We have investigated the crystallized morphology formed at each temperature T-c (20 degrees C <= T-c <= 45 degrees C) in double crystalline poly(epsilon-caprolactone)-block-polyethylene (PCL-b-PE) copolymers as a function of composition (or volume fraction of PE blocks phi(PE)) by employing small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) techniques. When PCL-b-PE with phi(PE) <= 0.58 was quenched from a microphase-separated melt into T-c, the crystallization of PE blocks occurred first to yield an alternating structure consisting of thin PE crystals and amorphous PE + PCL layers (PE lamellar morphology) followed by the crystallization of PCL blocks, where we can expect a competition between the stability of the PE lamellar morphology (depending on phi(PE)) and PCL crystallization (on T-c). Two different morphologies were formed in the system judging from a long period. That is, the PCL block crystallized within the existing PE lamellar morphology at lower T-c (<30 degrees C) to yield a double crystallized alternating structure while it crystallized by deforming or partially destroying the PE lamellar morphology at higher T-c (>35 degrees C) to result in a significant increase of the long period. However, the temperature at which the morphology changed was almost independent Of phi(PE). For PCL-b-PE with phi(PE) >= 0.73, on the other hand, the morphology after the crystallization of PE blocks was preserved at every T-c investigated. (C) 2007 Elsevier Ltd. All rights reserved.