Evidence of the Giant Barocaloric Effect in the PVA-Slime System by Molecular Dynamics Simulations

Advancements in the study of the barocaloric effect in
polymers
have opened promising applications in both the scientific and industrial
fields. Among these, elastic polymers based on poly(vinyl alcohol)
(PVA), such as slimes, have shown significant potential for solid-state
refrigeration and thermal battery applications due to their notable
pressure-induced thermal response, which occurs without an associated
structural phase transition. Thus, current research focuses on understanding
the mechanism behind this response to applied pressure with the aim
of optimizing its thermal performance. Therefore, we employed a molecular
dynamics simulation in order to explore the barocaloric effect in
the Slime system. We used pure PVA chains cross-linked by tetrahydroxyborate
ions to provide further details about our Slime system, promoting
a greater proximity between polymeric chains. Our results reveal that
these connections reduce the free volume in the Slime system compared
to pure PVA. This, combined with the applied simulated pressure, decreases
the mobility of the polymer chains, lowering their kinetic energy
while favoring potential energy. As a result, this contributes significantly
to the change in internal energy and, consequently, to the barocaloric
effect. Thus, our investigation shows a significant increase in entropy
from 56 JK–1 kg–1 for pure PVA
to 295 JK–1 kg–1 Slime system
and temperature change from 3 to 26 K at 300 MPa. These findings highlight
the importance of cross-linking between polymer chains, which enhances
the barocaloric effect in this system type, offering promising prospects
for practical applications.