Chemically Fueled Autonomous Sol→Gel→Sol→Gel→Sol Transitions.

Area of Science:

• Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Complex non-equilibrium phase behaviors are characteristic of natural self-assembling systems.
• Achieving intricate and autonomous phase transitions in synthetic systems remains a challenge.

Purpose of the Study:

• To demonstrate autonomous, multi-stage sol-gel-sol-gel-sol transitions using a chemically fueled reaction cycle.
• To investigate the formation of transient hydrogels via thiazinane metathesis.

Main Methods:

• Utilized a chemically fueled reaction cycle based on thiazinane metathesis.
• Initiated transitions by adding fuel to deactivated thiazinane monomers in a closed system.
• Characterized the resulting hydrogels and solution phases.

Main Results:

• Achieved two consecutive transient gelations: an initial imine-based hydrogel followed by a stable aldehyde-based hydrogel.
• The imine-based hydrogel formed within seconds and rapidly lost mechanical strength.
• The aldehyde-based gel nucleated from the solution and remained stable for over a day.
• Demonstrated two successive re-entrant phase transitions autonomously.

Conclusions:

• A chemically fueled reaction cycle can autonomously drive complex, multi-stage phase transitions.
• Thiazinane metathesis provides a versatile platform for creating tunable, transient hydrogel systems.
• This work offers a new strategy for designing dynamic materials with programmable phase behaviors.