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Park et al. Soft Sci 2024;4:28 https://dx.doi.org/10.20517/ss.2024.22 Page 17 of 28

Figure 8. (A) The representative starting materials for preparing bio-based acrylate monomers. All starting materials can be obtained
from plants or trees; (B) The photocatalyst (blue) and co-initiators (green) for visible-light-driven polymerization. Using the
[27]
photocatalyst and co-initiators, the PIS mechanisms were proposed . Reproduced with permission. Copyright © 2024 Springer Nature;
[190]
(C) The concept and preparation method for debondable adhesives. The UV is a stimulus for adhesion control . The mechanism of
adhesion control was proved through MD simulation. Reproduced with permission. Copyright © 2024 Wiley VCH GmbH; (D) Thermo-
switchable adhesion is achieved by controlling the number of hydrogen bonding sites [196] . Reproduced with permission. Copyright ©
2024 Royal Society of Chemistry. PIS: Photoinitiating system; UV: ultraviolet.

monomers have introduced candidates such as stearyl acrylate, 2-octyl acrylate, and tetrahydrogeranyl
acrylate (THGA) [172-174] . Functional monomers, such as HBA and HEA, can be derived from CO or
2
biomass-derived ethylene glycol [158,175] .

Baek et al. have utilized tetrahydrogeranyl (meth)acrylates to create UV-curable adhesives with a T between
g
-20 and 30 °C, demonstrating the potential for plant-derived ingredients in flexible adhesives [171,172] . Park et
[91]
al. successfully prepared OCAs for foldable displays using fully terpene-based monomers . They selected
two terpenes: tetrahydrogeraniol from geranium and citronellol from rose oil. THGA, chosen as a low T
g
monomer, and vicinal diol-contained citronellol-based acrylate (CDA) were identified as suitable functional
monomers for flexible adhesives. The resulting OCAs exhibited low T and moduli across a wide
g
temperature range. Their foldability was confirmed through a 2 mmR dynamic folding test under various
conditions.