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A General Strategy to Fabricate Strong and Tough Low-Molecular-Weight Gelator-Based Supramolecular Hydrogels with Double Network Structure Feng Chen, Qiang Chen, Lin Zhu, Ziqing Tang, Qingfeng Li, Gang Qin, Jia Yang, Yanxian Zhang, Baiping Ren, and Jie Zheng Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/acs.chemmater.8b00063 • Publication Date (Web): 06 Feb 2018 Downloaded from http://pubs.acs.org on February 6, 2018
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Chemistry of Materials
A General Strategy to Fabricate Strong and Tough Low-Molecular-Weight Gelator-Based Supramolecular Hydrogels with Double Network Structure Feng Chen, Qiang Chen*, Lin Zhu, Ziqing Tang, Qingfeng Li, Gang Qin, Jia Yang, Yanxian Zhang, Baiping Ren, and Jie Zheng* F. Chen, Prof. Q. Chen, L. Zhu, Z. Tang, Prof. G. Qin, Dr. J. Yang School of Materials Science and Engineering Henan Polytechnic University No.2001 Century Avenue, Jiaozuo, 454003, China E-mail:
[email protected] Dr. Q. Li The Key Laboratory of Rare Earth Functional Materials and Applications, Zhoukou Normal University, Zhoukou 466001, China Y. Zhang, B. Ren, Prof. J. Zheng Department of Chemical and Biomolecular Engineering The University of Akron, Akron, Ohio, 44325, USA E-mail:
[email protected] 1 ACS Paragon Plus Environment
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ABSTRACT Low-molecular-weight gelators (LMWGs)-based supramolecular hydrogels, self-assembled by small molecules via noncovalent interactions, have been recently attracted great attentions due to their unique structure-property relationship and potential applications spanning from functional materials to biomedical devices. Unfortunately, many LMWGs-based supramolecular hydrogels are mechanical weak and can not even be handled by conventional tensile and tearing tests. Here, we propose several design principles to fabricate new LMWG-based hydrogels with a true double-network structure (G4.K+/PDMAAm DN gels), consisting of the supramolecular self-assembly of guanosine, B(OH)3 and KOH as the first, physical G4.K+ network and the covalently cross-linked poly(N, N’-dimethyacrylamide) (PDMAAm) as the second, chemical network. Different from those LMWGs-based supramolecular hydrogels, G4.K+/PDMAAm DN gels exhibit high tensile properties (elastic modulus=0.307 MPa, tensile stress=0.273 MPa, tensile strain=17.62 mm/mm, and work of extension=3.23 MJ/m3) and high toughness (tearing energies=1640 J/m2). Meanwhile, the dynamic, noncovalent bonds in the G4.K+ network can reorganize and reform after being broken, resulting in rapid self-recovery property and excellent fatigue resistance. The stiffness/toughness of G4.K+/PDMAAm DN gels can be recovered by 65%/58% with 1 min resting at room temperature, and the recovery rates are further improved with the increase of temperatures and resting times. Interestingly, G4.K+/PDMAAm DN gels also exhibit UV-triggered luminescence due to the unique G4-quartets structure in G4.K+ supramolecular first network. A new toughening mechanism is proposed to interpret the high strength and toughness of G4.K+/PDMAAm DN gels. We believe that our design principles, along with new G4.K+/PDMAAm DN gel system, will provide a new viewpoint for realizing the tough and strong LMWGs-based gels.
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Chemistry of Materials
1. Introduction Development of mechanically strong and multifunctional hydrogels is critical for a variety of applications, including tissue scaffolds, 1, 2 superabsorbents, 3 drug delivery carriers, 4
agriculture and food chemistry. 5-7 However, conventional hydrogels are often very weak or
brittle, and they usually break at a tensile stress of < 1 MPa and/or a strain of 58% for G4.K+/PDMAAm DN gel > 40% for PDGI/PAAm DN gel > 30% for GG/PAAm DN gel. Beyond R.T., G4.K+/PDMAAm DN gel achieve 67% and 69% of toughness recovery after 5 min resting at 80oC and 100 oC, respectively (Figure 9d), as 23 ACS Paragon Plus Environment
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compared to 74% recovery for Ca2+-Alg/PAAm gel at 80oC for 1 day resting and 40% recovery for Agar/PAAm DN gel at 100oC for 5 min resting. Taken together, our G4.K+/PDMAAm DN gels are superior to LMWGs-based hybrid DN gels in terms of mechanical properties, and comparable to other typical hybrid DN gels in terms of both mechanical and self-recovery properties. Table 1. Comparison of G4.K+/PDMAAm DN gels to other hybrid DN gels. DN Gel
1
.
+
G K /PDMAAm
σcom
Ecom
σten
Eten
T
Ref.
Rtoughness 2
(MPa)
(kPa)
(MPa)
(kPa)
(J/m )
(%)
19.2
316
0.273
307
1640
58 (1 min, R.T.)
Our work
2
PS-DN
0.213
329
/
/
334.8
100 (
