6533b823fe1ef96bd127eb1a

RESEARCH PRODUCT

Ring opening polymerization of $\varepsilon$-caprolactone in the presence of wet $\beta$-cyclodextrin: Effect of the operative pressure and of water molecules in the $\beta$-cyclodextrin cavity

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International audience; The ring opening polymerization (ROP) of $\varepsilon$-caprolactone (CL) in the presence of $\beta$-cyclodextrin ($\beta$-CD) wasperformed in batch reactors both at room pressure and with the reaction system pressurized with CO$_2$, N$_2$ orAr. Significant enhancements of the polymerization rate was observed when the ROP was carried out withwet $\beta$-CD under pressure. For example, after 24 hours at 120° C with a $\beta$-CD/CL molar ratio of about1/100, the monomer conversion increased from 4 to 98–99% when the pressure was changed from 0.1to 12.5–13.0 MPa independent of the nature of the compressing gas. MALDI-TOF analyses indicated thata major fraction of polymer chains obtained in pressurized systems was initiated by water molecules. Thecollected results suggest that at 12–13 MPa wet b-CD can catalyse both the ring opening of $\varepsilon$-caprolactone and the polymerization of the obtained linear species and that high energy water moleculeslocated inside the cavity of the cyclic oligosaccharide must play a role in initiating the polymerization. Thetrend of number average molecular weight and the results of MALDI-TOF analyses obtained inpolymerizations performed for long reaction times and in a hydrolysis test of commercial poly($\varepsilon$-caprolactone) indicate that wet $\beta$-CD can work as an artificial lipase enzyme under the adopted conditions.