The bulk morphology of a crystalline/amorphous diblock copolymer under diff
erent thermal, conditions was studied. The diblock copolymer, poly((ethylen
e oxide)-b-1,4-polybutadiene), forms a microphase-separated lamellar morpho
logy in the molten state. For samples crystallized within the range of 20-5
0 degreesC, TEM coupled with electron diffraction revealed a microphase-sep
arated, alternating lamellar morphology with the PEO crystalline chains ori
ented perpendicular to the interface between the PEO and PBD domains. A sig
nificant increase in the microphase-separated, lamellar domain spacing was
observed upon crystallization. On the length scale of tens of microns, as p
robed by polarizing optical microscopy, a nonspherultic crystalline texture
(with the absence of the Maltese cross), corresponding to the microphase-s
eparated lamellar grain morphology, was observed. In contrast to the integr
al chain folding observed in PEO homopolymer, the increase in PEO lamellar
thickness with decreasing undercooling is continuous in the block copolymer
. In addition, the equilibrium melting temperature and lamellar spacing wer
e determined.