Brønsted acid-catalyzed polymerization of ε-caprolactone in water: A mild and straightforward route to poly(ε-caprolactone)-graft-water-soluble polysaccharides

The polymerization of ε-caprolactone (ε-CL) has been assessed in water using various Brønsted acids as catalysts. The reaction was found to be quantitative at 100 °C, leading to number–average molecular weights up to 5000 g mol−1. The Brønsted acid-catalyzed polymerization of ε-CL in water was further conducted in the presence of water-soluble polysaccharides thereby affording graft copolymers. The approach enables an easy, mild access to dextran hydroxyesters. For low degree of substitution, the latter self-assembles in water to form nanoparticles. Poly(ε-CL)-graft-methylcellulose copolymers can also be obtained via a similar approach. It is noteworthy that the methodology reported herein is a one-step route to poly(ε-CL)-graft-water-soluble polysaccharides, operating in mild conditions, that is, at low temperatures, using readily available metal-free catalysts and water as a solvent.