THE EFFECT OF BLENDING SEQUENCE ON PHASE MORPHOLOGY OF NYLON 6/ABS/SMA BLENDS

The preparation process-dependent phase morphology of blends composed of nylon 6 and acrylonitrile-butadiene- styrene(ABS)over a composition range of 30-70 wt% using a styrene-maleic anhydride(SMA)copolymer as the compatibilizing agent with a constant content(5phr)was investigated.The results of the scanning electron microscope (SEM)observation revealed that compared with the binary blends of nylon 6 and ABS,the existence of SMA caused a composition shift of phase inversion to a higher weight fraction of...     

STEREOREGULAR POLY(CYCLOHEXENE CARBONATE)S:UNIQUE CRYSTALLIZATION BEHAVIOR

<正>An example of crystalline CO_2-based polymer from the asymmetric alternating copolymerization of CO_2 and cyclohexene oxide is reported.Isotacticity of poly(cyclohexene carbonate)(PCHC)has the critical influence on the crystallinity,and only copolymers with a isotacticity of more than 90%are crystallizable.The stereoregular PCHC is a typical semi-crystalline thermoplastic,and possesses a high melting point(T_m)of 215-230℃and a decomposition temperature of ca.310℃.The spherulitic morphology of(R)-PCHC grows in a clockwise spiral from a center,and that of (S)-PCHC is a counterclockwise spiral,while the stereocomplex of(S)-PCHC/(R)-PCHC(1/1 mass ratio)presents lath-like dendritic crystal.The novel crystalline CO_2-based polycarbonate represents a rare example of optically active polymers with unique crystallization behavior.Our findings reflect the critical influence of stereoregularity on the crystallization for this kind of polymeric materials,and may lead to developments of thermal-resistance CO_2 copolymers for application in engineering thermoplastics.     

MECHANICAL BEHAVIORS OF POLYURETHANE-UREA ELASTOMERIC FIBERS UNDER STATIC STRETCHING DEFORMATION

The mechanical behaviors of polyether (ET) and polyester (ES) soft segment urethane-ureaelastomeric fibers constrained at different levels of elongation have been investigated by means ofdynamic mechanical tests and force-temperature measurements. The dynamjc mechanical re-sponse of the ET urethane-urea showed some difference from that of the ES as a function of exten-sion ratio. For force-temperature measuring the existence of a low temperature transition corre-sponding to the glass transition (T_(g's)) of the ester or ether soft segments, stress-softening tempera-ture (T_s) and initial melting temperature (T_(mh)) of hard segment crystallites was observed. The resultof cyclic testing of a constrained sample as a function of temperature indicated that the irreversibledecrease in stress implied a permanent change in sample microstructure.     

AN ESR STUDY OF ELECTROCHEMICAL REDUCTION OF NITROBENZENE

By means of a highly sensitive electrolytic cell installed in the ESR cavity, the authors investi-gated in situ the kinetic behavior of the primary electroreduction product (a radical anion) in a sol-vent mixture of water and ethanol over a wide range of pH. For the first time they observed somefurther complex kinetic behaviors of the electroreduction process of nitrobenzene. Through a study ofthe behavior of the radical anion (φ-NO_2~-.) with variations of pH, concentration of nitrobenzene(φ-NO_2) and electroreduction potential, they advanced a reaction scheme of the electroreduction ofnitrobenzene and simulated the experimental curves in order to evaluate the kinetic parameters of thereaction steps concerned.     

Efficient synthesis of poly(oxymethylene) dimethyl ethers over PVP-stabilized heteropolyacids through self-assembly

A series of polyvinylpyrrolidone-stabilized heteropolyacids(PVP-HPAs)are generated by self-assembly of HPAs and PVP in methanol.The PVP-HPAs are then employed as catalysts for the synthesis of poly(oxymethylene)dimethyl ethers(DMMn,n1)by the methanolysis of trioxane.The results suggest that the acidity of PVP-HPAs is tunable by changing the ratio of PVP and HPAs,which is a key factor for the selectivity of the DMMn product.By optimizing the composition and reaction conditions,two types of PVP-HPA,PVP-phosphotungstic acid(PVP-HPW)in a PVP/HPW ratio of 1/4:1 and PVP-silicotungstic acid(PVP-HSi W)in a PVP/HSi W ratio of 1/4:3/4,respectively afford 52.4%and 50.3%yields of DMM2–5.The optimized catalysts are reusable for a minimum of 10 times without a significant drop in performance.     

