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Fragility and basic process energies in vitrifying systems.

Martinez-Garcia JC, Rzoska SJ, Drozd-Rzoska A, Starzonek S, Mauro JC - Sci Rep (2015)

Bottom Line: Finding the fundamental meaning of fragility is the 'condicio sine qua' for reaching the long expected conceptual breakthrough in this domain.The limited adequacy of broadly used so far semi-empirical relationships between fragility and the activation energy is shown.Results presented remain valid for an arbitrary complex system and collective phenomena if their dynamics is described by the general super-Arrhenius relation.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, Berne CH-3012, Switzerland.

ABSTRACT
The concept of 'fragility' constitutes a central point of the glass transition science serving as the 'universal' metric linking previtreous dynamics of qualitatively distinct systems. Finding the fundamental meaning of fragility is the 'condicio sine qua' for reaching the long expected conceptual breakthrough in this domain. This report shows that fragility is determined by the ratio between two fundamental process energies, viz. the activation enthalpy and activation energy. The reasoning, avoiding any underlying physical model, is supported by the experimental evidence ranging from low molecular weight liquids and polymers to plastic crystals and liquid crystals. All these lead to the new general scaling plot for dynamics of arbitrary glass former. The limited adequacy of broadly used so far semi-empirical relationships between fragility and the activation energy is shown. Results presented remain valid for an arbitrary complex system and collective phenomena if their dynamics is described by the general super-Arrhenius relation.

No MeSH data available.


Related in: MedlinePlus

Degree of nonlinearity at “Arrhenius-type” plotted as ln(ΔEa(T)) vs. Tg/T for representative glass formers.The figure indicates the lack of correlation between increasing curvature, coupled to fragility, and the value of ΔEa(Tg). The clear disagreement with eq. (3) is stressed by the inset: the blue, dashed line is related to eq. (3) and the solid, black line is based on the MFR.
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f3: Degree of nonlinearity at “Arrhenius-type” plotted as ln(ΔEa(T)) vs. Tg/T for representative glass formers.The figure indicates the lack of correlation between increasing curvature, coupled to fragility, and the value of ΔEa(Tg). The clear disagreement with eq. (3) is stressed by the inset: the blue, dashed line is related to eq. (3) and the solid, black line is based on the MFR.

Mentions: However, the most fundamental eqs. (1) and (2) directly indicate that the increasing SA behavior is associated with the rising nonlinearity at the “Arrhenius-type” plot ln(ΔEa(T)) vs. 1/T. Fig. 3 presents such plot, revealing the lack of a correlation between the increasing curvature of the apparent activation energy, coupled to rising fragility m, and the value of ΔE(Tg). This is in clear disagreement with mentioned above basic prediction (eq. (3)). Moreover, the simply linearization based on eqs. (1) and (2) yields , i.e. the linear function with the intercept at cte = ln[R ln 10] > 0 and the directional factor b = 1. Such prediction is anti-correlated with experimental data, as shown in the inset in Fig. 3 via the dashed line. Consequently, the used so far basic link between the activation energy and fragility ΔEa(Tg) = RTgmln10, i.e. (eq. (3))2141620212223242526, is inherently invalid.


Fragility and basic process energies in vitrifying systems.

Martinez-Garcia JC, Rzoska SJ, Drozd-Rzoska A, Starzonek S, Mauro JC - Sci Rep (2015)

Degree of nonlinearity at “Arrhenius-type” plotted as ln(ΔEa(T)) vs. Tg/T for representative glass formers.The figure indicates the lack of correlation between increasing curvature, coupled to fragility, and the value of ΔEa(Tg). The clear disagreement with eq. (3) is stressed by the inset: the blue, dashed line is related to eq. (3) and the solid, black line is based on the MFR.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4321169&req=5

f3: Degree of nonlinearity at “Arrhenius-type” plotted as ln(ΔEa(T)) vs. Tg/T for representative glass formers.The figure indicates the lack of correlation between increasing curvature, coupled to fragility, and the value of ΔEa(Tg). The clear disagreement with eq. (3) is stressed by the inset: the blue, dashed line is related to eq. (3) and the solid, black line is based on the MFR.
Mentions: However, the most fundamental eqs. (1) and (2) directly indicate that the increasing SA behavior is associated with the rising nonlinearity at the “Arrhenius-type” plot ln(ΔEa(T)) vs. 1/T. Fig. 3 presents such plot, revealing the lack of a correlation between the increasing curvature of the apparent activation energy, coupled to rising fragility m, and the value of ΔE(Tg). This is in clear disagreement with mentioned above basic prediction (eq. (3)). Moreover, the simply linearization based on eqs. (1) and (2) yields , i.e. the linear function with the intercept at cte = ln[R ln 10] > 0 and the directional factor b = 1. Such prediction is anti-correlated with experimental data, as shown in the inset in Fig. 3 via the dashed line. Consequently, the used so far basic link between the activation energy and fragility ΔEa(Tg) = RTgmln10, i.e. (eq. (3))2141620212223242526, is inherently invalid.

Bottom Line: Finding the fundamental meaning of fragility is the 'condicio sine qua' for reaching the long expected conceptual breakthrough in this domain.The limited adequacy of broadly used so far semi-empirical relationships between fragility and the activation energy is shown.Results presented remain valid for an arbitrary complex system and collective phenomena if their dynamics is described by the general super-Arrhenius relation.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, Berne CH-3012, Switzerland.

ABSTRACT
The concept of 'fragility' constitutes a central point of the glass transition science serving as the 'universal' metric linking previtreous dynamics of qualitatively distinct systems. Finding the fundamental meaning of fragility is the 'condicio sine qua' for reaching the long expected conceptual breakthrough in this domain. This report shows that fragility is determined by the ratio between two fundamental process energies, viz. the activation enthalpy and activation energy. The reasoning, avoiding any underlying physical model, is supported by the experimental evidence ranging from low molecular weight liquids and polymers to plastic crystals and liquid crystals. All these lead to the new general scaling plot for dynamics of arbitrary glass former. The limited adequacy of broadly used so far semi-empirical relationships between fragility and the activation energy is shown. Results presented remain valid for an arbitrary complex system and collective phenomena if their dynamics is described by the general super-Arrhenius relation.

No MeSH data available.


Related in: MedlinePlus