Morphology of thin nanocomposite films of asymmetric diblock copolymer and magnetitenanoparticles

Abstract

Thin self-assembled nanocomposite films of an asymmetric diblockcopolymer and nanoparticles are fabricated. The morphologies of the filmsof the diblock copolymer poly(styrene-block-n-butyl methacrylate), P(Sd-b-BMA), with different volume fractions of large magnetiteFe3O4 nanoparticles are studied before and after annealing. Neutron reflectometry revealsremarkable evidence that confining asymmetric copolymer to a limit of two layersforces the film, after the annealing, to form a mixed cylindrical–lamellar two-layerstructure. This complex morphology is very stable and is preserved after theincorporation of nanoparticles up to 10% volume fraction. The other striking resultis that the monodispersed nanoparticles with affinity to the polystyrene (PS)domain and with a size of 10 nm, which is close to the size of the PS chains, areassembled by the diblock copolymer matrix, so the distribution of the nanoparticles isreduced solely to the PS domain of the film. Our studies demonstrate that forasymmetric block copolymers in thin film geometry the self-assembly is stronglyinfluenced by the interfacial and surface energies of the blocks and substrate.