Block copolymers confined in a nanopore: pathfinding in a curving and frustrating flatland

Sevink, G. J. A. and Zvelindovsky, Andrei (2008) Block copolymers confined in a nanopore: pathfinding in a curving and frustrating flatland. Journal of Chemical Physics, 128 (8). ISSN 0021-9606

Full content URL: http://scitation.aip.org/content/aip/journal/jcp/1...

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Item Type:Article
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Abstract

We have studied structure formation in a confined block copolymer melt by means of dynamic density functional theory. The confinement is two dimensional, and the confined geometry is that of a cylindrical nanopore. Although the results of this study are general, our coarse-grained molecular model is inspired by an experimental lamella-forming polysterene-polybutadiene diblock copolymer system K. Shin, Science 306, 76 (2004), in which an exotic toroidal structure was observed upon confinement in alumina nanopores. Our computational study shows that a zoo of exotic structures can be formed, although the majority, including the catenoid, helix, and double helix that were also found in Monte Carlo nanopore studies, are metastable states. We introduce a general classification scheme and consider the role of kinetics and elongational pressure on stability and formation pathway of both equilibrium and metastable structures in detail. We find that helicity and threefold connections mediate structural transitions on a larger scale. Moreover, by matching the remaining parameter in our mesoscopic method, the Flory-Huggins parameter , to the experimental system, we obtain a structure that resembles the experimental toroidal structure in great detail. Here, the most important factor seems to be the roughness of the pore, i.e., small variations of the pore radius on a scale that is larger than the characteristic size in the system. © 2008 American Institute of Physics.

Keywords:Density functional theory, Molecular modeling, Monte Carlo methods, Nanopores, Polymer melts, Polystyrenes, Alumina nanopores, Coarse-grained molecular models, Mediate structural transitions, Metastable structures, Block copolymers
Subjects:F Physical Sciences > F162 Polymer Chemistry
F Physical Sciences > F320 Chemical Physics
Divisions:College of Science > School of Mathematics and Physics
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ID Code:14925
Deposited On:17 Sep 2014 10:50

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