Crystallization in Ordered Polydisperse Polyolefin Diblock Copolymers

Journal Article · Tue Dec 07 04:00:00 EST 2010 · Macromolecules

DOI:https://doi.org/10.1021/ma100609k· OSTI ID:1002925

Li, Sheng; Register, Richard A; Landes, Brian G; Hustad, Phillip D; Weinhold, Jeffrey D ^[1]

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1. Dow

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.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: USDOE
• OSTI ID: 1002925
• Journal Information: Macromolecules, Journal Name: Macromolecules Journal Issue: (10) ; 05, 2010 Vol. 43
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

43 PARTICLE ACCELERATORS
CHAINS
COPOLYMERS
CRYSTAL GROWTH
CRYSTALLIZATION
DISTRIBUTION
DOMAIN STRUCTURE
KINETICS
LAMELLAE
MOLECULAR WEIGHT
OCTENES
ORIENTATION
POLYETHYLENES
POLYMERIZATION
POLYOLEFINS
SCATTERING
SYNCHROTRONS