The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Hans Wolfgang Spiess - One of the best experts on this subject based on the ideXlab platform.
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high resolution solid state nmr studies of poly vinyl phosphonic Acid proton conducting polymer molecular structure and proton dynamics
Journal of Physical Chemistry B, 2007Co-Authors: Young Joo Lee, Bahar Bingol, Wolfgang H Meyer, Tatiana Murakhtina, Daniel Sebastiani, Gerhard Wegner, Hans Wolfgang SpiessAbstract:The structure and the local proton mobility of poly(vinyl phosphonic Acid) were studied by solid-state NMR under fast magic-angle spinning. At elevated temperatures, the signature of the hydrogen-bonded P−OH protons is observed in 1H magic-angle spinning (MAS) NMR as a single resonance at 10.5 ppm. Both 1H double-quantum NMR and variable-temperature experiments demonstrate that P−OH protons are mobile and thus able to contribute to proton conductivity. Below room temperature, two different types of hydrogen-bonded P−OH resonances are observed at 10.5 and 15 ppm, and 1H double-quantum NMR demonstrates that these protons are immobile on the NMR time scale. By means of first-principles calculations of a model polymer, we have assigned the additional hydrogen-bonded species at lower temperatures to phosphonic Acid Anhydride and charged Anhydride. Also, in the 31P MAS NMR spectrum, two distinct resonances appear, arising from “normal” phosphonic Acid and phosphonic Acid Anhydride. 31P double-quantum NMR experi...
Gernot Frenking - One of the best experts on this subject based on the ideXlab platform.
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donor acceptor stabilized silicon analogue of an Acid Anhydride
Journal of the American Chemical Society, 2011Co-Authors: Rajendra S Ghadwal, Ramachandran Azhakar, Herbert W Roesky, Kevin Propper, Birger Dittrich, Susanne Klein, Gernot FrenkingAbstract:A stable silicon analogue of an Acid Anhydride {PhC(ButN)2}Si{═O·B(C6F5)3}O–Si(H){═O·B(C6F5)3}{(NBut)(HNBut)CPh} (4) with a O═Si–O–Si═O core has been prepared by treating monochlorosilylene PhC(ButN)2SiCl (1) with H2O·B(C6F5)3 in the presence of NHC (NHC = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene). Compound 4 has been characterized by elemental analysis and multinuclear NMR spectroscopic investigations. The molecular structure of 4 has been established by single-crystal X-ray diffraction studies, and DFT calculations support the experimental results.
Young Joo Lee - One of the best experts on this subject based on the ideXlab platform.
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high resolution solid state nmr studies of poly vinyl phosphonic Acid proton conducting polymer molecular structure and proton dynamics
Journal of Physical Chemistry B, 2007Co-Authors: Young Joo Lee, Bahar Bingol, Wolfgang H Meyer, Tatiana Murakhtina, Daniel Sebastiani, Gerhard Wegner, Hans Wolfgang SpiessAbstract:The structure and the local proton mobility of poly(vinyl phosphonic Acid) were studied by solid-state NMR under fast magic-angle spinning. At elevated temperatures, the signature of the hydrogen-bonded P−OH protons is observed in 1H magic-angle spinning (MAS) NMR as a single resonance at 10.5 ppm. Both 1H double-quantum NMR and variable-temperature experiments demonstrate that P−OH protons are mobile and thus able to contribute to proton conductivity. Below room temperature, two different types of hydrogen-bonded P−OH resonances are observed at 10.5 and 15 ppm, and 1H double-quantum NMR demonstrates that these protons are immobile on the NMR time scale. By means of first-principles calculations of a model polymer, we have assigned the additional hydrogen-bonded species at lower temperatures to phosphonic Acid Anhydride and charged Anhydride. Also, in the 31P MAS NMR spectrum, two distinct resonances appear, arising from “normal” phosphonic Acid and phosphonic Acid Anhydride. 31P double-quantum NMR experi...
Ching-ping Wong - One of the best experts on this subject based on the ideXlab platform.
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Moisture Absorption in Uncured Underfill Materials
2016Co-Authors: Shijia Luo, Ching-ping WongAbstract:Abstract—This paper presents a systematic study on moisture absorption in uncured underfill based on epoxy cured with Acid Anhydride [methylhexahydrophthalic Anhydride (MHHPA)] and epoxy cured with non-Acid Anhydride curing agent. The influence of absorbed moisture on curing properties, thermomechanical property, and adhesion property of underfill after curing has been investigated. For epoxy cured with non-Acid Anhydride, the moisture absorption is low, and the absorbed moisture has no significant effect on the properties of cured underfill materials. For epoxy cured with Acid Anhydride, the moisture absorption before curing can be more than 2.0%, and the absorbed moisture can affect the properties significantly. The absorbed moisture can catalyze the curing reaction between Acid Anhydride and epoxy. The glass transition temperature of the cured samples is reduced after the underfill absorbs the moisture before curing. The adhesion strength decreases dramatically after the underfill absorbs the moisture before curing. Index Terms—Adhesion, epoxy, moisture absorption, underfill. I
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Moisture absorption in uncured underfill materials
IEEE Transactions on Components and Packaging Technologies, 2004Co-Authors: Ching-ping WongAbstract:This paper presents a systematic study on moisture absorption in uncured underfill based on epoxy cured with Acid Anhydride [methylhexahydrophthalic Anhydride (MHHPA)] and epoxy cured with non-Acid Anhydride curing agent. The influence of absorbed moisture on curing properties, thermomechanical property, and adhesion property of underfill after curing has been investigated. For epoxy cured with non-Acid Anhydride, the moisture absorption is low, and the absorbed moisture has no significant effect on the properties of cured underfill materials. For epoxy cured with Acid Anhydride, the moisture absorption before curing can be more than 2.0%, and the absorbed moisture can affect the properties significantly. The absorbed moisture can catalyze the curing reaction between Acid Anhydride and epoxy. The glass transition temperature of the cured samples is reduced after the underfill absorbs the moisture before curing. The adhesion strength decreases dramatically after the underfill absorbs the moisture before curing.
Rajendra S Ghadwal - One of the best experts on this subject based on the ideXlab platform.
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donor acceptor stabilized silicon analogue of an Acid Anhydride
Journal of the American Chemical Society, 2011Co-Authors: Rajendra S Ghadwal, Ramachandran Azhakar, Herbert W Roesky, Kevin Propper, Birger Dittrich, Susanne Klein, Gernot FrenkingAbstract:A stable silicon analogue of an Acid Anhydride {PhC(ButN)2}Si{═O·B(C6F5)3}O–Si(H){═O·B(C6F5)3}{(NBut)(HNBut)CPh} (4) with a O═Si–O–Si═O core has been prepared by treating monochlorosilylene PhC(ButN)2SiCl (1) with H2O·B(C6F5)3 in the presence of NHC (NHC = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene). Compound 4 has been characterized by elemental analysis and multinuclear NMR spectroscopic investigations. The molecular structure of 4 has been established by single-crystal X-ray diffraction studies, and DFT calculations support the experimental results.
