A Polymer with Mechanochemically Active Hidden Length.

Area of Science:

• Polymer Chemistry
• Materials Science
• Mechanochemistry

Background:

• Incorporating hidden length into polymer chains enhances mechanical properties by allowing localized strain relief.
• Current designs focus on sacrificial bonds, but not mechanochemical reactivity within the hidden length itself.

Purpose of the Study:

• To demonstrate the advantages of integrating mechanochemical reactivity into the hidden length of polymer chains.
• To introduce a novel mechanophore for enhanced polymer mechanical properties.

Main Methods:

• Synthesis of a new mechanophore integrating (Z)-2,3-diphenylcyclobutene-1,4-dicarboxylate into macrocyclic cinnamate dimers.
• Mechanical stretching of the polymer and DFT calculations to analyze energy dissipation and fracture mechanics.
• Sonicated solutions to study mechanochemical reactions and validate computational models.

Main Results:

• Stretching the polymer more than doubles its contour length without fracture.
• The new mechanophore exhibits an 11-fold increase in chain fracture energy compared to simple polyesters.
• High energy-dissipating capacity is maintained up to approximately 3 nN.

Conclusions:

• Adding mechanochemical reactivity to hidden length offers significant advantages over traditional designs.
• The developed mechanophore provides superior mechanical properties and energy dissipation.
• The study validates computational models and suggests methods for quantifying single-chain forces.