POS1-0627
Intrinsic Chain-End Stabilization Enables Chain-Transfer-Agent-Free Living Cationic Ring-Opening Polymerization of Cyclic Enol Ethers
Topic
S1. Polymer Synthesis
When and Where
Sep 30, 2026
08:30 - 09:30
Room 301 (Grand Ballroom)
Session Chairs
Heesuk KIM
Jinhye BAE
Presenter(s)
Semin Son (Ajou University)
Co-Author(s)
Abstract
Cationic ring-opening polymerization (CROP) of cyclic enol ethers prepared by the inverse-electron-demand hetero Diels–Alder (IEDDA) reaction of vinyl ketones and vinyl ethers provides a distinct route to vinyl polymers bearing head-to-head alternating sequences and tunable properties. However, controlled CROP has been limited by poor chain-end stability, as the propagating oxocarbenium ion promotes undesirable chain-transfer reactions. Our previous cationic reversible addition–fragmentation chain-transfer (cRAFT) approach addressed this issue but required chain-transfer agents (CTAs) and afforded only limited molecular weights (Mn up to 27 kg/mol).
Here, we report a CTA-free living CROP enabled by intrinsic chain-end stabilization. DFT calculations revealed that the propagating species preferentially adopts a ring-closed cationic form, more stable than the classical oxocarbenium ion by 15.4 kcal/mol. By preserving this stable cation using triflimide (Tf2NH) as a simple Brønsted acid initiator, living polymerization was achieved without any CTA or metal catalyst.
The method affords polymers with Mn up to 507 kg/mol and low dispersities (Đ = 1.08–1.27), far surpassing prior systems. Living character was confirmed by first-order kinetics and linear Mn–DP relationships. Well-defined block copolymers were readily accessible by sequential monomer addition.
Across nine monomers with varied side chains, glass transition temperatures spanning 8–107 °C, elongation at break from 2.5% to >800%, and tensile strengths up to 20 MPa were achieved. Wavelength-selective photodegradation of individual blocks was demonstrated in a diblock copolymer system.
These results establish CROP of cyclic enol ethers as a platform for high-molecular-weight, mechanically tunable, and photodegradable vinyl polymers, with the counteranion-engineering strategy providing a broadly applicable principle for living cationic polymerization.
Here, we report a CTA-free living CROP enabled by intrinsic chain-end stabilization. DFT calculations revealed that the propagating species preferentially adopts a ring-closed cationic form, more stable than the classical oxocarbenium ion by 15.4 kcal/mol. By preserving this stable cation using triflimide (Tf2NH) as a simple Brønsted acid initiator, living polymerization was achieved without any CTA or metal catalyst.
The method affords polymers with Mn up to 507 kg/mol and low dispersities (Đ = 1.08–1.27), far surpassing prior systems. Living character was confirmed by first-order kinetics and linear Mn–DP relationships. Well-defined block copolymers were readily accessible by sequential monomer addition.
Across nine monomers with varied side chains, glass transition temperatures spanning 8–107 °C, elongation at break from 2.5% to >800%, and tensile strengths up to 20 MPa were achieved. Wavelength-selective photodegradation of individual blocks was demonstrated in a diblock copolymer system.
These results establish CROP of cyclic enol ethers as a platform for high-molecular-weight, mechanically tunable, and photodegradable vinyl polymers, with the counteranion-engineering strategy providing a broadly applicable principle for living cationic polymerization.
