In block copolymers, microphase separation allows for the formation of long range ordered phases. This behavior can be directed by templating microscale features on a surface followed by back filling with an appropriate block copolymer. The polymer then phase separates, providing a way to create nanoscale features using microscale lithography. Mixed polymer brushes can accomplish similar results. In this system two polymers, polystyrene and poly(methyl methacrylate), are grafted from the surface utilizing free radical initiators covalently bound to the substrate. We demonstrate that mixed polymer brushes also microphase separate similar to that seen with block copolymers, so the composition of the brush determines the phase behavior of the system. Lithography could also be employed to direct long range ordering in mixed polymer brush systems. Polymer brushes offer several distinct advantages over spin-coated block copolymers systems. Since the polymers are attached to the surface, they are more robust towards both mechanical and chemical processes. The substrate also does not need to be planar; brushes can be grown from a wide variety of surface geometries such as spheres or cylinders. Finally, features such as right angles, which are traditionally difficult to replicate with block copolymers, should be more readily accessible using a mixed polymer brush system. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Pursuing ordered microphase separation in mixed polymer brushes

249th National Meeting (2015)

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