Dually responsive multiblock copolymers via RAFT polymerization: Synthesis of temperature- and redox-responsive copolymers of PNIPAM and PDMAEMA

We report synthesis of temperature- and redox-responsive multiblock copolymers by reversible addition-fragmentation chain transfer (RAFT) polymerization. Well-defined α,ω-bis(dithioester)-functionalized poly(N-isopropylacrylamide) (PNIPAM) and poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) were prepared using 1,4-bis(thiobenzoylthiomethyl)benzene and 1,4-bis(2-(thiobenzoylthio)prop-2-yl)benzene as RAFT agents, respectively. Dually responsive multiblock copolymers were synthesized in a single aminolysis/oxidation step from the α,ω-bis(dithioester)-terminated PNIPAM and PDMAEMA. The copolymers and their stimulus-responsive behavior were characterized by size exclusion chromatography, NMR, light scattering and atomic force microscopy. Due to the presence of redox-sensitive disulfide bonds between the blocks, the copolymers were readily reduced to the starting polymer blocks. The presence of temperature-responsive PNIPAM blocks provided the copolymers with the ability to assemble into core-shell nanostructures with hydrophobic PNIPAM as a core and cationic PDMAEMA as stabilizing shell when above the phase transition temperatures of PNIPAM. The temperature-induced assembly of the copolymers also showed substantial pH sensitivity. The phase transition temperature increased with decreasing pH, while molecular weight of the assemblies decreased.     

Effect of sonochemistry: Li- and Mn-rich layered high specific capacity cathode materials for Li-ion batteries

Li- and Mn-rich layered Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ cathode material was synthesized using sonochemical method followed by annealing at 700, 800, and 900 °C for 10 h. The material was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and electrochemical techniques. Its performance as a cathode material for Li-ion batteries was examined. With the sample annealed at 900 °C, an initial specific capacity of 240 mAh g^?1 was obtained, which decreased to 215 mAh g^?1 after 80 cycles, thus retaining about 90 % of its initial capacity. In contrast, samples annealed at lower temperatures exhibited lower capacity retention upon cycling. Thus, the final annealing temperature was found to have a significant effect on the electrochemical stability of this material in terms of capacity, average voltage, and rate capability. The advantage of this synthesis, which includes a sonochemical stage, compared with a conventional co-precipitation synthesis, was also confirmed.     

金属含量对Ni-Pd/H-Y上正癸烷加氢异构化反应活性和产物选择性的影响

在Y分子筛上浸渍0.1 wt% Pd和0.1–0.5 wt% Ni,用X射线衍射表征了该催化剂的结晶度,用透射电镜测得平均金属粒径.催化剂中Pd和Ni的化学态用X射线光电子能谱测定,其酸性则用氨-程序升温脱附进行了表征,发现一些酸位被Ni2+离子交换.采用程序升温还原表征了HY分子筛负载的Pd, Ni和Pd-Ni催化剂的还原性能.正癸烷加氢异构化反应在200–450 oC和1 atm条件下进行.结果发现,当0.1 wt% Pd/HY中Ni添加量增至0.3 wt%时,正癸烷转化率和异构化选择性增加.单支链和双支链异构体选择性的增加表明该反应遵循质子化环丙烷中间体机理. Ni添加量超过阈值导致活性和异构化选择性急剧下降.综上可见,双金属催化剂更有利于选择性生成双支链异构体,其辛烷值更高.     

A study of host-guest complexation between amodiaquine and native cyclodextrin. Characterization in solid state and its in-vitro anticancer activity

Amodiaquine (AQ) has been used widely as an antimalarial drug. Amodiaquine is a mannich base 4-amino quinolone with a mode of action similar to that of chloroquine. The inclusion complex of AQ with β-Cyclodextrin (β-CD) in solution phase is studied from the ground and excited state with UV-Visible and fluorescence spectroscopy, respectively. A binding constant and stoichiometric ratio between AQ and β-CD are calculated by BH equation. The solid complexes are prepared by physical method (PM), kneading method (KM) and co-precipitation method (CP). The solid complex is characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and powder X-ray diffraction. The CP method gives the solid product with a better yield than that of physical mixture and KM products. The orientation and structure of the complex are proposed based on the analysis of Patch-Dock server. The anticancer activity also performed for pure AQ and their complex with β-CD. It is clearly shown that an improvement of anticancer activity of AQ while forming complex with β-CD. The solid inclusion complex behaves as the better anticancer ability than AQ alone.     

