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Development of Block Co-Polymers as Self-Assembling Templates for Magnetic Media and Spin-Valves

Published online by Cambridge University Press:  01 February 2011

Vishal Vitthal Warke
Affiliation:
warke001@bama.ua.edu, University of Alabama, Department of Chemistry and MINT Center, Tuscaloosa, AL, 35487, United States
Chris Redden
Affiliation:
chredden@hotmail.com, University of Alabama, Department of Chemistry and MINT Center, Tuscaloosa, AL, 35487, United States
Martin Bakker
Affiliation:
bakker@bama.ua.edu, University of Alabama, Department of Chemistry and MINT Center, Tuscaloosa, AL, 35487, United States
David Nikles
Affiliation:
dnikles@mint.ua.edu, University of Alabama, Department of Chemistry and MINT Center, Tuscaloosa, AL, 35487, United States
Kunlun Hong
Affiliation:
hongkq@ornl.gov, Oak Ridge National Laboratory, Center for Nanophase Materials Science, Oak Ridge, TN, 37831, United States
Jimmy Mays
Affiliation:
jimmymays@utk.edu, Oak Ridge National Laboratory, Center for Nanophase Materials Science, Oak Ridge, TN, 37831, United States
Phil Britt
Affiliation:
brittpf@ornl.gov, Oak Ridge National Laboratory, Center for Nanophase Materials Science, Oak Ridge, TN, 37831, United States
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Abstract

Poly(styrene)-Poly(methylmethacrylate) block co-polymers (PS-b-PMMA) of appropriate block length and PS to PMMA ratio self-assemble into a 2-D hexagonal phase in which the PS majority phase is continuous and surrounds cylinders of the minority, PMMA phase. By UV irradiation and washing with acetic acid it is possible to remove the minority phase to leave empty channels. It is also possible to rearrange the PMMA phase with acetic acid to leave somewhat smaller pores. For most substrates the interactions between the polymer and the substrate surface are such that one block is preferentially adsorbed to the substrate resulting in alignment of the PMMA domains parallel to the substrate surface. It is possible to orient the polymer perpendicular to the surface by first adding a thin film of a random PS-PMMA co-polymer before applying the PS-b-PMMA block co-polymer. However thin films of the random PS-PMMA do not give good surface coatings, and thicker films are generally too thick for the pores in the PS-b-PMMA block co-polymer to be propagated to the substrate surface. For a few substrates, thin PS-b-PMMA films naturally adopt a perpendicular orientation after annealing, washing with acetic acid produces arrays of pores of diameter as small as 3 nm. For a number of other substrates the interaction between the polymer blocks and the surface is such that upon annealing the polymer rearranges to form micron sized domains which are not polymer coated, surrounded a areas which have a thicker polymer coating. We have observed this behavior with both carbon coated substrates and with ITO glass substrates. In both cases the areas of polymer are perpendicularly oriented, and upon washing with acetic acid give rise to pores that extend completely through the polymer film. In some cases films on ITO glass are continuous even after annealing. After washing with acetic acid it was possible to electrodeposit nickel into the pores to give nickel nano-pillars of 18 nm diameter.

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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