jz201681v_si_liveslides.zip (8.52 MB)
Anomalous Transformation of Vapor-Deposited Highly Stable Glasses of Toluene into Mixed Glassy States by Annealing Above Tg
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posted on 2015-12-16, 21:13 authored by A. Sepúlveda, E. Leon-Gutierrez, M. Gonzalez-Silveira, M. T. Clavaguera-Mora, J. Rodríguez-ViejoVapor-deposited glasses have recently emerged as a remarkable new
class of materials that can form much denser and stable glasses than
those obtained by cooling the liquid. These new amorphous materials
reach lower regions of the energy landscape and may impact important
technologies that use vapor-deposition. Here, we report on the formation
of a glass with two distinct glassy states obtained through the partial
annealing of highly stable vapor-deposited glassy films of toluene.
The resulting glass exhibits two clear heat capacity overshoots with
different onset and fictive temperatures. The transformation times
of the ultrastable glass are around 105 times slower than
the structural relaxation time (τα) of supercooled
liquid toluene. We show that the nature of the transformed glass depends
on the annealing temperature above Tg.
This finding suggests the formation of distinct supercooled liquids
at temperatures slightly above Tg during
the transformation of the highly stable glass. Our results are compatible
with the existence of polyamorphism in toluene.