Using Block Copolymer Micellar Thin Films as Templates for the Production of Catalysts for Carbon Nanotube Growth

We report a novel approach that uses block copolymer micelles as a means to create large area arrays of iron-containing nanoclusters capable of catalyzing the growth of carbon nanotubes (CNTs). The amphiphilic block copolymer poly(styrene-block-acrylic acid) (PS-b-PAA) forms micelles in solution which are capable of self-organizing into ordered structures on surfaces. By spin-coating these solutions onto a variety of substrates, we can create quasi-hexagonal arrays of PAA spheres within a PS matrix. The carboxylic acids groups in the PAA domains can be utilized in an ion-exchange protocol to selectively sequester iron ions, which results in iron-containing nanoclusters that are nearly monodisperse in size (diameter ~8 nm) and patterned at a density of approximately 1011 particles per cm2. In principle, this route for synthesizing iron-containing nanoclusters offers the capability of controlling the cluster size and spacing by altering the molecular weight of the block copolymer. In this report, we demonstrate the ability of these block-copolymer-templated iron-containing nanocluster arrays to catalyze the growth of CNTs in a thermal chemical vapor deposition (CVD) process. We present transmission electron microscope (TEM) and scanning electron microscope (SEM) images of the asgrown CNTs still attached to their growth substrate, which allows us to characterize both the CNTs and the catalytic nanoclusters after CVD growth.