- High-Sensitivity Microcalorimetry and Gel Permeation Chromatography in Tandem Reveal the Complexity of the Synthesis of Poly-(2-isopropyl-2-oxazoline) Stars
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A series of star poly(2-isopropyl-2-oxazolines) (S-PIPOZ) was prepared by two different approaches: "coupling-onto (CO)"and "core-first (CF)". On the one hand, for "the core-first"approach, SCF-PIPOZ were prepared by direct cationic ring opening polymerization from a tetra tosylate-functionalized pentaerythrityl core. On the other hand, for the "coupling-onto"approach, SCO-PIPOZ were synthesized by coupling via copper alkyne-azide cycloaddition between L-PIPOZ-N3 and a tetrafunctionalized alkyne core. Taking advantage of the thermosensitive properties of PIPOZ, high-sensitivity microcalorimetry analyses (HS-DSC), in addition to commonly used 1H nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and spectrophotometry (UV analyses), proved to be powerful tools. On the one side, microcalorimetry analysis facilitates purification of the polymers by setting the appropriate temperature for centrifugal fractionation, and on the other side, it helps in the resolution of their microstructures. SCO-PIPOZ demonstrated good correlation between the 1H NMR, GPC, and UV results and showed sharp unimodal HS-DSC endotherms. Contrary to the SCO-PIPOZ data, SCF-PIPOZ results revealed a discrepancy between the molecular weights measured by 1H NMR and GPC. This issue was resolved with the help of HS-DSC, which allowed detection of different populations of polymers to analyze them before and after isolation by isothermal centrifugal fractionation. Cleavage of the arms of the isolated SCF-PIPOZ showed incomplete/not uniform synthesis of S-PIPOZ by the "core-first"approach. These results highlight the importance of HS-DSC coupled with the commonly used analytical techniques for both refinement and elucidation of the microstructure of architecturally complex thermosensitive polymers such as star polymers.
- Bullet, Jean-Richard,Korchagina, Evgeniya V.,Winnik, Fran?oise M.
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- The graphene oxidizing antimicrobial element
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Described herein is a crosslinked graphene material based element that provides anti-microbial capabilities. Described is an element that can also comprise a support. Also described is an element where the support can be the article to be protected microbes. Also described are methods for killing microbes or for preventing microbial fouling by applying the aforementioned anti-microbial elements and related devices.
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- Cinchona alkaloid-based chiral catalysts act as highly efficient multifunctional organocatalysts for the asymmetric conjugate addition of malonates to nitroolefins
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New pentaerythritol tetrabromide-based chiral quaternary ammonium salts acting as organocatalysts (7a and 7b) have been prepared and used as organocatalysts for enantioselective Michael addition reactions between various nitroolefins and Michael donors (malonates) under mild reaction conditions, such as lower concentration of base and catalyst and room temperature, with very good chemical yields (up to 97%) and ee's (up to 99%).
- Ashokkumar, Veeramanoharan,Siva, Ayyanar
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p. 10216 - 10225
(2015/10/20)
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- Solution-phase synthesis of short oligo-2'-deoxyribonucleotides by using clustered nucleosides as a soluble support
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5'-O-(4,4'-Dimethoxytrityl)thymidine was attached to a pentaerythrityl- derived core, and the resulting tetravalent nucleoside cluster and the next dendritic generations served as a soluble support for the synthesis of short oligo-2'-deoxyribonucleotides
- Kungurtsev, Vyacheslav,Laakkonen, Jouni,Molina, Alejandro Gimenez,Virta, Pasi
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p. 6687 - 6693
(2013/11/06)
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- The synthesis of spirophanes from a pentaerythrityl core
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Various thia- and oxa-spirobicyclic cyclophanes were synthesized from a pentaerythrityl building block and appropriate dithiols/bisphenols.
- Rajakumar, Perumal,Sekar, Karuppannan,Srinivasan, Kannupal
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p. 1905 - 1907
(2007/10/03)
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- Molecular Tectonics. Porous Hydrogen-Bonded Networks Built from Derivatives of Pentaerythrityl Tetraphenyl Ether
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The symmetric four-armed geometry of pentaerythrityl tetraphenyl ether (5) makes it a valuable starting point for building complex molecular and supramolecular structures. In particular, it provides a core to which multiple sites of attractive intermolecular interaction can be attached, thereby creating compounds predisposed to form complex networks by association. To facilitate exploitation of the pentaerythrityl tetraphenyl ether core in such ways, we have prepared more than 20 new derivatives by efficient methods. Of special interest are compounds 3 and 4, which incorporate four diaminotriazine groups attached to the meta and para positions of the pentaerythrityl tetraphenyl ether core. Crystallization of compounds 3 and 4 from DMSO/dioxane is directed by hydrogen bonding of the diaminotriazine groups according to well-established motifs, thereby producing three-dimensional networks. In forming these networks, each molecule of compound 3 forms a total of 12 hydrogen bonds with six others, whereas each molecule of compound 4 forms a total of 16 hydrogen bonds with four others. Both networks are highly porous and define significant interconnected channels for the inclusion of guests. In crystals of compounds 3 and 4, the fraction of the volume accessible to guests is 66% and 57%, respectively. In both cases, the pentaerythrityl tetraphenyl ether cores adopt conformations that deviate substantially from tetrahedral geometry. It is noteworthy that the inherent flexibility of the core does not favor the formation of close-packed guest-free structures.
- Laliberte, Dominic,Maris, Thierry,Wuest, James D.
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p. 1776 - 1787
(2007/10/03)
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