Diblock copolymers based on 1,4-dioxan-2-one and ε-caprolactone: Characterization and thermal properties

Various poly(ε-caprolactone-block-1,4-dioxan-2-one) (P(CL-block-PDX)) block copolymers were prepared according to the living/controlled ring-opening polymerization (ROP) of 1,4-dioxan-2-one (PDX) as initiated by in situ generated ω-aluminium alkoxides poly (ε-caprolactone) (PCL) chains in toluene at 25°C.^{[1] 1}H NMR, PCS and TEM measurements have attested for the formation of colloids attributed to a growing PPDX core surrounded by a solvating PCL shell during the polymerization of PDX promoted by ω-A1 alkoxide PCL chains in toluene. The thermal behavior of the P(CL-block-PDX) copolymers was studied by DSC showing two distinct melting temperatures (as well as two glass transition temperatures) similar to those of the respective homopolyesters. Finally, the thermal degradation of the P(CL-block-PDX) block copolymers was investigated by TGA simultaneously coupled to a FT-IR spectrometer and a mass spectrometer for evolved gas analysis (EGA). The degradation occurred in two consecutive steps involving a first unzipping depolymerization of the PPDX blocks followed by the degradation of the PCL blocks via both ester pyrolysis and unzipping reactions.