Thermodynamic features of perfectly crystalline poly(3‐hexylthiophene) based on Flory's relation

Poly(3‐hexylthiophene) (P3HT) as a conjugated polymer has many electrical and photovoltaic applications. However, reliable values for the equilibrium melting temperature ( ${T°}_m$) and for the enthalpy of fusion of a perfect P3HT crystal ( ${\Delta H°}_m$) are still in doubt. In the published works, ${\Delta H°}_m$ ranges from 33 to 99 J/g. Here, the melting point of P3HT in P3HT‐diluent mixtures is measured with changing the diluent concentration. By satisfying the requirements of Flory relation, “working with the same polymer crystals” and “working in the equilibrium state,” usually neglected in the literature, a reliable value of ${\Delta H°}_m$ = 83 ± 2 J/g is obtained. The reported values for ${T°}_m$ of P3HT are also in a wide range, 260?300 °C. In this work, accurate applying of the Hoffman‐Weeks relation, against the effects of lamellar thickening, yields ${T°}_m$ = 272 ± 2 °C rather than 300 ± 2°C reported in the literature. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 431–437     

Preparation of novel palladium nanoparticles supported on magnetic iron oxide and their catalytic application in the synthesis of 2‐imino‐3‐phenyl‐2,3‐dihydrobenzo[d]oxazol‐5‐ols

Novel Pd nanoparticles were prepared in five successive stages: 1) preparation of the Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs), 2) coating of Fe₃O₄ MNPs with SiO₂ (Fe₃O₄@SiO₂), 3) functionalization of Fe₃O₄@SiO₂ with 3‐chloropropyltrimethoxy‐ silane (CPTMS) ligand (Fe₃O₄@SiO₂@CPTMS), 4) further functionalization with 3,5‐diamino‐1,2,4‐triazole (DAT) ligand (Fe₃O₄@SiO₂@CPTMS @DAT), and 5) the complexation of Fe₃O₄@SiO₂@CPTMS@DAT with PdCl₂ (Fe₃O₄@SiO₂@CPTMS@ DAT@Pd). Then, the obtained Pd nano‐catalyst characterized by different methods such as the elemental analysis (CHN), FT‐IR, XRD, EDX, SEM, TEM, TG‐DTA and VSM. Finally, the Pd catalyst was applied for the synthesis of various 2‐imino‐3‐phenyl‐2,3‐dihydrobenzo[d]oxazol‐5‐ols.     

Synthesis and characterization of novel silica coated magnetic nanoparticles with tags of β-cyclodextrin: application as an eco-friendly and chiral micro-vessel catalyst in the enantioselective reduction of ketones

Research on Chemical Intermediates - In this work, we report the synthesis of a novel, green and recoverable organic–inorganic magnetic nanocomposite by grafting β-cyclodextrin on the...     

On rigid covers associated to the three-cuspidal quartic

We determine the fundamental group of the complement of the three-cuspidal quartic minus the tangent lines through the cusps. The existence of a rigid covering of this complement whose monodromy group is isomorphic to the simple group PSL₂(\mathbbF₇)\mathrm{PSL}_{2}(\mathbb{F}_{7}) is proved.     

Elemental content of aerosol particles in an underground tram station

Particulate matter is an important air pollutant, especially in closed environments like a tunnel. The aim of this study was to determine the mass, black carbon, and elemental concentrations of particulate matter of two size fractions at an underground tram station in Hammarkullen, Gothenburg, Sweden. Samples were collected during June 2007 using a dichotomous virtual impactor separating the sampled aerosol particles into coarse (PM_(2.5–10)) and fine (PM_2.5) fractions. To minimize the possible influence of waiting passengers, the platform for trams going towards the suburb Angered was chosen. The elemental analysis of the samples, collected on Teflon filters, was carried out using energy dispersive x‐ray fluorescence (EDXRF) spectrometry, resulting in concentrations of 14 elements in most of the samples. Principal component analysis (PCA) was applied to identify possible sources for the elements in the particles. Owing to the tunnel environment, the elemental difference between the fine and coarse particle fractions was not as large as that in similar particles collected under normal outdoor ambient conditions. Likewise, the influence of the local weather situation was not significant. Particle content from the tram traffic was identified by PCA, with Fe being the major element in both coarse and fine particles. The particle mass concentration was higher in the tunnel compared to the ambient concentration at the monitoring station Femman in downtown Gothenburg. In some days, the mass concentration exceeded the Swedish daily ambient air quality standard of 50 µg m^?3, but it was lower than the limits in the environmental work act, 5 mg m^?3. Copyright © 2009 John Wiley & Sons, Ltd.     

Lie‐group method for solving the problem of fission product behavior in nuclear fuel

Calculation of the gas atom concentration is an important feature of all physical models of fission gas release. We apply Lie‐group method for determining symmetry reductions to the diffusion equation describing the fission gas release from nuclear fuel. The resulting nonlinear ordinary differential equation is solved numerically using nonlinear finite difference method. Effects of the dimensionless group constant, the time, and the grain radius on the concentration diffusion function have been studied, and the results are plotted. It is found that the concentration of gas atoms increases as the dimensionless group constant, the power index, and the time increase, and it decreases with increase of the grain radius. Copyright © 2013 John Wiley & Sons, Ltd.     

Does Fluorine Participate in Halogen Bonding?

When R is sufficiently electron withdrawing, the fluorine in the R?F molecules could interact with electron donors (e.g., ammonia) and form a noncovalent bond (F ??? N). Although these interactions are usually categorized as halogen bonding, our studies show that there are fundamental differences between these interactions and halogen bonds. Although the anisotropic distribution of electronic charge around a halogen is responsible for halogen bond formations, the electronic charge around the fluorine in these molecules is spherical. According to source function analysis, F is the sink of electron density at the F ??? N BCP, whereas other halogens are the source. In contrast to halogen bonds, the F ??? N interactions cannot be regarded as lump–hole interactions; there is no hole in the valence shell charge concentration (VSCC) of fluorine. Although the quadruple moment of Cl and Br is mainly responsible for the existence of σ‐holes, it is negligibly small in the fluorine. Here, the atomic dipole moment of F plays a stabilizing role in the formation of F ??? N bonds. Interacting quantum atoms (IQA) analysis indicates that the interaction between halogen and nitrogen in the halogen bonds is attractive, whereas it is repulsive in the F ??? N interactions. Virial‐based atomic energies show that the fluorine, in contrast to Cl and Br, stabilize upon complex formation. According to these differences, it seems that the F ??? N interactions should be referred to as “fluorine bond” instead of halogen bond.     

Nano-Fe3O4 -encapsulated silica particles bearing sulfonic acid groups as a magnetically separable catalyst for the green and efficient synthesis of 14-aryl-14H-dibenzo[a,i]xanthene-8,13-dione derivatives

Research on Chemical Intermediates - In this research, an efficient and environmentally friendly ("green") method for one-pot synthesis of xanthene derivatives was developed in the...     

An Experimental and Theoretical Study on Influence of H‐bonding on the Synthesized Azo Derivatives Structures

We have reported a simple and efficient reaction for the synthesis of some new functionalized azo structures which were prepared by electron deficient acetylenic compounds in the presence of triphenylphosphine. The characterization of the synthesized azo compounds has been determined by FTIR, UV‐Vis, ¹H NMR, ¹³C NMR and Mass spectroscopic techniques. The influence of H‐bonding on the products has been shown by different experimental analysis. Also, the regioselectivity of the reaction, tautomerization equilibrium and the stability of products was investigated using DFT calculations at the B3LYP/6‐31G level of theory.