Hydrazine as a Nucleophile and Antioxidant for Fast Aminolysis of RAFT Polymers in Air

The bifunctional role of hydrazine as a potent nucleophile and antioxidant was investigated for the rapid aminolysis of RAFT polymers within minutes in air with effective suppression of the formation of disulfides. Using both dithioesters and trithiocarbonates as model compounds, we showed that hydrazine exhibited a significantly improved aminolysis rate when compared with a commonly used primary alkyl amine. On the basis of the exellent results with CTAs, we further studied the aminolysis of RAFT polymers prepared with either dithioesters or trithiocarbonates. In accord with the aminolysis results on CTAs, hydrazine aminolyzed RAFT polymers in an impressively short time and, more importantly, it significantly suppressed the formation of disulfides as comfirmed with GPC.

     

Electrochemical behavior of β2-agonists at graphite nanosheet modified electrodes

In this paper, the voltammetric characteristics of several β₂-agonists including salbutamol, ractopamine, bamethane, isoxsuprine, ritodrine, fenoterol, terbutaline, metaproterenol, clenbuterol, clenproperol, mabuterol, cimaterol, cimbuterol and brombuterol were comparatively evaluated using graphite nanosheet (GN) modified glassy carbon (GC) electrodes. All the compounds can be oxidized at GN modified electrodes with enhanced peak current and reduced peak potential compared with naked GC electrodes. The electrochemical behaviors of the compounds are different due to different substituent groups on the aromatic rings. For the first time, an ECE process was observed for salbutamol and its analogues. The capability of determining β₂-agonists individually or simultaneously from aqueous solution using differential pulse voltammetry and amperometry with the developed electrode was also investigated.     

Five New C19‐Diterpenoid Alkaloids from Aconitum hemsleyanum

Five new C₁₉‐diterpenoid alkaloids, named hemsleyaconitines A–E ( 1 – 5 , resp.), were isolated from Aconitum hemsleyanum Pritz. By UV, IR, MS, 1D‐ and 2D‐NMR analyses, their structures were elucidated as 18‐dehydroxygeniculatine D ( 1 ), 6‐hydroxy‐14‐O‐veratroylneoline ( 2 ), 14‐O‐acetyl‐8‐ethoxysachaconitine ( 3 ), 18‐veratroylkaracoline ( 4 ) and 8‐O‐ethylaustroconitine B ( 5 ).     

Zinc Coordination Complex for use in Uniform ZnS Microflowers Synthesis

Uniform snowball zinc sulfide (ZnS) microflowers with nanosheet covering were synthesized using the one step reaction of zinc coordination compounds with thiourea at 160 °C for 24 h. X‐ray single crystal diffraction, electron microscopy, energy‐dispersive X‐ray spectrometry, and X‐ray diffraction were used to characterize the products. The flower‐like ZnS crystals may have some application in catalyst or solar cell devices. This work is also expected to be applied in the fabrication of other transition metal sulfide crystals with special morphology.     

超声辅助电化学合成形貌可控的三维铂催化剂

在室温条件下, 采用超声辅助电化学方法合成了几种三维铂纳米电催化剂. 利用透射电子显微镜(TEM)、X射线粉末衍射(XRD)以及电化学测试对该三维铂纳米电催化剂进行了表征. 结果表明, 这些铂纳米电催化剂的形貌、结构可以通过添加不同的形貌控制剂来调控, 在水溶液、聚乙烯吡咯烷酮(PVP)溶液和十六烷基三甲基氯化铵(CTAC)溶液中分别得到了立方海绵状铂、分枝状铂和球形多孔状铂. 其中, 球形多孔状铂纳米电催化剂由于其多孔的结构, 因此具有更高的电化学活性面积, 对氧气还原和甲醇氧化反应具有更好的催化作用.     

One Pot Synthesis of Amphiphilic Hyperbranched Poly-(amino ester)and Its Dynamic Surface Activity

Amphiphilic hyperbranched poly(amino ester)s with hydrophilic multi‐ethoxylated triacrylate backbone and hydrophobic long alkyl side chain were firstly synthesized via one pot Michael addition polymerization. The poly‐(amino ester) could dissolve in cold water and self‐assemble into loose micelle. Under 50–1000 ms bubble, the dynamic surface tension (DST) of the poly(amino ester) aqueous solution (0.5 wt%) still maintained in the range of 32–28 mN/m. The aqueous solutions of poly(amino ester)s with different molecular weights showed the lower critical solution temperature (LCST) in the range of 8–50°C, which could also be tuned by its pH. Capped with hydrophobic groups on the terminal units and partially neutralized with acid, the poly(amino ester)s still kept their stable dynamic surfactant behaviors, indicating promising application.     

