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Dynamics of Shear-Induced Alignment of a Lamellar Diblock:  A Rheo-optical, Electron Microscopy, and X-ray Scattering Study

Chen, Z.-R. and Issaian, A. M. and Kornfield, J. A. and Smith, S. D. and Grothaus, J. T. and Satkowski, M. M. (1997) Dynamics of Shear-Induced Alignment of a Lamellar Diblock:  A Rheo-optical, Electron Microscopy, and X-ray Scattering Study. Macromolecules, 30 (23). pp. 7096-7114. ISSN 0024-9297. https://resolver.caltech.edu/CaltechAUTHORS:20180719-141226290

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Abstract

In-situ rheo-optical methods are used to guide electron microscopy (TEM) and X-ray scattering (SAXS) studies of structure development during flow-induced alignment in a lamellar block copolymer melt (nearly symmetric polystyrene−polyisoprene diblock, ODT ≃ 172 °C). The progress of shear-induced alignment is recorded in real-time using flow birefringence; at selected points during alignment samples are taken for ex-situ characterization by TEM and SAXS along all three axes (v, ∇v, ∇ × v) of the flow geometry. Three different trajectories are examined:  perpendicular alignment and two qualitatively different routes to parallel alignment in the high-frequency regime (ω > ω'_c). In general, the initial “fast” process not only enhances the projection of the orientation distribution that corresponds to the final state but also increases other projections of the distribution; the late-stage “slow” process eliminates these other projections and perfects a single alignment. For example, the highest frequency path to parallel alignment begins by transforming poorly organized regions into layers that are predominantly oriented along the parallel and transverse directions. The transition to the slow process is marked by the development of a characteristic texture in which tilt wall boundaries normal to the flow direction separate bands that form a repeating “chevron” pattern (layers tilted up and down about the ∇×v axis). The coarsening of this pattern dominates the slow process, during which the transverse projection is also eliminated.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://dx.doi.org/10.1021/ma9706743DOIArticle
ORCID:
AuthorORCID
Kornfield, J. A.0000-0001-6746-8634
Additional Information:© 1997 American Chemical Society. Received May 13, 1997; Revised Manuscript Received September 2, 1997. This research was carried out with the support of the NSF-CTS 9421015, AFOSR-Liquid Crystals MURI, Chevron and Raychem. We thank Hans Spiess and Uli Wiesner for inspiring this work; Glenn Fredrickson, Scott Milner, Zhen-Gang Wang, Ron Larson, Frank Bates, Karen Winey, and Nitash Balsara for insightful discussions; and Richard Spontak, Steve Hudson, and Faith Morrison for valuable feedback on the manuscript.
Funders:
Funding AgencyGrant Number
NSFCTS-9421015
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Chevron CorporationUNSPECIFIED
RaychemUNSPECIFIED
Issue or Number:23
Record Number:CaltechAUTHORS:20180719-141226290
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180719-141226290
Official Citation:Dynamics of Shear-Induced Alignment of a Lamellar Diblock:  A Rheo-optical, Electron Microscopy, and X-ray Scattering Study Z.-R. Chen, A. M. Issaian, J. A. Kornfield, S. D. Smith, J. T. Grothaus, and M. M. Satkowski Macromolecules 1997 30 (23), 7096-7114 DOI: 10.1021/ma9706743
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88010
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:19 Jul 2018 21:31
Last Modified:03 Oct 2019 20:02

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