Determination of polarity parameters for liquid crystals using solvatochromic method in anisotropic and isotropic phases

The use of liquid crystals (LCs) as anisotropic solvents is desired for various potential applications and usually for other organic and inorganic compounds. In this work, solvent polarity parameters are obtained using a spectroscopic method for four LCs with a range of high and low dielectric anisotropy (?ε). Solvatochromic polarity parameters for these LCs were defined via Kamlet–Abboud–Taft polarity functions characterizing different temperatures and phases, isotropic and anisotropic, and using the Reichardt’s dye and 2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridinio) phenolate standard probe. The investigated polarity parameters reveal the effects of LC media on the photo-physical behaviour of solute molecules in isotropic and anisotropic media. Subsequently, a new LC polarity parameter (Z_o) is introduced as an overall matrix anisotropy polarity parameter to characterize variation between isotropic and anisotropic phases. The values of Z_o are sorted from higher to lower dielectric anisotropies (?ε).     

Synthesis and characterization of chitosan-based polyurethane elastomer dispersions

Abstract  

A number of aqueous polyurethane dispersions were synthesized by the reaction of poly(ε-caprolactone) and isophorone diisocyanate, extended with different mass ratios of chitosan and dimethylol propionic acid. Their chemical structures were characterized by using FTIR, ¹H NMR, and ¹³C NMR spectroscopy, and thermal properties were determined by TGA. Incorporation of chitosan into the polyurethane backbone improved thermal stability. The hydrophilicity of the prepared polymers was also examined by contact angle measurements. For all samples, the contact angles increased by increasing the amount of chitosan. The increased contact angle is ascribed to the decrease of the hydrophilicity of the polyurethanes, which is reduced by the increasing amount of chitosan with respect to dimethylol propionic acid chain extender.     

Synthesis and characterization of optically active polyamides based on 2-(1,3-isoindolinedione-2-yl)glutaric acid by direct polycondensation

<正>Five new optically active polyamides(PAs) 6a-6e were prepared by direct polycondensation reaction of 2-(1,3- isoindolinedione-2-yl)-glutaric acid 4 as a new chiral diacid with various aromatic diamines 5a-5e in a medium consisting of triphenyl phosphite(TPP),calcium chloride,pyridine(Py) and N-methyl-2-pyrrolidone(NMP).The polycondensation reaction produced a series of polyamids 6a-6e in quantitative yields with inherent viscosities of 0.26-0.39 dL/g.The resulting polymers were fully characterized by means of ~1H-NMR,FT-IR spectroscopy,elemental analysis,inherent viscosity and specific rotation.Thermal properties of these polymers were investigated using thermal gravimetric analysis (TGA) and differential thermal gravimetry(DTG).Phthalimide rings as a bulky pendent group in the polymer chains disturb the interchain and intrachain interactions and make these PAs readily soluble in polar,aprotic solvents such as N,N-dimethyl acetamide(DMAc),N,N-dimethyl formamide(DMF),dimethyl sulfoxide(DMSO),N-methyl-2-pyrrolidone(NMP) and sulfuric acid.     

Synthesis, experimental and theoretical characterization of N,N'-dipyridoxyl (1,4-butanediamine) Schiff-base ligand and its Cu(II) complex

A new N,N'-dipyridoxyl(1,4-butanediamine) [=H(2)BS] Schiff-base ligand and its Cu(II) salen complex, [Cu(BS)(H(2)O)(CH(3)OH)], were synthesized and characterized by IR, UV-vis, (1)H NMR, mass spectrometry and elemental analysis. Also, full optimization of the geometries, (1)H NMR chemical shifts (for the H(2)BS) and vibrational frequencies were calculated by using density functional theory (DFT) method. Structure of the H(2)BS ligand is not planar, i.e. two pyridine rings are not in the same plane. In the structure of the Cu complex, the Schiff-base ligand acts as a dianionic tetradentate ligand in N, N, O(-), O(-) manner. The coordinating atoms of BS(2-) occupy equatorial positions of the octahedral complex, where the H(2)O and CH(3)OH ligands locate at axial positions. The calculated results are in good agreement with the experimental data, confirming the suitability of the proposed and optimized structures for the H(2)BS ligand and its Cu complex.     

Feed-forward modelling and fuzzy logic based control strategy for powertrain efficiency improvement in a parallel hybrid electric vehicle

With the stricter limitations on both fuel consumption and air pollution, the advantages of a hybrid electric vehicle are becoming more evident than ever. In the present study, an energy management system for a hybrid electric vehicle is developed. Because the plant under consideration is nonlinear, multi-domain, time-varying, has multiple uncertainties and, in addition, the designed control strategy must be able to obey the driver's commands and achieve the par-internship for a new generation of vehicle regulations, the fuzzy logic approach is chosen. A feed-forward hybrid vehicle simulation model is used to demonstrate the validity and the convenience of the current approach and its results have been compared with the other parallel hybrid electric vehicle control strategies. Simulation results show considerable improvement in the efficiency of the internal combustion engine and, consequently, fuel consumption and acceleration performances.     

