The scientists applied this technique to two types of triblock terpolymers. These differed with regard to the chemical properties of the middle blocks. The block sequences of the macromolecules were A-B-C and A-D-C, respectively. The first results in nanoparticles with a single bonding site and tends to form spherical clusters, while the latter creates nanoparticles with two bonding sites and thus tends to form linear superstructures. Importantly, in both cases the structure of the nanoparticles is preprogrammed by the chemical structure of the source macromolecule in the same way as the structure of a protein is determined by its amino acid sequence.
However, the process of self-assembly does not end with the nanoparticles. If the nanoparticles formed by each type of macromolecule were left to their own, spherical superstructures would result on the one hand and linear superstructures on the other. Mller's team has developed and implemented a different approach. The nanoparticles with one and two bonding sites are mixed so that they aggregate together into a completely new superstructure in a process of co-assembly. In the final superstructure, the nanoparticles originating from the A-B-C molecules and nanoparticles formed by the A-D-C molecules alternate in a precisely defined pattern.
When viewed under a transmission electron microscope, the new superstructure bears a strong resemblance to a caterpillar larva, because it also consists of a series of clearly separate, regularly ordered sections. Mll
|Contact: Dr. Axel H. E. Müller|
Johannes Gutenberg Universitaet Mainz