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Super-strong and tough poly(vinyl alcohol)/poly(acrylic acid) hydrogels reinforced by hydrogen bonding


Synthetic hydrogels or water-containing polymeric materials are much inferior to biological tissues and solid plastics in many aspects of mechanical properties, it is a great challenge to develop hydrogels with mechanical properties comparable with or even superior to biological tissues and plastics. Here, we report a type of super-strong and tough hydrogen bonded poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) hydrogels by immersing as-prepared PVA hydrogels in aqueous PAA solutions and then cold-drawing the hydrogels to different strains. The immersing process introduces PAA chains into PVA hydrogels, which leads to the increase of cross-linking density by hydrogen bonding and hence the much improved mechanical properties and low water contents (35.9-40.2 wt.%). The cold-drawing leads to the orientation of polymer chains, which enables the formation of more and stronger hydrogen bonds. The mechanical properties of the cold-drawn gels are dramatically enhanced, with tensile strength and elastic modulus up to 140 and 100 MPa, respectively, as well as super-high toughness (117 MJ·m-3) and fracture energy (101 kJ·m-2). Very impressively, the ultra-high tensile strengths of the cold-drawn hydrogels are superior to those of biological tissues and most solid engineering plastics. Characterizations and comparative studies prove that the enhancement of mechanical properties is mainly due to the formation of more hydrogen bonding rather than the loss of water or the change of crystallinity. The study provides a new strategy for preparing super-strong physically cross-linked hydrogels and other polymeric materials. This super-strong and tough hydrogel may find potential applications in biomedical and load-bearing fields.

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Publication details

The article was received on 28 Sep 2018, accepted on 05 Nov 2018 and first published on 07 Nov 2018

Article type: Paper
DOI: 10.1039/C8TB02556H
Citation: J. Mater. Chem. B, 2018, Accepted Manuscript
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    Super-strong and tough poly(vinyl alcohol)/poly(acrylic acid) hydrogels reinforced by hydrogen bonding

    T. Liu, C. Jiao, X. Peng, Y. Chen, Y. Chen, C. He, R. Liu and H. Wang, J. Mater. Chem. B, 2018, Accepted Manuscript , DOI: 10.1039/C8TB02556H

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