Synthesis, crystal structure and intermolecular magnetic interactions of a new N-TEMPO-3,5-di-tert-butylsalicylaldimine radical

A new N-TEMPO-3,5-di-tert-butylsalicylaldimine radical (1) has been synthesized and characterized by single crystal X-ray diffraction, elemental analysis, IR, UV–vis, and EPR spectroscopy and temperature dependent magnetic susceptibility. X-ray diffraction revealed that H-atoms of γ-CH in TEMPO and CH₃ in salicylaldimine moieties, are located in close contact with the neighboring N–O radical group in crystal 1. The temperature dependence of the magnetic susceptibility (χ_m) of 1 has been fitted by the Curie–Weiss law with θ = −0.3 K within 10–300 K, suggesting the presence of a weak intermolecular antiferromagnetic interaction between radical centers at T < 10 K. It has been demonstrated that radical 1 possesses crystal structure involving co-existence of antiferromagnetic and ferromagnetic interactions through C–H?O–N contacts of γ-CH and ^tBu groups hydrogen atoms, in which the former path dominates over the latter.     

Operator splitting for numerical solution of the modified Burgers' equation using finite element method

The aim of this study is to obtain numerical behavior of a one‐dimensional modified Burgers' equation using cubic B‐spline collocation finite element method after splitting the equation with Strang splitting technique. Moreover, the Ext4 and Ext6 methods based on Strang splitting and derived from extrapolation have also been applied to the equation. To observe how good and effective this technique is, we have used the well‐known the error norms L₂ and L_∞ in the literature and compared them with previous studies. In addition, the von Neumann (Fourier series) method has been applied after the nonlinear term has been linearized to investigate the stability of the method.     

Rayleigh Scattering of 59.5 keV γ-Rays by Mo and Sn

The differential cross sections for coherent scattering of 59.5 keV γ-rays by Mo and Sn were measured using a high-purity germanium detector. The results were compared with predictions of form factor theories and S-matrix calculations.     

Thermally curable polyvinylchloride via click chemistry

Novel side‐chain benzoxazine functional polyvinylchloride (PVC‐Benzoxazine) was synthesized by using “Click Chemistry” strategy. First, approximately 10% of chloro groups of PVC were converted to azido groups by using NaN₃ in N,N‐dimethylformamide. Propargyl benzoxazine was prepared independently by a ring closure reaction between p‐propargyloxy aniline, paraformaldehyde, and phenol. Finally, azidofunctionalized PVC was coupled to propargyl benzoxazine with high efficiency by click chemistry. The spectral and thermal analysis confirmed the presence of benzoxazine functionality in the resulting polymer. It is shown that PVC containing benzoxazine undergoes thermally activated curing in the absence of any catalyst forming PVC thermoset with high thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3512–3518, 2008     

New polyphenylene‐g‐polystyrene and polyphenylene‐g‐polystyrene/poly(ε‐caprolactone) copolymers by combined controlled polymerization and cross‐coupling processes

1,4‐Dibromo‐2‐(bromomethyl)benzene and 1,3‐dibromo‐5‐(bromomethyl)benzene were used as initiators in the atom transfer radical polymerization of styrene in conjunction with CuBr/2,2′‐bipyridine as a catalyst. The resulting polystyrene (PSt)‐based macromonomers, possessing at one end a 2,5‐dibromophenylene or 3,5‐dibromophenylene moiety, were used in combination with 2,5‐dihexylbenzene‐1,4‐diboronic acid for Suzuki coupling in the presence of Pd(PPh₃)₄ as a catalyst or with the system NiCl₂/2,2′‐bipyridine/triphenylphosphine/Zn for Yamamoto polymerization. Polyphenylenes (PPs) with PSt chains as substitution groups were obtained. The same macromonomers were used in Yamamoto copolycondensation reactions, in combination with a poly(ε‐caprolactone) (PCL) macromonomer, and this resulted in PPs with PSt/PCL side chains. The obtained PPs had good solubility properties in common organic solvents at room temperature similar to those of the starting macromonomers. The new polymers were characterized with ¹H (¹³C) NMR, IR, and gel permeation chromatography. The optical properties of the polymers were monitored with UV and fluorescence spectroscopy. The thermal behaviors of the macromonomers and final PPs were investigated with differential scanning calorimetry and compared. The morphology of PPs containing PSt and PCL blocks was characterized with atomic force microscopy, and a microphase‐separated layered morphology was observed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 879–896, 2005     

Mechanistic and kinetic studies on the photoinitiated polymerization of tetrahydrofuran

Polymerization of tetrahydrofuran (THF) (bulk) promoted by a free radical source, 2,2-dimethoxy-2-phenyl acetophenone (DMPA), in the presence of 4,4′-di-(methylphenyl)iodonium hexafluorophosphate was studied in detail. Rate dependence of the polymerizing system on both DMPA and the iodonium salt was studied dilatometrically. Rate saturation for the iodonium salt was attributed to the formation of iodobenzene, which may react with propagating cations to form an iodonium salt. DMPA was shown to be an efficient transfer agent in the cationic polymerization of THF. A transfer constant for DMPA was estimated to be 2.8 and, whilst the precise details of the overall mechanism cannot be deduced from the present results, it may result in functionalized polytetrahydrofuran chains having photochemically active end groups.     

