Humidity-Responsive Shape Memory Polyurea with a High Energy Output Based on Reversible Cross-Linked Networks

Area of Science:

• Materials Science
• Polymer Chemistry

Background:

• High-performance shape memory polymers (SMPs) are crucial for advanced applications like sensors, wearable electronics, and artificial muscles.
• Existing SMPs often lack multifunctionality, such as combined responsiveness and extreme environment tolerance.

Purpose of the Study:

• To develop a transparent, humidity-responsive shape memory polyurea with enhanced mechanical properties and multi-environmental adaptability.
• To investigate the structure-property relationships governing the material's shape memory and responsive behaviors.

Main Methods:

• Fabrication of a polyurea via a bioinspired hard-soft nanophase structure and hierarchical hydrogen bonding.
• Characterization using small-angle X-ray scattering (SAXS) to determine domain periodicity.
• Evaluation of mechanical properties (tensile strength, recovery stress) and environmental tolerance (low-temperature malleability).

Main Results:

• The developed polyurea demonstrated high tensile strength (51 MPa) and recovery stress (12 MPa) with significant energy output (0.98 J/g).
• The material exhibited excellent malleability at -196 °C and humidity-responsive shape change (160° rolling in 20 s).
• SAXS analysis revealed a phase-separated domain periodicity of 12 nm, linked to hierarchical hydrogen bonding.

Conclusions:

• The bioinspired nanophase structure and hierarchical hydrogen bonding are key to achieving high-performance, humidity-sensitive SMPs.
• This polyurea offers a promising platform for advanced functional materials in diverse technological fields.
• The zipper-like reversible linking property of the hydrogen bonding network underpins the material's unique performance.