Cyclic Macroscopic Assembly and Disassembly Driven by Ionic Strength Fuel: A Waste-Free Approach

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Chemical Engineering

Background:

• Existing nonequilibrium assembly systems often rely on chemical fuels that generate waste.
• Programmable pH cycles, redox reactions, and metastable bond formations are common but problematic approaches.

Purpose of the Study:

• To develop a novel, waste-free strategy for the cyclic assembly and disassembly of macroscopic hydrogels.
• To utilize an ionic strength-mediated approach for controlled nonequilibrium processes.

Main Methods:

• Employing ammonium carbonate as a chemical fuel to regulate hydrogel attractions via ionic strength.
• Utilizing ionic strength-controlled charge screening and hydrogel elasticity changes for temporal regulation.
• Leveraging the decomposition of ammonium carbonate into volatile byproducts to prevent waste accumulation.

Main Results:

• Demonstrated cyclic and reversible assembly/disassembly of macroscopic hydrogels.
• Achieved waste-free operation due to the complete decomposition of ammonium carbonate.
• Showcased a self-clearance mechanism preventing process damping with continuous fuel supply.

Conclusions:

• The ionic strength-mediated approach offers a sustainable alternative for nonequilibrium systems.
• This method enables the creation of self-adaptive materials with cyclic assembly capabilities.
• The concept is applicable to both macroscopic and microscopic nonequilibrium systems.