Dynamic thermal field processing of block copolymer (BCP) thin film is a highly attractive roll-to-roll directed self-assembly method for molecular level organization of BCP nanostructures over large areas without requiring physical or chemical guiding templates. We introduce here a facile directed self-assembly method to rapidly fabricate unidirectionally aligned BCP nanopatterns at large scale, on rigid or flexible template-free substrates via a thermally induced dynamic gradient soft-shear field. A localized differential thermal expansion at the interface between a BCP film and a confining polydimethylsiloxane (PDMS) layer due to a dynamic thermal field imposes the gradient soft-shear field. PDMS undergoes directional expansion (along the annealing direction) in the heating zone and contracts back in the cooling zone, thus setting up a single cycle of oscillatory shear (maximum lateral shear stress ~ 12 � 104 Pa) in the system. Here we present results that focus on identifying the molecular mechanism responsible for these highly oriented BCP thin films that can be up to 1 �m thick. Grazing incidence small-angle X-ray scattering measurements show absolutely no sign of isotropic population and reveal ~99% aligned orientational order with an angular spread ??fwhm =5� (full width at half-maximum). We report the critical dependence of cylinder orientation on the PDMS layer dimension relative to the dimensions of the heated-zone. Finally, we demonstrate a new route towards rapid fabrication of hierarchically patterned vertically oriented cylinders as well.

Dynamic thermal field induced-gradient soft-shear for highly oriented and hierarchically patterned block copolymer thin films

246th National Meeting (2013)

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