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. 2023 Oct 2;13(41):28658-28665.
doi: 10.1039/d3ra05413f. eCollection 2023 Sep 26.

Hemiaminal dynamic covalent networks with rapid stress relaxation, reprocessability and degradability endowed by the synergy of disulfide and hemiaminal bonds

Siyao Zhu  1   2 , Yan Wang  3 , Jiaxin Qin  1   2 , Li Chen  1   2 , Liying Zhang  1 , Yi Wei  1 , Wanshuang Liu  1
Affiliations

Hemiaminal dynamic covalent networks with rapid stress relaxation, reprocessability and degradability endowed by the synergy of disulfide and hemiaminal bonds

Siyao Zhu et al. RSC Adv. .

Abstract

This work proposes a strategy to address the challenge of achieving rapid reprocessability of vitrimers at mild temperatures by introducing dynamic disulfide and hemiaminal bonds into hemiaminal dynamic covalent networks (HDCNs). The resulting HDCNs, termed HDCNs-DTDA, were prepared through a facile polycondensation between formaldehyde and 4,4'-dithiodianiline. The dual dynamic bond system in the HDCNs-DTDA enables rapid stress relaxation under mild temperature (65 °C for 54 s), which is significantly faster than that observed in HDCNs containing a single dynamic bond (HDCNs-DDM). The HDCNs-DTDA also exhibit a glass transition temperature of 96 °C, excellent solvent resistance and high recovery rates (97%) of tensile strength after reprocessing. In addition, HDCNs-DTDA can be easily degraded in HCl and thiol solutions at room temperature to enable chemical recyclability. Finally, HDCNs-DTDA demonstrates fast shape memory behaviors using thermal stimulation.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. (a) Synthetic route of HDCNs DTDA from DTDA and PFA. (b) Preparation procedures of HDCNs DTDA. (c) Synthetic route of HDCNs from DDM and PFA.
Fig. 1
Fig. 1. FTIR spectra of DTDA, HDCNs-DTDA, DDM and HDCNs-DDM.
Fig. 2
Fig. 2. Stress relaxation of HDCNs-DDM (a) and HDCNs-DTDA (b) at different temperatures. Arrhenius fitted line of the characteristic relaxation time τ versus 1000/T for HDCNs (c).
Fig. 3
Fig. 3. Photographs of both HDCNs-DTDA before and after reprocessing treatment (a); representative tensile strength–strain curves of original and reprocessed HDCNs-DDM (b) and HDCNs-DTDA (c) with different reprocessing times. Mechanism of reversible network rearrangement for HDCNs-DTDA (d).
Fig. 4
Fig. 4. Storage modulus versus temperature curves of original and reprocessed HDCNs-DDM (a) and HDCNs-DTDA (b). Tan δ versus temperature curves of original and reprocessed HDCNs-DDM (c) and HDCNs-DTDA (d).
Fig. 5
Fig. 5. Thiol–disulfide bond exchange reaction between HDCNs-DTDA and 2-mercaptoethanol (a); chemical degradation of HDCN-DTDA in the 2-mercaptoethanol/DMF solution. (b) Percentage of residual weight of HDCNs-DTDA as a function of time in the 2-mercaptoethanol/DMF solution (c).
Fig. 6
Fig. 6. Chemical degradation (a) and degradation time (b) of HDCNs-DTDA in HCl solutions containing different organic solvents.
Fig. 7
Fig. 7. Photographs of the HDCNs-DTDA samples in different solvents (a) before and (b) after staying for 120 h at ambient temperature.
Fig. 8
Fig. 8. Photographs of the thermally induced shape memory behavior of HDCNs-DTDA with different original shapes.
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