Related Experiment Video
Updated: Aug 27, 2026

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
Published on: November 21, 2017
Thermodynamic and Kinetic Control of Ring-Chain Interconversion in Entropy-Driven Ring-Opening Polymerization of a
1Beijing National Laboratory For Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center for Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing, China.
Abstract:
Entropy-driven ring-opening polymerization (ED-ROP) of macrocyclic (thio)esters offers a promising platform for chemically recyclable polymers through intrinsically reversible ring-chain equilibria, yet its broader development remains constrained by low monomer reactivity, highly dilute depolymerization conditions, and the limited repolymerizability of recycled macrocyclic oligomers (MCOs). Here we report a 14-membered sulfur-containing macrocyclic di(ester-thioester), 14-DET, whose thioester linkages enhance monomer reactivity and enable controllable macrocycle-mediated recycling. Using efficient salen- or salan-based lanthanum catalysts, 14-DET undergoes rapid ED-ROP at ambient temperature to afford poly(ester-alt-thioester), P(14-DET), with number-average molar mass (Mn) up to 163 kDa and high sequence alternation (PAB H up to 0.97). Modulation of temperature, concentration, and time directs the reversible ring-chain system toward high-molar-mass polymer, MCOs, or the 28-membered cyclic dimer (14-DET)2, revealing distinct thermodynamic and kinetic regimes, including transient kinetically controlled polymer formation at 0°C before equilibration toward the precipitated cyclic dimer. Notably, both recovered (14-DET)2 and MCOs generated during monomer synthesis can be directly repolymerized to regenerate high-molar-mass P(14-DET), providing feedstock flexibility and improving overall material utilization. These results establish a closed-loop "monomer-dimer-polymer" cycle and demonstrate a macrocycle-mediated recycling paradigm in which the cyclic dimers and MCOs serve as valuable polymerizable feedstocks.
Related Concept Videos
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Base-Catalyzed Ring-Opening of Epoxides
Anionic Chain-Growth Polymerization: Mechanism
Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
Olefin Metathesis Polymerization: Overview
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...