Simultaneous Photoreduction and Nitrogen Doping of Graphene Oxide for Supercapacitors by Direct Laser Writing

Graphene-based supercapacitors have attracted tremendous attention owing to their outstanding electrochemical performance. In terms of material, nitrogen(N)-doped graphene(NDG) displays enhanced specific capaci-tance and rate performance compared with bare graphene used as a supercapacitor electrode. However, it still remains a challenge to develop a facile and simple method of NDG in cost-effective manner. Here, we used a simple direct laser writing technique to accomplish the simultaneous photoreduction and N-doping of graphene oxide(GO) using urea as a N source. The N content of the resultant reduced N-doped graphene oxide(NGO) reached a maximum value of 6.37%. All reduced NGO(NRGO)-based supercapacitors exhibited a higher specific capacitance than those based on pure reduced GO(RGO). Interestingly, the electrochemical performance of NRGO-based supercapacitors varied with different contents ofN species. Therefore, we can control the properties of the obtained NRGOs by adjusting the doping ratios, an important step in developing effective graphene-based energy storage devices.     

Solid-solid phase transition of (1-C14H29NH3)2ZnCl4 in nanopores of silica gel for thermal energy storage

Latent heat storage performance of a layered perovskite-type compound, 1-C_(14)H_(29)NH_3)_2ZnCl_4(C_(14)Zn),embedded in a series of silica gel(SG) with pore sizes of d = 15–200 nm is investigated using differential scanning calorimetry(DSC), and powder X-ray diffractions(XRD). C_(14)Zn in the nanopores of silica gel shows size-dependent phase transition temperature, enthalpy change and supercooling. They have a stable transition temperature and heat capacity at each size in a short-term thermal cycling. Similar Xray diffraction patterns are observed for the nano-sized and the bulk C_(14)Zn. The encapsulation of a phase change material in nanopores is a new way of tuning its thermal energy storage properties for a wider range of temperature regulation.     

In-situ synthesis of nanoparticles via supersolubilizing micelle self-assembly

In-situ synthesis of nano-particles using the self-assembly of molten salt and super soluble micellae was proposed based on a phenomenon of super solubilization of molten salt in reverse micellae and its self-assembly when the concentration reached up to 95%(w/w).The mechanism of the self-assembly indicates that the self-assembly of molten salt occurs in a reverse micelle where a homogenous phase is established between 5%(w/w)of a surfactant with a VB value of less than 1 and a hydrocarbon spe- cies.This synthesis has some unique features,such as being free of water,highly effective deposition and narrow distribution of particle size.     

A Novel Protoilludane Sesquiterpene from the Wood of Xanthoceras sorbifolia

In the course of our searching for anti-HIV agents from natural sources, we have isolated a triterpene and a doubly linked proanthocyanidin dimer as HIV-1 protease inhibitors from the wood of Xanthoceras sorbifolia Bunge (Sapindaceae)1. Further investigation of this plant has led to the isolation of a protoilludane sesquiterpene (1). The present paper describes the isolation and structural determination of this novel sesquiterpene. The EtOH eluate of a MeOH extract of the wood of X. so…     

EFFECTS OF SOME Ca~(2+) BLOCKER ON RECEPTOR POTENTIALS OF CRAYFISH RETINA

One drug known to inactivate calmodulin and two others to block Ca~(2+) channels were applied to isolated superfused retinae of the crayfish Astacus leptodactylus and their influence on the receptor potentials (RP) was studied. Trifluoperazine causes an increase of the amplitude of maximum (h_(max))of RP and a prolongation of the time of half decrease (t_2). Furthermore, trifluoperazine could antagonise the effect of raised calcium concentration of superfusate, which decreases h_(max) and shortens t_2 of the RP. Iproveratril and D-600 cause a transient increase and thereafter a progressive decrease of h_(max) of the RP. There is a difference between effects of both drugs on t_2 of the RP. The mechanisms of effects of these drugs on the sensitivity of the isolated retina are discussed.     

