A New Polymer Flooding Agent Prepared Through Intermacromolecular Complexation

Abstract

This paper reports a new polymer flooding agent used for enhanced oil recovery (EOR), poly(acrylamide-acrylic acid) [P(AM-AA)]/poly(acrylamide-dimethyldiallylammonium chloride) [P(AM-DMDAAC)] polyelectrolyte complex. The solution viscosity of prepared P(AM-AA)/P(AM-DMDAAC) complex is enhanced due to the strong interaction between the two oppositely charged copolymers, i.e., P(AM-AA) and P(AM-DMDAAC), which were prepared through radical copolymerization. The ionic content could be controlled by changing the reaction conditions. The structures of the two copolymers were characterized through FT-IR, ¹H NMR, and acidic and precipitation titration. The formation as well as the factors affecting the P(AM-AA)/P(AM-DMDAAC) polyelectrolyte complex were investigated by means of viscosity measuring and light transmittance testing. The experimental results show that the composition of the copolymers, the pH value, and the concentration of the polymer solutions have remarkable effects on the formation of P(AM-AA)/P(AM-DMDAAC) polyelectrolyte complex and the solution viscosity. When DMDAAC content in P(AM-DMDAAC) is 3.2 mol%, AA content in P(AM-AA) is 48–58 mol%, the weight ratio of P(AM-AA) to P(AM-DMDAAC) is 70/30–30/70, the pH value of the solution is 6–10, and the concentration of solution is 1000–3500 ppm, then a homogeneous solution of P(AM-AA)/P(AM-DMDAAC) poly-electrolyte complex could be obtained which exhibits a much higher solution viscosity compared with its components.     

Oxidation of Ascorbate by Ni(III) Complexes with Tetraaza-macrocyclic Ligands in Neutral Aqueous Solutions. A Pulse-Radiolysis Study

Abstract

The mechanisms and kinetics of oxidation of ascorbate, AH^?, by Ni(III)Lⁱ _aq and by LⁱNi(III) (HPO₄)₂ ^? complexes (L¹ = meso-(5,12)-7,7,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; L² = 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane) in neutral aqueous solutions have been investigated.

The oxidation of ascorbate by the LⁱNi(III) (HPO₄)₂ ^? and Ni(III)L¹ _aq proceeds via two consecutive reactions well separated in time. The products of the first reaction are the A^.? radical anion and the corresponding Ni(II) complex. The oxidations by the LⁱNi(III)(HPO₄)₂ ^? complexes proceed via the outer sphere mechanism, whereas the detailed mechanism of reaction of Ni(III)L¹ _aq cannot be determined. The rate of reaction decreases with the increase in the concentration of phosphate, thus indicating that LⁱNi(III)(HPO₄)(H₂O)⁺ and LⁱNi(III)OH²⁺ are stronger oxidizing agents than LⁱNi(III)(HPO₄)^? ₂.

The oxidation of ascorbate by Ni(III)L² _aq proceeds via three consecutive reactions which are well separated in time. Thus the results clearly point out that this process occurs via the inner sphere mechanism. The first transient observed is tentatively identified as L²(H₂O)Ni(II)(A^.?)²⁺, i.e., an unexpected complex of the ascorbate anion radical. Also in this process the last transient observed is the A^.? anion radical. The stabilization of the ascorbyl radical in a transient complex might be of biological significance.     

UFLC–MS/MS method for simultaneous determination of six lignans of Schisandra chinensis (Turcz.) Baill. in normal and insomniac rats brain microdialysates and homogenate samples: towards an in‐depth study for its sedative‐hypnotic activity

Schisandra chinensis (Turcz.) Baill., a traditional Chinese medicine, has been clinically used for the treatment of insomnia for centuries. The insomnia mechanism and the possible active ingredients of S. chinensis remain largely unknown. The objective of this study was to develop a method to detect its components which could pass through the blood brain barrier (BBB) by determining the brain microdialysate and brain tissue homogenate samples and then obtain the pharmacokinetic profile in brain for comprehensive understanding of its hypnotic clinical efficacy. Therefore, an efficient, sensitive and selective ultra fast liquid chromatography/tandem mass spectrometry method for the simultaneous determination of six sedative and hypnotic lignans (schisandrin, schisandrol B, schisantherin A, deoxyshisandrin, γ‐schisandrin and gomisin N) of Schisandra chinensis (Turcz.) Baill. in rat brain tissue homogenate and brain microdialysates has been developed and validated. The analysis was performed on a Shim‐pack XR‐ODS column (75 mm × 3.0 mm, 2.2 µm) using gradient elution with the mobile phase consisting of acetonitrile and 0.1% formic acid water. The method was validated in brain homogenate and microdialysate samples, which all showed good linearity over a wide concentration range (r² > 0.99), and the obtained lower limit of quantification was 0.1 ng · ml^?1 for the analytes in brain microdialysate samples. The intra‐ and inter‐day assay variability was less than 15% for all analytes. The study proved the six lignans, as sedative and hypnotic ingredients, could pass through the BBB with brain targeting, distributed mainly in the hypothalamus and possessed complete pharmacokinetics process in brain. The results also indicated that significant difference in pharmacokinetic parameters of the analytes was observed between two groups, while absorptions of these analytes in insomniac group were significantly better than those in normal group. Copyright © 2013 John Wiley & Sons, Ltd.     

