From Strong to Fragile Glass Formers: Secondary Relaxation in Polyalcohols

Döß, A.; Paluch, Marian; Sillescu, H.; Hinze, G.

doi:10.1103/physrevlett.88.095701

Cited by 201 publications

(98 citation statements)

References 37 publications

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“…By varying the chain length n ¼ 1, 2, 3 and E7 and in a polymer (nE69), they found in dielectric spectra for nr3 b-relaxations manifest as excess wings, whereas a broad hump for nE7, and a distinct peak for the polymer (nE69). A similar result was observed in polyalcohols by Dö et al 47 These findings suggest that shortening the chain structures could suppress b-relaxations (other possible reasons are also noted in Ngai et al 48 ). In Pd-Ni-Cu-P MG systems, several studies from the electronic and atomic structural perspectives have uncovered that with the increasing of Cu contents, the MGs acquire deeper binding energy and develop more covalent-like bonding, and especially chain-like Pd-P-Pd/Cu atomic configuration was suggested [49][50][51] .…”

Section: Discussionsupporting

confidence: 75%

Chemical influence on β-relaxations and the formation of molecule-like metallic glasses

et al. 2013

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Secondary (also known as Johari-Goldstein or b-) relaxations are an intrinsic feature of supercooled liquids and glasses. They are important in many respects but the underlying mechanisms are not well understood. A long-standing puzzle is why some glasses show b-relaxations as pronounced peaks, whereas others as unobvious excess wings. Here we demonstrate that these different behaviours are related to the fluctuations of chemical interactions by using prototypical systems of metallic glasses. A general rule is summarized: pronounced b-relaxations are associated with systems where all the atomic pairs have large similar negative values of enthalpy of mixing, whereas positive or significant fluctuations in enthalpy of mixing suppress b-relaxations. The emerging physical picture is that strong and comparable interactions among all the constituting atoms maintain string-like atomic configurations for the excitations of b-events and can be considered as the formation of molecule-like metallic glasses.

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Section: Discussionsupporting

confidence: 75%

Chemical influence on β-relaxations and the formation of molecule-like metallic glasses

et al. 2013

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“…4. As reported in previous works [7][8][9], all three parameters for sugar alcohols show a strong dependence on both N C and N OH (filled symbols). However, since N C = N OH for sugar alcohols, the figures are identical and it is impossible to separate the effects of the two parameters.…”

Section: Resultsmentioning

confidence: 48%

“…1). It has been reported that sugar alcohols exhibit systematic increases in fragility and T g with increasing chain length [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…The temperature dependence of the relaxation time in the supercooled state is often characterized by fragility [3] and T g , and the link between these quantities and chemical structure has been discussed for a long time [4][5][6][7][8][9]. In polymeric materials, Kunal et al have found the qualitative relation between fragility and T g and stiffness of chain: Fragility is dominated by relative flexibility of the side group compared to flexibility of the backbone, whereas T g depends primarily on the backbone flexibility and the side group bulkiness [5].…”

Section: Introductionmentioning

confidence: 99%

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Systematic study of the glass transition in polyhydric alcohols

Nakanishi

Nozaki

2011

Phys. Rev. E

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We have investigated the glass transitions of trihydric alcohols using broadband dielectric spectroscopy, and compare the results with those previously reported for sugar alcohols. Although a systematic glass transition feature related to molecular size has been reported for sugar alcohols, the essential factor governing this feature is still unclear because the number of carbon atoms (N C ) and the number of OH groups (N OH ) per molecule are identical in sugar alcohols. By examining trihydric alcohols (N C = N OH ), we conclude that N OH is dominant for the characteristics of the slow dynamics, such as fragility and glass transition temperature. This result suggests that the topological structure of the hydrogen-bonding network (coordination number) plays an important role in the glass transition of polyhydric alcohols. Furthermore, the orientational correlation factor evaluated using the Kirkwood-Fröhlich theory reveals a similarity in hydrogen bond formation among a variety of polyhydric alcohols. Based on these two experimental results, we discuss a possible physical picture of the glass transition of polyhydric alcohols.

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“…Among them, the emergence of secondary relaxations, especially of the so-called Johari-Goldstein (JG) β-relaxation, has attracted the attention of the large scientific glass community. [4][5][6][7][8][9][10][11][12][13] This JG process is associated with local, noncooperative motions of the molecular unit as a whole, thus different from secondary relaxations -due to intramolecular degrees of freedom (e.g., side-chain motions in polymers) and indeed it was found even in single rigid molecules. 4,12 Despite the large quantity of available experimental and simulations studies, the nature of the local JG relaxation is still far from being understood.…”

Section: Introductionmentioning

confidence: 99%

Emergence of glassy-like dynamics in an orientationally ordered phase

et al. 2012

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The dynamics of a simple rigid pseudoglobular molecule (2-adamantanone) has been studied by means of dielectric spectroscopy and examined under the constraints imposed by the space group of the crystal structure determined by x-ray powder diffraction. The low-temperature monoclinic structure of 2-adamantanone, with one molecule per asymmetric unit (Z = 1), displays a statistical intrinsic disorder, concerning the site occupancy of the oxygen atom along three different sites. Such a physically identifiable disorder gives rise to large-angle molecular rotations which inherently lead to time-average fluctuations of the molecular dipole, thus contributing to the dielectric susceptibility. The dielectric spectra for the low-temperature "ordered" phase displays a universal feature of glassy-like materials, i.e., coexistence of α-and β-relaxation processes. The former is clearly identified with the strongly restricted reorientational motions within the long-range "ordered" crystalline lattice. The latter, never observed before in fully translationally and highly orientationally ordered phases, displays all the properties of an original Johari-Goldstein β-relaxation, in spite of the strong character of this glass-like phase. These findings can be explained according to the coupling model, applied to such "ordered" phases.

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From Strong to Fragile Glass Formers: Secondary Relaxation in Polyalcohols

Cited by 201 publications

References 37 publications

Chemical influence on β-relaxations and the formation of molecule-like metallic glasses

Chemical influence on β-relaxations and the formation of molecule-like metallic glasses

Systematic study of the glass transition in polyhydric alcohols

Emergence of glassy-like dynamics in an orientationally ordered phase

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