New Ga/N‐based Active Lewis Pairs,Trifunctional Ga–Ga Compounds,Reactions with Cyanamide and Dual Insertion of Isocyanate

Hydrogallation of Me₃Si–C≡C–NR'₂ with R₂Ga–H (R = tBu, CH₂tBu, iBu) yielded Ga/N‐based active Lewis pairs, R₂Ga–C(SiMe₃)=C(H)–NR'₂ ( 7 ). The Ga and N atoms adopt cis‐positions at the C=C bonds and show weak Ga–N interactions. tBu₂GaH and Me₃Si–C≡C–N(C₂H₄)₂NMe afforded under exposure of daylight the trifunctional digallium(II) compound [MeN(C₂H₄)₂N](H)C=C(SiMe₃)Ga(tBu)–Ga(tBu)C(SiMe₃)=C(H)[N(C₂H₄)₂NMe] ( 8 ), which results from elimination of isobutene and H₂ and Ga–Ga bond formation. 8 was selectively obtained from the ynamine and [tBu(H)Ga–Ga(H)tBu]₂[HGatBu₂]₂. 7a (R = tBu; NR'₂ = 2,6‐Me₂NC₅H₈) and H₈C₄N–C≡N afforded the adduct tBu₂Ga‐C(SiMe₃)=C(H)(2,6‐Me₂NC₅H₈) · N≡C–NC₄H₈ ( 11 ) with the nitrile bound to gallium. The analogous ALP with harder Al atoms yielded an adduct of the nitrile dimer or oligomers of the nitrile at room temperature. The reaction of 7a with Ph–N=C=O led to the insertion of two NCO groups into the Ga–C_vinyl bond to yield a GaOCNCN heterocycle with Ga bound to O and N atoms ( 12 ).     

Quantum conductance investigation on carbon nanotube–based antibiotic sensor

Journal of Solid State Electrochemistry - Nanostructured carbon material (NSCM) based chemiresistive sensors are popular for sensing different analytes because of their high sensitivity, low cost,...     

Magnetic and Heat Resistant Poly(imide-ether) Nanocomposites Derived from Methyl Rich 9<Emphasis Type="Italic">H</Emphasis>-xanthene: Synthesis and Characterization

In this study a new series of magnetic and heat resistant nanocomposites were prepared based on a highly soluble poly(imide-ether) (PIE) reinforced with two different types of magnetic nanoparticles via a solution intercalation technique. New PIE with good solubility and desired molar mass containing bulky xanthene rings and amide groups in the side chains was synthesized via thermal cyclization of the poly(amic acid) precursor, obtained from the reaction of a new diamine derived from 9H-xanthene and 4,4′-oxydiphthalic dianhydride (ODPA). Improved solubility was attributed to the presence of xanthene group and flexible ether linkage in the polyimide backbones that reduce the chain-chain interaction and enhance solubility by penetrating solvent molecules into the polyimide chains. Fe₃O₄ nanoparticles (MNPs) which synthesized from chemical co-precipitation route were coated with silica (SiO₂), sequentially with (3-aminopropyl)triethoxysilane and poly-melamine-terephthaldehyde (MNPs-PMT), and then separately dispersed in the poly(amic acid) solutions and thermally imidized to form PIE/Fe₃O₄ and PIE/MNPs-PMT nanocomposites. The nanostructures and properties of the resultant materials were investigated using FTIR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The properties of the nanocomposites were strongly related to the dispersion and interaction between the nanoparticles and PIE matrix. The thermogravimetric analysis (TGA) results showed that the addition of MNPs-PMT nanoparticles resulted in a substantial increase in the thermal stability of the corresponding PIEN. The temperature at 10% weight loss (T₁₀) was increased from 416 °C to 428 °C for PIEN containing 3 wt% MNPs-PMT as compared to neat PIE, as well the char yield enhanced. Furthermore, the MNPs-PMT nanoparticles had better dispersion in the polymer matrix due to the strong intermolecular hydrogen bond interactions between the NH and C=N groups of surface-modified nanoparticles and the PIE matrix than the uncoated Fe₃O₄ nanoparticles, and exhibited a better intercalated morphology and improved thermal properties. Also, the PIEN nanocomposites under applied magnetic field exhibited the hysteretic loops of the superparamagnetic nature.     

Novel Flame‐Retardant and Thermally Stable Poly(Amide‐imide)s Based on Bicyclo[2,2,2]oct‐7‐Ene‐2,3,5,6‐Tetracarboxylic Diimide and Phosphine Oxide in the Main Chain: Synthesis and Characterization

Six novel poly(amide‐imide)s PAIs 5a‐f were synthesized through the direct polycondensation reaction of six chiral N,N′‐(bicyclo[2,2,2]oct‐7‐ene‐tetracarboxylic)‐bis‐L‐amino acids 3a‐f with bis(3‐amino phenyl) phenyl phosphine oxide 4 in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), triphenyl phosphite (TPP), calcium chloride (CaCl₂) and pyridine. The polymerization reaction produced a series of flame‐retardant and thermally stable poly(amide‐imide)s 5a‐f with high yield and good inherent viscosity of 0.39–0.83 dLg^?1. The resultant polymers were fully characterized by means of FTIR, ¹H NMR spectroscopy, elemental analyses, inherent viscosity, specific rotation and solubility tests. Thermal properties and flame retardant behavior of the PAIs 5a‐f were investigated using thermal gravimetric analysis (TGA and DTG) and limited oxygen index (LOI). Data obtained by thermal analysis (TGA and DTG) revealed that these polymers show good thermal stability. Furthermore, high char yields in TGA and good LOI values indicated that resultant polymers exhibited good flame retardant properties. N,N′‐(bicyclo[2,2,2]oct‐7‐ene‐tetracarboxylic)‐bis‐L‐amino acids 3a‐f were prepared in quantitative yields by the condensation reaction of bicyclo[2,2,2]oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride 1 with L‐alanine 2a , L‐valine 2b , L‐leucine 2c , L‐isoleucine 2d , L‐phenyl alanine 2e and L‐2‐aminobutyric acid 2f in acetic acid solution. These polymers can be potentially utilized in flame retardant thermoplastic materials.