Rod-like ZSM-23 zeolites with different length/diameter values(L/D) were synthesized using dimethylamine(DMA) and isopropylamine(IPA) as templates, respectively. The samples were characterized by means of XRD, SEM, XRF, N2 sorption and NH3-TPD. The crystals(ZSM-23-IPA) shows special nanoscaled and uniformed morphology with L/D<5, and more external surface areas by controlling the initial gel composition and hydrothermal reaction parameters. On n-dodecane hydroisomerization reaction, it also shows high conversion, selectivity and i-C12 yield, which is associated with the more exposed active sites. Furthermore, Pt-ZSM-23-IPA catalyst also shows very good performance on real crude oil test. It indicates that ZSM-23 catalyst with low L/D value would be applied in the future for improving the low-temperature fluidity of lubricant oil in industry.

    Preparation and Photocatalytic Hydrogen Evolution Performance of In2O3/ZrO2-TiO2 Hollow Spheres
    ZHANG Jingjing, LI Li, HAO Yuting, SUN Leilei, ZHANG Xinyue
    2017, 38(2):  238-245.  doi:10.7503/cjcu20160544
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    Using polystyrene spheres(PS) latex as the template, In2O3/ZrO2-TiO2 hollow spheres were prepared by one-step method combined with calcination treatment. The structure, composition and morphology of the composite were characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), ultraviolet-visible diffuse reflectance spectroscopy(UV-Vis DRS), scanning electron microscopy(SEM) and N2 absorption-desorption measurements. The results showed that In2O3/ZrO2-TiO2 hollow sphere was mainly anatase TiO2 and its optical absorption red-shifted slightly. In2O3/ZrO2-TiO2 hollow spheres also showed higher activity for hydrogen production, its hydrogen production was higher than that of P25, ZrO2, hollow sphere ZrO2-TiO2 and powder In2O3/ZrO2-TiO2.

    Modification of Nano-sized Fe2O3 Photocatalysts with N-doped Graphene and g-C3N4
    WANG Jinshuang, QIN Chuanli, WANG Hongjian, LI Jiadong, ZHANG Xuliang, CHEN Shuangying, JING Liqiang
    2017, 38(2):  246-251.  doi:10.7503/cjcu20160524
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    Alpha iron-trioxide(α-Fe2O3) nanoparticles were synthesized by a phase-separated hydrolysis-solvothermal method, and then modified by coupling 3%(mass fraction) graphene, nitrogen-doped graphene and g-C3N4 as the two-dimensional hetero-materials by a simple wet chemical process. Detailed comparative studies of their effects on photocatalytic activities of α-Fe2O3 were carried out. The results show that the photocatalytic activities of nano α-Fe2O3 for reducing CO2 to CO and for degrading phenol are enhanced after coupling with all two-dimensional hetero-materials. The modification of nitrogen-doped graphene on α-Fe2O3 is better than graphene and the modification of g-C3N4 on α-Fe2O3 is the best. Based on the measurements of surface photovoltage responses, photoelectrochemical curves, and hydroxyl radical amounts, it is confirmed that the introduction of two-dimensional hetero-materials would promote the photogenerated charge separation and increase the content of the active intermediate(hydroxyl radicals) consequently, leading to the improved photocatalytic activity of nano α-Fe2O3.

    Production of Phenolic Compounds from Bagasse Lignin via Catalytic Pyrolysis of CaZr1-xFexO3
    CHEN Yanguang, WANG Xinhui, HAN Hongjing, WANG Haiying, AN Hongyu, SONG Hua, GONG Xuzhong, ZHANG Jian
    2017, 38(2):  252-260.  doi:10.7503/cjcu20160515
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    Chemical conversion is an important approach to obtain chemical products from bagasse lignin(BL) which favors in resource and high-value utilization of lignin. A series of perovskite-type mixed ionic and electronic conductors CaZr1-xFexO3(CZF-x; x=0, 0.2, 0.4, 0.8, 1.0) were prepared via the solid state reaction method. The crystal form, morphology, metal valence state and thermal stability were characterized by X-ray diffraction(XRD), scanning electron microscope(SEM), X-ray photoelectric spectroscopy(XPS) and thermogravimetric analysis and differential thermal analysis(TG-DTA). Catalytic performance for producing phenolic compounds from bagasse lignin via catalytic pyrolysis was evaluated in a fixed bed micro-reactor. The results show that the CaZr1-xFexO3 pellets after calcinations deposit randomly in the form of irregular grains of flake with compact structure. As the doping amount of Fe increases, the characteristic peaks of mixed ionic and electronic conductor shift to large angle, the cell volume of crystal and the grain size decrease. Moreover, the pyrolysis temperature of BL was significantly reduced under the action of CaZr0.2Fe0.8O3(CZFO-0.2). In the test of fixed bed micro-reactor, the yield of liquid product was 23.71%. The phenolic product was mainly consisting with phenols, guaiacyl groups, catechol and syringyl groups; their selectivities were 35.19%, 6.18%, 10.68% and 14.21% respectively. The rest of liquid products were benzenes and methoxy aromatics. The deactivated catalyst was regenerated by oxidation to removing the coke coated on the surface and exhibited the high structural stability and the better catalytic activity. Due to the enhancement of breakage for aromatic alkyl side chain by CZFO-0.2, the contents of CH4 and CmHn in BL pyrolysis gas increased.

