Prediction of branch on branch and topological characteristics of low‐density polyethylene polymerization by a novel stochastic approach

A novel approach using Monte Carlo method applied to simulation of low‐density polyethylene (LDPE) polymerization in tubular reactor showing topological characteristics, and the comprehensive kinetic mechanism has been taken into consideration. The results show the precise details of the structure of a chain in the three levels of the backbone, the main branches, and branches on branch. The chain types include dead polymer, dead polymer with unsaturated end, and live polymer with primary radical, secondary radical, and tertiary radical. In this work, the branches on branch were identified in terms of number, length, and position of the branch. Sixty percent of branches on branch are 1 to 5 carbons long, and the longest branch on branch is about 50 carbons. Thus, this study provides a tool for more accurately mapping the polymer chains architecture, superior to determine the number, and position of long‐ and short‐chain branches in past researches. Finally, this approach will advance the prediction of microstructure‐related properties of polymer one step further.     

Cyclic peptide nanocapsule as ion carrier for halides: a theoretical survey

In this work, the encapsulations of halide ions including F^?, Cl^?, and Br^? by cyclic peptide nanocapsule as ion carrier (F^?, Cl^?, and Br^? @(Ala4...Ala4)) were investigated using the dispersion corrected density functional theory (DFT) employing CAM-B3LYP functional and the 6–311?+?G (d, p) basis set in the gas phase. The electronic binding energy (E_bind), binding enthalpy (H_bind), and binding Gibbs free energy (G_bind) for each anion were calculated and showed that the stability order of the complexes based on their calculated E_bind is F^??>?Cl^??>?Br^? @(Ala4...Ala4). The calculated value of G_bind for F^? @(Ala4...Ala4) was ??29.77 kcal/mol showing the formation of this complex is thermodynamically favorable while the formation of Br^? @(Ala4...Ala4) is 14.35 kcal/mol which shows that the encapsulation of Br^? is not possible. The calculated value of G_bind for Cl^? @(Ala4...Ala4) was ??0.57 kcal/mol which shows that Cl^? ion can be reversibly stored inside the nanocapsule. The NBO analysis was also performed to investigate the charge transfer between two cyclic peptides in the complexes and also between the anion and the nanocapsule. The NBO analysis showed that the strongest hydrogen bonds between two cyclic peptides are in the complex.     

A green and efficient oxidation of benzylic alcohols using H2O2 catalyzed by montmorillonite K-10 supported CoCl2

Primary and secondary benzylic alcohols were oxidized to the corresponding carbonyl compounds in good to high yields by environmentally friendly and green oxidant, H2O2 catalyzed by montmorillonite K-10 supported cobalt（Ⅱ） chloride.     

Asymmetric syntheses with BINOL-based imidoyl azide

Thermal decomposition of 2,4,6-trimethylphenyl and (+)-2′-methoxy-1,1′-binaphthalen-2-yl (4-methylphenylsulfonyl)azidimidocarbonates in the presence of norbornene, methyl acrylate, and camphene was studied. (+)-2′-Methoxy-1,1′-binaphthalen-2-yl (4-methylphenylsulfonyl)azidimidocarbonate reacted with norbornene to give (+)-exo-2′-methoxy-1,1′-binaphthalen-2-yl N-(4-methylphenylsulfonyl)-3-azatricyclo-[3.2.1.0^2,4]octane-3-carboximidoate, while in the reaction with methyl acrylate a mixture of stereoisomeric methyl 1-[(2′-methoxy-1,1′-binaphthalen-2-yloxy)(4-methylphenylsulfonylimino)methyl]aziridine-2-carboxylates was obtained. The reaction of 2,4,6-trimethylphenyl (4-methylphenylsulfonyl)azidimidocarbonate with (−)-camphene involved insertion of intermediate nitrene into the exocyclic double bond with formation of 2,4,6-trimethylphenyl N-(3,3-dimethylbicyclo[2.2.1]heptan-2-ylidenemethyl)-N′-(4-methylphenylsulfonyl)-imidocarbamate as a 3: 1 mixture of E,E and E,Z diastereoisomers in good yield. Published in Russian in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 10, pp. 1495–1500. The text was submitted by the authors in English.     

