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. 2019 Dec 17;9(3):272-276.
doi: 10.1002/open.201900295. eCollection 2020 Mar.

Bioinspired Healable Mechanochromic Function from Fluorescent Polyurethane Composite Film

Xiaoke Song  1   2 , Jun-Peng Wang  1 , Yan Song  1 , Tao Qi  1   2 , Guo Liang Li  1   2
Affiliations

Bioinspired Healable Mechanochromic Function from Fluorescent Polyurethane Composite Film

Xiaoke Song et al. ChemistryOpen. .

Abstract

Camouflage and wound healing are two vital functions for cephalopods to survive from dangerous ocean risks. Inspired by these dual functions, herein, we report a new type of healable mechanochromic (HMC) material. The bifunctional HMC material consists of two tightly bonded layers. One layer is composed of polyvinyl alcohol (PVA) and titanium dioxide (TiO2) for shielding. Another layer contains supramolecular hydrogen bonding polymers and fluorochromes for healing. The as-synthesized HMC material exhibits a tunable and reversible mechanochromic function due to the strain-induced surface structure of composite film. The mechanochromic function can be further restored after damage because of the incorporated healable polyurethane. The healing efficiency of the damaged HMC materials can even reach 98 % at 60 °C for 6 h. The bioinspired HMC material is expected to have potential applications in the information encryption and flexible displays.

Keywords: bifunction; bioinspired materials; healable; mechanochromic.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Structures and functions of the bioinspired healable mechanochromic (HMC) material. (a) The camouflage and wound healing bifunctions of cephalopods due to the muscle‐controlled color changes and the reconstruction of proteins. (b) The HMC material with mechanochromic and self‐healing bifunctions arising from hierarchical nanostructures. (c) The chemical structures of the fluorochromes of rhodamine B (1), fluorescein (2) and 9,10‐bis(4‐methoxyphenyl)‐2‐chloroanthracene (3), respectively. (d) The digital photos of the as‐synthesized HMC material.
Figure 2
Figure 2
Mechanochromic property of the as‐synthesized healable mechanochromic (HMC) material. (a) Optical micrographs of the HMC material at different strains; the insets are photographs at the corresponding strains under UV light. (b) Fluorescence spectra of the HMC material under different strains. (c) Repeatable mechanochromism of the HMC material after 60 % strain application followed by standing for 1 h. (d) Digital images of the healable fluorescent polymer and HMC materials with different thicknesses of PVA/TiO2 layers. (e) Relative fluorescence intensity of the HMC materials with different thicknesses of PVA/TiO2 layers at strains from 0 to 100 %.
Figure 3
Figure 3
The self‐healing function of the healable mechanochromic (HMC) material. (a) Scheme of the self‐healing mechanism. (b) SEM image of the self‐healing sample. Stress‐strain curves of healable samples (c) after 24 h at different temperatures and (d) after different times at 60 °C.
Figure 4
Figure 4
The mechanochromic function after self‐healing of the healable mechanochromic (HMC) material. (a) The process of damage and self‐healing. (b) The digital photo and fluorescent display of the healed specimen under tension. (c) Relative fluorescence intensity at different strains of the virgin and healed samples. (d) Reusability of the healable mechanochromic function of the bioinspired HMC material.
Figure 5
Figure 5
Applications of this type of the healable mechanochromic (HMC) material. (a) Extensive application of the HMC material for different fluorochrome‐based HMC materials. The fluorochromes of i, ii and iii are rhodamine B, fluorescein and 9,10‐bis(4‐methoxyphenyl)‐2‐chloroanthracene, respectively. (b) Stress‐relative fluorescence intensity curve of the HMC material. (c) Scheme of the high level encryption due to the healable mechanochromic function of the HMC material. (d) Separated, healed and stretched HMC materials for encryption.
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References

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