Web Release Date: June 6,
Crystallization Temperature-Dependent Crystal Orientations within Nanoscale Confined Lamellae of a Self-Assembled Crystalline-Amorphous Diblock Copolymer
and
Contribution from the Maurice Morton Institute and Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, Department of Chemistry, The State University of New York at Stony Brook, Stony Brook, New York 11794-3400, and Institute Charles Sadron, 6 Rue Boussingault, Strasbourg 67083, France
Received January 25, 2000
Abstract:
For a lamella-forming poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer (
nPEO
= 8.7K and nPS = 9.2K), the glass transition temperature of the PS blocks is 62 
C, and the melting temperature
of the PEO crystals is around 51 C when the sample is crystallized below 40 C. The PEO blocks thus
crystallize in a one-dimensionally confined lamellar space of 8.8 nm, as studied recently by one-dimensional
small-angle X-ray scattering (SAXS) and transmission electron microscopy. In this report, the crystal orientation
(the c-axis of the PEO crystals) within nanoscale confined lamellae has been investigated using combined
two-dimensional SAXS and wide-angle X-ray scattering experiments. The c-axis orientation in the PEO crystals
is observed for the first time to change from random to perpendicular, then to inclined, and finally to parallel
to the lamellar surface normal, depending only on the crystallization temperature (Tc). Detailed crystallographic
analyses indicate that the c-axis orientation at each Tc corresponds to a uniform orientation rather than a mixture
of different crystal orientations.
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