Off-center Mechanophore Activation in Block Copolymers

Area of Science:

• Polymer Science
• Materials Science
• Mechanochemistry

Background:

• Block copolymers (BCPs) are vital in materials science but can degrade via mechanochemistry.
• Mechanically induced bond scission in BCPs may have unpredictable effects.
• BCP heterogeneity might alter force distribution and localization during stress.

Purpose of the Study:

• To investigate how BCP heterogeneity influences mechanochemical force transduction.
• To determine if BCPs exhibit different mechanochemical responses compared to homopolymers.
• To explore force localization and activation of mechanophores in BCPs.

Main Methods:

• Synthesized a linear block copolymer with an embedded gem-dichlorocyclopropane (gDCC) mechanophore and a poly(methyl methacrylate) block.
• Subjected the BCP to mechanical stress in solution to observe mechanochemical ring-opening of gDCC.
• Compared the mechanochemical response of the BCP to that of homopolymers.

Main Results:

• Mechanochemical ring-opening of gDCC was accelerated in BCPs compared to homopolymers, despite mechanophores being at chain ends.
• BCPs demonstrated higher mechanophore activation selectivity.
• Mechanochemical response was prominent even far from the BCP chain center.

Conclusions:

• BCP heterogeneity significantly impacts mechanochemical response.
• Forces along BCP chains efficiently activate mechanophores, even distant ones.
• This highlights the potential for controlled mechanochemical activation in complex polymer architectures.