- Diels-Alder polysulfones as dielectric materials: Computational guidance & synthesis
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Herein, we describe the synthesis and characterization of polymers formed by the Diels-Alder (DA) reaction between various difurans and divinylsulfone, and evaluate their dielectric properties. These syntheses were planned with computational support a priori in the form of HOMO/LUMO calculations for the dienes and dienophiles, with the calculated ΔE for the DA reactions ranging between 9.33 and 9.42 eV. We describe the structure-property relationship observed when changing an atom in the linking unit between two furan rings (-CH2-, -O-, -S-, -NH-) with respect to the dielectric constant and loss tangent. Dielectric constants for the polymers range between 4.96 and 5.98, with dielectric loss tangents ranging from 0.4 to 0.9% at 1 kHz and room temperature. Bandgaps of the polymers are elucidated with UV/Visible spectroscopy, and range from 2.15 to 2.61 eV. The retro DA onset is determined using three analytical methods: thermogravimetric analysis, dynamic scanning calorimetry, and gas chromatography/mass spectrometry polymer desorption spectroscopy, and is determined to be over 125 °C in all cases.
- Lorenzini, Robert G.,Greco, Jordan A.,Birge, Robert R.,Sotzing, Gregory A.
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- Intramolecular Reactions of Tethered Furan-Based Bis(p-quinodimethanes)
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Tethered bis-2,5-dimethylene-2,5-dihydrofurans were generated in the gas phase by flash vacuum pyrolysis (FVP) of diester precursors. These furan-based bis(p-quinodimethanes) are shown to undergo reactions leading to macrocycles. The observed products strongly support a mechanism involving cyclic diradical intermediates. Formation of the furan-based p-quinodimethane and the corresponding cyclization chemistry was studied by high-level ab initio calculations. The theoretical studies reveal the importance of the entropy-driven elimination steps in the high-temperature FVP chemistry.
- Klumpp, Douglas A.,Gilbert, Thomas M.,Trahanovsky, Walter S.
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- Porous interpenetrated zirconium-organic frameworks (PIZOFs): A chemically versatile family of metal-organic frameworks
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We present the synthesis and characterization of porous interpenetrated zirconium-organic frameworks (PIZOFs), a new family of metal-organic frameworks obtained from ZrCl4 and the rodlike dicarboxylic acids HO 2C[PE-P(R1,R2)-EP]CO2H that consist of alternating phenylene (P) and ethynylene (E) units. The substituents R 1,R2 were broadly varied (alkyl, Oalkyl, oligo(ethylene glycol)), including postsynthetically addressable substituents (amino, alkyne, furan). The PIZOF structure is highly tolerant towards the variation of R 1 and R2. This together with the modular synthesis of the diacids offers a facile tuning of the chemical environment within the pores. The PIZOF structure was solved from single-crystal X-ray diffraction analysis. The PIZOFs are stable under ambient conditions. PIZOF-2, the PIZOF prepared from HO2C[PE-P(OMe,OMe)-EP]CO2H, served as a prototype to determine thermal stability and porosity. It is stable up to 325°C in air as determined by using thermogravimetry and powder X-ray diffraction. Argon sorption isotherms on PIZOF-2 revealed a Brunauer-Emmett-Teller (BET) surface area of 1250 m2 g-1 and a total pore volume of 0.68 cm3 g-1. Copyright
- Schaate, Andreas,Roy, Pascal,Preusse, Thomas,Lohmeier, Sven Jare,Godt, Adelheid,Behrens, Peter
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supporting information; experimental part
p. 9320 - 9325
(2011/10/02)
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- An Expedient Route for the Stereoselective Construction of Bridged Polyheterocyclic Ring Systems Using the Tandem "Pincer" Diels-Alder Reaction
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The tandem "pincer" Diels-Alder reaction, consisting of two consecutive [4 + 2] cycloadditions between two dienes and an acetylenic bis-dienophile, has been applied toward the rapid construction of bridged polyoxacyclic ring systems when furan derivatives are used as the diene components. The study has demonstrated the stereoselectivity (exo-exo adduct), the chemoselectivity ("pincer" vs "domino"), as well as the regioselectivity of the reaction. The reaction has been successfully applied to a variety of 2-substituted furans and tethered bis-furans in combination with mono-activated and diactivated dienophiles. The synthesis of unsymmetrical cycloadducts starting from the aza- and oxanorbornadiene-type intermediate has also been realized.
- Lautens, Mark,Fillion, Eric
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p. 4418 - 4427
(2007/10/03)
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