Self-Amplified HF Release and Polymer Deconstruction Cascades Triggered by Mechanical Force

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Chemistry

Background:

• Hydrogen fluoride (HF) is crucial for material transformation, including polymer degradation and remodeling.
• Responsive *in situ* generation of HF in materials is key for developing adaptive material systems.
• Current methods for HF generation in materials are often limited to thermal triggers.

Purpose of the Study:

• To report the mechanochemically coupled generation of HF from alkoxy-gem-difluorocyclopropane (gDFC) mechanophores.
• To investigate the mechanism of HF generation and its application in polymer degradation.
• To explore new adaptive material systems based on mechanically triggered HF release.

Main Methods:

• Synthesis of alkoxy-gem-difluorocyclopropane (gDFC) mechanophores via difluorocarbene addition to enol ethers.
• Mechanochemical activation of gDFC mechanophores to induce rearrangement and HF generation.
• Ab initio steered molecular dynamics simulations to elucidate the reaction mechanism and selectivity.
• Hydrolysis of the intermediate α-fluoro allyl ether for HF release and polymer chain cleavage.
• Application of mechanically generated HF for polymer degradation and optical response using fluoride indicators.

Main Results:

• Alkoxy-gDFC mechanophores successfully generate HF upon mechanical stimulation.
• The mechanochemical rearrangement exhibits preferential fluoride migration to the alkoxy-substituted carbon, confirmed by simulations.
• Polymer degradation was achieved through acid-catalyzed hydrolysis of the intermediate, leading to self-amplifying HF generation.
• Degradation of polybutadiene containing embedded HF-cleavable silyl ethers was demonstrated (11 mol %).
• An optical response was observed using fluoride indicators in conjunction with mechanically generated HF.

Conclusions:

• Alkoxy-gDFC mechanophores provide a novel route for mechanically coupled HF generation.
• This mechanism enables responsive polymer remodeling and degradation, complementing existing thermal methods.
• The findings pave the way for new adaptive material systems triggered by mechanical force.