Coarsening mechanisms of block copolymer thin films in curved space.

VEGA DA

Göttingen

Exposición; Conferencia invitada; 2016

göttingen universität

In this work we study the processes of self-organization of block copolymer thin films deposited ontopographically patterned curved substrates. A phase field approach is employed to analyze the couplingbetween block copolymer textures with hexagonal and smectic symmetries and the local mean andGaussian curvatures of the substrate.Mechanisms of phase separation, defect formation and defect dynamics are found to strongly deviatefrom their counterparts in flat systems.In crystalline systems the process of defect formation is deeply affected by the curvature, and at the onsetof a phase transition the early density of defects becomes highly inhomogeneous. We observe that even asingle growing crystal can produce varying densities of defects depending on its initial position and localorientation with regard to the substrate. This process is completely different from flat space, where grainboundaries are formed due to the impingement of different propagating crystals.In smectic textures, the substrate´s curvature produces out-of-plane deformations of the block copolymersuch that equilibrium textures are modified and dictated by the underlying geometry. On substrates ofvarying mean curvature and zero Gaussian curvature, simulations show that topological defects arerapidly expelled from regions with large curvature. These results compare well with availableexperimental data of poly(styrene)-co-poly(ethylene-alt-propylene) thin films.