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Date of Award

9-2011

Document Type

Campus Access

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Polymer Science and Engineering

First Advisor

Thomas P. Russell

Second Advisor

Ryan C. Hayward

Third Advisor

Mark Tuominen

Subject Categories

Condensed Matter Physics | Materials Science and Engineering | Polymer Chemistry

Abstract

We have studied the wetting and self-assembly behavior of block copolymer thin films on chemical patterns in various geometries. Carboxylic-terminated, mesh-like patterns were generated on OTS modified silicon wafers by AFM electro-oxidation lithography. The films were pinned on the carboxylic regions due to the strong interaction of the minor component block with the surface which was also found to suppress film dewetting over the unpatterned methyl regions. We have found that the cylindrical microdomains orient normal to the methyl-terminated patterns and remain laterally confined within them. Defect-free, hexagonally packed cylindrical microdomains could be obtained thanks to the "corralling" action of the patterns. Domain deformation or point defects arose when the dimensions or shapes of the patterns were not commensurate with the natural packing of the copolymers. Tetragonal packing of microdomains was observed when a square-shaped confinement geometry, with dimension comparable to 2L 0 (natural period), was used. The stretching or compression of polymer chains was found to accomendate the incommensurable confinement imposed by chemical patterns, and a free energy model was applied for interpretation. Solvent annealing was conbined with chemical dot patterns to direct the self-assembly of block copolymers in thin films, and silicon oxide nanodots were fabricated through a tone-reversal process.

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