A Thermal and Manufacturable Approach to Stabilized Diblock Copolymer Templates

Leiston-Belanger, J. M.; Russell, T. P.; Drockenmuller, E. and Hawker, C. J.;
38, 7676-7683.

Stabilization of the morphology in thin diblock copolymer films is critical for the generation of robust templates for subsequent device fabrication. Copolymers containing thermally cross-linkable groups, such as benzocyclobutene (BCB), can be annealed to induce an ordered microdomain morphology and then subsequently heated to cross-link the system, locking in the morphology and eliminating the need for multistep processing. Poly[(styrene-r-BCB)-b-lactic acid] (PSBCB-b-PLA) was synthesized by a combination of living free radical and ring-opening polymerizations. Thin films (30 nm) of PSBCB-b-PLA annealed at 170 °C, followed by cross-linking at 200 °C, showed that the ordered and oriented microdomain morphology was preserved. For PSBCB-b-PLA, with PLA volume fractions of 0.24 and 0.36, arrays of cylindrical microdomains of PLA oriented normal to the surface were produced in a cross-linked PS matrix. Washing these films with a weak base degraded and removed the PLA, producing a nanoporous cross-linked template.