Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 2018 Mar 8;4(1):21.
doi: 10.3390/gels4010021.

Hydrogels Based on Dynamic Covalent and Non Covalent Bonds: A Chemistry Perspective

Francesco Picchioni  1 , Henky Muljana  2   3
Affiliations
Review

Hydrogels Based on Dynamic Covalent and Non Covalent Bonds: A Chemistry Perspective

Francesco Picchioni et al. Gels. .

Abstract

Hydrogels based on reversible covalent bonds represent an attractive topic for research at both academic and industrial level. While the concept of reversible covalent bonds dates back a few decades, novel developments continue to appear in the general research area of gels and especially hydrogels. The reversible character of the bonds, when translated at the general level of the polymeric network, allows reversible interaction with substrates as well as responsiveness to variety of external stimuli (e.g., self-healing). These represent crucial characteristics in applications such as drug delivery and, more generally, in the biomedical world. Furthermore, the several possible choices that can be made in terms of reversible interactions generate an almost endless number of possibilities in terms of final product structure and properties. In the present work, we aim at reviewing the latest developments in this field (i.e., the last five years) by focusing on the chemistry of the systems at hand. As such, this should allow molecular designers to develop a toolbox for the synthesis of new systems with tailored properties for a given application.

Keywords: dynamic covalent bonds; hydrogels; reversible polymeric network.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Incorporation of catechol groups in a polymeric network. Adapted and re-drawn from [15].
Figure 2
Figure 2
Schematic representation of reversible covalent bonds. (A): catechol-Fe chemistry; (B): furan-maleimide as example of cycloaddition reactions; (C): imine/enamine formation; (D): dynamic acylhydrazone exchange reaction; (E): boric ester formation and hydrolysis.
Figure 3
Figure 3
Schematic diagram for the strategy behind the use of reversible covalent bonds in hydrogels. (●) = reversible bonds along the backbone; (∆) = reversible bonds as crosslinking points; (●) = loading of the network (substrate).
Figure 4
Figure 4
Schematic drawing of reversible complexation of DMA with Fe3+ ions. Adapted and re-drawn from [38] with permission.
Figure 5
Figure 5
Dynamic hydrogels based on di-sulfide and acylhydrazone chemistry. Adapted and re-drawn from [39].
Figure 6
Figure 6
Double cross link network based on Diels-Alder and acylhydrazone reversible chemistry. Adapted and re-drawn from [9].
Figure 7
Figure 7
Dynamic covalent hydrogels with triblock copolymer micellization. Adapted and re-drawn from [33]. Yellow: hydrophobic block and/or domain. Blue: hydrophilic block and/or domain. Green: crosslinker.
Figure 8
Figure 8
Hydrogels based on poly(ethylene-glycol) (PEG) with the use of thiol-ene addition and a borax-diol chemistry. Adapted and re-drawn from [35].
Figure 9
Figure 9
Adapted and re-drawn from [43]. Insert: green denotes the polymeric network. Yellow/orange structure: see (B,C). (A) chemical structure of host (B) chemical structure (C) host guest coupling (D) dynamic equilibrium for reversible crosslinking. Di-methylacrylamide is used here as an example of a monomer that can be used.
Figure 10
Figure 10
Polysaccharide hydrogels based on covalent enamine bond. Adapted and re-drawn from [29].
See this image and copyright information in PMC

References

    1. Ahmed E.M. Hydrogel: Preparation, characterization, and applications: A review. J. Adv. Res. 2015;6:105–121. doi: 10.1016/j.jare.2013.07.006. - DOI - PMC - PubMed
    1. Chen L., Yin Y., Liu Y., Lin L., Liu M. Design and fabrication of functional hydrogels through interfacial engineering. Chin. J. Polym. Sci. 2017;35:1181–1193. doi: 10.1007/s10118-017-1995-5. - DOI
    1. Liu J., Zhu K., Jiao T., Xing R., Hong W., Zhang L., Zhang Q., Peng Q. Preparation of graphene oxide-polymer composite hydrogels via thiol-ene photopolymerization as efficient dye adsorbents for wastewater treatment. Colloids Surf. A Physicochem. Eng. Asp. 2017;529:668–676. doi: 10.1016/j.colsurfa.2017.06.050. - DOI
    1. Piatkowski M., Janus L., Radwan-Praglowska J., Raclavsky K. Microwave-enhanced synthesis of biodegradable multifunctional chitosan hydrogels for wastewater treatment. Express Polym. Lett. 2017;11:809–819. doi: 10.3144/expresspolymlett.2017.77. - DOI
    1. Zhang Z., Du J., Li Y., Wu J., Yu F., Chen Y. An aptamer-patterned hydrogel for the controlled capture and release of proteins via biorthogonal click chemistry and DNA hybridization. J. Mater. Chem. B. 2017;5:5974–5982. doi: 10.1039/C7TB00883J. - DOI - PubMed