Authors: Guang-Zhong Yin, Xiao-Mei Yang, Alba Marta López, Javier García Molleja, Mei-Ting Wang, and De-Yi Wang Published in: Advanced Materials Technologies 2023, 2300658 Because of copyright transfer to Wiley-VCH only the first page is provided. Available at: https://doi.org/ 10.1002/admt.202300658

1. RESEARCH ARTICLE
www.advmattechnol.de
Graphene Functionalization of Polyrotaxane-Encapsulated
PEG-Based PCMs: Fabrication and Applications
Guang-Zhong Yin,* Xiao-Mei Yang, Alba Marta López, Javier García Molleja,
Mei-Ting Wang, and De-Yi Wang*
Phase change materials (PCMs) have received much attention regarding the
thermal regulation of electronic devices. However, the main limitations of
using organic PCMs are the low thermal conductivity and leakage during the
phase change process. This work aims to improve these limitations to
increase the thermal conductivity of the leakage-proof PCM formed by a
polyrotaxane that serves as a support material to encapsulate PEG. For this
purpose, different contents of graphene nanoplatelets (GNP) are blended. To
facilitate its postindustrial production and to meet ecological standards, the
synthesis of this PCM is simple and only using water as a solvent. The PCMs
can be thermally processed conveniently by a hot press. Furthermore, the
PCMs achieve high enthalpy values (132.9–142.9 J g−1
) due to the action of
GNPs as thermally conductive fillers. The PCMs exhibited an increase of
60–257% in thermal conductivity values with higher GNP content, and show
great shape stability and no leakage during phase change. These
improvements solve the main problems of organic PCMs, thus making
PLR-PEG-GNP-based materials a good candidate for use as thermal energy
storage materials in industrial applications as thermoregulators of solid-state
disks or realizing the “shaving peaks and filling valleys” effect for
thermoelectric generators.
1. Introduction
In recent decades, with the development of 5G technologies,
the thermoregulation of devices (e.g., laptops, smartphones, new
photovoltaic solar cells, cameras, transportation methods, etc.)
has become a problem since they consume increasing energy and
therefore generate more heat. The heat must be dissipated if we
G.-Z. Yin, D.-Y. Wang
Escuela Politécnica Superior
Universidad Francisco de Vitoria
Ctra. Pozuelo-Majadahonda Km 1.800, Pozuelo de Alarcón,
Madrid 28223, Spain
E-mail: amos.guangzhong@ufv.es;deyi.wang@imdea.org
G.-Z.Yin,X.-M.Yang,A.M.López,J.G.Molleja,D.-Y.Wang
IMDEA Materials Institute
C/EricKandel,2,Getafe,Madrid28906,Spain
M.-T.Wang
Shenyang University of Chemical Technology
Shenyang 110142,P.R.China
The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/admt.202300658
DOI: 10.1002/admt.202300658
want the useful life of the devices
to be long-lasting.[1]
The use of eco-
friendly materials and the develop-
ment of green energy management
materials have become necessary to
avoid environmental problems in the
future, such as pollution, depletion
of fossil resources, and increased
adverse effects of climate change.[2]
Among thermal energy storage ma-
terials, phase change materials (PCMs)
stand out. These materials can store en-
ergy in the form of latent heat and re-
lease the energy when there is a differ-
ence in environmental temperature. This
energy exchange occurs when there is
a phase change in the material itself.[3]
The exchange takes place in an en-
dothermic process; when the tempera-
ture of the surroundings increases, the
PCM absorbs energy in a fusion process
with the collapse of the solid crystalline
structure. When the temperature drops,
the crystallization process proceeds, and
the energy is released back to the
surroundings.[4]
The many applications
of PCMs include temperature-adaptable greenhouses,[5]
solar en-
ergy storage,[6]
cooling of electronic circuitry,[7]
building appli-
cations, the textile industry,[8]
and so on. The general problems
of PCMs regarding their commercialization and production are
low thermal conductivity, poor form stability, supercooling, and
PCM leakage during the phase change that causes failures in
the process.[9]
Another issue is the difficulty of obtaining flex-
ible PCMs because many of the prepared materials are rigid
or in powder form, and require further processing for practical
applications.[10]
In the fields of energy storage and electronic de-
vices, flexible, lightweight, and wearable devices are being devel-
oped, so the materials must have proper mechanical strength and
flexibility.
Among these organic PCMs, polyethylene glycol (PEG)-based
PCMs are widely used in the fields of solar energy harvesting,[11]
waste heat energy recovery,[12]
and electric energy storage.[13]
Among the properties of PEG are its large phase transformation
enthalpy, wide transition temperature, chemical stability, ease of
chemical modification, low vapor pressure, low cost, and noncor-
rosive nature.[14]
However, like all organic PCMs, they have the
same typical drawbacks, which are low thermal conductivity and
leakage during the phase change from solid to liquid.
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