Block copolymer self-assemply in curved space

D. A. VEGA; N. A. GARCÍA; A. D. PEZZUTTI; L. R. GÓMEZ

Halle

Congreso; 4th International Workshop - Theory and Computer Simulation of Polymers: New Developments; 2015

Martin-Luther-University, Halle-Wittenberg, Institute of Physics, 06120 Halle (Saale)

In this work we study the processes of self-organization of block copolymer thin films deposited on topographically patterned curved substrates. A phase field approach is employed to analyze the coupling between block copolymer textures with hexagonal and smectic symmetries and the local mean and Gaussian curvatures of the substrate.Mechanisms of phase separation, defect formation and defect dynamics are found to strongly deviate from their counterparts in flat systems.In crystalline systems the process of defect formation is deeply affected by the curvature, and at the onset of a phase transition the early density of defects becomes highly inhomogeneous. We observe that even a single growing crystal can produce varying densities of defects depending on its initial position and local orientation with regard to the substrate. This process is completely different from flat space, where grain boundaries 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 copolymer such that equilibrium textures are modified and dictated by the underlying geometry. On substrates of varying mean curvature and zero Gaussian curvature, simulations show that topological defects are rapidly expelled from regions with large curvature. These results compare well with available experimental data of poly(styrene)-co-poly(ethylene-alt-propylene) smectic thin films.