Web Release Date: January 27,
Initial-Stage Growth Controlled Crystal Orientations in Nanoconfined Lamellae of a Self-Assembled Crystalline-Amorphous Diblock Copolymer
Maurice Morton Institute and Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909
Department of Materials Science and Engineering, Massachusetts Institute and Technology, Cambridge, Massachusetts 02139
Department of Chemistry, The State University of New York at Stony Brook, Stony Brook, New York 11794-3400
Institute Charles Sadron, 6 Rue Boussingault, Strasbourg 67083, France
Received October 31, 2000
Revised Manuscript Received December 12, 2000
Abstract:
Crystallization temperature (Tc)-dependent crystal orientations within nanoconfined lamellae
have been studied in a self-assembled poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer.
The copolymer possesses number-average molecular weights of 
nPEO = 8.7K and nPS = 9.2K, and it
forms a microphase-separated lamellar structure in the melt. It has been found that the PEO crystal
(the c axis) orientations are determined by only varying the Tc.1 Based on real-time simultaneous two-dimensional (2D) small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) experiments, the formation of crystal orientation is found in an early stage of PEO crystallization confined
between the PS lamellae. To understand whether the crystal orientation is determined during the primary
nucleation or crystal growth step, specifically designed self-seeded crystallization experiments are carried
out using 2D SAXS and WAXS techniques. Experimental results suggest that primary nuclei (self-seeds)
do not possess specific orientation with respect to the PS lamellar surface normal, disregarding the history
of crystal orientation in the samples generated before the self-seeding process. It is found that the initial
stage of crystal growth determines the final crystal orientation in the nanoconfined lamellae. Studies of
the correlation lengths (apparent crystallite sizes) along both [120] directions of the PEO crystals with
various crystal orientations indicate that the PEO crystals formed in nanoconfined lamellae undergo a
change from a one-dimensional to a two-dimensional growth with increasing Tc.
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