Centro de Física de Materiales (CSIC-UPV/EHU), Paseo Manuel de Lardizabal 5, 20018 San Sebastián, Spain.
Phys Rev Lett. 2013 Aug 30;111(9):095701. doi: 10.1103/PhysRevLett.111.095701. Epub 2013 Aug 27.
We investigated the kinetics of enthalpy recovery of several glass-forming polymers at temperatures significantly below the glass transition temperature (Tg) and for aging times up to one year. We find a double-step recovery at relatively low aging temperatures for the longest investigated aging times. The enthalpy recovered after the two-step decay approximately equals that expected by extrapolation from the melt. The two-step enthalpy recovery indicates the presence of two time scales for glass equilibration. The equilibration time of the first recovery step exhibits relatively weak temperature dependence, whereas that of the second step possesses pronounced temperature dependence, compatible with the Vogel-Fulcher-Tammann behavior. These results, while leaving open the question of the divergence of the relaxation time and that of a thermodynamic singularity at a finite temperature, reveal a complex scenario of glassy dynamics.
我们研究了几种玻璃态聚合物在显著低于玻璃化转变温度（Tg）的温度下和长达一年的老化时间内的焓弛豫动力学。我们发现，在最长的老化时间下，在相对较低的老化温度下存在双步恢复。两步衰减后恢复的焓大致等于从熔体外推得到的预期焓。两步焓恢复表明玻璃平衡存在两个时间尺度。第一步恢复的平衡时间表现出相对较弱的温度依赖性，而第二步的平衡时间具有明显的温度依赖性，与 Vogel-Fulcher-Tammann 行为一致。这些结果虽然没有解决松弛时间的发散性和有限温度下热力学奇点的问题，但揭示了玻璃动力学的复杂情况。
