Dielectric behavior of single crystals of poly(ethylene oxide)

Ishida, Yōichi; Matsuo, Masato; Takayanagi, Motowo

doi:10.1002/pol.1965.110030415

Cited by 60 publications

(28 citation statements)

References 7 publications

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“…The b PEO transition (T max % À40 to À21 8C) is attributed to long-range segmental chain reorientations directly correlated with the amount of amorphous phase in the amorphous-crystalline two-phase structure of PEO. [44] Association of the b PEO mode with a cooperative glass transition phenomenon in disordered regions is supported by the disappearance of this signal in single-crystal laminate solution-grown PEO (with M w > 10 5 ). The presence of the b PEO band well above the frequently reported calorimetric T g of PEO (e.g., À57 8C for high-molecular-weight material) is attributed to the high degree of crystallinity.…”

Section: Dielectric Characterization Of Cured Er þ Peo Blendsmentioning

confidence: 79%

Thermophysical Properties and Molecular Relaxations in Cured Epoxy Resin + PEO Blends: Observations on Factors Controlling Miscibility

Kalogeras

Vassilikou‐Dova

Christakis

et al. 2006

Macro Chemistry & Physics

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Summary: Thermophysical properties and molecular relaxations in aromatic amine‐cured diglycidyl ether of bisphenol‐A (DGEBA) epoxy oligomer and poly(ethylene oxide) (PEO) mixtures were determined by DSC and dielectric techniques (TSC, DRS). The binary blends were judged to be fully miscible in the amorphous state (wPEO < 40 wt.‐%), as evidenced by the single composition‐dependent glass transition temperatures Tgs. In the amorphous blends, negative deviations of dielectric/thermal Tg‐estimates from the linear mixing rule or the behavior predicted by the Fox equation reveal weaker intermolecular interactions, compared to strong self‐association of hydroxyls in the cured thermoset. Morphological changes in PEO‐rich blends (wPEO ≥ 40 wt.‐%) are in accordance with their complicated interface structure, previously reported to consist of amorphous PEO regions, branched epoxy resin chains and an imperfect epoxy resin network located between PEO lamellae. In these blends, PEO crystallites exert steric hindrances in the amorphous regions, causing strong Tg upshifts. Changes in the relaxation dynamics of glyceryl segments (e.g., in the activation energy barrier and relaxation strength) are in accordance with the idea that the close matching between the molecular polarities of PEO, epoxy resin and the cure agent significantly contributes to the observed miscibility.

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Section: Dielectric Characterization Of Cured Er þ Peo Blendsmentioning

confidence: 79%

Thermophysical Properties and Molecular Relaxations in Cured Epoxy Resin + PEO Blends: Observations on Factors Controlling Miscibility

Kalogeras

Vassilikou‐Dova

Christakis

et al. 2006

Macro Chemistry & Physics

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“…3a). Furthermore, the glass transition temperature ( T g ) of PEO is 220 K, much lower than that of zeonex323334, which causes the dielectric to decrease as the temperature decreases.…”

Section: Resultsmentioning

confidence: 99%

Revealing the spin–vibronic coupling mechanism of thermally activated delayed fluorescence

et al. 2016

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Knowing the underlying photophysics of thermally activated delayed fluorescence (TADF) allows proper design of high efficiency organic light-emitting diodes. We have proposed a model to describe reverse intersystem crossing (rISC) in donor–acceptor charge transfer molecules, where spin–orbit coupling between singlet and triplet states is mediated by one of the local triplet states of the donor (or acceptor). This second order, vibronically coupled mechanism describes the basic photophysics of TADF. Through a series of measurements, whereby the energy ordering of the charge transfer (CT) excited states and the local triplet are tuned in and out of resonance, we show that TADF reaches a maximum at the resonance point, substantiating our model of rISC. Moreover, using photoinduced absorption, we show how the populations of both singlet and triplet CT states and the local triplet state change in and out of resonance. Our vibronic coupling rISC model is used to predict this behaviour and describes how rISC and TADF are affected by external perturbation.

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“…The dielectric γ b -relaxation mode also incorporates a secondary γ PEO process around -170°C that is related to thermal depolarization through local twisting movements (crank-shaft or kink motion) in PEO chains in defective regions within crystallites and in noncrystalline regions. 43 IV. B. Frequency-Domain Dielectric Analysis.…”

Section: Relaxation Dynamics Of the Er-i-peo Networkmentioning

confidence: 99%

Nanoscale Confinement Effects on the Relaxation Dynamics in Networks of Diglycidyl Ether of Bisphenol-A and Low-Molecular-Weight Poly(ethylene oxide)

et al. 2007

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Thermoplastic poly(ethylene oxide) (PEO) (M w(PEO) ≈ 4000) has been used to prepare thermosetting nanocomposites incorporating diglycidyl ether of bisphenol A (DGEBA) epoxy oligomer. Blends with various PEO/DGEBA weight ratios were cured using stoichiometric portions of 4,4′-diaminodiphenylmethane. The resulting semi-interpenetrating polymer networks were studied by several techniques. Nanoscale confinement effects, thermal (glass transition, melting and crystallization temperatures) and structural features of our materials are similar to those for networks with much higher M w(PEO) and different curing agents; however, the polyether crystallization onset occurs in our case at a lower PEO concentration; shorter PEO chains organize themselves more easily into crystalline domains. Very low estimates of the k parameter of the Gordon-Taylor equation, used to fit the compositional dependences of the dielectric and calorimetric glass transition temperatures, and a strong plasticization of the motion of the glyceryl segments ( -relaxation) in the epoxy resin were observed. These illustrate an intensified weakening in the strength of the intermolecular interactions in the modified networks, as compared to the high strength of the self-association of hydroxyls in the neat resin. The significance of hydrogen-bonding interactions between the components for obtaining structurally homogeneous thermoseti-thermoplastic networks is discussed.

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Dielectric behavior of single crystals of poly(ethylene oxide)

Cited by 60 publications

References 7 publications

Thermophysical Properties and Molecular Relaxations in Cured Epoxy Resin + PEO Blends: Observations on Factors Controlling Miscibility

Thermophysical Properties and Molecular Relaxations in Cured Epoxy Resin + PEO Blends: Observations on Factors Controlling Miscibility

Revealing the spin–vibronic coupling mechanism of thermally activated delayed fluorescence

Nanoscale Confinement Effects on the Relaxation Dynamics in Networks of Diglycidyl Ether of Bisphenol-A and Low-Molecular-Weight Poly(ethylene oxide)

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