Pendent No More: Direct Backbone Integration of Stenhouse Salt Enables Multi-Responsive Commodity Polyurethanes

Area of Science:

• Polymer Chemistry
• Materials Science
• Organic Chemistry

Background:

• Donor-acceptor Stenhouse adducts (DASAs) exhibit excellent photochromic properties.
• Previous integration of DASAs into polymers used pendent group architectures, limiting performance and efficiency.
• This approach led to compromises in switching efficiency and material properties.

Purpose of the Study:

• To overcome limitations of pendent DASA integration in polymers.
• To develop mechanically robust and responsive polymeric materials.
• To enable precise control over photochromic switching in elastomers.

Main Methods:

• Utilized symmetric Stenhouse salts for direct backbone integration into polyurethane.
• Synthesized backbone-integrated Stenhouse salt polyurethanes.
• Incorporated photoacid generators for photolithographic patterning.

Main Results:

• Achieved mechanically robust polyurethanes with high strain-to-break (>1100%) and tensile strength (44 MPa).
• Demonstrated fully reversible colorimetric responses (ΔE > 50) to various chemical stimuli.
• Enabled micrometer-scale photolithographic patterning for controlled chromophore switching.
• Eliminated chromophore leaching and ensured high reproducibility.

Conclusions:

• Backbone integration of Stenhouse salts offers superior performance compared to pendent systems.
• Developed versatile, responsive elastomers with excellent mechanical properties.
• Potential applications include food packaging, security, protective gear, and medical devices.