Effect of chain length on fragility and thermodynamic scaling of the local segmental dynamics in poly(methylmethacrylate) (Articolo in rivista)

Type
Label
  • Effect of chain length on fragility and thermodynamic scaling of the local segmental dynamics in poly(methylmethacrylate) (Articolo in rivista) (literal)
Anno
  • 2007-01-01T00:00:00+01:00 (literal)
Alternative label
  • Casalini, R; Roland, CM; Capaccioli, S (2007)
    Effect of chain length on fragility and thermodynamic scaling of the local segmental dynamics in poly(methylmethacrylate)
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Casalini, R; Roland, CM; Capaccioli, S (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 126 (literal)
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • George Mason Univ, Dept Chem, Fairfax, VA 22030 USA; USN, Res Lab, Div Chem, Washington, DC 20375 USA; Univ Pisa, Dipartimento Fis, I-56127 Pisa, Italy; Univ Roma La Sapienza, CNR, INFM, CRS SOFT, I-00185 Rome, Italy (literal)
Titolo
  • Effect of chain length on fragility and thermodynamic scaling of the local segmental dynamics in poly(methylmethacrylate) (literal)
Abstract
  • Local segmental relaxation properties of poly(methylmethacrylate) (PMMA) of varying molecular weight are measured by dielectric spectroscopy and analyzed in combination with the equation of state obtained from PVT measurements. Significant variations of glass transition temperature and fragility with molecular weight are observed. In accord with the general properties of glass-forming materials, single molecular weight dependent scaling exponent gamma is sufficient to define the mean segmental relaxation time tau(alpha) and its distribution. This exponent can be connected to the Gruneisen parameter and related thermodynamic quantities, thus demonstrating the interrelationship between dynamics and thermodynamics in PMMA. Changes in the relaxation properties ('dynamic crossover') are observed as a function of both temperature and pressure, with tau(alpha) serving as the control parameter for the crossover. At longer tau(alpha) another change in the dynamics is apparent, associated with a decoupling of the local segmental process from ionic conductivity. (C) 2007 American Institute of Physics. (literal)
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