Parallel and perpendicular lamellar phases in copolymer-nanoparticle multilayer structures

Recent results in developing novel nanocomposite multilayer structures are presented. We used symmetric polystryrene-block-polymethylmethacrylate (deuterated) P(S-b-MMAd) lamellar thin films as a self-assembling matrix for the lamellar arrangement of Fe₃O₄ nanoparticles. Pure copolymer films showed an unusual structure with a perpendicular to the surface orientation of the lamellae, in the part of the film towards the free surface. This is a new phenomenon because up to now this orientation was obtained only on specially prepared substrates. After the incorporation of nanoparticles into the copolymer matrix, the system switched to a lamellar structure parallel to the surface. Further increasing of the nanoparticles concentration led to a more perfect lamellar structure, which shows that the limit for a high concentration of nanoparticles, important for nanotechnology has not yet been reached.