Chain Dynamics on Crossing the Glass Transition: Nonequilibrium
Effects and Recovery of the Temperature Dependence of the Structural
Relaxation
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Abstract
In
this paper we report thermally stimulated depolarization current
results on the chain and segmental dynamics of two monodisperse polyisoprenes
accessing both dynamics at ultralow frequency range and exploring
the relationship between segmental and chain time scales when crossing
the glass transition. In this range, we have recorded experimental
evidence of nonequilibrium effects on the slowest chain mode dynamics.
The nonequilibrium effects seem to occur simultaneously for both chain
and α-relaxation. Moreover, detailed analysis strongly indicates
the recovery of an even T-dependence for the chain and α-relaxation
dynamics on crossing glass transition and in the glassy state. The
obtained results can be understood taking into account the different
temperature dependences of the length scales involved in the segmental
and chain relaxations