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Multiple-Responsive and Amphibious Hydrogel Actuator Based on Asymmetric UCST-Type Volume Phase Transition
Luqin Hua1, Manqing Xie1, Yukun Jian2
1State Key Laboratory Base of Novel Functional Materials and Preparation Science, Ningbo Key Laboratory of Specialty Polymers, School of Materials Science & Chemical Engineering , Ningbo University , Ningbo 315211 , Zhejiang , China.
ACS Applied Materials & Interfaces
|October 31, 2019
Summary
This study introduces a novel upper critical solution temperature (UCST) hydrogel actuator using poly(acrylic acid) and poly(acrylamide). This smart material exhibits shape changes upon cooling, offering new possibilities for soft robotics and flexible electronics.
Area of Science:
- Materials Science
- Polymer Chemistry
- Soft Robotics
Background:
- Thermoresponsive hydrogels are crucial for applications like artificial muscles and soft robotics.
- Most existing hydrogels utilize lower critical solution temperature (LCST) behavior, limiting their applications.
- Upper critical solution temperature (UCST) hydrogels are less common but offer unique advantages.
Purpose of the Study:
- To develop a novel, multiple-responsive UCST hydrogel actuator.
- To investigate the actuation mechanism based on polymer complexation and phase transition.
- To explore the tunability and complex shape-forming capabilities of the hydrogel.
Main Methods:
- Fabrication of a bilayer hydrogel using heterogeneous photopolymerization of poly(acrylic acid) (PAAc) and poly(acrylamide) (PAAm).
- Creation of an interpenetrating network (IPN) of PAAm/PAAc in one layer and a single PAAm network in the other.
- Utilizing photomasks to pattern IPN domains for controlled deformation into 2D and 3D shapes.
Main Results:
- The bilayer hydrogel exhibits anisotropic UCST transition, contracting in the PAAm/PAAc layer and swelling in the PAAm layer upon cooling, leading to actuation.
- Actuation amplitude is tunable by adjusting the composition of the polymer layers.
- The hydrogel demonstrates responsiveness to temperature, urea, and various salts (Na2SO4, NaCl, NaSCN) due to changes in hydrogen bonding within the IPN.
- Active motion was achieved in both aqueous and oil environments.
Conclusions:
- A novel, multiple-responsive UCST hydrogel actuator was successfully developed.
- The hydrogel's actuation is driven by asymmetrically distributed polymer-polymer hydrogen bonds, leading to anisotropic phase transitions.
- This work provides a new platform for designing intelligent materials with tunable and complex shape-morphing capabilities for advanced applications.
