Redox-Triggered Buoyancy and Size Modulation of a Dynamic Covalent Gel

Gobinda Das, Sharadhi Nagaraja, Vimala Sridurai, Digambar Shinde, Matthew Addicoat, Thirumurugan Prakasam, Felipe Gándara, Florent Ravaux, Sudhir Kumar Sharma, Geetha G. Nair, Zhiping Lai, Ramesh Jagannathan, Mark A. Olson, Ali Trabolsi

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


The development of stimuli-responsive materials capable of transducing external stimuli into mechanical and physical changes has always been an intriguing challenge and an inspiration for scientists. Several stimuli-responsive gels have been developed and applied to biomimetic actuators or artificial muscles. Redox-active actuators in which the mechanical motion is driven chemically or electrochemically have attracted much interest, and their actuation mechanism is based on the change in electrostatic repulsion and the loss or gain of counterions to balance newly formed charges. Actuation can also be promoted by changing the hydration state of the material, leading to the release/adsorption of water molecules from the network, inducing a direct shrinking/swelling of the material, respectively. A cationic crystalline dynamic covalent gel was obtained via the formation of imine bonds between 2,6-diformyl pyridine and triamino guanidinium chloride. The gel exhibits a reversible contraction/expansion behavior in response to base (oxidation, −H+, −e–) and acid (reduction +H+, +e–), respectively. The oxidation induces a color change and contraction of the gel with a concomitant increase in its strength. As synthesized, the cationic gel is denser than water and sinks when placed in water. Upon oxidation, the radical cationic gel expels water molecules, rendering it less dense than water and the gel is propelled to the surface without any loss of its structural integrity. These results demonstrate that a careful choice of amine and aldehyde linkers can give rise to imine-linked materials capable of tolerating and resisting extreme acidic and basic conditions while performing work.
Original languageEnglish (US)
Pages (from-to)4148-4155
Number of pages8
JournalChemistry of Materials
Issue number11
StatePublished - Apr 24 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The research described here was sponsored by New York University Abu Dhabi (NYUAD), UAE. G.D., T.P., S.K.S., R.J., and A.T. thank NYUAD for its generous support of the research program at NYUAD. The research was carried out by using the Core Technology Platform resources at NYUAD. M.A.A. thanks the UK Materials Chemistry Consortium for HPC time on Thomas (EP/P020194).


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