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

ACS Nano. 2012 Nov 27;6(11):10335-42. doi: 10.1021/nn304266f. Epub 2012 Oct 29.


As demand for smaller, more powerful, and energy-efficient devices continues, conventional patterning technologies are pushing up against fundamental limits. Block copolymers (BCPs) are considered prime candidates for a potential solution via directed self-assembly of nanostructures. 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 × 10(4) Pa) in the system. We successfully apply this process to create unidirectional alignment of BCP thin films over a wide range of thicknesses (nm to μm) and processing speeds (μm/s to mm/s) using both a flat and patterned PDMS layer. 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 Δθ(fwhm) ≤ 5° (full width at half-maximum). This method may pave the way to practical industrial use of hierarchically patterned BCP nanostructures.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Crystallization / methods*
  • Dimethylpolysiloxanes / chemical synthesis*
  • Hardness
  • Materials Testing
  • Membranes, Artificial*
  • Nylons / chemical synthesis*
  • Shear Strength
  • Temperature
  • Thermal Conductivity


  • Dimethylpolysiloxanes
  • Membranes, Artificial
  • Nylons
  • poly(dimethylsiloxane)-polyamide copolymer