(338a) Invited Talk: Pattern Formation in Block Copolymer and Grafted Nanoparticle Thin Films

This presentation focuses on simulations of pattern formation in block copolymer and grafted nanoparticle thin films. In the block copolymer simulations, we utilize a recently developed theoretically informed coarse graining model [1], which preserves chain connectivity, microphase separation and finite compressibility of the melt. In static block copolymer films, we find, in agreement with experiments, a remarkable cascade of morphological transitions from parallel to perpendicular orientations when the film height is varied [2]. We demonstrate that the emergence of a stable parallel configuration stems from entropic effects due to the conformational asymmetry and the confinement of the system. For the sheared films, we find that the thin films exhibit shear thinning behavior strongly correlated with the disentanglement and shear alignment of the constituent polymers, and show that shear can be employed to induce long-range ordering to the spontaneously self-assembled microdomains [3]. Finally, a "top down" coarse-graining methodlogy is utilized to investigate the self assembly of solvent-free grafted nanoparticles into thin free-standing films. We find that the nanoparticles self-assemble into a variety of morphologies ranging from dispersed particles, finite stripes, long strings, to percolating networks [4].

[1] D. Q. Pike, F. A. Detcheverry, M. Müller, and J. J. de Pablo, "Theoretically informed coarse grain simulations of polymeric systems," J. Chem. Phys., 131:084903 (2009).
[2] A. Nikoubashman, R. A. Register, and A. Z. Panagiotopoulos, "Sequential Domain Realignment Driven by Conformational Asymmetry in Block Copolymer Thin Films,"  Macromolecules, 47:1193-8 (2014).
[3] A. Nikoubashman, R. L. Davis, P. M. Chaikin, B. T. Michal, R. A. Register, and A. Z. Panagiotopoulos, "Thin Films of Homopolymers and Cylinder-Forming Diblock Copolymers under Shear," submitted (2014).
[4] T. Lafitte, S. K. Kumar, and A. Z. Panagiotopoulos, "Self-assembly of polymer-grafted nanoparticles in thin films," Soft Matter, 10:786-94 (2014).