Search

Due to their unique properties and use in high performance materials, the ability to obtain fluorinated polymers utilizing straightforward synthetic methods remains of interest. In this study, we report the facile synthesis of new fluoropolymers via nucleophilic addition of a di‐thiol to perfluorocyclopentene. Initially, model studies were completed with perfluorocyclopentene, benzenethiol and tetramethylsilane‐protected benzenethiol to identify the optimal reaction conditions for the polymerization. These reaction conditions were then utilized to prepare perfluorocyclopentene‐thioether polymers from perfluorocyclopentene and 4,4′‐thiobisbenzenethiol. The isolated polymers had molecular weight distributions consistent with step‐growth polymers and 19F NMR spectroscopy revealed that the addition of the nucleophile to perfluorocyclopentene was controlled. Analysis by DSC showed that the polymers were amorphous with glass transition temperatures around 65 °C. TGA in both air and nitrogen showed an initial degradation temperature around 370 °C, while the air analysis produced an additional plateau with a degradation temperature near 592 °C. This is the first known report of utilizing perfluorocyclopentene for the preparation of perfluorinated‐thioether polymers. © 2024 Society of Industrial Chemistry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

The aryl diester compound, 2-methyl-1,4-phenylene bis(3,5-dibromobenzoate), C21H12Br4O4, was synthesized by esterification of methyl hydroquinone with 3,5-dibromobenzoic acid. A crystalline sample was obtained by cooling a sample of the melt (m.p. = 502 K/DSC) to room temperature. The molecular structure consists of a central benzene ring with anti-3,5-dibromobenzoate groups symmetrically attached at the 1 and 4 positions and a methyl group attached at the 2 position of the central ring. In the crystal structure (space group P1), molecules of the title aryl diester are located on inversion centers imposing disorder of the methyl group and H atom across the central benzene ring. The crystal structure is consolidated by a network of C--H...Br hydrogen bonds in addition to weaker and offset interactions involving the central benzene rings as well as the rings of the attached 3,5-dibromobenzoate groups. [ABSTRACT FROM AUTHOR]

Biodiesel is an important alternative fuel synthesized by the trans-esterification of vegetable oils, animal fats, and recycled greases. In this experiment, students prepared biodiesel through the base-catalyzed trans-esterification of several vegetable oils, which were subsequently analyzed in comparison with conventional petroleum-based fuels to assess their physical properties and to obtain a thermochemical profile. The experiment as described here could be employed by university faculty as a project in a major's level laboratory course, but we envision the ideal fit to be a module within an advanced or integrated laboratory course. Students completing the project gain valuable experience in chemical synthesis and in extensive product characterization and analysis. This project reinforces critical skills in isolation of pure products from complex mixtures and in the careful preparation of samples for chemical analysis. Finally, students are afforded the opportunity to compare theoretical predictions from chemical modeling in combination with GC-MS analysis with the practical results gained by performing bomb calorimetry.

Reaction of triplet O2 with the bridged dipotassium dicyclopentadienyl salt, ansa-[(CHBut)2(Ph2C5H2)2]K2(THF)3 1, in dry MeCN facilitated an intramolecular cyclopentadienyl ring-C to ring-C bond formation and the precipitation of the crude product 4,5-di-tert-butyl-1,3,6,8-tetraphenyl-4,5,8a,8b-tetrahydro-as-indacene 2 as an off-white solid in a 73% yield (>95% pure, 1H NMR). Characterization of 2 was carried out using multinuclear NMR spectroscopy (1H and 13C), single-crystal X-ray crystallography, FTIR spectroscopy, and thermal analytical techniques (SDT, DSC). The molecular structure consisted of a rigid, C2-symmetric six-membered ring in a chair conformation with four of the ring-C atoms fused to 1,3-diphenylcyclopentadiene rings and the other two ring-C atoms substituted with trans di-axial But groups. [ABSTRACT FROM AUTHOR]

Improving the performance of composite energetic materials comprised of a solid metal fuel and a source of oxidizer (known as thermites) has long been pursued as thermites for pyrolant flares and rocket propellants. The performance of thermites, involving aluminum as the fuel, can be dramatically improved by utilizing nanometer-sized aluminum particles (nAl) leading to vastly higher reaction velocities, owing to the high surface area of nAl. Despite the benefits of the increased surface area, there are still several problems inherent to nanoscale reactants including particle aggregation, and higher viscosity composited materials. The higher viscosity of nAl composites is cumbersome for processing with inert polymer binder formulations, especially at the high mass loadings of metal fuel necessary for industry standards. In order to improve the viscosity of high mass loaded nAl energetics, the surface of the nAl was passivated with covalently bound monolayers of perfluorinated carboxylic acids (PFCAs) utilizing a novel fluorinated solvent washing technique. This work also details the quantitative binding of these monolayers using infrared spectroscopy, in addition to the energetic output from calorimetric and thermogravimetric analysis. Dataset: Supplementary file of thermal analysis Dataset License: CC-BY [ABSTRACT FROM AUTHOR]