| Summary: | Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001. === Vita. === Includes bibliographical references. === Various block copolymer microdomain structures are controlled in bulk as well as in thin film by employing flow fields, directional solidification, and substrates. In bulk systems, flow fields generated by the 'roll casting' process orient amorphous cylindrical microdomains along the flow direction in a semicrystalline block copolymer. Subsequent crystallization of the crystalline block is significantly influenced by the pre-existing oriented amorphous cylindrical microdomains. The orientation of crystalline lamellae is achieved parallel to the cylinder axis, completely suppressing spherulite formation. Microdomain structures of block copolymers are also controlled in thin films by directional solidification of a crystallizable solvent. This new method is based on the use of crystalline organic materials, which are solvents for the block copolymers above their melting temperatures. The directional crystallization of the solvent induces the directional microphase separation of the block copolymer. Furthermore, the flat (001) crystal face of benzoic acid or anthracene provides both a surface for epitaxy of a semicrystalline polyethylene block as well as a confining surface for the thin polymer film which forms between the crystallizing solvent and the glass or silicon wafer substrate. Several semicrystalline and non-crystalline block copolymers were directionally solidified using a crystallizable solvent. A bi-axially ordered edge-on crystalline lamellar structure is obtained due to the epitaxy between a melt-compatible semicrystalline block copolymer and benzoic acid single crystal. Directional solidification generates vertically aligned lamellar and cylindrical microdomain structures of conventional non-crystalline block copolymers such as PS/PMMA and PS/PI. === (cont.) The combination of epitaxy and directional solidification with a strongly segregated cylinder forming semicrystalline block copolymer produces a perpendicularly aligned cylindrical microstructure with each cylinder containing precisely one crystalline lamella. In addition, the utilization of the degenerate epitaxy between anthracene and the polyethylene block in a semicrystalline block terpolymer alters the classic block copolymer microstructure into a new pattern structure. This new process was also performed on a topographically pre-patterned silicon oxide substrate and produced two types of spatially patterned cylinders (vertical and in-plane), depending on the local film thickness. The selective removal of the diene domains by reactive ion etching points the way towards a host of nano-technological applications such as high density magnetic storage media and photonic crystals. === by Cheolmin Park. === Ph.D.
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