Shape Memory Polymer Foam with Programmable Apertures.

Area of Science:

• Materials Science
• Polymer Chemistry
• Smart Materials

Background:

• Polyester urethane urea (PEUU) materials offer tunable properties for advanced applications.
• Developing materials with integrated thermal actuation and insulation is crucial for energy-efficient structures.

Purpose of the Study:

• To introduce a novel PEUU foam with self-sufficient thermal responsive behavior.
• To characterize the thermal, mechanical, and actuation properties of the new PEUU foam.
• To explore potential applications in adaptive building envelopes.

Main Methods:

• Reactive foaming using a specific blend of polyols, diisocyanate, chain extender, and water as a blowing agent.
• Differential scanning calorimetry (DSC) for thermal phase transitions.
• Hyperelastic modeling (Neo-Hookean and Ogden) to simulate mechanical properties.
• Thermomechanical treatment to induce and measure actuation under varying load conditions.
• Measurement of thermal conductivity in pristine and compressed states.

Main Results:

• The PEUU foam exhibited ester-based phase transitions between 25 °C and 61 °C (melting) and 48 °C to 20 °C (crystallization).
• The Ogden model accurately predicted mechanical behavior (R² > 0.99).
• Thermomechanical treatment resulted in actuation up to 13.7% (with load) and over 10% (load-free).
• Thermal conductivity values were 0.039 W·(m·K)⁻¹ (pristine) and 0.052 W·(m·K)⁻¹ (50% compressed).
• Three demonstrators showcased temperature-driven aperture control.

Conclusions:

• The novel PEUU foam possesses excellent self-sufficient thermal actuation and insulation properties.
• Its programmable behavior makes it highly suitable for dynamic insulation systems in adaptive building envelopes.
• This material innovation holds significant potential for the construction industry, enabling energy-efficient building designs.