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Reversible sol–gel transitions are difficult to achieve in conventional water-swollen hydrogels in open aqueous environments, because polymer chains dissolve or diffuse once the network disassembles. Here, we present a proof-of-concept to overcome this limitation by introducing a water-immiscible and non-cytotoxic ionic liquid (IL) phase that confines polymer networks and prevents dissolution during reversible phase transitions. We report a photoreversible ion gel that crosses the rheological boundary (tan δ∼ 1) under light, enabling reversible sol–gel switching within this closed IL environment. The material integrates an ABC triblock copolymer, P(AzoAmr -NIPAm)b -PBuAb -PSt, with a solvent-quality-tunable blend of non-cytotoxic ILs ([P4,4,4,1][TFSI]/[P8,8,8,8][TFSI]). The photoresponsive A-block, P(AzoAmr -NIPAm), exhibits a polarity-dependent solubility change with the cis / trans isomerization of azobenzene, providing a reversible light-controlled self-assembly. Time-resolved rheology confirmed repeated crossings of tan δ= 1 under alternating UV–vis illumination at 52◦C. The switching mechanism is governed by the lifetime of reversible junctions, consistent with transient network theory. In addition, hMSCs adhered to and spread on the ion gel at 37◦C, indicating the cytocompatibility of the ion gel itself. This light-programmable, water-immiscible ion gel has the potential to provide a reversible liquid-solid mechanical cue for next-generation mechanobiology.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: ionic liquids, polymer gels, block copolymers, cell culturing, mechanobiology, stimuli-responsive polymers

Date published: 2026-01-28

Publisher: Wiley

Journal:

• Macromolecular Rapid Communications (ISSN: 10221336) vol. 47 issue. 7 e00909

Funding:

• Japan Society for the Promotion of Science 22KJ010202
• Japan Society for the Promotion of Science 23H02030
• Japan Society for the Promotion of Science 23K17481

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1002/marc.202500909

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Updated at: 2026-04-09 09:52:44 +0900

Published on MDR: 2026-04-09 12:24:44 +0900