Morphological study on binary blends of poly(ε-caprolactone)-block-polybutadiene and poly(ε-caprolactone)

Abstract

The morphology and melting behavior of binary blends of poly(ε-caprolactone)-block-polybutadiene (PCL-b-PB) and poly(ε-caprolactone) homopolymer (PCL) were investigated by small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) as a function of the homopolymer fraction φhomo in the system. Three sets of the blends were prepared considering the degree of miscibility between PCL-b-PB and PCL in the melt. The morphology after crystallization of PCL and the PCL block in PCL-b-PB depended strongly on the miscibility in the melt; when PCL was uniformly dissolved with the PCL block in the microdomain structure of PCL-b-PB, an alternating structure of lamellae and amorphous layers (lamellar morphology) was formed in which the PCL block and PCL together made a lamellar crystal, suggesting the formation of a mixed crystal composed of the PCL block and PCL. When PCL was localized in the microdomain structure or macroscopically segregated in the melt, two separate crystalline regions were observed over a wide range of φhomo, each consisting of PCL and PCL+PCL-b-PB. The lamellar morphology is qualitatively discussed as a function of φhomo from the viewpoint of the chain conformation of the PB block.