Two-dimensional Nitrogen-doped Mesoporous Carbon/Graphene Nanocomposites from the Self-assembly of Block Copolymer Micelles in Solution

The self-assembly of block copolymer in solution has proven to be an effective strategy for building up a wide range of nanomaterials with diverse structures and applications. This paper reports a facile self-assembly approach towards two-dimensional(2D) sandwich-like mesoporous nitrogen-doped carbon/reduced graphene oxide nanocomposites(denoted as m NC/r GO) with well-defined large mesopores. The strategy involves the synergistic self-assembly of polystyrene-block-poly(ethylene oxide)(PS-b-PEO) spherical micelles, m-phenylenediamine(m PD) monomers and GO in solution and the subsequent carbonization at 900 ℃. The resultant m NC/r GO nanosheets have an average pore size of 19 nm, a high specific surface of 812 m~2·g~(-1) and a nitrogen content of 2.2 wt%. As an oxygen reduction reaction(ORR) catalyst, the unique structural features render the metal-free nanosheets excellent electrocatalytic performance. In a 0.1 mol·L~(-1) KOH alkaline medium, m NC/r GO exhibits a four-electron transfer pathway with a high half-wave-potential(E_(1/2)) of +0.77 V versus reversible hydrogen electrode(RHE) and a limiting current density(JL) of 5.2 mA·cm~(-2), which are well comparable with those of the commercial Pt/C catalysts.     

Simultaneous determination of CGP 22 848 and its major metabolite (free carboxylic acid) CGP 35 652 in plasma by HPLC

Summary A specific method for the quantitative determination of CGP 22 848 (a basic compound) and its major metabolite CGP 35 652 (a free carboxylic acid metabolite) in plasma using CGP 17 582 as internal standard is described. Separation of components is by reversed-phase chromatography using a mobile phase consisting of pH 3 phosphate buffer-acetonitrile (76:24, v/v) at a flow-rate of 1 ml/min in conjunction with a Radialpak C18 cartridge combined with a radial compression separation system or by using a mobile phase consisting of pH 3 phosphate buffer-acetonitrile (80:20, v/v) at a flow-rate of 0.8 ml/min in conjunction with a Novapak C18 column. Rapid extraction of CGP 22 848 and CGP 35 652 from plasma is achieved using reversed-phase C18 columns (Bond-Elut or Supelco). With 250 μl of plasma, concentrations down to 0.078 μM (25 ng/ml) of CGP 22 848 B and 0.326 μM (100 ng/ml) of CGP 35 652 A can be determined. A wavelength of 221 nm was used to monitor CGP 22 848, 280 nm for CGP 35 652 and 320 nm for the internal standard.     

Synthesis and Characterization of Novel Dimethylgallium Complexes

Recently, great attention has been paid to Group IIIA organometallic compounds owing to their wide range of uses in the areas of ceramic semi-conductor materials and diagnosis of diseases1. However, most of the relevant studies are limited to monoaminomethylated phenols as ligands2. In this paper, we report the synthesis of compounds (1a and 2a) as a new ligand and their dimethylgallium complexes (1b and 2b) (Scheme 1). General procedures for preparation of 1a, 2a and 1b, 2b were accorde…     

Amine-catalyzed polycyclotrimerization of arylene bipropiolate: A metal-free and regioselective route to hyperbranched polymer

This paper presents a new synthetic route to hyperbranched polymer. An arylene bipropiolate monomer,dimethylmethylenebis(1,4-phenylene) bipropiolate,was prepared by a one-step esterification reaction of bisphenol A with propiolic acid. Polycyclotrimrtization of the monomer was effected by reflux in dimethylformamide(DMF),producing a soluble hyperbranched poly(aroxycarbonylphenylene) in a good yield. The polymer was perfectly branched with a degree of branching of 100%.     

Electrochemical Metalloimmunoassay Based on Enlargement of Gold Nanoparticle Label Treated with Ag Enhancement System

A novel sensitive electrochemical immunoassay with colloidal gold as the antibody labeling tag and subse-quent signal amplification by silver enhancement is described. Colloidal gold was treated by a light-sensitive silver enhancement system which made silver deposit on the surface of colloidal gold(form Au/Ag core-shell structure), followed by the release of the metallic silver atoms anchored on the antibody by oxidative dissolu-tion of them in an acidic solution and the indirect determination of the dissolved Ag ions by anodic stripping voltamrnetry(ASV) at a carbon fiber microelectrode. The electrochemical signal is directly proportional to the amount of analyte(goat IgG) in the standard or a sample, The method was evaluated by means of a non-competitive heterogeneous immunoassay of immunoglobulin G(IgG) with a concentration as low as 0. 2 ng/mL. The high performance of the method is related to the sensitive ASV determination of silver( I ) at a car-bon fiber microelectrode and to the release of a large number of Ag^ ions from each silver shell anchored on the analyte (goat IgG).     

