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Controlling tosylation versus chlorination during end group modification of PCL
Ivo A O Beeren1, Pieter J Dijkstra1, Philippe Massonnet2
1Department of Complex Tissue Regeneration, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Universiteitssingel 40, 6211 LK Maastricht, The Netherlands.
European Polymer Journal
|June 29, 2026
Summary
Researchers discovered a solvent-dependent reaction for modifying synthetic polymers like poly (ε-caprolactone) (PCL). Polar aprotic solvents unexpectedly yield chlorinated polymers, while inert solvents produce tosylated polymers, enabling new functionalization strategies.
Area of Science:
- Polymer Chemistry
- Materials Science
- Biomedical Engineering
Background:
- Synthetic biodegradable polymers like poly (ε-caprolactone) (PCL) are crucial for medical devices and tissue engineering.
- Current polymers often lack inherent functional groups, necessitating end-group modification for attaching bioactive molecules.
- Existing modification methods can be complex, requiring interconversion of end groups.
Purpose of the Study:
- To investigate the solvent-dependent reactivity of poly (ε-caprolactone) diol end groups during tosylation.
- To explore a novel method for introducing functional groups onto synthetic polymers.
- To demonstrate the translatability of the observed reaction to other polymer systems.
Main Methods:
- Poly (ε-caprolactone) diol was reacted with p-toluenesulfonyl chloride in various solvents (dichloromethane, dimethylformamide, dimethyl sulfoxide, chloroform).
- The resulting polymer end groups were analyzed to determine the reaction products (tosylate ester or chloride).
- The reaction was also performed on polyethylene glycol (PEG) to assess broader applicability.
Main Results:
- Reaction in polar aprotic solvents (DMF, DMSO) unexpectedly yielded chlorinated poly (ε-caprolactone) end groups.
- Reaction in inert solvents (DCM, chloroform) successfully produced the expected tosylated poly (ε-caprolactone) ester.
- The chlorination reaction was successfully translated to polyethylene glycol, demonstrating its versatility.
Conclusions:
- Solvent choice critically dictates the outcome of poly (ε-caprolactone) diol end-group modification with p-toluenesulfonyl chloride.
- Polar aprotic solvents promote a chloride displacement (Sn2) of the tosyl group, leading to chlorination.
- This study presents a new, facile strategy for introducing 'clickable' chloride groups onto synthetic polymers, particularly those soluble only in polar aprotic solvents.
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