Effect of temperature and volume on structural relaxation time: Interpretation in terms of decrease of configurational entropy

Prevosto, D.; Capaccioli, S.; Lucchesi, M.; Rolla, Pierangelo

doi:10.1016/j.jnoncrysol.2005.03.057

Cited by 8 publications

(4 citation statements)

References 35 publications

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“…The increase of pressure produces an increase of density of the system and an increase of the value of T g . The pressure dependence of the glass transition temperature, T g (P), has been tentatively interpreted in terms of entropy theories or simple fitted by some polynomials functions of the pressure [22][23][24][25][26][27]. In the case of our systems a second order polynomial is necessary to take into account the data in the full investigated pressure interval (Fig.…”

Section: Resultsmentioning

confidence: 99%

Relationship between structural and secondary relaxation in glass formers: Ratio between glass transition temperature and activation energy

Prevosto¹,

Capaccioli

Lucchesi

et al. 2008

Philosophical Magazine

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The relationship between structural and secondary dynamics is one of the most recently considered and possibly important issues of the dynamics in glass formers. One relation of interest is the ratio between the activation energy of the secondary relaxation and RT(g), where T(g) is the glass transition temperature, and R is the gas constant. This relationship has been recently rationalized by the Coupling Model in terms of many-body dynamics and was applied to the intermolecular Johari-Goldstein secondary relaxation. This article investigates the pressure dependence of this ratio and attempts to verify the validity of the Coupling Model predictions under such conditions

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Section: Resultsmentioning

confidence: 99%

Relationship between structural and secondary relaxation in glass formers: Ratio between glass transition temperature and activation energy

Prevosto¹,

Capaccioli

Lucchesi

et al. 2008

Philosophical Magazine

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“…R is 1.44±0.04 for DPVC and 1.35±0.15 for PPGE. The two functions g T (P) and g P (T) are expected to be different because isobaric changes include configurational, harmonic, and anharmonic terms of the potential energy, whereas isothermal ones, depending on the expansivity, have no contribution from the harmonic term of the potential energy [37,32]. If R was 1, the expression in Eq.…”

Section: Resultsmentioning

confidence: 99%

“…(2) to represent set of isobaric data in molecular and polymeric glass-formers can be found in ref. [30,32,33]. The present experimental study comprises an extensive study of dynamics under isothermal compression of two glass formers: diphenyl-vinylene carbonate and polyphenylglycidylether, already partially studied [34,35,31,36].…”

Section: Introductionmentioning

confidence: 99%

Relation between configurational entropy and relaxation dynamics of glass-forming systems under volume and temperature reduction

Capaccioli

Prevosto

Lucchesi

et al. 2009

Journal of Non-Crystalline Solids

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The structural relaxation dynamics of two molecular glass forming systems have been analyzed by means of dielectric spectroscopy, under cooling and compression conditions. The relation of the dynamic slowing down with the reduction of the configurational entropy, S C , as predicted by Adam and Gibbs (AG), was also investigated. As S C is not directly accessible by experiments, it was estimated, following a common procedure in literature, from the excess entropy S exc of the supercooled liquid with respect to the crystal, determined from calorimetric and expansivity measurements over the same T-P range of dynamics investigation. The AG relation, predicting linear dependence between the logarithmic of structural relaxation time and the product of temperature with configurational entropy, was successfully tested. Actually, a bilinear relation between S exc and S C was found, with different proportionality factors in isothermal and isobaric conditions. Using such results, we derived an equation for predicting the pressure dependence of the glass transition temperature, in good accordance with the experimental values in literature.

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“…Its merits 46 and drawbacks 47 are discussed in recent reviews of the glass transition. Here, we just point out that despite its heuristic nature and the inability to catch the rich and complex dynamics of glass-forming liquids ͑e.g., Johari-Goldstein secondary relaxations, 48 dynamical heterogeneity 49 ͒, the AG theory is able to properly describe the structural dynamics of a large number of glass-forming liquids, as shown by a large number of experiments 50 as well as simulations. 51 While in simulations the configurational entropy is directly provided by the energy landscape, an important approximation of the AG theory applied to experiments is the replacement of the experimentally inaccessible configurational entropy by the entropy of the liquid in excess to the crystal, which can be evaluated through standard calorimetric measurements.…”

Section: Application Of the Ag-sc Modelmentioning

confidence: 98%

Dielectric relaxation of polychlorinated biphenyl/toluene mixtures: Component dynamics

Cangialosi

Alegría

Colmenero

2008

The Journal of Chemical Physics

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The dynamics of homogenous polychlorinated biphenyl (PCB54)/toluene mixtures have been investigated by means of broadband dielectric spectroscopy. The mixture presents dynamical heterogeneity, alike miscible polymer blends, which is manifested with the presence of two relaxational processes. The relatively slow one has been attributed to the motion of PCB54 in the mixture, whereas the relatively fast one was related to the toluene dynamics in the mixture. These results have been interpreted according to the self-concentration concept, first introduced to describe the dynamics of miscible polymer blends, which relies on the limited size of the cooperative length scale in glass-forming liquids. The self-concentration concept has been incorporated in the Adam-Gibbs theory of the glass transition relating the characteristic relaxation time and the length scale for structural relaxation to the configurational entropy. This allowed the determination of the cooperative length scale of PCB54 and toluene both in mixture and alone through the fitting of a single parameter, namely, that connecting the cooperative length scale to the configurational entropy. This length scale resulted to be in the range of 1-2 nm for all systems. Finally, the out-of-equilibrium dynamics of toluene induced by the selective freezing in of PCB54 has been examined and its relation to the Johari-Goldstein relaxation of pure toluene was critically discussed.

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Effect of temperature and volume on structural relaxation time: Interpretation in terms of decrease of configurational entropy

Cited by 8 publications

References 35 publications

Relationship between structural and secondary relaxation in glass formers: Ratio between glass transition temperature and activation energy

Relationship between structural and secondary relaxation in glass formers: Ratio between glass transition temperature and activation energy

Relation between configurational entropy and relaxation dynamics of glass-forming systems under volume and temperature reduction

Dielectric relaxation of polychlorinated biphenyl/toluene mixtures: Component dynamics

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