Liquid Chromatographic Assay of Peptides Activity with Inhibiting Angiotensin Converting Enzyme

A rapid, simple and interference-free method was developed to evaluate the inhibitory activity of hydro-lyzed peptides from egg white protein against the angiotensin-converting enzyme. The total reaction volume was 60 μL, saving the cost. The assay was based on a HPLC separation and quantification of the synthetic substrate hip-puryl-L-histidyl-L-leucine and its hydrolyzed product―hippuric acid; the separation was performed on a C 18 column eluted by a mobile phase of acetonitrile/water(0.5% TFA) at a volume ratio of 25:75. At a signal to noise ratio(S/N) of 10, the detective limit of the quantitation of hippuric acid was (0.4600±0.0097) μmol/L. The standard curve shows a linear response with a slope of 49488 and a correlation coefficient of 0.9995. The assay was adequate for the study of ACE inhibition by Captopril and peptides derived from food protein, and showed a very good correlation with the previous methods.     

Anti-corrosive Hybrid Electrolytes for Rechargeable Aqueous Zinc Batteries

Aqueous zinc(Zn)-metal cells with cost-effective components and high safety have long been a promising large-scale energy storage system,but Zn anodes are intrinsically unstable with common aqueous electrolytes,causing substantial underutilization of the theoretical capacity.In this work,we report a strictly neutral aqueous Zn electrolyte at a low cost by leveraging the dynamic hydrolysis equilibrium of a dual-salt Zn(Ac)2/NaAc(Ac:CH3COO?)formulation.With the pH regulation,the corrosion and hydrogen evolution encountered in Zn anodes can be suppressed significantly.This hybrid aqueous electrolyte not only enables dendrite-free Zn plating/stripping at a nearly 95%Coulombic efficiency[an increase of 24%compared to that of the single-salt 1 mol/L Zn(Ac)2 electrolyte],but also supports the reversible operation of Zn cells paired with either Na3V2(PO4)3 or iodine cathodes—the former delivers a high output voltage of 1.55 V with an energy level of 99.5 W·h/kg(based on the mass of the cathode),and the latter possesses a high specific capacity of 110.9 mA·h/g while yielding long-term cyclability(thousands of cycles).These findings open up a new avenue of modifying practical electrolytes having targeted properties to stabilize multivalent metal anodes.     

Hydrochlorination of acetylene using expanded multilayered vermiculite (EML-VMT)-supported catalysts

Catalyst supports have very important effects on catalyst performance.A novel expanded multilayered vermiculite(EML-VMT) is successfully used as the catalyst support for the acetylene hydrochlorination.By mixing carbon on the surface of EML-VMT[i.e.,EML-VMT-C),the HgCl_2/EML-VMT-C achieved a high acetylene conversion of 97.3%,a vinyl chloride selectivity of 100%and a turn over frequency(TOF) value of 8.83 × 10~(-3)s~(-1) at a temperature of 140 C,an acetylene gas hourly space velocity(GHSV) of 108 h~(-1)',and a feed volume ratio V(HC1)/V(C_2H_2) of 1.15.Moreover,the HgCl_2/EML-VMT-C shows good stability.The EML-VMT also shows potential in the preparation of other EML-VMT-supported catalysts.     

Development and Validation of a Reverse-phase High Performance Liquid Chromatography Method for Determination of Exenatide in Poly（lactic-co-glycolic acid） Microspheres

Exenatide(synthetic exendin-4), which has been approved by the Food and Drug Administration(FDA) for the adjunctive treatment of patients with type 2 diabetes, is an incretin mimetic agent. The development and validation of a RP-HPLC method for the quantification of the exenatide in poly(lactic-co-glycolic acid)(PLGA) microspheres is described. Separation was performed on a C4 column via a mobile phase consisting of ACN:KH2PO4(0.02 mol/L, pH=2.5) gradient elution from 30:70 to 45:55(volume ratio) in 30 min. Multi-diode array detection(DAD) appears to be most appropriate to evaluate the spectral purity of exenatide. The limits of detection and quantification of exenatide were 0.4 and 1.2 μg/mL, respectively. The calibration curve of exenatide was linear in a range of 0.025―0.2 mg/mL with a correlation coefficient of 0.9995. The results of validation study show that this method is specific, accurate(recovery95%), precise(RSD2.0%) and robust.     

Synthesis of a novel cyclodextrin dimer linked by a macrocyclic polyamine

The first example of cyclodextrin dimer appending a macrocyclic polyamine spacer on the primary faces was synthesized via two approaches: 1,a direct reaction of l,7-bis(2'-aminoethyl)-4,10-dimethyl-l,4,7,10-tetraazacyclododecane (1) with an excess of 6-deoxy-6-O-tosyl-β-cyclodextrin; 2,a condensation of 1 with two equivalents of 6-deoxy-6-formyl-β-cyclodextrin,which was followed by a reduction with NaBH4.