| We investigate the physics and applications of diblock copolymer thin films (mono-layer and bilayer thickness). We demonstrate that a monolayer film of sphere-forming diblock copolymer can be used as a model system for the study of two-dimensional melting transitions. We report a first order transition from the liquid to the hexatic phase; a second transition from the hexatic to the 2-D crystalline phase is not observed, presumably due to it being masked by the glass transition. We also investigate various modalities of obtaining long-range order in diblock copolymer thin films. A thermal processing procedure consisting of a propagating melting-solidification front is shown to decrease the density of topological defects by several orders of magnitude. Another technique, involving the slow shearing of the diblock copolymer film, is shown to produce alignment in mono- and bi-layers of cylinder-forming as well as in bilayers of sphere-forming copolymers. A phenomenological model for the alignment is developed and tested by cell-dynamics simulations. |
