Abstract
Abstract The morphology and crystallization kinetics in the blends of a symmetric poly(ethylene oxide)-block-polybutadiene (PEO-b-PB) and a PB homopolymer were investigated by small angle X-ray scattering (SAXS) and DSC. In the melt state, morphological transition from lamellae to hexagonally packed cylinders to bcc packed spheres was observed with increasing volume fraction of PB (|PB). The crystallization kinetics of PEO blocks confined in the nano-scaled microdomains exhibited a parallel transition with the morphological transformation. The distinct correlation was largely associated with the homogeneous nucleation-controlled crystallization in the microdomains, where the proportionality between nucleation rate and microdomain volume rendered the basis for the direct correlation. The crystallization was homogeneous nucleation controlled since impurities were unable to be induced nucleation in the nano-scaled microdomains. The homogeneous nucleation controlled mechanism was further verified the by first-order kinetic behavior associated with the cryatallinity development. In this case, the crystal kinetics in the lamellar melt was however not HN controlled. The crystallization rate decreased slightly as |PB increased because the crystallization behavior was not only dominated by nucleation but also influenced by crystal growth since the crystal growth was capable of propagating over a macroscopic length scale. The morphology of blends after crystallization was also detected by SAXS and it was also found that the initial microdomain structure was neither fully preserved nor completely disrupted into 1-D stacked lamellar morphology upon crystallization. An "intermediate structure" was likely formed after the crystallization.