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RESEARCH ARTICLE
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Integrating MXene Film With Recyclable Polyethylene
Glycol-co-Polyphosphazene Copolymer as Solid–Solid Phase
Change Material for Versatile Applications
Yongkang Wang, Husitu Lin, Meijie Huang, Shiliang Zhou, Yang Zhou, Xinfang Zhang,*
Huan Liu,* Zhanpeng Wu,* and Xiaodong Wang*
Phase-change materials (PCMs) stand a pivotal advancement in thermal
energy storage and management due to their reversible phase transitions to
store and release an abundance of heat energy. However, conventional solid–
liquid PCMs suffer from fluidity and leakage in their molten state, limiting their
applications at advanced levels. Herein, a novel Zn2+-crosslinked polyethylene
glycol-co-polyphosphazene copolymer (PCEPN-Zn) as a solid–solid PCM
through dynamic metal-ligand coordination is first designed and synthesized.
The as-synthesized PCEPN-Zn is further integrated with an MXene film
to construct a double-layered phase-change composite through layer-by layer
adhesion. Owing to the introduction of MXene film with low emissivity, good
light absorptivity, and nonflammability, the resultant phase-change composite
not only presents a high latent-heat capacity, good thermal stability, high
thermal reliability, and excellent shape stability, but also exhibits a superior
self-healing ability, good recyclability, high adhesivity, and good flame-retardant
performance. It can be easily adhered to on most objects for various
application scenarios. With a combination of the excellent functions derived
from PCEPN-Zn and MXene film, the developed phase-change composite
exhibits broad prospects for versatile applications in the thermal management
of CPUs and Li-ion batteries, thermal infrared stealth of high-temperature
objects, heat therapy in the clinic, and fire-safety for various scenarios.
1. Introduction
Solid–liquid phase-change materials (PCMs), with an ability to
store and release latent heat through reversible phase transitions,
have stood a pivotal advancement in thermal energy utilization.[1]
They can reduce the demand of external energy and fill the en-
ergy gap between time and space, which is highly required in
diverse fields such as infrared stealth technologies,[2]thermal
Y. Wang, H. Lin, M. Huang, S. Zhou, Y. Zhou, X. Zhang, H. Liu, Z. Wu,
X. Wang
State Key Laboratory of Organic–Inorganic Composites
Beijing University of Chemical Technology
Beijing 100029, China
E-mail: zhangxf@mail.buct.edu.cn;liu.huan@mail.buct.edu.cn;
wuzp@mail.buct.edu.cn;wangxd@mail.buct.edu.cn
The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/smll.202407626
DOI: 10.1002/smll.202407626
management of electronics and batteries,[3]
energy-saving intelligent buildings,[1d]and
solar photothermal energy storage.[4]The
solid–liquid PCMs normally suffer from
leakage and volume expansion during the
reversible phase transitions, limiting their
utilization at advanced levels.[5]In this
regard, form-stable PCMs have been de-
veloped by physical adsorption,[6]chem-
ical microencapsulation,[7]and chemical
crosslinking techniques[8]to prevent the
leakage of solid–liquid PCMs and make
them reliable for thermal energy utilization.
However, the physically adsorbed solid–
liquid PCMs still have to suffer from a
leakage risk after repeated phase transi-
tion cycles. The chemically microencapsu-
lated solid–liquid PCMs are limited due to
their complex synthetic process. In addi-
tion, the adsorbed and microencapsulated
solid–liquid PCMs are not suitable for di-
rect use as bulk materials because of their
poor mechanical properties.[9]
The introduction of a crosslinked poly-
mer network into solid–liquid PCMs to
form solid–solid PCMs can offer an effec-
tive solution for the obviation of leakage
issues in solid–solid PCMs toward their thermal energy
utilization.[10]The solid–solid PCMs maintain their solid
state during the thermal energy storage/release process owing
to a solid-state switching transition from a crystalline solid to
the semicrystalline or amorphous one. Such a crosslinking
approach endows solid–liquid PCMs with tunable mechan-
ical strength and flexibility, better solvent resistance, and
enhanced chemical stability.[11]Therefore, solid–solid PCMs
can directly be employed as bulk materials in desired shapes.
Although chemical crosslinking techniques can pose benefits
for solid–liquid PCMs, such a crosslinking structure still brings
a limitation in practical application. Most of solid–solid PCMs
are crosslinked by irreversible covalent linkages, which makes
them hardly reprocessed, healed, and degraded. As a result,
solid–liquid PCMs are bound to experience a recycling problem.
This potentially results in environmental pollution, resource
concern, and service life reduction, thus hindering the compre-
hensive and sustainable development of solid–solid PCMs.[12]
To address such a challenge, researchers introduced various
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