Abstract
AbstractWe studied the crystallization kinetics and crystalline morphology of poly(ethylene oxide)-block-poly(1,4-butadiene) (PEO-b-PB) exhibiting various mesophase structures in the melt. In order to establish a proper model system in which the crystallization can be effective confined within the nano-scaled microdomains while maintaining high degree of crystallizability of the crystalline blocks, the amorphous PB blocks in PB-b-PEO were crosslinked by a photo-initiated crosslinking reaction so that the crystallization-induced disruption of microdomain structure may be effectively avoided. Small angle X-ray scattering (SAXS) results revealed that the microdomain morphology in the melt effectively preserved upon crystallization of the PEO block after the PB matrix crosslinked. The kinetics of the crystallization confined in the microdomains displayed a parallel transition with the transformation of microdomain morphology. Such a distinct correlation stemmed largely from the homogeneous nucleation controlled crystallizations where the direct proportionality between nucleation rate and microdomain volume rendered the basis for the direct correlation. The homogeneous nucleation controlled crystallizations in the compositions containing cylindrical and spherical PEO microdomains was further verified from the isothermal crystallization study. In spite of the effective confinement imposed by the crosslinked PB phase, crystallization in the lamellar phase still proceeded through a mechanism analogous to the spherulitic crystallization of homopolymer.