Anomalous Behavior in Blends of a Polychlorinated Biphenyl with Polystyrene Oligomer Investigated by Mechanical and Dielectric Spectroscopy

Casalini, R.; Santangelo, P. G.; Roland, C. M.

doi:10.1021/jp021579l

Cited by 13 publications

(14 citation statements)

References 23 publications

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“…[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] At each temperature, and τ were determined from the location and width of the dielectric loss peak, respectively. Prompted by our recent work on the glass transition, [24][25][26] we have plotted log(τ) as a function of 1/ .…”

Section: Experimental Results For the Relationship Between And τmentioning

confidence: 99%

Relationship between the Nonexponentiality of Relaxation and Relaxation Time in the Problem of Glass Transition

2008

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By analyzing the experimental data for various glass-forming liquids and polymers, we find that the nonexponentiality, , and the relaxation time, τ, are commonly related: log(τ) is an approximately linear function of 1/ , followed in most cases by a crossover to a higher linear slope. We rationalize this relationship in the recently developed elastic approach to the glass transition. The key to the observed common relationship between and τ is that the two quantities are governed by the same parameter, the liquid elasticity length, d el . The increase of d el on lowering temperature increases τ and decreases , resulting in the observed common relationship between and τ. In this picture, we also discuss the crossovers of and τ at low temperature.

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Section: Experimental Results For the Relationship Between And τmentioning

confidence: 99%

Relationship between the Nonexponentiality of Relaxation and Relaxation Time in the Problem of Glass Transition

2008

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“…Dielectric relaxation times are known to exhibit a crossover at T B from one to a second VFT dependence, with re-sults published for, among various glass formers, phenolphthalein-dimethyl-ether ͑PDE͒, phenyl salicylate ͑salol͒, propylene carbonate ͑PC͒, ortho-terphenyl ͑OTP͒, 15,29 and 54% chlorinated biphenyl ͑PCB54͒. 30 We now reanalyze the same data, but for each case employ only a single VFT dependence to fit the experimental ␣ and the calculated 0 . In Refs.…”

Section: Resultsmentioning

confidence: 99%

Connection between the high-frequency crossover of the temperature dependence of the relaxation time and the change of intermolecular coupling in glass-forming liquids

2003

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In this paper, an interpretation of the high-frequency crossover, observed for glass formers at temperature far above the glass transition, is described in terms of the large change in the heterogeneous character of the dynamics. For five prototypical glass formers, dielectric relaxation data spanning many decades were analyzed. Unlike the temperature behavior of the dielectric ͑structural͒ relaxation times ␣ , which deviate from a Vogel-Fulcher-Tamman ͑VFT͒ relationship, the non-cooperative relaxation times, 0 , calculated using the coupling model, are well described by a single VFT over the entire temperature range. Thus, the dynamic crossover evident in ␣ and other relaxation properties is suppressed for 0 . This result suggests that the crossover is a direct consequence of the strong increase in intermolecular cooperativity ͑many-body effects͒, which also causes the dynamics of the system to become heterogeneous and non-exponential. This interpretation is consistent with recent findings concerning the pressure and temperature dependence of the dynamic crossover. Finally, a possible relationship of 0 to thermodynamic properties of the glass former is discussed.

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“…However, the addition of lower T g polybutadiene decreases the PCB relaxation time 31,32,33,34 . This interesting anomaly was subsequently seen in PCB/polystyrene mixtures 35,36 , and more generally in both polymer solutions 37,38 and blends 39 .…”

Section: Introductionmentioning

confidence: 86%

Effect of chemical structure on the isobaric and isochoric fragility in polychlorinated biphenyls

Roland

Casalini

2005

The Journal of Chemical Physics

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Pressure-volume-temperature data, along with dielectric relaxation measurements, are reported for a series of polychlorinated biphenyls (PCB), differing in the number of chlorine atoms on their phenyl rings. Analysis of the results reveals that with increasing chlorine content, the relaxation times of the PCB become governed to a greater degree by density rho relative to the effect of temperature T. This result is consistent with the respective magnitudes of the scaling exponent gamma yielding superpositioning of the relaxation times measured at various temperatures and pressures, when plotted versus rho(gamma)/T. While at constant (atmospheric) pressure, fragilities for the various PCB are equivalent, the fragility at constant volume varies inversely with chlorine content. Evidently, the presence of bulkier chlorine atoms on the phenyl rings magnifies the effect which the density has on the relaxation dynamics.

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Anomalous Behavior in Blends of a Polychlorinated Biphenyl with Polystyrene Oligomer Investigated by Mechanical and Dielectric Spectroscopy

Cited by 13 publications

References 23 publications

Relationship between the Nonexponentiality of Relaxation and Relaxation Time in the Problem of Glass Transition

Relationship between the Nonexponentiality of Relaxation and Relaxation Time in the Problem of Glass Transition

Connection between the high-frequency crossover of the temperature dependence of the relaxation time and the change of intermolecular coupling in glass-forming liquids

Effect of chemical structure on the isobaric and isochoric fragility in polychlorinated biphenyls

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