Light-Programmable Morphology in Photothermal Polyurethanes Based on Stenhouse Salt as Photothermal Agent

Area of Science:

• Polymer Chemistry
• Materials Science
• Soft Robotics

Background:

• Spatially controlled photothermal heating is crucial for soft robotics and adaptive structures.
• Current methods often require multistep processing to incorporate photothermal additives.
• A need exists for efficient, single-step methods for photothermal material fabrication.

Purpose of the Study:

• To develop semicrystalline thermoplastic polyurethanes with backbone-integrated Stenhouse salt chromophores.
• To enable single-step, micron-scale photopatterning and spatially selective photothermal heating.
• To achieve light-addressable control over local crystallinity and material mechanics.

Main Methods:

• Triflic acid-catalyzed step-growth synthesis of Stenhouse salt-functionalized polyurethanes.
• White-light photopatterning through a photomask to induce irreversible photobleaching.
• Green-light illumination to induce spatially selective photothermal heating and control crystallinity.

Main Results:

• Achieved single-step, micron-scale photopatterning with ΔT ≈ 15 °C.
• Maintained excellent mechanical properties (E ≈ 300 MPa; σy ≈ 12 MPa).
• Created coexisting amorphous and semicrystalline zones, enabling programmed mechanics like sequential yielding.

Conclusions:

• The developed polyurethanes offer a scalable, one-pot method for creating photothermally active materials.
• Light-addressable control over local crystallinity and mechanics is demonstrated without additive redistribution.
• This approach opens new avenues for advanced functional materials in soft robotics and beyond.