    Preparation by Phase Transformation Method and Electrochemical Performance of β-Ni(OH)2 Nanowires
    LI Xingsheng, HE Wenxiu, ZHANG Yongqiang, YU Huiying, LI Ziqing
    2017, 38(2):  261-266.  doi:10.7503/cjcu20160511
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    β-Nickel hydroxide nanowires with diameters of 20—30 nm and lengths up to several micrometers were prepared via a simple phase transformation method. The structure and morphology of the samples were characterized using X-ray powder diffraction(XRD) and field emission scanning electron microscopy(FESEM). The electrochemical performances were measured using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The results show that Paraotwayite type α-nickel hydroxide nanowires have successfully transformed to β-nickel hydroxide nanowires in sodium hydroxide solution after being hydrothemally treated for 30 min. The reversibility and rate performance of electrode materials α-nickel hydroxide and β-nickel hydroxide nanowires are superior to those of β-nickel hydroxide nanosheets at different scan rates.

    Morphology-controlled Preparation and Photocatalytic Properties of Cu2O/ZnO Microstructures
    LI Ru, YU Liangmin, YAN Xuefeng, JIANG Tao
    2017, 38(2):  267-274.  doi:10.7503/cjcu20160502
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    The cuprous oxide/zinc oxide(Cu2O/ZnO) microstructure were prepared by a mild solution strategy. The integration of polymorphic Cu2O with wurtzite ZnO is a facile approach of elevating photocatalytic activity toward methyl orange degradation. The morphology and photocatalytic activity were investigated by adjusting Cu2+/Zn2+ ratio. Nearly 77.5% of methyl orange was photodegradated over Cu2O/ZnO photocatalyst after 5.5 h light irradiation. The potential photodegradation mechanism was demonstrated by designing a pseudo cell comprised of polymorphic Cu2O/ZnO anode, Pt counter electrode and sandwiched methyl orange solution.

    Polymer Chemistry
    Preparation and Properties of Double Network Hydrogels Based on Gellan Gum and Polyethylene Glycol Acrylate
    WANG Zhengguang, HU Duo, WU Dongwei, LU Lu, ZHOU Changren
    2017, 38(2):  275-283.  doi:10.7503/cjcu20160650
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    Hydrogels have the similar 3D micro-environment as the native extracellular matrix and hold great potential in future biomedical applications. However the mechanical performance limited their applications. The double network hydrogel(DN gel) attracts much attention due to its high mechanical properties. This study aimed to prepare a series of DN gels based on gellan gum and polyethylene glycol acrylate(PEGDA) to improve the toughness of gellan gum hydrogel for 3D cell culture and tissue repair. The DN hydrogels exhibited better mechanical properties, with the tensile fracture energy up to 1.01 × 103 J/m2, which was similar to the value of natural articular cartilage. Our study suggests that the DN gel based on gellan gum and PEGDA present promising mechanical performance and cell seeding efficiency. These hydrogels may have prospective applications in the fields of wound dressing, artificial cartilage and tissue engineering scaffold materials which require high mechanical properties.

