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Yan et al. Soft Sci. 2025, 5, 8 https://dx.doi.org/10.20517/ss.2024.66 Page 15 of 34

Figure 5. Flexible PCCs based on porous scaffolds. (A) Preparation, mechanical properties, thermal storage capacity, photothermal
conversion, and photothermoelectric conversion properties of PDMS/BN/PPy/PW PCCs. Reproduced with permission from ref [126] .
Copyright 2024, Elsevier; (B) Preparation, mechanical properties, energy storage density, thermal conductivity, and photothermal
conversion of CPC@PEG PCCs. Reproduced with permission from ref [127] . Copyright 2020, Elsevier; (C) Preparation of composite
PCMs, thermal storage capacity, mechanical properties, and thermal therapy mechanisms. Reproduced with permission from ref [128] .
Copyright 2020, Elsevier. PCCs: Phase change composites; PDMS: polydimethylsiloxane; BN: boron nitride; PPy: polypyrrole; PW:
paraffin wax; CPC: CS/PVA/CNTs; PEG: polyethylene glycol; PCMs: phase change materials.

impregnation of PEG into the sponges to prepare PCCs with flexible layered frameworks [Figure 5C] .
[128]
The developed CNT sponge-based composite PCM exhibited high thermal energy storage capacity and
excellent thermal stability even after 100 melt-freeze cycles, and the functional mask designed with it
comprises an inner thermal conditioning layer (CNT sponge-based PCM layer) and an outer air-purifying
layer (pristine CNT sponge layer) for thermal therapy of allergic rhinitis. By continually releasing heat, the
inner CNT sponge-based PCMs dominate thermal therapy, whereas the outer air purification layer only
serves as a supplementary function by trapping particulates and purifying the air that is inhaled. The
cleansed air amplifies the thermotherapy effect, and the original layered CNT sponge layer works well as a
PM trap. The PEG-based mask can supply sufficient thermal energy to warm the airflow into the nasal
cavity and sustain the temperature plateau at 43.5 °C for 33 min, according to the heat release performance.
The associated medical results also demonstrate that the thermotherapy mask can greatly reduce the nasal
mucosa’s inflammatory damage, which certainly broadens the way for flexible PCCs in the medical field.

Based on polymer encapsulation
The use of polymer encapsulation is also a major means of solving the solid-liquid PCM leakage problem by
dispersing the micromolecular PCM into a macromolecular polymer matrix to form a shape-stable mixture,
with the crosslinked polymer matrix acting as a support material to prevent leakage of the molten
PCM [129,130] . Commonly used polymers include polyethylene, PU, block copolymers olefin block copolymers
(OBC), etc. ; the polymer matrix also helps improve the flexibility of the composite material,
[131]
supplemented with various thermally conductive fillers to prepare phase change thermal management
materials with ultra flexibility has broad application prospects. Wu et al. used a dual network of polymers
and graphite nanosheets as a functional matrix for PCMs to prepare composite PCMs with high thermal
conductivity, flexibility, and shape stabilization, in which PW was used as the PCM, and the
macromolecular olefinic OBC formed a crosslinked polymer network to encapsulate the molten PCM and
give the composite film was flexible, and expanded graphite (EG) with a long chain structure and high
thermal conductivity formed a permeable network of aligned interconnected graphite nanosheets to confer
high thermal conductivity properties to the PCC [Figure 6A] . The prepared flexible phase change film
[132]
exhibits high energy storage density (169.5 J/g) and excellent thermal conductivity (radial thermal
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conductivity of up to 4.2-32.80 W·m ·K ), and also good flexibility and mechanical strength under bending
and stretching, which expands its scope of application. Furthermore, the flexible film was used for thermal
management of lithium batteries, reducing their operating temperature by more than 12 °C and
demonstrating efficient and reliable performance. Also using a combination of polymers and conductive
nanosheets to immobilize PCMs, Wu et al. synthesized hybrid semi-interpenetrating composites
(PEG@PU) by infiltrating PEG into the crosslinking network of PU; they then assembled them by pressure-
induced assembly with reticulated graphite nanoparticles (RGNP) doping to prepare a highly conductive
[133]
and thermally flexible PCCs (PEG@PU-RGNP) [Figure 6B] . The hybrid network allowed the PCCs to
demonstrate excellent properties, including superior mechanical strength, shape stability, and thermal
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storage. In addition, the PCCs exhibit a thermal conductivity of up to 27.00 W·m ·K and an electrical
conductivity of 51.0 S/cm, which is superior to that of the latest PEG-based PCCs, and the flexible PCC can
be applied for efficient battery thermal management to meet the main requirements for cold environment