Structure and photoluminescence properties of TiO<Subscript>2</Subscript> nanoparticles synthesized from a novel luminescent nano-titanium complex

A new titanium complex [Ti(Me–Q)₂(Cl)₂] (1) is prepared by reacting titanium tetrachloride with 2-methyl-8-hydroxyquinoline in a fast and facile process. The complex is fully characterized based on its ¹H and ¹³C NMR, IR, and UV spectra and elemental analysis. The prepared nanostructured compound is synthesized by the sonochemical method. This new nanostructure is characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), IR spectroscopy, and elemental analysis. Thermal stability of single crystalline and nanosize samples of the prepared compound is studied by thermal gravimetric (TG) and differential thermal analysis (DTA). The prepared complexes both bulk and nanosized are utilized as a precursor for the preparation of TiO₂ nanoparticles by direct thermal decomposition at 600°C in air. The morphology and size of TiO₂ nanoparticles are determined by SEM, powder XRD, and IR spectroscopy and the results show that the TiO₂ nanoparticle size depends on the initial particle size of 1. Photoluminescence (PL) properties of the nanostructured and crystalline bulk prepared complex and their TiO₂ nanoparticle cores are investigated.     

Poly(<Emphasis Type="Italic">n</Emphasis>-octyl methacrylate) viscosity index improver: Kinetic study via on-line <Superscript>1</Superscript>H-NMR technique

The free radical solution polymerization of n-octyl methacrylate has been studied in benzene-d ₆ in the presence of 2,2′-azobisisobutyronitrile as thermal initiator. An on-line nuclear magnetic resonance spectroscopy was applied to record the reaction data and to determine the monomer conversion at different times during the polymerization reaction. Effect of monomer and initiator concentration as well as reaction temperature on polymerization rate was studied. The order of the reaction with respect to initiator (0.45) was consistent with the classical kinetic rate equation, while the order of reaction with respect to monomer (1.87) was much greater than unity. An overall activation energy (E _a = 53.8 kJ/mol) was obtained over the temperature range 328?338 K. Also, the efficiency of the synthesized poly(n-octyl methacrylate) for improving the viscosity index of the lube oil was investigated.     

A comparative MP2 study between water- and acid-assisted proton transfer: allophanic acid as a case of study

Electronic structures of allophanic acid were studied using MP2/6-311++G(d,p) level of theory. Five most stable tautomers were selected and stability of them was studied in detail. Obtained data showed that tautomer 1 having hydrogen atom in the central nitrogen N3 and also in a trans conformation of carbonyl and amino functional groups becomes the most stable one. Then, interconversion of these tautomers to each other was investigated step by step through internal rotation and proton transfer routes. Results indicated that movement of protons determines rate-determining step of all paths A–E. Effects of different solvents were carefully surveyed for each tautomer, and among investigated solvents, water made slight stabilization. Activation barrier for proton exchange assisted by one water molecule and one formic acid molecule was also studied, separately. Both molecules had a great influence on lowering barrier especially for proton transfer routes. Comparative MP2 study showed that the barrier will be lowered much more when acid-assisted proton exchange takes place.     

Simulation of thin disk laser pumping process for temperature dependent Yb:YAG property

A novel model of Cw diode pumped Yb:YAG thin disk laser has been presented to simulate absorption pump power distribution by Monte-Carlo ray tracing. Comparing obtained results with the common distribution function indicate the offered model is quite trustful. So these findings help to evaluate temperature distribution due to the 3D finite element analyses (FEA) based on heat conduction equation. To improve our simulation the temperature dependent of crystal property such as the absorption coefficient, thermal conductivity, stimulated emission cross section and Boltzman population factors are considered by a numerical iterative approach.     

The effect of oxidation temperature on the nano crystalline structure of ZrO2 films deposited on silicon and glass substrates

Zirconium oxide (ZrO₂) films have been prepared by using ex situ thermal oxidation of sputtered Zr films on glass and silicon substrates. XRD patterns show that a highly monoclinic (111) preferential orientation of ZrO₂ phase can be formed with increasing the oxidation temperature. According to XRD patterns in all thermal oxidized samples silicon oxide phase is present as interfacial layer at the Zr (ZrO₂) / Si (glass) interface. In the case of silicon substrates, crystallite sizes obtained from ZrO₂ peak with higher intensity reveal an increase with substrate temperature. AFM measurement shows on the whole a decrease of average surface roughness with oxidation temperature. The electrical property of the prepared films is investigated by means of four point probe measurement. An abrupt increase of sheet resistivity occurs when the crystallinity of ZrO₂ phase enhances at higher temperature. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)