Ultrasound-induced aqueous removal of nitric oxide from flue gases: effects of sulfur dioxide, chloride, and chemical oxidant

The effects of sulfur dioxide (SO(2)), sodium chloride (NaCl), and peroxymonosulfate or oxone (2KHSO(5).KHSO(4).K(2)SO(4) with active ingredient, HSO(5)(-)) on the sonochemical removal of nitric oxide (NO) have been studied in a bubble column reactor. The initial concentration of NO studied ranged from about 500 to 1040 ppm. NaCl in the concentration range of 0.01-0.5 M was used as the electrolyte to study the effect of ionic strength. At the low NaCl concentration (0.01 M), the percent fractional removal of NO with initial concentration of 1040 ppm was enhanced significantly, while as the NaCl concentration increased, the positive effects were less pronounced. The presence of approximately 2520 ppm SO(2) in combination with 0.01 M NaCl further enhanced NO removal. However, with a NO initial concentration of 490 ppm, the addition of NaCl was detrimental to NO removal at all NaCl concentration levels. The combinative effect of sonication and chemical oxidation using 0.005-0.05 M oxone was also studied. While the lower concentrations of HSO(5)(-) enhanced NO removal efficiency, higher concentrations were detrimental depending on the initial concentration of NO. It was also demonstrated that in the presence of ultrasound, the smallest concentration of oxone was needed to obtain optimal fractional conversion of NO.     

Cu1.5[Cr(CN)6]⋅6.5H2O nanoparticles: synthesis, characterization, and magnetic properties

We have synthesized nanoparticles of Cu_1.5[Cr(CN)₆]⋅6.5H₂O of varying size by using poly(vinylpyrrolidone) (PVP) as a protecting polymer. The particle size variation has been achieved by varying the amount of the PVP surfactant with the reactants. The prepared nanoparticles have been investigated by using X-ray diffraction, transmission electron microscopy, and direct-current magnetization techniques. The nanoparticles crystallize in a face centred cubic structure (space group: Fm3m). The approximate particle sizes for the three samples are 18, 9, and 5 nm, respectively. Non-PVP nanoparticles (18 nm) show a magnetic ordering temperature of 65 K. A decrease in the magnetic ordering temperature was observed with decreasing particle size. These nanoparticles are magnetically very soft, showing negligibly small values of the coercivity and remanent magnetization. The maximum magnetization and spontaneous magnetization values at 5 K are found to decrease with decreasing particle size. The observed magnetization behaviour of the nanoparticles has been attributed to the increasing surface spin disorder with decreasing particle size.     

Application of the complex point source method to the Schrödinger equation

The paraxial wave equation is a reduced form of the Helmholtz equation. Its solutions can be directly obtained from the solutions of the Helmholtz equation by using the method of complex point source. We applied the same logic to quantum mechanics, because the Schrödinger equation is parabolic in nature as the paraxial wave equation. We defined a differential equation, which is analogous to the Helmholtz equation for quantum mechanics and derived the solutions of the Schrödinger equation by taking into account the solutions of this equation with the method of complex point source. The method is applied to the problem of diffraction of matter waves by a shutter.     

Development of New Atom Transfer Radical Polymerization System by Iron (III)‐Metal Salts Without Using any External Initiator and Reducing Agent

Atom transfer radical polymerization (ATRP) catalyzed by high oxidation state metal salts of FeX₃ is developed for the first time in the absence of both external initiator and reducing agent. Methyl methacrylate (MMA) and styrene are polymerized successfully using FeX₃/Phosphorous ligands with well‐controlled molecular weight distributions (=1.5). The molecular weight of the polymers increases with monomer consumption with the progress of time and the polymerization behaviors show a decent ATRP trend. Activators and initiators are suggested to generate in situ by the addition reaction of MMA and one equivalent of FeX₃. The PMMA synthesized from without‐initiator system is characterized by ¹H, ¹³C and DEPT (distortionless enhancement by polarization transfer nuclear magnetic resonance) nuclear magnetic resonance spectroscopy. Chain extension and copolymerization experiments prove the livingness of the obtained polymer.