MgH2/PEG initiating system for ring opening polymerization of lactone and lactide

Abstract

Dihydroxy-terminated poly(ethylene glycol) and MgH2 form an efficient initiating system for the ring opening polymerization of ε-caprolactone and Llactide. Polycaprolactone-block-polyethylene glycol-block-polycaprolactone and polylactide-block-polyethylene glycol-block-polylactide were synthesized in bulk at 120 °C for 16 h under argon. MgH2 provided a faster polymerization rate compared with other initiating systems based on non toxic metals used under vacuum. Molecular weight of copolymers varied according to the monomer / ethylene oxide units ratio. The developed procedure led to easy polymerization with better control of the design, molecular weight and polydispersity of the final material. Copolymers were characterized by SEC, DSC, 1H and 13C NMR and IR. Micelles in aqueous solutions were prepared by finding balance between hydrophobic polyester and hydrophilic polyethylene glycol blocks. Interest for this method is since the use of MgH2, environmental chemical, absence of solvent and vacuum techniques and the possible recovery of solid material without further operation.