Crystallization in Ordered Polydisperse Polyolefin Diblock Copolymers

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The morphologies of polydisperse ethylene octene diblock copolymers, synthesized via a novel coordinative chain transfer polymerization process, are examined using two-dimensional synchrotron small-angle and wide-angle X-ray scattering on flow-aligned specimens. The diblock copolymers comprise one amorphous block with high 1-octene content and one semicrystalline block with relatively low 1-octene content, and each block ideally exhibits the most-probable distribution. Near-symmetric diblocks with a sufficiently large octene differential between the amorphous and semicrystalline blocks show well-ordered lamellar domain structures with long periods exceeding 100 nm. Orientation of these domain structures persists through multiple melting/recrystallization cycles, reflecting a robust structure which self-assembles in the melt. The domain spacings are nearly 3-fold larger than those in near-monodisperse polyethylene block copolymers of similar molecular weights. Although the well-ordered lamellar domain structure established in the melt is preserved in the solid state, the crystallites are isotropic in orientation. These materials display crystallization kinetics consistent with a spreading growth habit, indicating that the lamellae do not confine or template the growing crystals. The exceptionally large domain spacings and isotropic crystal growth are attributed to interblock mixing resulting from the large polydispersity; short hard blocks dissolved in the soft-block-rich domains swell the domain spacing in the melt and allow hard block crystallization to proceed across the lamellar domain interfaces.
Publisher
AMER CHEMICAL SOC
Issue Date
2010-05
Language
English
Article Type
Article
Keywords

X-RAY-SCATTERING; MICROPHASE-SEPARATED STRUCTURE; GEL-PERMEATION CHROMATOGRAPHY; BLOCK-COPOLYMERS; MOLECULAR-WEIGHT; TRIBLOCK COPOLYMERS; POLYMER CRYSTALLIZATION; ETHYLENE; BEHAVIOR; BLENDS

Citation

MACROMOLECULES, v.43, no.10, pp.4761 - 4770

ISSN
0024-9297
DOI
10.1021/ma100609k
URI
http://hdl.handle.net/10203/207388
Appears in Collection
CBE-Journal Papers(저널논문)
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