Shape Actuation via Internal Stress-Induced Crystallization of Dual-Cure Networks

Area of Science:

• Materials Science
• Polymer Chemistry
• Mechanical Engineering

Background:

• Shape-memory polymers (SMPs) offer tunable mechanical properties.
• Actuation in polymers is typically driven by external stimuli.
• Developing efficient and reversible polymer actuators is crucial for advanced applications.

Purpose of the Study:

• To demonstrate a single-phase, two-way shape actuator based on poly(ε-caprolactone) (PCL).
• To investigate the mechanism of elongation upon cooling and contraction upon heating in a PCL network.
• To achieve reproducible and stable actuation cycles with high strain recovery.

Main Methods:

• Fabrication of a partially cross-linked, semicrystalline PCL network.
• Stretching the PCL network to high strain followed by further cross-linking.
• Utilizing differential scanning calorimetry (DSC) and X-ray scattering for mechanism confirmation.

Main Results:

• The PCL actuator exhibits reversible actuation, elongating >15% upon cooling and contracting upon heating.
• The material demonstrates high uniformity and no observable creep over multiple actuation cycles.
• Stress-induced crystallization upon cooling and melting upon heating drives the shape change.

Conclusions:

• A novel, single-phase, two-way PCL-based shape actuator was successfully demonstrated.
• The actuator exhibits robust performance with significant reversible strain and excellent cycling stability.
• The findings open avenues for developing advanced smart materials with controlled shape-memory effects.