2H1NA/β-cyclodextrin inclusion complex: Preparation,characterization and chemosensory application for detecting Ag+

The inclusion complex of 2-hydroxy-1-naphthoic acid (2H1NA) with β-cyclodextrin (β-CD) has been investigated using UV-visible and fluorescence spectral techniques in liquid states, FTIR, NMR, XRD and SEM techniques in solid state, molecular docking techniques in virtual states. The binding constants of for the formation of 1:1 2H1NA:β-CD inclusion complex is estimated by UV-visible and fluorescence spectral techniques. The chemosensory power of 2H1NA:β-CD complex was investigated thoroughly for various metal cations and we found the emission of complex showed a drastic increase in the intensity for Ag⁺. Competition experiments of 2H1NA:β-CD complex with Ag⁺ in presence of other metal ions (Na⁺, K⁺, Hg⁺, Al²⁺, Ca²⁺, Ba²⁺, Cd²⁺, Co²⁺, Fe²⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, Sn²⁺, Ti²⁺, Zn²⁺, Cr³⁺, Fe³⁺) showed that no significant variation was found in the fluoresce intensity of 2H1NA:β-CD complex upon adding all other cations. The linearity range, LOD and LOQ are determined from the selectivity and sensitivity studies for Ag⁺. Our result suggests that the 2H1NA:β-CD inclusion complex would be promising material for developing solid state sensory device for sensing Ag⁺.     

Novel simulated moving-bed adsorber for the fractionation of gas mixtures

The separation of propylene-propane mixture is an energy intensive operation commercially practiced using cryogenic distillation. The separation by pressure swing adsorption has been studied as an alternative. A fixed-bed pressure swing adsorption yields the heavy component as a pure product. The product recovery and the productivity are not high. In a moving-bed process, because of the counter-current solid-gas contact, the separation achieved is similar to that of the fractionation by distillation. Although the moving-bed operation offers the upper limit for the performance of a cyclic adsorptive process, due to mechanical complexities in the handling of solids the 'simulated' moving-bed is preferred. By moving the inlet and outlet ports of streams located along the length of the bed, a moving-bed process can be realized in a fixed bed. We describe here a 'moving-port' system which permits injection or withdrawal of the fluid along the axial direction in a fixed bed. A fixed bed embedded with the moving-port systems emulates a simulated moving-bed adsorber. The proposed adsorber can fractionate a binary gas mixture into two product streams with high purities. It is similar to the Sorbex process of UOP but does not have the eluent as an additional separating agent. A parametric study indicates that high purity products and a higher productivity by an order of magnitude can be achieved with simulated moving-beds compared to the fixed beds.     

Sonochemistry and its dosimetry

The effects of ultrasound originate primarily in acoustic cavitation. The cavitation bubbles collapse violently enough to lead to interesting chemical effects, known as sonochemistry. There is a great need to relate the efficiency of sonochemical reaction to the energy of ultrasonic irradiation used to produce them. In this paper, three OH radical dosimeters, Fricke dosimeter, terephthalate dosimeter, and iodide dosimeter, are compared from the analytical point of view. The dosimeters based on photometry, i.e., Fricke and iodide, produced reliable and reproducible results, but the sensitivity is not enough for special applications, such as chemical monitoring of single bubble cavitation. The dosimeter based on fluorometry, terephthalate dosimeter, offered high sensitivity, 1.2×10¹¹ molecules ml⁻¹. The effects of some experimental parameters in sonochemistry, i.e., solution temperature and the dissolved gas species, were evaluated with the dosimeters.     

Influence of the Oxide Content in the Catalytic Power of Raney Nickel in Hydrogen Generation

The influence of oxides in the hydrogen evolution on Raney nickel electrocatalysts was characterized by electrochemical impedance measurements. In addition, these materials show competitive overpotentials for hydrogen evolution with a modified Watts bath as a binder for the Raney nickel. The optimum result was ?190?mV of overpotential at 100?mA?cm^?2. Oxygen in the Raney Ni catalyst affects its electroactivity toward hydrogen evolution. The source of oxygen is related to the presence of chloride ions in the modified Watts bath. A Watts bath binds Raney Ni particles to the surface of the catalysts and chloride regulates the oxygen content in the nickel binder during electrodeposition. High oxygen content increases the hydrogen evolution overpotential of the electrode. The electroactivity of the synthesized porous coatings was evaluated by polarization curves and impedance plots. In addition, surface characterization by X-ray diffraction, field emission–scanning electron microscopy equipped with energy-dispersive analysis, and X-ray photoelectron spectroscopy is reported.     

Graphene sheet-encased silica/sulfur composite cathode for improved cyclability of lithium-sulfur batteries

Journal of Solid State Electrochemistry - The “shuttle effect” of polysulfides is a serious issue, resulting in a decrease in the life-cycle of lithium-sulfur (Li-S) batteries. To...