Crystallization of double crystalline block copolymer/crystalline homopolymer blends: 1. Crystalline morphology

Abstract

The crystalline morphology formed in binary blends of poly(ε-caprolactone)- block-polyethylene (PCL-b-PE) copolymers and PCL homopolymers has been examined using synchrotron small-angle X-ray scattering (SR-SAXS) and differential scanning calorimetry (DSC) as a function of the homopolymer fraction in the blend. The PE block crystallized first on quenching from a lamellar microdomain structure to set a hard lamellar morphology (PE lamellar morphology) in the blend, followed by the crystallization of PCL chains (i.e., PCL homopolymers + PCL blocks). Two binary blends were studied by considering the miscible state of PCL homopolymers in the microdomain structure: when the PCL homopolymers were uniformly mixed with PCL blocks, they formed a mixed crystal. When the PCL homopolymers were localized between PCL blocks in the microdomain structure, DSC results suggested the possible formation of separate PCL crystals in the PE lamellar morphology. The effect of the advance crystallization of PE blocks on the subsequent crystallization of PCL chains was discussed as compared with the crystalline morphology formed in PCL-block-polybutadiene copolymer/PCL homopolymer blends, where the crystallization of PCL chains started directly from a microdomain structure without forming the hard lamellar morphology.