Isothermal crystallization of poly(ε-caprolactone-ethylene glycol) block copolymers

The isothermal crystallization of three different types of poly[epsilon-caprolactone-co-ethylene glycol] (PCL-PEG) incompatible block copolymers [A-B, (A)(2)-B, and A-B-A] was investigated using DSC. The PEG weight fraction in the copolymers was slightly varied From 18 to 22 wt%. It was established that the kinetic parameters from the Avrami equation (the half time of crystallization, tau(0.5), and the rate constant of overall crystallization, z) for the PCL constituent, which crystallizes first, are similar to the kinetic parameters of the corresponding homopolymer (PCL). The growth retardation of the constituent which crystallizes second (PEG block) is attributed to the mutual influence between the PEG constituent and the PCL crystal phase which fixes (hardened) the total copolymer structure.