ARTICLE
Electric Field Induced Selective Disordering in Lamellar Block Copolymers )
Markus Ruppel,† Christian W. Pester,‡ Karol M. Langner,§ Geert J. A. Sevink,§ Heiko G. Schoberth,‡,# Kristin Schmidt,^ Volker S. Urban, Jimmy W. Mays,† and Alexander Bo¨ker‡,* Chemical Sciences Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee 37831, United States, ‡DWI an der RWTH Aachen e.V., RWTH Aachen University, Aachen, NRW 52056, Germany, §Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands, ^ Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States, and Biology and Soft Matter Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee 37831, United States. #Present address: Institute for Materials and Process Simulations, University of Bayreuth, 95440 Bayreuth, Germany. )
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ABSTRACT External electric fields align nanostructured block
copolymers by either rotation of grains or nucleation and growth depending on how strongly the chemically distinct block copolymer components are segregated. In close vicinity to the orderdisorder transition, theory and simulations suggest a third mechanism: selective disordering. We present a time-resolved small-angle X-ray scattering study that demonstrates how an electric field can indeed selectively disintegrate ill-aligned lamellae in a lyotropic block copolymer solution, while lamellae with interfaces oriented parallel to the applied field prevail. The present study adds an additional mechanism to the experimentally corroborated suite of mechanistic pathways, by which nanostructured block copolymers can align with an electric field. Our results further unveil the benefit of electric field assisted annealing for mitigating orientational disorder and topological defects in block copolymer mesophases, both in close vicinity to the orderdisorder transition and well below it. KEYWORDS: selective disordering . block copolymer . electric field . SAXS
B
lock copolymer self-assembly readily furnishes periodic morphologies with length scales on the order of 10 100 nm, and it is considered a powerful and cost-effective paradigm for fabricating highly ordered and densely packed nanostructures in thin films, bulk, and solutions.1 Molecular design affords the generation of a wide variety of geometries with domain sizes below the limits of conventional optical lithography (
