CRYSTALLIZATION OF BLOCK COPOLYMERS .1. SMALL-ANGLE X-RAY-SCATTERING STUDY OF AN EPSILON-CAPROLACTONE BUTADIENE DIBLOCK COPOLYMER

The morphology formed in a crystalline-amorphous diblock copolymer, epsilon-caprolactone-block-butadiene (PCL-b-PB), has been investigated by small-angle X-ray scattering (SAXS) at various temperatures. The process of the morphology formation is also observed by time-resolved SAXS employing synchrotron radiation. Crystallization of the PCL block brings about a dramatic change in the shape of the SAXS pattern; a diffuse intensity maximum arising from the correlation hole effect of disordered block copolymers could be observed at the melt, while it was replaced by a strong intensity peak at a smaller angle for temperatures below T(m) (melting temperature of the PCL block). The time-resolved SAXS curves revealed that the copolymer, which was quenched from the melt into a temperature below both T(m) and T(s) (microphase-separation temperature of the copolymer), immediately showed a sharp diffraction due to the microstructure of the copolymer, followed by a strong intensity peak at a smaller angle owing to the crystallization of the PCL block. This indicates that an energetic gain in crystallization overwhelms that in microphase separation, so that the microstructure is completely destroyed by the following crystallization of the PCL block.