A Multicross-Linked Eutectogel with Mechanical Enhancement and Diverse Engineered Functionality Prepared Using Amino Acid-Based Deep Eutectic Solvents

Eutectogels are emerging green materials with various appealing properties and functionalities. However, the present eutectogels suffer from a weak mechanical performance, which restricts their practical applications. Amino acid-based natural deep eutectic solvents (AANDESs), owing to their diversity, accessibility, and environmental friendliness, offer new opportunities for flexible eutectogel design and performance enhancement. Herein, a proline-citric acid (ProCA) DES has been discovered that demonstrates the desired compatibility with poly(acrylic acid) (PAA), and PAA-ProCA eutectogels were successfully prepared through facile photopolymerization. The resultant eutectogels exhibited tunable mechanical properties upon composition variations. PAA-ProCA eutectogels of multinetworks exhibited dynamic structure change and combined energy adsorption mechanisms at multilength scales, giving rise to the synergistic enhancement in mechanical strength (43.14 MPa) and toughness (196.4 MJ/m³) without compromising deformability. Notably, the reversible stress-whitening was observed during eutectogel stretching and releasing, which not only indicated stress conditions in real time but also manifested the repeatable energy dissipation capability to improve fatigue resistance under heavy loading. Furthermore, the eutectogels showed versatile functionalities, including adjustable self-adhesion to diverse substrates, effective impact protection, UV absorption, motion sensing, and signaling. This work provides a new strategy to design and develop multifunctional eutectogels with exceptional mechanical properties and adaptivity.