T-shaped trifunctional crosslinker-toughening hydrogels
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shaped trifunctional crosslinker-toughening hydrogels *
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LI QingYu, XU ZiYang, ZHANG DongFei, YANG JianHai & LIU WenGuang
School of Materials Science and Engineering, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300350, China Received January 23, 2020; accepted February 10, 2020; published online June 12, 2020
Currently, development of a single network hydrogel with a high fracture toughness in swelling equilibrium remains challenging. In this work, a novel T-shaped trifunctional crosslinker (T-NAGAX) with dual vinyl on the backbone and dual amide group on the side chain is synthesized by Michael addition and acylation. The T-NAGAX is used to prepare chemically crosslinked hydrogel by one-pot photo-initiated polymerization. The resulting single network hydrogels of representative polyacrylamide (PAAm), poly(N-acryloyl 2-glycine) (PACG), and poly(N-isopropyl acrylamide) (PNIPAM) crosslinked with T-NAGAX with additional hydrogen-bonds exhibit much better fracture toughness than that of the corresponding hydrogels crosslinked by N,N'methylene bisacrylamide, a conventional crosslinker; higher mechanical strengths are observed in the T-NAGAX crosslinked hydrogels. These hydrogels are promising to be exploited as load-bearing soft tissue substitutes. This T-NAGAX crosslinker can be expanded to toughen various types of hydrogels. single network, hydrogen bond, hydrogel, toughness, crosslinker Citation:
Li Q Y, Xu Z Y, Zhang D F, et al. T-shaped trifunctional crosslinker-toughening hydrogels. Sci China Tech Sci, 2020, 63, https://doi.org/10.1007/ s11431-020-1537-6
1 Introduction Hydrogels are three-dimensional chemically or physically crosslinked polymer networks retaining a large amount of water, and have a high similarity with soft tissues, so they are ideal soft and wet biomaterials for tissue regeneration and reconstruction [1]. However, it is challenging to develop hydrogels with high mechanical strength and toughness for applications of load-bearing soft tissues such as cartilage and blood vessel, since most covalently crosslinked single network hydrogels suffer from the heterogeneity of network structure and/or lack efficient energy-dissipation mechanisms [2]. When a force is applied to these hydrogels, stress is concentrated around the shortest chain and also cannot be dissipated, thus leading to a failure of the sample at a very low force [3]. Accordingly, many strategies have been explored to synthesize strong and flexible hydrogels with a *Corresponding authors (email: [email protected]; [email protected])
homogeneous network structure, such as the slide-ring hydrogels [4], tetra-PEG hydrogels [5]. Those hydrogels exhibit better strength and elongation, but the toughness is lower [3]. Different from the above approaches for the construction of a homogeneous structure, a double-network (DN) approach retaining the heterogeneity of network structure was developed. In the DN, a loosely crosslinked, soft, ductile and neutral second network is incorporated within
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