    Synergistic Flame Retardant and Suppression Smoke Mechanism of Cerium Phenylphosphonate and Decabromodiphenyl Oxide in Glass-fiber Reinforced Poly(1,4-butylene terephthalate) Composites
    GUO Zhenghong, FANG Zhengping, CHEN Chao
    2017, 38(2):  284-293.  doi:10.7503/cjcu20160630
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    Glass fiber reinforced poly(1,4-butylene terephthalate)(PET-GF)/ decabromodiphenyl oxide(DBDPO)/cerium phenylphosphonate(CeHPP) composites were prepared by melt blending. Cone test was employed to investigate the comprehensive combustion behavior and the thermal gravimetric-infrared spectrometry(TG-FTIR) was used to analyze the release amount and component of volatile gases produced during thermal degradation. The scanning electron microtopography(SEM) of char residues was observed, and the elements and contents in char residues were tested by energy dispersive X-ray spectrometer(EDX) and X-ray photoelectron spectroscopy(XPS). The experimental results showed that the compounding of CeHPP and DBDPO in PET-GF restrained the thermo-oxidative degradation of PET-GF/DBDPO/CeHPP composites, retarded the combustion of condensed phases and reduced the smoke release. CeHPP formed the continuous and compact carbon char during combustion, dispersing among the surface of polymer matrix and glass fibers and restricting DBDPO and its decomposition products in condensed phases. Therefore, the synergism flame retardant effects of gaseous phase and condensed phase were achieved, suppressing the smoke release to gaseous phase effectively.

    Influence of Polyphosphate Flame Retardant Couple with Ammonium Polyphosphate on Epoxy Resin
    LI Pei, FU Hai, ZHAO Ou, LAI Fang, CHEN Shimei, MEI Guiyou, ZHAO Wei, BAN Daming
    2017, 38(2):  294-302.  doi:10.7503/cjcu20160599
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    A novel polyphosphate flame retardant, poly(2-10-hydrogen-9-oxa-phosphaphenanthrene hydroquinone phenyl phosphate)(POPP), aimed at improving the flame retardancy of EP was prepared. POPP and ammonium polyphosphate(APP) at the mass ratio of 1:2 were added into EP to form a series of flame retardant modified epoxy resin(FR-EP). The chemical bond adsorptions of FR-EP were investigated by infrared spectroscopic analysis. The thermal stability was study by thermal gravimetric analysis(TGA). Flame retardant properties as well as burning behavior of epoxy resin composites have been investigated by limited oxygen index(LOI) and vertical burning test(UL-94). Fire properties of modified epoxy resin were test by Cone calorimeter. The morphological characteristics of char residue after Cone test were studied by scanning electron microscope(SEM). The result shows that POPP increase burning behavior at lower adding amount, which help epoxy resin to pass UL-94 V-0 at 5%. But POPP modified epoxy resin gave out only 24.2% of LOI value. POPP/APP flame retardant increase not only UL-94 grade but also much higher LOI value. A UL-94 V-0 grade was obtained when 5% POPP/APP were added into the epoxy matrix and 27.7% LOI value. When adding amount of POPP/APP are increased to 15%, a higher LOI value of 33.8% can be get. Results of TGA test indicate that decomposition temperature of FR-EP decrease along with increase of flame retardant amount. But modified samples give out more char residue. By incorporation of POPP/APP, THR, HRR, EHC, TSR and COP of FR-EP were reduced obviously, and promote char residue dramatically. PkHRR decrease from 831.5 kW/m2 to 346.8 kW/m2 at 15% of adding amount. Morphology study shows that good flame retardant property of FR-EP is contributed to well-formed char residue structure. These structures of char are net-like and type may prevent little burning product from moving out to the surface of matrix. Moreover, this char residue protects inner material from heat.

    Flame-retardant Property of Carrageenan Fiber
    ZHANG Weiwei, XUE Zhixin, LIU Jingjing, YAN Miao, XIA Yanzhi
    2017, 38(2):  303-311.  doi:10.7503/cjcu20160559
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    Carrageenan fibers(CAFs) were obtained through the wet spinning technique with barium salt as coagulation bath. The fibers were characterized by limiting oxygen index(LOI), Cone calorimeter(Cone), scaning electron microscopy-energy dispersive spectrometer(SEM-EDS), X-ray diffraction(XRD), thermogravimetry(TG)-differential scanning calorimetry(DSC)-Fourier transform infrared spectroscopy(FTIR) and pyrolysis(Py)-gas chromatography(GC)-mass spectrometry(MS). The results showed that carrageenan fiber(CAF) took on better flame retardancy than calcium alginate fiber(ALF) and agar fiber(AGF). The LOI of CAF was up to more than 50, and the fiber kept red state without flame in the whole Cone process. Some other Cone parameters presenting lower value, such as heat release rate, total heat release, indicated that CAF has good flame retardancy. The sulfate ester combined with barium ion through complexing action of CAF, and they played an important role in the formation of carbon residue and changing the breakup processes of carra-geenan macromolecule. In addition, flame-retardant mechanism could be attributed to sulfonyl free radical, which can combine with hydroxyl radicals rapidly to terminate the combustion reaction. Meanwhile, the dense structure of barium salt layer and hollow fiber structure were also crucial factors of flame retardant performance for CAF.

