Melt and Solid-State Structures of Polydisperse Polyolefin Multiblock Copolymers

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Crystallization in polydisperse ethylene octene multiblock copolymers, polymerized via chain shuttling chemistry, is examined using two-dimensional synchrotron small- and wide-angle X-ray scattering on flow-aligned specimens. The multiblocks are composed of alternating crystalline (hard) blocks of low 1-octene content and amorphous (soft) blocks of high 1-octene content; the block lengths and the number of blocks per chain are characterized by most-probable distributions. These polymers self-assemble into lamellar domain morphologies in the melt, and the melt morphology is retained in the solid state. Despite extensive mixing between hard and soft blocks, the high crystallinity (>50%) of the hard blocks leads to an alignment of the crystallites within the domain structure, with the orthorhombic polyethylene c-axis generally perpendicular to the lamellar domain normal. The interlamellar domain spacings exhibited by the multiblocks, which exceed 100 nm, are estimated to be 5 times larger than those in near-monodisperse block copolymers having a similar chemical composition and a number-average molecular weight equivalent to the multiblock's "constituent diblock" repeating unit. This swelling factor exceeds the value of 3 previously reported for analogous polydisperse olefin diblock copolymers, due to the lower segregation strength and enhanced phase mixing of the multiblocks studied here.
Publisher
AMER CHEMICAL SOC
Issue Date
2012-07
Language
English
Article Type
Article
Keywords

OLEFIN BLOCK-COPOLYMERS; X-RAY-SCATTERING; SEMICRYSTALLINE DIBLOCK COPOLYMERS; GEL-PERMEATION CHROMATOGRAPHY; ABA TRIBLOCK COPOLYMERS; MOLECULAR-WEIGHT; VISCOELASTIC PROPERTIES; LAMELLAR MICRODOMAINS; MICROPHASE-SEPARATION; MECHANICAL-PROPERTIES

Citation

MACROMOLECULES, v.45, no.14, pp.5773 - 5781

ISSN
0024-9297
DOI
10.1021/ma300910m
URI
http://hdl.handle.net/10203/207382
Appears in Collection
CBE-Journal Papers(저널논문)
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