Carbenium-Based Cationic Ring-Opening Polymerization of CO₂-Based Disubstituted δ-Valerolactone

Area of Science:

• Polymer Chemistry
• Organic Synthesis
• Materials Science

Background:

• Ring-opening polymerization (ROP) of lactones is a key method for polyester synthesis.
• α-ethylidene-δ-vinyl-δ-valerolactone (EVL) is a CO2-derived monomer with functionalization potential.
• The homopolymerization of EVL via cationic ring-opening polymerization (CROP) presents unique challenges.

Purpose of the Study:

• To achieve the first cationic ring-opening polymerization (CROP) of EVL.
• To synthesize well-defined cyclic polyester PEVL.
• To investigate the polymerization mechanism and polymer properties.

Main Methods:

• Carbenium-based cationic ring-opening polymerization (CROP).
• Characterization using NMR, MALDI-ToF MS, and DFT calculations.
• Variable temperature polymerization studies and post-polymerization modification.

Main Results:

• Successful CROP of EVL yielding cyclic polyester PEVL with M_n up to 12.8 kg/mol and dispersity of 1.2.
• PEVL contains two structural units derived from EVL, confirmed by spectroscopic and computational methods.
• Tunable M_n from 6.5 to 12.8 kg/mol by adjusting temperature; low Tg of -33.6 °C.
• Post-polymerization functionalization demonstrated by thiol-ene click reaction, introducing a melting point of 42.2 °C.

Conclusions:

• The carbenium-based CROP mechanism enables controlled synthesis of cyclic PEVL.
• Fast intramolecular transfer and slow initiation contribute to cyclic topology fidelity.
• PEVL is a versatile platform for functional materials due to its low Tg and modifiable structure.