Morphology Evolution of PS-b-P2VP Diblock Copolymers via Supramolecular Assembly of Hydroxylated Gold Nanoparticles

We report on the strong segregation of core shell Au nanoparticles, with a shell layer consisting of a random copolymer brush of styrene and vinylphenol (PS-r-PVPh-SH), in poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) diblock copolymer. Because of the formation of multiple hydrogen bonds between the hydroxyl groups within the shell of the nanoparticles and the pyridine group in PS-b-P2VP, the Au nanoparticles were strongly localized into P2VP domains with a very high volume fraction of nanoparticles (phi(p) similar to 0.53). The spatial distribution of Au nanoparticles, observed by transmission electron microscopy (TEM), is compared with results of previous experiments where homopolymers were blended with block copolymers. If the diameter d of the nanoparticles is much less than the width D of the P2VP lamellar domains, these nanoparticles are more uniformly distributed across the P2VP domain than if d is comparable to D, in which case the nanoparticles are pushed toward the center of the P2VP domains. This behavior is similar to that observed when homopolymers are blended with block copolymers. Novel morphological transitions from spherical to cylindrical P2VP morphologies and from lamellae to cylindrical PS morphologies were observed during coassembly of these functional nanoparticles with block copolymers.