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Keywords:

  • amorphous;
  • blends;
  • computer modeling;
  • dielectric properties;
  • glass;
  • melt;
  • molecular modeling;
  • polybutadiene;
  • relaxation

Abstract

Amorphous polymers exhibit a primary (glass, or α-) relaxation process and a low-temperature relaxation process associated with polymer backbone motion usually referred to as the β-relaxation process. The latter process can be observed below the glass transition temperature of the polymer and usually merges with the α-relaxation process at temperatures somewhat above the glass transition temperature. While it is widely held that both the α-relaxation and β-relaxation processes are engendered by localized (segmental) motions of the polymer backbone, and that there is a strong mechanistic connection between them, the molecular mechanisms of the α-relaxation and β-relaxation processes in amorphous polymers are not well understood. Recently, atomistic molecular dynamics simulations of melts and blends of 1,4-polybutadiene have provided insight into the relationship between the α- and β-relaxation processes in glass-forming polymers and an improved understanding of their molecular origins. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 627–643, 2007