Ionic liquids (ILs) constitute a class of solvents containing organic cation along with organic/inorganic anion characterized by low melting point (<100 °C) and negligible vapor pressure. These solvents are promising alternatives for conventional organic solvents by virtue of being environmentally benign. No toxic gases are released by ILs upon their usage. The physicochemical properties of ILs can easily be tailored by varying the structure/combination of cation and anion ranging from lipophilic to lipophobic, viscous to nonviscous, polar to nonpolar, and water miscible to immiscible. Other desirable properties of ILs are high thermal stability, nonflammability, and large electrochemical window. ILs have been emerged as “green solvents” over the period of time, and the industrial applications of ILs have been increasing progressively, which are diversified from the solvent for the syntheses (organic, inorganic, or polymer) to catalysis, analytical separations, extractions, electrochemistry, lubrication, and so on. Some of the relatively newer industrial applications of ILs are the fabrication of supported liquid membranes (SILM) for the selective separation of different metal ions/organic compounds/biologically important compounds in dilute streams, and gas mixtures, biomass transformation into fuel, and chemicals and nuclear waste management. Many of these have been developing at pilot plant and commercial levels.
This article describes the synthesis of some novel aromatic amide-amine curing agents by reacting 1 mole of p-amino benzoic acid with 1 mole of each of 1,4-phenylene diamine (P), 1,5-diamino naphthalene (N), 4,4 0 -(9-fluorenyllidene)-dianiline (F), 3,4 0 -oxydianiline (O), and 4,4 0 -diaminodiphenyl sulphide (DS) and were designated as PA, NA, FA, OA, and SA, respectively. The aromatic amideamines so synthesized were characterized with the help of spectroscopic techniques, viz., Fourier Transform Infrared, proton nuclear magnetic resonance, and carbon nuclear magnetic resonance. The curing kinetics of the epoxy resins obtained by reacting amines with diglycidyl ether of bisphenol-A blended with tris(glycidyloxy)phosphine oxide in a ratio of 3 : 2, respectively, were investigated by DSC technique using multiple heating rate method (5,10,15,20 C/ min). Activation energies were determined by fitting the experimental data into Kissinger and Flynn-Wall-Ozawa Kinetic models. The activation energies obtained through Flynn-Wall-Ozawa method were slightly higher than Kissinger method but were comparable. However, both the energies were found to be dependent on the structure of amines. The thermal stability and weight loss behavior of isothermally cured thermosets were also investigated using thermogravimetric analysis in nitrogen atmosphere.
In literature, the applicability of solution‐phase perylene diimides (PDIs) semiconductors are limited due to their restricted solubility in solvents. In contrast, we synthesized a highly soluble and novel valine‐functionalized PDI derivative (perylene diimide diacid, PDIDA) whose optical and electrical properties were carefully assessed by experimental and density functional approaches. Notably, on valine substitution, the ultraviolet‐visible absorption band centered at 524 nm was attributed to the predominant HOMO ➔ LUMO electronic transition (weighing coefficient = 99 %). Interestingly, the nonuniform variation (W‐shaped) in absorption energy for HOMO ➔ LUMO electronic transition in PDIDA with solvent dielectric constant was experimentally witnessed. The latter was computationally attributed to the more S1 stabilization over So solvent stabilization, particularly in ethanol and dimethyl sulfoxide (DMSO). Furthermore, upon 525 nm excitation, the maximum fluorescence emission was observed at 533 nm with photoluminescence quantum yield as high as 0.77. Interestingly, similar to absorption studies, pronounced influence of solvent polarity was evident on the emission maximum particularly in ethanol and DMSO. Subsequently, electrochemical investigation proved that the PDIDA sustained the intrinsic n‐type semiconductivity with a dielectric constant (εr) 5, a current of 0.54 mA at 5 V, and an electrical conductivity of 1.88 × 10−5 Sm−1. Owing to the above remarkable properties of the synthesized PDIDA, it holds potential applications in photovoltaics, fluorescence‐based detectors and n‐type channel field effect transistors, and so forth.
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