Controlling patterns by geometry in block copolymer thin films

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Self-assembling block copolymers provide a powerful framework for producing nanopatterns for a diversity of applications, including nanoporous membranes for ultra-purification, solar cells, nanotemplates, organic optoelectronics, and UV polarizers, and many others. However, one frequent problem with the self-assembly approach is lack of long-range order due to pattern undulations and defects. Numerous methods to produce patterns with well-defined orientational order have been proposed, such as shear alignment, alignment through electric fields, zone and solvent annealing, or grapho- and chemo-epitaxy. Here, we explore another possible aligning factor, the geometry in which the block copolymer film system is embedded. In the previous funding period, we have demonstrated that geometry can be an effective guiding field to induce long-range order and to prescribe the distribution and density of topological defects. In this project, we propose to study the equilibrium and kinetic properties of self-assembling block copolymer thin films deposited onto curved substrates. The central challenge is to develop a meaningful theory that allows identifying the leading parameters that control the intrinsic order in curved films carrying self-assembled patterns. The proposed study involves the treatment of ordering and defect dynamics on a wide range of length and time scales, spanning from molecular scales up to those that govern the mesoscopic kinetics of ordering under the action of experimentally accessible geometric fields. Special attention will be paid to the coupling between pattern morphologies and local symmetry and geometry. These problems will be tackled by a combined experimental and simulation effort.