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

Abstract

Nonequilibrium assembling systems developed so far have relied on chemical fuels to drive the programmable pH cycles, redox reactions, and metastable bond formations. However, these methods often result in the unwanted accumulation of chemical waste. Herein, we present a novel strategy for achieving cyclic and waste-free nonequilibrium assembly and disassembly of macroscopic hydrogels, utilizing an ionic strength-mediated approach. Our strategy involves using ammonium carbonate as a chemical fuel to temporally regulate the attractions between oppositely charged hydrogels via ionic strength-controlled charge screening and hydrogel elasticity changes. This chemical fuel effectively mediates the assembly/disassembly processes and prevents waste accumulation, as ammonium carbonate can completely decompose into volatile chemical waste. The cyclic and reversible assembly process can be achieved without significant damping due to the self-clearance mechanism, as long as the chemical fuel is repeatedly supplied. This concept holds promise for creating macroscopic and microscopic nonequilibrium systems and self-adaptive materials.

An Encyclopedic Compendium on Chemosensing Supramolecular Metal‐Organic Gels

“…[350] Controlling the kinetics of competing chemical reactions can be studied to mediate the transient healing ability of metallo-supramolecular polymer networks. [351] Achieving cyclic macroscopic assembly/disassembly by the manipulation of ionic strength [352] for metallogelderived soft material can be done. Surface-mediated supramolecular self-assembly [353] can be explored for metalbased gels.…”

Transient regulation of gel properties by chemical reaction networks

“…27,70,72,77 We developed an ionic strength-mediated strategy to achieve cyclic and waste-free transient assembly and disassembly of macroscopic hydrogels. 78 Two polyelectrolyte hydrogels containing positive and negative charges were designed to demonstrate the concept of salt-fueled assembly/disassembly. The transient assembly/disassembly processes based on the temporally controlled electrostatic interactions were reversible and highly reproducible for many alternating exposure cycles between adding the ammonium carbonate as chemical fuels and accelerating the dissipation by heating.…”

“…63,110 (iii) Transient assembly of macroscopic gels: Taking the previous work of our group as an example, the pH or ionic strength of the systems changed during the assembly and disassembly processes, leading to the changes in the surface charge density of the polyelectrolyte hydrogels, so these systems can be characterized by zeta potential measurements. 28,78 In addition, the tensile test is also an important experiment to quantify the binding strength of the macroscopic assemblies. (iv) Transient healing ability of kinetically inert gels: The methods used to characterize the self-healing properties of polymer materials are available here, such as rheological and tensile tests.…”

Hydrogel Rivet with Unidirectional Shape Morphing for Flexible Mechanical Assembly

“…For instance, utilizing supramolecular assemble to combine two stimuli‐responsive hydrogels, [ 16–18 ] requires extensive efforts on the chemical design to strike a balance between the expected functionality and connection strength. [ 19–21 ] In contrast, traditional rigid robotics can easily integrate different functional components through simple mechanical assembly methods like screw connections and rivet connections.…”