Hydrogen Bonding Enables Polymer Hydrogels with pH-Induced Reversible Dynamic Responsive Behaviors

Area of Science:

• Materials Science
• Polymer Chemistry
• Smart Materials

Background:

• Poly(acrylic acid-co-N-vinylcaprolactam) (PAN) hydrogels possess multiple hydrogen bonds.
• These hydrogels exhibit pH-induced reversible dynamic responsive behaviors.

Purpose of the Study:

• To investigate the pH-induced transparency changes in PAN hydrogels.
• To demonstrate a dynamic memory system utilizing the reversible transparency evolution of PAN hydrogels.

Main Methods:

• Hydrogels were immersed in acidic and neutral (DI water) environments.
• The dynamic transparency evolution (opacity-transparency changes) was observed and analyzed.
• The hydrogel's ability to memorize, recall, and forget information was demonstrated.

Main Results:

• PAN hydrogels transition from transparent to opaque in acidic and neutral conditions due to nonequilibrium states.
• The hydrogels slowly regain transparency as swelling equilibrium is reached.
• The two-way dynamic transparency evolution enables information memorization and forgetting.

Conclusions:

• PAN hydrogels offer a unique platform for developing dynamic memory systems.
• The pH-responsive transparency changes are driven by hydrogen bonding dynamics and water diffusion.
• This research presents a novel approach for information storage and retrieval using smart hydrogels.