Changes of the lamellar period by nanoparticles in the nanoreactor scheme of thin films of symmetric diblock copolymers

Abstract

Nanometre-sized domains of block copolymers can be utilized as so-called nanoreactors to synthesize a variety of nanoparticles. In this nanoreactor scheme, the domain size and period of block copolymers should be expanded to incorporate nanoparticles. We investigated changes in the domain period by gold nanoparticles, employing thin films of symmetric polystyrene-block-poly(4-vinylpyridine) (PS–PVP) diblock copolymers. Since the PS–PVP thin film on the substrate had a multilayered structure of parallel lamellae with a film thickness quantized in terms of the lamellar period, thickness measurements after in situ synthesis of gold nanoparticles in the PVP lamellae enabled us to quantify changes in the lamellar period. In addition, we measured the amount of gold nanoparticles incorporated into the film using a quartz crystal microbalance. From these results, dependence of the lamellar period on the volume fraction of nanoparticles can be explained by an intermediate case of homogeneous distribution and local segregation of nanoparticles within the PVP lamellae.