Direct electrochemistry of hemoglobin on graphene/Fe3O4 nanocomposite-modified glass carbon electrode and its sensitive detection for hydrogen peroxide

Graphene/Fe₃O₄ nanocomposite was prepared for the immobilization of hemoglobin (Hb) to improve the electron transfer between Hb and glass carbon electrode (GCE). The characterization of nanocomposites was described by transmission electron microscopy, Fourier transform infrared, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The electrochemistry of Hb on the graphene/Fe₃O₄-based GCE was investigated by cyclic voltammetry and amperometric measurement. The modified electrode showed a wide linear range from 0.25 μmol/L to 1.7 mmol/L with a correlation coefficient of 0.9967. The detection limit of the H₂O₂ biosensor was estimated at 6.0?×?10^?6?mol/L at a signal-to-noise ratio of 3.     

Design and Synthesis of Tri-substituted Chiral Pyrrolidin-2-one Derivatives as CCR4 Antagonists

A series of tri-substituted chiral pyrrolidin-2-one derivatives have been designed and synthesized as CC chemokine receptor 4 （CCR4） antagonists. The structure of CCR4 was built by homology modeling. Asymmetric synthesis was applied to synthesize the R,R configuration chiral pyrrolidin-2-one scaffold. The stereoisomeric con- figurations of the compounds were identified by 2D I H-~H COSY spectroscopy and 1D NOESY spectroscopy. This method was more economical and convenient than traditional X-ray single crystal diffraction. In addition, the inter- actions between these compounds and the N-terminal extracellular tail of CCR4 were studied using capillary zone electrophoresis. The CCR4 chemotaxis inhibition effect was tested in CCR4-transfected HEK293 cells. Several compounds showed potent activities as CCR4 antagonists. Among these compounds, lc is the most active one. Its apparent binding constant of CZE experiment result is （1.569±0.11）× 10s L·mol ^-1, and its percentage inhibition of the HEK293/CCR4 cells migration with the concentration of I gmol·L ^-1 in DMSO is 59%. And compound If has slightly higher affinity to N-terminal of CCR4 according to its apparent binding constant than lb because of the in- troduced ester linkage. Further studies on the mechanism of these compounds are in progress.     

One inorganic-organic hybrid derived from reduced molybdophosphate and trinuclear cadmium(Ⅱ) fragment

One new polyoxometalate (POM)-based inorganic-organic hybrid [Cd3Ⅱ(HPO4)(Hbpp)(H2O)2]{CdⅡ[P4- Mo6O28H3.5(OH)3]2} (H4tpb)·7H2O (1) (bpp = 1,3-bis-(4-pyridyl)propane, tpb = 1,2,4,5-tetra(4-pyridyl)-benzene) constructed from reduced molybdophosphate [P4Mo6O28H3.5(OH)3]5.5- (P4Mo6), trinuclear CdⅡ-phosphate-Hbpp fragment and protonated tpb has been hydrothermally synthesized and structurally characterized by IR, elemental analyses and single crystal X-ray diffraction. The complex 1 crystallizes in the monoclinic system with the space group P21/c and cell parameters of a = 15.672(12)Å, b = 23.839(19)Å, c = 27.654(2)Å, β = 115.850(10)8, V = 9297.9(12) Å3, Z = 4, R1 = 0.0534 and wR2 = 0.1135. In complex 1, the P4Mo6 units are bridged by CdⅡ ions to form the classic sandwich-type [Cd(P4Mo6)2] dimers, which are further connected into a two dimensional network via the trinuclear CdⅡ subunits. The tpb is synthesized in situ from the bpp ligands and connects the adjacent 2D layers into a 3D supramolecular framework through hydrogen bonding interactions. The electrochemical and fluorescent properties of complex 1 have been investigated.     

