Self-Assembly of Coil/Liquid-Crystalline Diblock Copolymers in a Liquid Crystal Solvent
Abstract
Diblock copolymers having a random-coil polymer block (polystyrene, PS) connected to a side-group liquid crystal polymer (SGLCP) self-assemble in a nematic liquid crystal (LC), 4-pentyl-4′-cyanobiphenyl, into micelles with PS-rich cores and SGLCP-rich coronas. The morphologies of block copolymers with varying PS content are characterized as a function of temperature and concentration using small-angle neutron scattering, rheometry, and transmission electron microscopy. Unlike conventional solvents, the nematic LC can undergo a first-order transition between distinct fluid phases, accessing the regimes of both strong and slight selectivity in a single polymer/solvent pair. Micelles dissolve away above a microphase separation temperature (MST) that is often equal to the solution's isotropization point, TNI. However, increasing or decreasing the polymer's PS content can shift the MST to be above or below TNI, respectively, and in the former case, micelles abruptly swell with solvent at TNI. Comparable effects can be achieved by modulating the overall polymer concentration.
Additional Information
Copyright © 2008 American Chemical Society. Received July 16, 2008; Revised Manuscript Received October 18, 2008. Publication Date (Web): December 5, 2008. A portion of the results shown in this report are derived from work performed at Argonne National Laboratory. Argonne is operated by UChicago Argonne, LLC, for the U.S. Department of Energy under Contract DE-AC02-06CH11357. Another portion of this work was performed at Oak Ridge National Laboratory's Center for Nanophase Materials Sciences which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. This work benefited from use of the shared facilities supported by the MRSEC Program of the National Science Foundation under Award DMR-0080065. N.R.S., R.V., and J.A.K. acknowledge financial support from the AFOSR LC-MURI (f4962-97-1-0014); S.-Y.P. and J.A.K. acknowledge financial support from MOST and AFOSR NBIT 2007 program. We thank Ed Lang and Zuleika Kurji for assistance with neutron scattering experiments. National Defense Science and Engineering Graduate Fellowships awarded to N.R.S. and R.V. are greatly appreciated. Supporting Information: Table of solution transition temperatures, results from side-on diblock copolymer solutions, and dynamic moduli of end-on diblock copolymer solutions. This material is available free of charge via the Internet at http://pubs.acs.org.Attached Files
Supplemental Material - SCRUm09supp.pdf
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Additional details
- Eprint ID
- 13188
- Resolver ID
- CaltechAUTHORS:SCRUm09
- DE-AC02-06CH11357
- Department of Energy
- Oak Ridge National Laboratory
- DMR-0080065
- National Science Foundation
- f4962-97-1-0014
- Air Force Office of Scientific Research
- Ministry of Science and Technology (MOST) (Korea)
- Department of Defense
- Created
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2009-02-02Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field