Hydrophilicity‐Hydrophobicity Transformation, Thermoresponsive Morphomechanics, and Crack Multifurcation Revealed by AIEgens in Mechanically Strong Hydrogels

Yubing B Hu (1) , Lucile Barbier (2) , Zhao Li (1) , Xiaofan F Ji (1) , Heiva Le Blay (2) , Dominique Hourdet (2) , Nicolas Sanson (3) , Jacky W y Lam (1) , Alba Marcellan (2) , Ben Zhong Tang

1 Department of Chemistry The Hong Kong University of Science and Technology
2 SIMM - Sciences et Ingénierie de la Matière Molle (UMR 7615)
3 SU - Sorbonne Université

Biomimetic exploration of stimuli-responsive and crack-resistant hydrogels is of great academic and practical significance, although the rational design of tough hydrogels is limited by insufficient mechanism study due to the lack of imaging techniques to "see" hydrogels at mesoscale level. We designed a series of composite hydrogels with compartmentalized thermal response by incorporating aggregation-and polarity-sensitive fluorescent probes in a poly(N-isopropylacrylamide) (PNIPAM) network grafted with poly(N,N-dimethylacrylamide) side-chains. We explore the fluorescence technique as a powerful tool to directly visualize their hydrophilicity-hydrophobicity transformation and the composition-dependent microphase separation. Based on the morphological observation and mechanical measurements, the concept of morphomechanics with a comprehensive mechanism clarification is proposed. In this regard, the thermoresponsive toughening are attributed to the formation of multiple noncovalent interactions and the conformational changes of PNIPAM chains. The enhanced fracture energy by crack multifurcation is related to the tearing-like disruption of weak interfaces between the separated phases.

Mots clés: microphase separation; crack multifurcation; aggregation-induced emission

Domaines: Chimie

Yubing B Hu, Lucile Barbier, Zhao Li, Xiaofan F Ji, Heiva Le Blay, et al.. Hydrophilicity‐Hydrophobicity Transformation, Thermoresponsive Morphomechanics, and Crack Multifurcation Revealed by AIEgens in Mechanically Strong Hydrogels. Advanced Materials, 2021, pp.2101500. ⟨10.1002/adma.202101500⟩. ⟨hal-03357267⟩