Relationships between molecular structure and thermomechanical properties of bio‐based thermosetting polymers

Molecular dynamics simulations are used to study highly cross‐linked epoxy networks comprised of furanyl epoxy monomer, 2,5‐bis[(2‐oxiranylmethoxy)methyl]‐furan (BOF), that is cross‐linked by two furanyl amine hardeners, 5,5'‐methylenedifurfurylamine (DFDA) and 5,5'‐ethylidenedifurfirylamine (CH₃‐DFDA). Important properties of these fully furan‐based systems, including room temperature density, glass transition temperature, and Young's modulus are found to agree with previous experimental results. We also compare the simulated and experimental values of four fully furan‐based thermosetting materials to those using the conventional resin diglycidyl ether of bisphenol A (DGEBA) cured with the two furanyl hardeners. Our simulation results predict a slight decrease in density and Young's modulus, but no impact on the glass transition temperature, upon adding the methyl group in DFDA. Detailed analyses of the MD trajectories reveal the underlying mechanisms responsible for the observed structure/property relations, which center on the lack of collinear covalent bonds in the BOF molecular structure. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 285–292     

Regio- and stereoselective hydroxybromination and dibromination of olefins using ammonium bromide and oxone®

An efficient protocol for the synthesis of vicinal bromohydrins and dibromides from olefins is presented. Various olefins are regio- and stereoselectively hydroxybrominated and dibrominated with anti fashion, following Markonikov’s rule, using eco-friendly, non-toxic, and stable reagents such as NH₄Br and oxone® in CH₃CN/H₂O (1:1) and CH₃CN without employing catalyst in moderate to excellent yields. Bromohydrins are formed instantaneously.     

Functionalized Organotellurium Halides: Synthesis,Characterization, and Observation of Intra- and Intermolecular Secondary Bonding

Abstract

Activated tellurium, but not selenium, reacts with para-substituted benzoylmethyl bromides as well as with iodoacetamide at their melting points in absence of a solvent to give bis(p-substituted benzoylmethyl)tellurium dibromides, (p-YC₆H₄COCH₂)₂TeBr₂, (Y = H, Me, and MeO) and bis(acetamido)tellurium diiodide, (H₂NCOCH₂)₂TeI₂, respectively. Quick reduction of (p-YC₆H₄COCH₂)₂TeBr₂, with sodium metabisulphite in a two-phase system yields crystalline (p-YC₆H₄COCH₂)₂Te. These tellurides undergo smooth oxidative addition of halogens, interhalogen ICl or a pseudohalogen (SCN)₂. Intramolecular coordination of the carbonyl group in these functionalized diorganotellurium dihalides is evident from IR spectra and shorter Te···O (carbonyl) distances in comparison to the sum of van der Waals radii and completes six coordination around Te atom. Not unexpectedly, therefore, intermolecular secondary bonding effects of the type Te…O, Te···X and X···X are missing in (PhCOCH₂)₂TeBr₂, (p-MeOC₆H₄COCH₂)TeBr₂ and (PhCOCH₂)₂TeI₂. Instead, these compounds provide rare examples, among organotellurium compounds, of supramolecular architecture, where C–H···Br and C–H···O hydrogen bonds and π-π (phenyl ring) interactions appear to be the noncovalent intermolecular associative forces that dominate the crystal packing.     

Synthesis and characterization of a novel copolymer of glyoxal dihydrazone and glyoxal dihydrazone bis(dithiocarbamate) and application in heavy metal ion removal from water

We demonstrate synthesis of water insoluble, novel copolymer P_A1 from condensation of glyoxal dihydrazone and glyoxal dihydrazone bis(dithiocarbamate) monomers having high capacity to remove metal ions from aqueous solution. The presence of a high atomic percentage of nitrogen and sulfur atoms in P_A1 leads to strong ligating ability with metal ions. The monomers and the polymer have been characterized by FTIR, UV–Visible spectroscopy, CHNS elemental analysis, NMR, MALDI-MS, and TG/DTA. As a proof of concept, the P_A1 is tested for its ability to remove heavy metal ions Cu²⁺, Co²⁺, Fe²⁺, Ni²⁺, Mn²⁺, and CrO ₇ ^2? from aqueous solutions. P_A1 efficiently removed metals ions from the metal solutions. The highest absorption ability has been observed toward the iron salts where 0.969 g metal salt is absorbed by 1 g polymer. This study has implication for inexpensive and efficient polymer for purification of water.     

Computational Studies on Non‐covalent Interactions of Carbon and Boron Fullerenes with Graphene

First‐principles DFT calculations are carried out to study the changes in structures and electronic properties of two‐dimensional single‐layer graphene in the presence of non‐covalent interactions induced by carbon and boron fullerenes (C₆₀, C₇₀, C₈₀ and B₈₀). Our study shows that larger carbon fullerene interacts more strongly than the smaller fullerene, and boron fullerene interacts more strongly than that of its carbon analogue with the same nuclearity. We find that van der Waals interactions play a major role in governing non‐covalent interactions between the adsorbed fullerenes and graphene. Moreover, a greater extent of van der Waals interactions found for the larger fullerenes, C₈₀ and B₈₀, relative to smaller C₆₀, and consequently, results in higher stabilisation. We find a small amount of electron transfer from graphene to fullerene, which gives rise to a hole‐doped material. We also find changes in the graphene electronic band structures in the presence of these surface‐decorated fullerenes. The Dirac cone picture, such as that found in pristine graphene, is significantly modified due to the re‐hybridisation of graphene carbon orbitals with fullerenes orbitals near the Fermi energy. However, all of the composites exhibit perfect conducting behaviour. The simulated absorption spectra for all of the graphene–fullerene hybrids do not exhibit a significant change in the absorption peak positions with respect to the pristine graphene absorption spectrum. Additionally, we find that the hole‐transfer integral between graphene and C₆₀ is larger than the electron‐transfer integrals and the extent of these transfer integrals can be significantly tuned by graphene edge functionalisation with carboxylic acid groups. Our understanding of the non‐covalent functionalisation of graphene with various fullerenes would promote experimentalists to explore these systems, for their possible applications in electronic and opto‐electronic devices.     

Synthesis and performance characterization of PS-PPEES nanoporous membranes with nonwoven porous support

The present work describes about the synthesis and characterization of Polysulfone blend nanoporous membrane with nonwoven support. This Nonwoven support provides mechanical strength to membrane while filtration process and minimizes membrane fouling. Hence it helps in better membrane performance in terms of salt rejection, improved flux, thermal stability and fairly increases in proton conductivity. In this work we have used K.C.270 nonwoven material consisting of fine polyester fibers and has a thickness of below 110 μm.     

Synthesis,characterization and antibacterial activity of some new pyrazole based Schiff bases

In the present study a series of new Schiff bases were synthesized. All the synthesized compounds were characterized by IR, ¹H NMR, mass spectral and elemental analyses. Newly synthesized compounds were screened for their antibacterial (Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa) activity. The results revealed that, compounds 3f and 3c have exhibited significant biological activity against the tested microorganisms.     

O-(2-Aminobenoyl)-Hydroxylamine—A New Reagent for the Direct Conversion of Audehydes to Nitriles

Refluxing an ethanolic solution of O-(2-aminobenzoyl) -hydroxylamine (1) aldenydes and BF₃-Et₂ yields (78–94%) the corresponding nitriles.     

Convenient Synthesis of Bicyclic Lactones Related to the Trichothecenes

Short and convenient synthesis of bicyclic lactones (1) and (2), important intermediates in trichothecene synthesis is described.