Influence of Chain Length on the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi><mml:mtext mathvariant="normal">−</mml:mtext><mml:mi>β</mml:mi></mml:math>Bifurcation in Oligomeric Glass Formers

Mattsson, Johan; Bergman, Rikard; Jacobsson, Per; Börjesson, Lars

doi:10.1103/physrevlett.94.165701

Cited by 30 publications

(25 citation statements)

References 24 publications

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“…Similarly, crossovers in the high-frequency glassy behavior of oligo(propylene glycol) dimethyl ethers with variable chain length [26] apparently arise from polymeric conformations suggestive of collective entanglement in the H-bond network not describable by microscopic H-bonding hierarchies.…”

Section: Constraint Counting In Polyalcohols and Saccharidesmentioning

confidence: 99%

Ideally glassy hydrogen-bonded networks

Phillips

2006

Phys. Rev. B

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Section: Constraint Counting In Polyalcohols and Saccharidesmentioning

confidence: 99%

Ideally glassy hydrogen-bonded networks

Phillips

2006

Phys. Rev. B

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“…This suggests that for the stronger liquids, the ␤ relaxation is not only near the spectral position of the ␣ peak but also subject to an extremely broad loss profile with an accordingly low amplitude, which adds to the problem of discriminating a JG peak from an excess wing behavior. [45][46][47] The inset of Fig. 4 shows the ratio of the relaxation widths, w ␣ / w ␤ , for the ␣ and ␤ relaxations, restricted to the subset of systems for which the ␤ process is a true JG-type relaxation.…”

Section: Resultsmentioning

confidence: 99%

Primary and secondary relaxation time dispersions in fragile supercooled liquids

Wang

Richert

2007

Phys. Rev. B

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The relaxation time dispersions of the primary ͑␣͒ and secondary ͑␤͒ dielectric relaxations are studied for molecular glass-forming liquids regarding their dependence on structural relaxation time ͓or lack thereof observed as time-temperature superposition ͑TTS͔͒, their changes with fragility, and a possible correlation of the values for the ␣ and ␤ processes. Toward more fragile liquids, the width w ␣ of the ␣ peak at the glass transition temperature T g is known to increase significantly. Additionally, we observe that TTS extends over a broader range of peak relaxation times in the case of higher fragility, with the approach to exponential ͑Debye͒ relaxation being delayed to faster dynamics. The width w ␤ of the ␤ relaxation at T g is somewhat lower for more fragile liquids and appears correlated with that of the primary relaxation. The extrapolated coincidence of the dispersions of the ␣ and ␤ processes occurs at the fragility "limit" of m = 170, implying that w ␣ ഛ w ␤ for all molecular supercooled liquids. Materials of high fragility are also those with no clear low-frequency cutoff in the relaxation time distribution-i.e., their susceptibilities require Havriliak-Negami instead of Cole-Davidson fits. For sorbitol, the value of w ␤ is seen to change steadily through the ␣-␤-merging region, whereas w ␣ displays a kink at the crossover temperature.

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“…2, which shows that the good agreement between G 00 and 00 disappears as the peaks merge. The substance, tripropylene glycol (TPG), C 6 H 20 O 4 , is still a molecule and not yet a polymer (the whole series from the small molecule propylene glycol to long-chain polypropylene glycol is wellinvestigated by dielectrics [18][19][20]). TPG itself has been studied under aging [21] and under pressure [22].…”

Section: The Barrier Density Functions For Shear and Dielectricsmentioning

confidence: 99%

Mechanical and dielectric relaxation spectra in seven highly viscous glass formers

Buchenau

2007

Journal of Non-Crystalline Solids

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Published dielectric and shear data of six molecular glass formers and one polymer are evaluated in terms of a spectrum of thermally activated processes, with the same barrier density for the retardation spectrum of shear and dielectrics. The viscosity, an independent parameter of the fit, seems to be related to the high-barrier cutoff time of the dielectric signal, in accordance with the idea of a renewal of the relaxing entities after this critical time. In the five cases where one can fit accurately, the temperature dependence of the high-barrier cutoff follows the shoving model. The Johari-Goldstein peaks, seen in four of our seven cases, are describable in terms of gaussians in the barrier density, superimposed on the high-frequency tail of the a-process. Dielectric and shear measurements of the same substance find the same peak positions and widths of these gaussians, but in general a different weight. Ó 2007 Published by Elsevier B.V.

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Influence of Chain Length on theα−βBifurcation in Oligomeric Glass Formers

Cited by 30 publications

References 24 publications

Ideally glassy hydrogen-bonded networks

Ideally glassy hydrogen-bonded networks

Primary and secondary relaxation time dispersions in fragile supercooled liquids

Mechanical and dielectric relaxation spectra in seven highly viscous glass formers

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