“Post-functionalization of polyethers by photoinduced C–H amidation via polar-radical relay” by Seung Beom Baek, Youngho Kim, Wongyu Lee, Sangwon Seo, Dongwook Kim, Myungeun Seo, and Sukbok Chang was published in Nature Communications. This work was a collaborative research with Chang’s Lab at KAIST. The article is available at the following link:

https://www.nature.com/articles/s41467-025-63254-z#article-info

Polyethers such as polyethylene glycol (PEG) are widely used in biomedicine and energy storage thanks to their excellent solubility, biocompatibility, and ion-conducting properties. While end-group modification is well established, selective post-polymerization modification (PPM) of internal C–H bonds has remained a long-standing challenge, since such reactions often result in degradation or uncontrolled cross-linking.

In this study, we developed a metal-free, photoinduced α-C–H amidation reaction that enables direct incorporation of amino groups into polyether backbones. Operating through a polar-radical relay pathway under visible light, the method achieves remarkable regioselectivity at the ethereal α-position while preserving polymer integrity, thereby establishing a new platform for polyether PPM.

This breakthrough led to the synthesis of α-amino polyethers, a class of materials previously inaccessible by conventional polymerization or post-functionalization strategies. These newly functionalized polymers exhibit distinct thermal and physical properties—for instance, amidation changes PEG crystallinity, enabling precise control of glass transition and melting behavior. Importantly, the PPM strategy also proved effective for block copolymers and cross-linked polymer networks, underscoring its broad applicability.

Overall, this work demonstrates how visible-light-driven C–H functionalization can serve as a versatile PPM approach for polymer upcycling and advanced materials design, with promising applications in energy, biotechnology, and sustainable polymer science.

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