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New strategy for crosslinking acrylic polymers without conventional crosslinkers
A South Korean research team has shown that monofunctional acrylates can also be crosslinked without the addition of conventional crosslinkers – through the targeted activation of C-H bonds. The results offer new approaches for the development of robust polymer networks.
Acrylate-based polymers are in demand in numerous applications – for example in adhesives and sealants, coatings or 3D printing resins – thanks to their high chemical resistance and mechanical resilience. Until now, if you wanted a cross-linked structure, you had to use multifunctional monomers or chemical post-treatments. A team led by Min Sang Kwon from Yonsei University in Seoul has now shown that there is another way: certain monofunctional acrylates can also form cross-linked structures – simply through targeted hydrogen transfers during polymerisation.
At the centre of this is the so-called hydrogen atom transfer (HAT) between side chains of the monomers and reactive radicals. In a systematic study, the researchers tested ten commercially available acrylate monomers with three different photoinitiator systems. Particularly pronounced cross-linking effects were observed with 2-hydroxyethyl acrylate (HEA), 4-hydroxybutyl acrylate (HBA) and MEEEA.
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Thermodynamically favourable reactions enable stable networks
Using quantum chemical calculations, the authors were able to prove that particularly stable hydrogen transfers take place in these three acrylates. The structure of the side chain plays a decisive role here: in HEA and HBA, hydrogen bonds promote the reaction, while in MEEEA a favourable conformation of the ether chains contributes to stabilisation. The result is cross-linked polymer networks – without any conventional cross-linking agents.
This new perspective on monofunctional acrylates not only opens up new synthesis routes for cross-linked plastics, but could also improve the use of resources and reactivity in many industrial applications.
Source: Polymer Chemistry, Issue 21, 2025
