Block copolymer self-assembly and templating strategies

Abstract

Block copolymers microphase separate to form periodic patterns with period of a few nm and above without the need for lithographic guidance. These self-assembled nanostructures have a variety of bulk geometries (alternating lamellae, gyroids, cylinder or sphere arrays, tiling patterns, core-shell structures) depending on the molecular architecture of the polymer and the volume fraction of its blocks. And in thin films, surface interaction and commensurability effect influence the self-assembly and result in more diverse morphologies including hexagonal-packed perforated lamellae, square array of holes. The progress of self-assembly can be tracked in situ using Grazing Incidence Small Angle X-ray Scattering, and the annealed morphology can be revealed in 3D using TEM tomography. Moreover, non-bulk morphologies can be produced, the ordering of the microdomains can be improved and their locations directed using various templates and processing strategies. The blocks can themselves constitute a functional material, such as a photonic crystal, or they can be used as a mask to pattern other functional materials, functionalized directly by various chemical approaches, or used as a scaffold to assemble nanoparticles or other nanostructures. Block copolymers therefore offer tremendous flexibility in creating nanostructured materials with a range of applications in microelectronics, photovoltaics, filtration membranes and other devices.