Networked and chiral nanocomposites from ABC triblock terpolymer coassembly with transition metal oxide nanoparticles

Abstract

Multicomponent materials with ordered nanoscale networks are critical for applications ranging from microelectronics to energy conversion and storage devices which require charge transport along 3-dimensional (3D) continuous pathways. The network symmetry can facilitate additional properties such as macroscopic polarization for piezoelectric, pyroelectric, and second-order nonlinear optical properties in non-centrosymmetric morphologies. Although pure block copolymers are able to form multiple network morphologies, network tunability remains a challenge for coassembled systems. Here we report the coassembly of niobia nanoparticles with a poly(isoprene-b-styrene-b-ethylene oxide) (ISO) which resulted in multiple network morphologies, one of which was chiral and non-centrosymmetric. Detailed small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) measurements were most consistent with the alternating gyroid (G^A) morphology at low nanoparticle loadings and a transition to a centrosymmetric network morphology at higher loadings. This is the first report of multiple network morphologies from coassembly with a single polymer over a ∼10 vol% composition range. The nanoparticle spatial distribution was tomographically reconstructed. Nanocomposite calcination resulted in mesoporous networks. This general approach was further demonstrated with amorphous and anatase titania.