Optical and thermal behavior of novel fluorinated polyimides capable of preparing colorless, transparent and flexible films

A new diamine, 1,5-bis(2-amino-4-trifluoromethylphenoxy)naphthalene (DA1524) was synthesized by the nucleophilic substitution reaction of 1,5-dihydroxynaphthalene and 4-chloro-3-nitrobenzotrifluoride in the presence of potassium carbonate in N,N-dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C in ethanol. DA1524 was then utilized to prepare a novel class of CF₃-containing polyimides. Intrinsic viscosities [η] of the polymer solutions at 25 °C were measured by the extrapolation of their viscosity numbers till zero concentration. and values of the resulting polymers were determined using gel-permeation chromatography (GPC). The polymers showed a good film-forming ability, and some characteristics of their thin films including color and flexibility were investigated qualitatively. In addition, the absorption edge values (λ₀) obtained from their UV–vis curves were determined, and all the resulting polyimides films exhibited high optical transparency. Thermal stability of the polymers was investigated using TGA analyses. The T_g values of the polyimides obtained from their DSC plots were quantified. Solubility of the samples in a variety of organic solvents was also tested.     

Nonelectrolyte NRTL-NRF model to study thermodynamics of strong and weak electrolyte solutions

An electrolyte activity coefficient model is proposed by combining non-electrolyte NRTL-NRF local composition model and Pitzer–Debye–Hückel equation as short-range and long-range contributions, respectively. With two adjustable parameters per each electrolyte, the present model is applied to correlation of the mean activity coefficients of more than 150 strong aqueous electrolyte solutions at 298.15 K. Also the results of the present model are compared with the other local composition models such as electrolyte-NRTL, electrolyte-NRTL-NRF and electrolyte-Wilson-NRF models. Moreover, the present model is used for prediction of the osmotic coefficient of several aqueous binary electrolytes systems at 298.15 K. Also the present activity coefficient model is adopted for representation of nonideality of the acid gases, as weak gas electrolytes, soluble in alkanolamine solutions. The model is applied for calculation of solubility and heat of absorption (enthalpy of solution) of acid gas in the two {(H₂O + MDEA + CO₂) and (H₂O + MDEA + H₂S)} systems at different conditions. The results demonstrate that the present model can be successfully applied to study thermodynamic properties of both strong and weak electrolyte solutions.     

Synthesis and antibacterial evaluations of new pyridazino[4,3‐e][1,3,4]oxadiazines

Several derivatives of the new pyridazino[4,3‐e][1,3,4]oxadiazine ring system were prepared, and their antibacterial evaluations were performed on four different Gram‐negative and Gram‐positive bacteria. J. Heterocyclic Chem., (2010).     

Synthesis and characterization of Schiff-base-containing polyamides

A series of new Schiff base polyamides（PAs） were synthesized by polycondensation of benzilbisthiosemicarbazone diamine（LH₆） with different commercially available aliphatic and aromatic diacid chlorides. The monomer and all the PAs were characterized by FTIR,¹H-NMR,and elemental analysis.The prepared polyamides showed inherent viscosities in the range of 0.30-0.36 dL/g in DMF at 25℃,indicating their moderate molecular weight.The PAs were completely soluble in aprotic polar solvents such as dimethylformamide（DMF）,N-methylpyrolidone（NMP）, tetrachloroethane（TCE）,dimthylsulfoxide（DMSO） and also in H₂SO₄ and partially soluble in THF,acetone and chloroform at room temperature.Thermal analysis showed that these PAs were practically amorphous and exhibited 10%weight loss above 220℃.     

Thermodynamic and transport properties for binary and ternary mixtures of 2-methyltetrahydrofuran?+?chlorobenzene?+?cyclopentanone at T?=?298.15?K

Abstract  

Experimental densities ρ, viscosities η, and refractive indices n _D of the ternary mixtures consisting of 2-methyltetrahydrofuran + chlorobenzene + cyclopentanone and constituted binary mixtures were measured at T = 298.15 K for the liquid region and at ambient pressure for the whole composition range. Excess molar volumes V_\textm^\textEV_{\text{m}}^{\text{E}}, deviations in the viscosity Δη, and deviations in the refractive index Δn _D from the mole fraction average for the mixtures were derived from the experimental data. The excess partial molar volumes V_\textm,i^\textEV_{{\text{m}},i}^{\text{E}} were also calculated. The binary and ternary data of V_\textm^\textEV_{\text{m}}^{\text{E}}, Δη, and Δn _D were correlated as a function of the mole fraction by using the Redlich–Kister and the Cibulka equations, respectively. McAllister’s three-body interaction model is used for correlating the kinematic viscosity of binary mixtures with the mole fraction.     