刚性1,4-二(4-甲基咪唑)苯配体构筑的两个d10配位聚合物的合成、结构及荧光性质

利用过渡金属镉（锌）盐与1,4-二（4-甲基咪唑）苯、间苯二甲酸分别采用分层和水热法合成了化合物{[Cd（BMIB）（H₂O）₂]（NO₃）₂}_n（1）和{[Zn₂（BMIB）_1.5（OH）（IP）_1.5]·H₂O}_n（2）（BMIB=1,4-二（4-甲基咪唑）苯,IP^2-=间苯二甲酸根）,并对其进行了元素分析、IR及X射线衍射法表征。晶体结构研究表明：配合物1属于三斜晶系,P1空间群。晶胞参数：a=0.382 08（3）nm,b=0.904 72（7）nm,c=1.378 29（10）nm,α=98.581（4）°,β=97.020（3）°,γ=94.398（3）°。配合物2属于单斜晶系,C2/c空间群。晶胞参数：a=3.764 07（9）nm,b=1.017 18（5）nm,c=2.015 31（11）nm,β=120.860（2）°。配合物1是由配体BMIB连接镉离子形成一维链状结构,由氢键连接成二维层结构。而配合物2是由配体IP2-连接锌离子形成一维梯状结构,该一维梯通过羟基和BMIB连接成三维网络结构。此外,配合物1和2具有较好的荧光性能。     

手性自旋转换铁(Ⅱ)席夫碱配合物的合成、结构及其磁性研究

通过高氯酸亚铁,4-(咪唑-2-甲醛)丁腈和光学纯苯乙胺衍生物的自组装成功合成了2个纯手性单核自旋转换铁(Ⅱ)化合物fac-Λ-[Fe(R-L1)₃](ClO₄)₂(1),fac-Λ-[Fe(R-L₂)₃](ClO₄)₂(2).利用X-射线单晶衍射、元素分析(EA)、红外光谱(IR)、核磁共振氢谱(¹H NMR)、紫外光谱(UV)、圆二光谱(CD)等手段对配合物结构进行了表征.X-射线单晶衍射表明在化合物1和2中,铁(Ⅱ)金属中心与3个不对称双齿手性席夫碱配体中的6个氮原子配位形成八面体配位环境.每个结构基元中包含1个[Fe(L)₃]²⁺阳离子和2个高氯酸根阴离子.由于铁(Ⅱ)中心周围手性配体的螺旋协调配位使[Fe(L)₃]²⁺形成单一手性Λ构型.Fe(Ⅱ)N键长表明配合物1和2中的铁(Ⅱ)在低自旋状态.在[Fe(L)₃]²⁺中,相邻配体中的苯环和咪唑环形成分子内π-π相互作用.配合物1和2通过分子间C-H…π相互作用形成三维超分子结构.CD光谱证实配合物1和2在溶液中的光学活性.磁性测试表明配合物1和2分别在232和250 K发生自旋转换.由于配合物1和2具有相同的手性空间群和类似的堆积方式和分子间相互作用,导致1和2表现出不同自旋转换温度的原因主要是取代基效应.     

冬季平原河网水体溶存甲烷和氧化亚氮浓度特征及排放通量

以长江三角洲上海地区和海河流域天津地区水网为研究对象,对冬季河网表层水体溶存甲烷（CH4）和氧化亚氮（N2O）浓度、饱和度及水-气界面排放通量进行了研究.结果表明,冬季我国平原河网水体溶存CH4和N2O的浓度值都很高,呈高度过饱和状态：CH4浓度均值为0.86mol/L（饱和度：758%）,范围在（0.043±0.001）～（25.3±9.32）μmol/L之间;N2O浓度均值为86.8nmol/L（饱和度：488%）,范围在（9.71±0.41）～（691±35.2）nmol/L之间变化.天津排污河水体CH4和N2O浓度显著高于其他河流（均值分别为38.4mol/L和88.9nmol/L）.水体溶存CH4和N2O浓度、饱和度存在很大的地区差异,上海河网的CH4和N2O浓度和饱和度均值高于天津河网.河网水体水-气界面CH4和N2O排放通量变化范围很广,CH4通量在（1.35±0.22）～（665±246）mol/m2h之间,平均值为24.1mol/m2h,N2O通量在（0.19±0.02）～（22.6±5.05）mol/m2h之间,平均值为2.28mol/m2h.相关分析发现,河网水体溶存CH4浓度与DO显著负相关,与NH4＋显著正相关;N2O浓度则与NH4＋和NO3＋NO2显著正相关.河网水-气界面CH4和N2O排放通量均呈现出市区高郊区和农村低的空间分布规律,污染严重的河流已显然成为大气CH4和N2O的潜在排放源.