Shear-Aligned Block Copolymer Monolayers as Seeds to Control the Orientational Order in Cylinder-Forming Block Copolymer Thin Films

ABATE ANABELLA; VU GIANG; ALDO PEZZUTTI; NICOLÁS GARCÍA; RALEIGH L. DAVIS; FRIEDERIKE SCHMID; RICHARD A. REGISTER; DANIEL A. VEGA

MACROMOLECULES

AMER CHEMICAL SOC

Lugar: Washington; Año: 2016

0024-9297

We study the dynamics of coarsening of a cylinder-forming block copolymer thinfilm deposited on a prepatterned substrate made of a well-ordered block copolymer monolayer. During thermal annealing the shear-aligned bottom layer drives extinction of the disclinations and promotes a strong orientational correlation, disturbed only by dislocations and undulations along the cylinders of the minority phase. The thin bilayer system remains stable during annealing, in agreement with self-consistent field theory results that indicate that although the thickness of a stack of two monolayers is not at the optimum thickness condition, it is very close to equilibrium. Phase field simulations indicate that the bottom layer remains undisturbed during annealing and acts as a periodic external eld that stabilizes the orientation of those domains thatshare a similar orientation with the substrate. Misoriented cylinders are rapidly reorganized through an instability mechanism that drives the fragmentation of the cylinders.As annealing proceeds, the fragmented cylinders are reconstructed along the direction imposed by the ordered bottom layer. This mechanism removes the disclinations completely while leaving dislocations that can be slowly annihilated during annealing. These results indicate that with appropriate control over the self-assembling polymeric substrate, it should be possible to propagate order in thick block copolymer lams and to obtain structures with controlled orientational order.