Investigation of structure, vibrational and NMR spectra of oxycodone and naltrexone: a combined experimental and theoretical study

In this work, two important opioid antagonists, naltrexone and oxycodone, were prepared from thebaine and were characterized by IR, (1)H NMR and (13)C NMR spectroscopy. Moreover, computational NMR and IR parameters were obtained using density functional theory (DFT) at B3LYP/6-311++G** level of theory. Complete NMR and vibrational assignment were carried out using the observed and calculated spectra. The IR frequencies and NMR chemical shifts, determined experimentally, were compared with those obtained theoretically from DFT calculations, showed good agreements. The RMS errors observed between experimental and calculated data for the IR absorptions are 85 and 105 cm(-1), for the (1)H NMR peaks are 0.87 and 0.17 ppm and for those of (13)C NMR are 5.6 and 5.3 ppm, respectively for naltrexone and oxycodone.     

Dynamic NMR and computational study of 5,5-dimethyl-3,4-di-p-tolyl-2-cylopenten-1-one

The restricted rotation of p-tolyl moiety in 5,5-dimethyl-3,4-di-p-tolyl-2-cyclopenten-1-one was studied by variable temperature NMR spectroscopy at a temperature range of 218-368 K. A free rotation, in NMR time scale, was observed at temperatures higher than 368 K; while, the rotation froze below 248 K. From dynamic NMR analysis, the Arrhenius energy of activation ΔG? was calculated as 56.37 kJ mol(-1). The experimental results were confirmed by theoretical calculation using the density functional theory method B3LYP with basis sets, 6-31G and 6-31+G.     

Theoretical study on the electronic,structural, properties and reactivity of a series of mono-, di-, tri- and tetrachlorothiophenes as well as corresponding radical cation forms as monomers for conducting polymers

In this paper, electrical and structural properties of mono-, di-, tri- and tetrachlorothiophenes and their radical cations have been studied using the density functional theory and B3LYP method with 6-311++G** basis set. The effects of the number and position of the substituent of chlorine atoms on the properties of the thiophene ring for all chlorothiophenes and their radical cations have been studied. Vibrational frequencies, nuclear chemical shielding constants, spin-density distribution, size and direction of dipole moment vector, ionization potential, electric polarizabilities and NICS values of these compounds have been calculated as well. The analysis of these data showed that double bonds in 3-chlorothiophene are more delocalized and it is the best possible candidate monomer among all chlorothiophenes for the synthesis of corresponding conducting polymers with modified characteristics.     

Novel sulfur-doped niobium pentoxide nanoparticles: fabrication, characterization, visible light sensitization and redox charge transfer study

Novel sulfur-modified niobium(V) oxide nanoparticles (SNON) that firstly exhibited good visible light sensitization were fabricated by a modified sol–gel technique using a very stable sol containing niobium(V) chloride, oxalic acid, isopropanol as chelating agent and thiourea as sulfur source. The resulting S-doped Nb₂O₅ nanomaterials were characterized by cyclic voltammetry (CV), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDAX), scanning electron microscope (SEM), ultra-violet diffuse reflectance (UV-DRS) and thermogravimetry thermal Analysis (TG-DTA). As against the response of unmodified niobium(V) oxide nanoparticles (UNON), the doped samples show different electrochemical response indicating an induced charge transfer across the niobium pentoxide/solution interface, thus forming two anodic peaks and a cathodic peak. This important observation was confirmed by UV-DRS in terms of band bending due to sulfur doping. Upon sulfur-modification, the absorption edge extends into the visible light region. The SEM observation shows that the SNPN existed in the mode of polycrystalline structure and the average grain size 63 nm. The EDAX analysis of undoped Nb₂O₅ and sulfur doped Nb₂O₅ shows the Nb₂O₅ (98%) and S (2%) content of nanopowder. These SNON nanoparticles are expected to be suitable candidates as visible light niobium(V) oxide nanoparticles sensitization.