"Coordination-insertion" ring-opening polymerization of 1,4-dioxan-2-one and controlled synthesis of diblock copolymers with ε-caprolactone

This communication deals with the coordination-insertion ring-opening polymerization of 1,4-dioxan-2-one (DX) as initiated by aluminium triiso-propoxide (Al(OⁱPr)₃) either in bulk or in solution. First, polymerization of DX has been carried out in bulk at 100°C and compared to the ring-opening polymerization promoted by tin(II)octoate. Block copolymers of ε-caprolactone (CL) and DX have been then selectively obtained by first initiating CL polymerization with Al(OⁱPr)₃ in toluene and then adding DX to the living PCL macroinitiator solution at room temperature. In spite of the inherent poor solubility of poly(1,4-dioxan-2-one) in most organic solvents, DX polymerization has proven to proceed through a "living" mechanism. Interestingly enough, the semi-crystalline P[CL-b-DX] block copolymers displayed two well separated melting endotherms at ca. 55 and 102°C for PCL and PDX sequences, respectively.