Mechanochromic polymer blends made with an excimer-forming telechelic sensor molecule

Area of Science:

• Materials Science
• Polymer Chemistry
• Optical Sensing

Background:

• Monitoring mechanical stress and strain in polymers is crucial for understanding deformation processes.
• Optical methods offer a non-destructive way to investigate material behavior.
• Sensing damage and failure in critical polymer components is technologically important.

Purpose of the Study:

• To develop a simple method for optical monitoring of mechanical stress and strain in polymers.
• To utilize mechanochromic luminescent additives for real-time deformation sensing.
• To investigate the relationship between polymer deformation and changes in luminescence.

Main Methods:

• Synthesizing a mechanochromic luminescent additive (Py-PEB) by end-functionalizing poly(ethylene-co-butylene) (PEB) with pyrenes.
• Blending Py-PEB with various polymers like poly(ε-caprolactone) and poly(urethane) at low concentrations (0.1-1 wt%).
• Analyzing the changes in emission intensity ratio (excimer-to-monomer) upon mechanical deformation.

Main Results:

• Microphase separation occurs in polymer blends even at low Py-PEB concentrations due to poor miscibility.
• The luminescence emission is dominated by excimers in the blends.
• A decrease in the excimer-to-monomer emission intensity ratio directly correlates with applied stress or strain.
• The approach shows generalizability across different polar polymers.

Conclusions:

• Blending polymers with mechanochromic luminescent additives provides an effective optical method for stress and strain monitoring.
• The observed changes in luminescence serve as a direct indicator of material deformation and potential damage.
• Careful tuning of additive solubility is necessary for universal applicability, as demonstrated by experiments with poly(isoprene).