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Science 3 August 2007:
Vol. 317. no. 5838, pp. 647 - 650
DOI: 10.1126/science.1141768
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Reports

Block Copolymer Assembly via Kinetic Control

Honggang Cui,1 Zhiyun Chen,2 Sheng Zhong,1 Karen L. Wooley,2* Darrin J. Pochan1*

Block copolymers consist of two or more chemically different polymer segments, or blocks, connected by a covalent linkage. In solution, amphiphilic blocks can self-assemble as a result of energetic repulsion effects between blocks. The degree of repulsion, the lengths of the block segments, and the selectivity of the solvent primarily control the resultant assembled morphology. In an ideal situation, one would like to be able to alter the morphology that forms without having to change the chemistry of the block copolymer. Through the kinetic manipulation of charged, amphiphilic block copolymers in solution, we are able to generate different nanoscale structures with simple block copolymer chemistry. The technique relies on divalent organic counter ions and solvent mixtures to drive the organization of the block copolymers down specific pathways into complex one-dimensional structures. Block copolymers are increasingly used as templating materials; thus, the ability to control the formation of specific patterns and structures is of growing interest and applicability.

1 Department of Materials Science and Engineering and Delaware Biotechnology Institute, University of Delaware, Newark, Delaware 19716, USA.
2 Center for Materials Innovation, Department of Chemistry and Department of Radiology, Washington University in Saint Louis, Saint Louis, Missouri 63130, USA.

* To whom correspondence should be addressed. E-mail: klwooley{at}artsci.wustl.edu (K.L.W.); Pochan{at}udel.edu (D.J.P.)

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Science. ISSN 0036-8075 (print), 1095-9203 (online)