Surface organization of single hyperbranched polymer molecules, as studied by atomic force microscopy

The recent emergence of hyperbranched polymers has opened the door to the design of a large variety of new chain architectures that promise to be strong competitors for dendrimers in a variety of potential applications. For instance, «comb-like» polymers can be obtained from poly(chloroethyl vinyl ether)-g-polystyrene (PCEVE-g-PS) copolymers, with excellent control over the dimensions of the polystyrene branches and the PCEVE backbone. In this work, the nanometer scale organization of these materials is studied by means of Atomic Force Microscopy (AFM). We focus on the influence of the intrinsic molecular architecture of the hyperbranched PCEVE-g-PS on the organization of the material. Several parameters such as sample preparation conditions (the nature of the solvent and the substrate, the solution concentration) and annealing of the samples are also taken into account. In the case of very thin deposits, we observe a layer-by-layer organization (the height of one monolayer corresponding to ~7 nm). On the free surface, it is possible to image single polymer molecules and to analyze their size in terms of the polymer molecular weight. In thicker deposits, the molecules are found to adopt an extended conformation and to form lamellar arrangements.