Multi-modal mechanophores based on cinnamate dimers.

Area of Science:

• Polymer Science
• Mechanochemistry
• Materials Science

Background:

• Mechanophores are reactive sites in polymers that respond to mechanical stress.
• Existing mechanophores can enhance material toughness, exhibit mechanochromism, or enable self-healing.
• Combining these properties in a single molecule is a key challenge in polymer engineering.

Purpose of the Study:

• To investigate macrocyclic cinnamate dimers as novel mechanophores.
• To demonstrate their ability to enhance polymer toughness and facilitate optical self-healing.
• To explore the tunability of their mechanochemical properties.

Main Methods:

• Synthesis of macrocyclic cinnamate dimers.
• Mechanical testing of polymer chains containing these dimers.
• Spectroscopic analysis to observe dissociation and reformation.
• Single-chain force spectroscopy to measure extensibility.

Main Results:

• The dimers dissociate within a sub-second timescale under 1-2 nN stretching force.
• Stretching polymers with these dimers more than doubles contour length and increases absorbed strain energy by over 600 kcal/mol.
• Dissociation produces a chromophore, and dimers reform upon irradiation, enabling optical healing.
• Mechanochemical kinetics and properties are tunable via synthetic modifications.

Conclusions:

• Macrocyclic cinnamate dimers effectively combine toughness enhancement and optical self-healing capabilities.
• These dimers represent a versatile platform for designing advanced stress-responsive polymers.
• Tunable mechanochemical properties open avenues for tailored material design.