Morphology of melt-quenched poly(ε-caprolactone)-block-polyethylene copolymers

The morphology of a melt-quenched crystalline–crystalline diblock copolymer, poly(ε-caprolactone)-block-polyethylene (PCL-b-PE), was studied by small-angle X-ray scattering and transmission electron microscopy. The melting behavior of PCL-b-PE was also investigated by differential scanning calorimetry. The melting temperature of PCL blocks, Tm,PCL, was ca. 55 °C and that of PE blocks was ca. 96 °C. Therefore, the PE block always crystallized first during quenching from the microphase-separated melt into various temperatures Tc below Tm,PCL to yield an alternating structure composed of PE lamellae and amorphous layers (PE lamellar morphology), and subsequently the crystallization of PCL blocks started at Tc after some induction period. The PE lamellar morphology was preserved after the crystallization of PCL blocks at low crystallization temperatures (Tc<30 °C), that is, the PCL block crystallized within the PE lamellar morphology. At high crystallization temperatures (45 °C>Tc>30 °C), on the other hand, the crystallization of PCL blocks destroyed the PE lamellar morphology to result in a new lamellar morphology mainly consisting of PCL lamellae and amorphous layers (PCL lamellar morphology). The PE crystals were fragmentarily dispersed in the PCL lamellar morphology.