Polymerization of n-Octylallene with Rare Earth Catalyst Composed of Ln(P204)3/Al(i-Bu)3

Polymerization of n‐octylallene was successfully carried out using a conventional binary rare earth catalytic system composed of rare earth tris(2‐ethylhexylphosphonate) (Ln(P₂₀₄)₃) and tri‐isobutyl aluminum (Al(i‐Bu)₃) for the first time. The effects of catalyst, solvent, reaction time and temperature on the polymerization of n‐octylallene were studied. The resulting poly(n‐octylallene) has weight‐average molecular weight of 11000, molecular weight distribution of 1.4 and 96% yield under the moderate reaction conditions: [Al]/[Y] =50 (molar ratio), [n‐octylallene]/[Y] =100 (molar ratio), polymerized at 80°C for 20 h in bulk. The poly(n‐octylallene) obtained consisted of 1,2‐ and 2,3‐polymerized units, and was characterized by FT‐IR, ¹H NMR and GPC. Further investigation shows that the polymerization of n‐octylallene has some living polymerization characteristics, preparing the polymer with controlled molecular weight and narrower molecular weight distribution.     

Calorimetric study of the acidic character of V<Subscript>2</Subscript>O<Subscript>5</Subscript>–TiO<Subscript>2</Subscript>/SO<Subscript>4</Subscript><Superscript>2−</Superscript> catalysts used in methanol oxidation to dimethoxymethane

The surface acidic properties of sulfated vanadia–titania catalysts prepared by various methods were investigated by adsorption microcalorimetry, using ammonia as probe molecule. The acidic characteristics of the samples were shown to be strongly affected by the preparation method, calcination temperature, and sulfur content. The samples prepared by sol–gel and mechanical grinding exhibited higher acidity than co-precipitated samples. Moreover, increasing the calcination temperature of co-precipitated samples resulted in a decrease in surface area from 402 to 57 m² g⁻¹ and sulfur content from around 4 to 0.2 mass%, but up to a certain point generated a stronger acidity. The optimal calcination temperature appeared to be around 673 K.     

Density functional theory investigation on the electronic structure of furo[3,4-b]pyridine-type heterocyclics: from monomer to polymer

The geometries and electronic properties of six polymers based on furo[3,4-b]pyridine-type heterocyclics were studied using density functional theory (DFT) at the B3LYP/6-31G(d) level. Bond lengths, bond critical point (BCP) properties, nucleus-independent chemical shift (NICS), and Wiberg bond indexes (WBIs) are analyzed and correlated with conduction properties. The changes of bond length, BCP properties, NICS, and WBIs all show that the conjugational degree is increased with main chain extension. The changes of NICS also show that the conjugation is stronger in the central section than in the outer section. And the HOMO–LUMO energy gap (E _g) is decreased steadily upon chain elongation. The results suggest that the six polymers all have lower energy gaps (in the range of 0.39–0.58 eV), which indicate that these proposed polymers are good candidates for the conductive materials.     

Gene Cloning,Overexpression, and Characterization of the Nitrilase from <Emphasis Type="Italic">Rhodococcus rhodochrous</Emphasis> tg1-A6 in <Emphasis Type="Italic">E. coli</Emphasis>

A DNA fragment containing the entire coding sequence of nitrilase gene was amplified from Rhodococcus rhodochrous tg1-A6 with high nitrilase activity using PCR and sequenced. The open reading frame of the nitrilase gene contains 1,101 base pairs, which encodes a putative polypeptide of 366 amino acid residues. The nitrilase gene was cloned into an expression vector pET-28a and expressed in an Escherichia coli strain BL21(DE3). The enzymatic activity of nitrilase, which converts various nitriles to the corresponding carboxylic acids, was detected to reach 24.5 U/ml at 9 h in the recombinant bacteria.