Functional Group Transformation Approach to Chemically Recyclable Polymers from Ultra-Low to Moderate Strain...

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Chemistry

Background:

• Ring-opening metathesis polymerization (ROMP) is versatile but yields mostly non-recyclable polymers.
• Existing depolymerizable polyolefins via ROMP are limited by a narrow monomer ring strain energy (RSE) range (4.7–5.4 kcal/mol).

Purpose of the Study:

• To develop new, chemically recyclable polyolefins using a broader RSE range.
• To establish a structure-polymerizability-depolymerizability relationship for ROMP monomers.
• To enhance polymer recyclability through functional group transformation.

Main Methods:

• Synthesis of novel polyolefins from cycloheptene derivatives with RSEs from 3.8 to 7.2 kcal/mol.
• Investigation of structure-polymerizability-depolymerizability relationships.
• Application of a functional group transformation (FGT) strategy using reversible ketone-to-acetal chemistry.

Main Results:

• A wide RSE range (3.8–7.2 kcal/mol) was achieved for recyclable polyolefins.
• The FGT strategy improved the polymerizability of low-strain monomers and depolymerizability of moderate-strain polymers.
• Access to highly depolymerizable polyolefins was enabled, overcoming limitations of direct ROMP.

Conclusions:

• Novel cycloheptene-based polyolefins offer tunable thermal properties and enhanced chemical recyclability.
• The FGT approach broadens the scope of depolymerizable polymers and facilitates closed-loop recycling.
• This work advances sustainable polymer design through controlled RSE and versatile chemical transformations.