Synthesis and AFM structural imaging of dendrimer-like star-branched polystyrenes.

We report on the synthesis of large and densely tough dendrimer-like star-branched polystyrenes of generation 3, specially designed for their visualization by AFM imaging. For this purpose, an iterative methodology involving a sequential three stages synthetic approach has been adopted. The precisely designed G-3 polymers appear on AFM images as completely flattened objects with a symmetrical square-like shape and an average diameter of 250 nm and a height of less than 1 nm. Imaging of their internal structure indicates that they are constituted of four interconnected lobes, in relation with the use of a tetrafunctional core precursor. In addition, AFM images show the presence inside each object of all the branching points which appear as white harder zones regularly distributed in the less dense and softer PS matrix.