Versatile and Tunable Poly(Ethylene Glycol)-Based Hydrogels Crosslinked through the Ugi Reaction

This work was supported by the Applied Molecular Bioscience Unit – UCIBIO (UIDB/04378/2020); projects PTDC/BII‐BIO/28878/2017 (LISBOA‐01‐0145‐FEDER‐028878); PTDC/SAL‐SER/30388/2017 (POCI‐01‐0145‐FEDER‐030388); Ph.D. fellowships to CF (PD/BD/105871/2014); CE (SFRH/BD/113112/2015). The authors are grateful to Prof. Ana Rita C. Duarte from Associate Laboratory for Green Chemistry – LAQV, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa for facilitating the rheology studies.The four-component Ugi condensation reaction has been investigated to assemble chemically crosslinked hydrogels using multivalent star-shaped poly(ethylene glycol) components. The resulting biocompatible hydrogels are highly versatile in composition and function. It is shown that acid, aldehyde, and cyanide components can be varied yielding materials with precise structure and tunable stiffness. Additionally, the resulting hydrogels were proven extremely robust to consecutive drying-swelling cycles. This property was explored to develop a reversible humidity colorimetric sensor gel. Overall, this work demonstrates the application of the four-component Ugi reaction as a powerful tool to quickly generate crosslinked gels with precise control in chemical composition.authorsversionpublishe