Three-Dimensional Nanoscale Alignment of Metal Nanoparticles Using Block Copolymer Films as Nanoreactors

We present a simple dry process to create nanoscale arrangements of metal nanoparticles within block copolymer films. This process involves only one step such that the vapor of palladium(II) acetylacetonato (Pd(acac)2) is exposed to a polymer film in a nitrogen atmosphere at 180 °C for periods up to 2 h. The Pd(acac)2 vapor penetrates into the film and then is decomposed and reduced to a metallic state to form nanoparticles therein. When block copolymer films having nanoscale microdomain structures are used, the metal complex is selectively reduced in one of the phases to give nanoscale arrangements of the metal particles that reflect the microdomain structure of the used block copolymer. In symmetric diblock copolymers of poly(styrene)-block-poly(methyl methacrylate) (PS-b-PMMA), Pd(acac)2 is selectively reduced in the PS lamellae to yield Pd nanoparticles with the average diameter ranging from 3 to 4 nm with a narrow size distribution, depending on the molecular weight. As a result, the Pd nanoparticles...