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Making Hydrogels Stronger through Hydrophilicity-Hydrophobicity Transformation, Thermoresponsive Morphomechanics and Crack Multifurcation

preprint
submitted on 11.05.2020 and posted on 12.05.2020 by YUBING HU, Lucile Barbier, Zhao Li, Xiaofan Ji, Heiva Le Blay, Junkai Liu, Jacky W. Y. Lam, Alba Marcellan, Ben Zhong Tang

The development of mechanically strong, flexible and crack-resistant hydrogels is of great academic and practical significance and demands for the biomimetic exploration of energy dissipation pathways. The rational design of strong hydrogels is also limited by insufficient mechanism study, resulting from the lack of powerful technique to “see” hydrogels at morphological level. Herein, we constructed a thermoresponsive mechanically strong hydrogel from poly(N-isopropylacrylamide) (PNIPAM) and poly(N,N-dimethylacrylamide). Its hydrophilicity-hydrophobicity transformation and composition-dependent microphase separation are directly visualized by using luminogens with aggregation-induced emission as fluorescent indicators. Based on the morphological observation and mechanical measurements, the concept of morphomechanics with a comprehensive mechanism clarification is proposed. In this regard, thermoresponsive strengthened mechanical properties are attributed to the entanglement of PNIPAM chains and the formation of multiple noncovalent interactions, mainly hydrogen bonds. The enhanced fracture energy by crack multifurcation is related to the disruption of weak interfaces between two separated phases.

Funding

National Science Foundation of China (21788102, 21490570, and 21490574)

Research Grant Council of Hong Kong (16305618, 16304819, N-HKUST609/19, and C6009-17G)

Science and Technology Plan of Shenzhen (JCYJ20160229205601482, JCYJ20170818113602462, JCYJ20180306180231853, and JCYJ 20180306174910791)

Innovation and Technology Commission (ITC-CNERC14SC01)

National Key Research and Development Program of China (2018YFE0190200)

History

Email Address of Submitting Author

yhuas@connect.ust.hk

Institution

The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China

Country

China

ORCID For Submitting Author

0000-0003-3083-0067

Declaration of Conflict of Interest

The authors declare no conflict of interest.

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