    Lignin Impacts on the Preparation of Phenolic-resin/Lignin Block Copolymer Resin and the Reaction Mechanism
    CHAO Wei, YANG Xiaomin, ZHOU Yu, ZHU Yanchao, WANG Zichen
    2017, 38(2):  312-317.  doi:10.7503/cjcu20160517
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    Phenolic-resin/lignin block copolymer resin was in-situ prepared using alkali lignin under different extraction conditions, phenol and formaldehyde as reactants, industrial xylose production residue as raw material. To obtain the minimum formaldehyde release, the best extraction conditions of alkali lignin are as following: the sodium hydroxide concentration is 5%(mass fraction), the mass ratio of solid/liquid is 1:12, and the reaction time is 3 h. The formaldehyde release is 0.115% and boiling water soaked bonding strength is 1.197 MPa, which are superior to the GB/T14074-2006(≤0.3%, ≥0.7 MPa). TG, FTIR and SEM results show that alkali lignin involved in the reaction. It improved the thermal stability and bonding strength of phenolic-resin/lignin block copolymer resin, at the same time it decreases the formaldehyde release. All of them improved the storage and application of resin significantly. According to our experimental results, possible reaction mechanism was proposed.

    Preparation and Characterization of Novel Dopamine-based Bioadhesive Hydrogels
    CUI Guolian, DAN Nianhua, DAN Weihua
    2017, 38(2):  318-325.  doi:10.7503/cjcu20160443
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    In order to replace conventional sutures in wound closing applications, a favorable bioadhesive that has strong bonding strength, good biocompatibility and appropriate biodegradability is extremely needed. In this study, periodate oxidized alginate was modified by dopamine to obtain catechol-based oxidized alginate(COA) using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide/N-hydroxysuccinimide(EDC/NHS) as catalyst. Then COA was crosslinked with collagen to further obtain a novel COA-collagen bioadhesive hydrogel. The microstructure of COA was characterized by ultraviolet-visible(UV-Vis), Fourier transform infrared spectrophotometer(FTIR) and proton nuclear magnetic resonance(1H NMR) spectroscopy. Meanwhile, the structure, equilibrium swelling ratio, degradation rate, bonding strength and cytotoxicity of the hydrogel were also evaluated. The results showed that the grafting-copolymerization of dopamine to oxidized alginate happened successfully and the degree of the substitution(DS) of dopamine was 12.5%, 18% and 22%, respectively. The hydrogels exhibited typical porous network. The equilibrium swelling ratio of the hydrogels decreased firstly and increased with the substitution ratio of dopamine increasing at last. The degradation rate of the hydrogels became lower with the increase of dopamine substitution ratio. The bonding strength of the hydrogel increased from (20.43±4.21) kPa to (29.91±6.10) kPa after modified with dopamine. Moreover, the results obtained in the methyltetrazolium(MTT) study showed that no extra cytotoxicity, which was of importance to develop a kind of biomaterials. In conclusion, the results suggest that the COA-COL bioadhesive hydrogel can potentially be a promising alternative for use in wound closing applications.

    Preparation of Glycyrrhetinic Acid-modified Sodium Alginate Microgel Spheres for 3D Cell Culture
    YANG Meiyue, WANG Wei, TIAN Zhiqing, LI Yingying, YUAN Zhi
    2017, 38(2):  326-334.  doi:10.7503/cjcu20160316
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    In order to obtain microgel sphere containing hydrophobic ligands which can be used for 3D liver cell culture. Firstly, the sodium alginate(ALG) was modified with tertiary ammonia-glycyrrhetinic acid[GA-N(CH3)2]. Then, the high flux, monodisperse, size controllable microgel of GA-N(CH3)2 modified ALG[ALG-GA-N(CH3)2] was prepared by the technology of microfluidics with the assistant of agarose. The influence of different preparation condition, such as concentration of Span 80, substitution degree of hydrophobic ligand, concentration of ALG-GA-N(CH3)2, velocity of water/oil phase, on microdroplet preparation were also studied. The results showed that the introduction of tertiary ammonia can significantly improve the hydrophility of GA. And the monodisperse microgel with 200 μm diameter, which could be used for cell envelope culture, could be obtained under the condition below: the mass fraction of Span 80 is 2.0%, hydrophobic ligand substitution degree is less than 12%, concentration of sample is less than 15 mg/mL, the velocity of water is 1.5 mL/h and the velocity of oil is 6.0 mL/h. The microgel provides a new method for liver cell 3D culture and laid the foundation for its application in tissue engineering.