Nanoparticle-driven orientation transition and soft-shear alignment in diblock copolymer films via dynamic thermal gradient field

Abstract

Sharp dynamic thermal gradient (T ≈ 45 °C mm-1) field-driven assembly of cylinder-forming block copolymer (c-BCP) films filled with PS-coated gold nanoparticles (AuNPs; dNP ≈ 3.6 nm, φNP ≈ 0-0.1) is studied. The influence of increasing AuNP loading fraction on dispersion and assembly of AuNPs within c-BCP (PS-PMMA) films is investigated via both static and dynamic thermal gradient fields. With φNP increasing, a sharp transition from vertical to random in-plane horizontal cylinder orientation is observed due to enrichment of AuNPs at the substrate side and favorable interaction of PMMA chains with gold cores. Furthermore, a detachable capping elastomer layer can self-align these random oriented PMMA microdomains into unidirectional hybrid AuNP/c-BCP nanolines, quantified with an alignment order parameter, S. The incorporation of increasing loading fraction of PS-coated gold nanoparticles into cylinder-forming block copolymer films induces a facile vertical to random-in-plane horizontal morphology transition under dynamic thermal gradient field. Soft-shear could further align the hybrid nanostructures. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.