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Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
Chain Length Dependence of Chemically Controlled Reactions in Polymerization
Yue Mu1, Zhen Liu1, Michelle L Coote2
1School of Chemical Engineering, East China University of Science and Technology, Shanghai200237, China.
Journal of the American Chemical Society
|July 14, 2026
Summary
Chemically controlled polymerization reactions show unexpected chain length effects due to entropy. This challenges the assumption of independent rate coefficients, impacting reversible addition-fragmentation chain transfer (RAFT) polymerization and other polymer-polymer reactions.
Area of Science:
- Polymer Chemistry
- Chemical Kinetics
- Thermodynamics
Background:
- Traditionally, rate coefficients in chemically controlled polymerization are assumed to be chain-length independent.
- This assumption is critical for understanding polymerization kinetics and thermodynamics.
Purpose of the Study:
- To challenge the assumption of chain-length independent rate coefficients in chemically controlled polymerization.
- To investigate the impact of chain length on the kinetics and thermodynamics of polymer-polymer reactions, using reversible addition-fragmentation chain transfer (RAFT) polymerization as a case study.
Main Methods:
- Utilized multiscale modeling to simulate polymerization processes.
- Compared chain length convergence of reaction entropy for polymer-polymer RAFT agent reactions versus low molecular weight RAFT agent reactions.
- Analyzed Diels-Alder step-growth polymerization with varying chain lengths.
Main Results:
- Demonstrated significant chain length effects in chemically controlled polymer-polymer reactions.
- Observed delayed entropy convergence in RAFT polymerization involving polymeric RAFT agents (persisting to DP > 100) compared to low molecular weight agents (equilibrium within 10 monomer additions).
- Found that entropy contributions scale logarithmically with chain length, leading to chain length-dependent equilibrium constants.
Conclusions:
- Chain length effects are significant in the kinetics and thermodynamics of chemically controlled polymer-polymer reactions due to fundamental entropic considerations.
- Findings provide a mechanistic basis for resolving experimental discrepancies in rate coefficients and understanding rate retardation in RAFT systems.
- Highlights the importance of considering chain length dependence in polymerization modeling and analysis.
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