Prof. Dr. Axel Müller

We investigate a novel morphological transition of surface immobilized triblock terpolymer micelles, the splitting into well-defined clusters of satellite micelles upon pH-changes. The multicompartment micelles are formed in aqueous solution of ABC triblock terpolymers consisting of a hydrophobic polybutadiene block, a weak polyanionic poly(methacrylic acid) block and a weak polycationic poly(2-(dimethylamino)ethyl methacrylate) block. They are subsequently immobilized on silicon wafer surfaces by dip-coating. The splitting process is triggered by a pH change to strongly basic pH, which goes along with a charge reversal of the micelles. We find that the aggregation number of the sub-micelles is well-defined and that larger micelles have a tendency to split into a larger number of sub-micelles. Furthermore, there is a clear preference for clusters consisting of doublets and triplets of sub-micelles. The morphology of surface-immobilized clusters can be “quenched” by returning to the original pH. Thus, such well-defined micellar clusters can be stabilized and are available as colloidal building blocks for the formation of hierarchical surface structures. We discuss the underlying physico-chemical principles of the splitting process considering changes in charge and total free energy of the micelles upon pH change.