Kinetic Study of Radical Polymerization VI. Copolymer Composition and Kinetic Parameters for Coplymerization of Styrene‐Itaconic Acid by On‐Line 1H‐NMR

Free radical solution copolymerization of styrene (St) and itaconic acid (IA) in dimethylsulfoxide‐d₆ (DMSO‐d₆) as the solvent and the use of 2,2′‐azobisisobutyronitrile (AIBN) as the initiator at 78°C was investigated by an on‐line ¹H‐NMR spectroscopy technique. Individual monomer conversion vs. reaction time, which was calculated from the ¹H‐NMR spectra data, was used to study the drift in monomer mixture composition vs. conversion. It was found that in general, both monomers were incorporated almost equally into the copolymer. However, when the mole fraction of IA was low, the tendency of IA toward incorporation into the copolymer chain was somewhat higher than St and by increasing the mole fraction of IA in the reaction mixture, the inverse tendency was observed. Overall monomer conversion as a function of time was calculated from individual monomer conversion data and used for the estimation of k_p /k_t ^0.5 for various monomer mixture compositions. This ratio was decreased with increasing the amount of IA in the initial feed, indicating a decrease in the rate of copolymerization. Changes in the copolymer composition vs. overall monomer conversion were investigated experimentally from the NMR spectra. This was in good agreement with the changes in monomer mixture composition vs. reaction progress. Plotting the copolymer composition vs. initial monomer feed showed tendency of the system toward alternating copolymerization.     

Modeling and numerical simulation of electrical and optical characteristics of a quantum dot light-emitting diode based on the hopping mobility model: Influence of quantum dot concentration

We present a comprehensive numerical framework for the electrical and optical modeling and simulation of hybrid quantum dot light-emitting diodes (QD-LEDs). We propose a model known as hopping mobility to calculate the carrier mobility in the emissive organic layer doped with quantum dots (QDs). To evaluate the ability of this model to describe the electrical characteristics of QD-LEDs, the measured data of a fabricated QD-LED with different concentrations of QDs in the emissive layer were taken, and the corresponding calculations were performed based on the proposed model. The simulation results indicate that the hopping mobility model can describe the concentration dependence of the electrical behavior of the device. Then, based on the continuity equation for singlet and triplet excitons, the exciton density profiles of the devices with different QD concentrations were extracted. Subsequently, the corresponding luminance characteristics of the devices were calculated, where the results are in good agreement with the experimental data.     

Creation of cluster state of four ions in ion-trap system by individual addressing

The cluster state is a special, highly entangled quantum state that forms the universal resource, on which measurement-based quantum computation can be performed. In this study, a new scheme is presented for creating four-ions cluster state in ion-trap system. This scheme is based on resonant sideband excitation in which the population is transferred to target states by precise control of pulse area. Meanwhile, the scheme is consist of combination of elementary stages belonging to a universal set whereby cluster state has been created in five interaction stages by individually addressed ions with red- or blue-sideband resonance laser pulses. The paper studies the population transfer of the system by numerical solutions of the master equation, considering the effect of decoherence channels due to dissipation in the phonon modes. The presented scheme does not require control of the turn-off ratio and time delay among pulses.     

Dirac particle in generalized Pöschl–Teller field including a Coulomb‐like tensor coupling: super‐symmetric solution

In the presence of pseudo‐spin (p‐spin) and spin symmetries, we use the super‐symmetric formalism to solve the Dirac equation with the generalized Pöschl–Teller potential including the Coulomb‐like tensor interaction with any arbitrary spin‐orbit quantum number κ.. Using the Greene–Aldrich usual approximation scheme to deal with pseudo‐centrifugal or centrifugal rotational kinetic energy l (l + 1) ∕ r² or , we obtain the Pseudo‐spin and spin‐symmetric energy eigenvalue equation and the normalized upper and lower components of the radial wave functions in closed form. The presence of the tensor coupling interaction removes the degeneracy in the p‐spin and spin doublets. Copyright © 2013 John Wiley & Sons, Ltd.     

Helium ion distributions in a 4 kJ plasma focus device by 1 mm-thick large-size polycarbonate detectors

Helium ion beam profile, angular and iso-ion beam distributions in 4 kJ Amirkabir plasma focus (APF) device were effectively observed by the unaided eyes and studied in single 1 mm-thick large-diameter (20 cm) polycarbonate track detectors (PCTD). The PCTDs were processed by 50 Hz–HV electrochemical etching using a large-size ECE chamber. The results show that helium ions produced in the APF device have a ring-shaped angular distribution peaked at an angle of ∼±60°$\sim \pm 60\mathrm{°}$ with respect to the top of the anode. Some information on the helium ion energy and distributions is also provided. The method is highly effective for ion beam studies.     

Modules satisfying the weak Nakayama property

Let R$R$ be a commutative ring with identity. We will say that an R$R$-module M$M$ satisfies the weak Nakayama property, if IM=M$IM=M$, where I$I$ is an ideal of R$R$, implies that for any x∈M$x\in M$ there exists a∈I$a\in I$ such that (a−1)x=0$(a-1)x=0$. In this paper, we will study modules satisfying the weak Nakayama property. It is proved that if R$R$ is a local ring, then R$R$ is a Max ring if and only if J(R)$J\left(R\right)$, the Jacobson radical of R$R$, is T$T$-nilpotent if and only if every R$R$-module satisfies the weak Nakayama property.     

p‐toluenesulfonic acid‐catalyzed synthesis of polysubstituted quinolines via Friedländer reaction under ball‐milling conditions at room temperature and theoretical study on the mechanism using a density functional theory method

The synthesis of polysubstituted quinolines was accomplished through Friedländer annulation between 2‐aminoaryl ketones and different active methylene compounds at room temperature using ball‐milling technique in the presence of p‐toluenesulfonic acid. The mechanism of the reaction investigated by density functional theory‐based modeling is also reported. This study aims at giving insight into the mechanism of the Friedländer reaction in the presence of acid catalysts. Copyright © 2014 John Wiley & Sons, Ltd.     

Dual thermo- and pH-sensitive poly(2-hydroxyethyl methacrylate-co-acrylic acid)-grafted graphene oxide

A two-step modification was used to attach atom transfer radical polymerization (ATRP) initiator onto graphene oxide surface. ATRP polymerization of 2-hydroxyethyl methacrylate (HEMA) was performed via “grafting from” approach. Due to uncontrolled ATRP of acrylic acid (AA), the Br-terminated P(HEMA) chains were converted to reversible addition–fragmentation chain transfer agent and polymerization of AA was done. The structure of modified nanosheets was characterized using X-ray diffraction analysis, Raman spectroscopy, proton nuclear magnetic resonance, scanning electron microscopy, and etc. These nanosheets showed dual pH- and thermo-sensitive properties as measured by UV–visible spectroscopy in different pH (2–13) and temperature (15–55 °C) values. Generally, UV absorbance of P(HEMA-co-AA)-grafted nanosheets was higher than P(HEMA)-grafted nanosheets. Also, it seems that the poly(acrylic acid) block induces more pH sensitivity behavior than P(HEMA) block. Lower critical solution temperature of polymer-grafted nanosheets were shifted to higher temperature when chain extension was performed.